Search birdRS Box

Search birdRS blog posts

Browse the Blog Posts

Or scan through the blog archive below for items of interest as only the latest post is shown below, thanks.

Tuesday, 30 September 2014

Journal of Ornithology: Volume 155, Issue 4, October 2014. Table of Contents

Journal of Ornithology

Volume 155, Issue 4, October 2014

Original Articles
Jurassic archosaur is a non-dinosaurian bird
Stephen A. Czerkas, Alan Feduccia 
Pages 841-851

A taxonomic review of Picumnus exilis (Aves: Picidae) reveals an underestimation of Piculet species diversity in South America
Marco Antonio Rêgo, Glaucia Del-Rio, Luís Fábio Silveira 
Pages 853-867

Do Cory’s Shearwaters Calonectris borealis choose mates based on size?
Cristina Perry Nava, Sin-Yeon Kim, Maria Carvalho Magalhães… 
Pages 869-875

Dawn chorus start time variation in a temperate bird community: relationships with seasonality, weather, and ambient light
Adrianna Bruni, Daniel J. Mennill, Jennifer R. Foote 
Pages 877-890

Large-scale climate variability and rodent abundance modulates recruitment rates in Willow Ptarmigan (Lagopus lagopus)
Mikkel A. J. Kvasnes, Hans Chr. Pedersen, Torstein Storaas… 
Pages 891-903

Rainfall on wintering grounds affects population change in many species of Afro-Palaearctic migrants
Nancy Ockendon, Alison Johnston, Stephen R. Baillie 
Pages 905-917

Stress in wild Greater Rhea populations Rhea americana: effects of agricultural activities on seasonal excreted glucocorticoid metabolite levels
A. Lèche, G. Bazzano, C. Hansen, J. L. Navarro, R. H. Marin… 
Pages 919-926

Sex and individual differences in cooperative nest construction of sociable weavers Philetairus socius
Gavin M. Leighton 
Pages 927-935

Sex-specific traits in Common Tern Sterna hirundo chicks: associations with rearing environment, parental factors and survival
María M. Benito, Jacob González-Solís, Peter H. Becker 
Pages 937-949

Effects of neckbands on body condition of migratory geese
Kevin Kuhlmann Clausen, Jesper Madsen 
Pages 951-958

Male territories and the lek-like mating system of MacQueen’s Bustard Chlamydotis macqueenii
Samuel Riou, Olivier Combreau 
Pages 959-967

Gastro-intestinal microbiota of two migratory shorebird species during spring migration staging in Delaware Bay, USA
Kirsten Grond, Hodon Ryu, Allan J. Baker, Jorge W. Santo Domingo… 
Pages 969-977

Fuel for the road: the pre-migratory fuel loading of adult Eurasian Reed Warblers (Acrocephalus scirpaceus)
Dmitry Kobylkov, Vlad Kosarev, Andrey Mukhin 
Pages 979-986

The alarm call system of breeding Brown Thornbills (Acanthiza pusilla): self-defence or nest defence?
Nicole A. Schneider, Michael Griesser 
Pages 987-996

Vegetation type variation in marsh habitats: does it affect nest site selection, reproductive success, and maternal investment in Reed Warblers?
Alžbeta Darolová, Ján Krištofík, Herbert Hoi 
Pages 997-1008

Patterns of within-clutch variation in yolk lutein in the Yellow-legged Gull Larus michahellis: the effects of egg laying order and laying date
Abdessalem Hammouda, Slaheddine Selmi, Jessica Pearce-Duvet 
Pages 1009-1015

Aggression, body condition, and seasonal changes in sex-steroids in four hummingbird species
Paulina L. González-Gómez, William S. Blakeslee… 
Pages 1017-1025

Disentangling the origin of crossbills using morphology and isotopic (δ2H) characters. Are southern European crossbills restricted to population-specific key resources?
Juan Arizaga, Daniel Alonso, Keith A. Hobson 
Pages 1027-1035

What flight heights tell us about foraging and potential conflicts with wind farms: a case study in Lesser Black-backed Gulls (Larus fuscus)
Anna-Marie Corman, Stefan Garthe 
Pages 1037-1043

Variation and long-term trends in the timing of breeding of different Eurasian populations of Common Redstart Phoenicurus phoenicurus
Jiří Porkert, Sergey Gashkov, Juha Haikola, Esa Huhta… 
Pages 1045-1057

Short Notes
Nocturnal singing in a temperate bird community
Kerry Perrault, Lynnea M. Lobert, Mandy Ehnes, Jennifer R. Foote 
Pages 1059-1062

Nutritional status does not explain the increase of carotenoid-based coloration associated with age in Great Tits Parus major
Mathieu Giraudeau, Margarida Barcelo, Juan Carlos Senar 
Pages 1063-1066

High glucose concentrations are associated with symptoms of mild anaemia in Whiskered Terns: consequences for assessing physiological quality in birds
Piotr Minias 
Pages 1067-1070

Unravelling migration routes and wintering grounds of European rollers using light-level geolocators
Inês Catry, Teresa Catry, José Pedro Granadeiro… 
Pages 1071-1075

Technical Note
Measuring the eye size of mist-netted birds: a comparison of two non-invasive methods
Claudia Schütz, Christian H. Schulze 
Pages 1077-1079

Response to Lingham-Soliar: feather structure, biomechanics and biomimetics: the incredible lightness of being
Colin Palmer 
Pages 1081-1082

Response to comments by C. Palmer on my paper, Feather structure, biomechanics and biomimetics: the incredible lightness of being
Theagarten Lingham-Soliar 
Pages 1083-1085

Tuesday, 16 September 2014

The Numerical Competency of Two Bird Species (Common Myna, House Crow): Trop Life Sci Res. August 2014; 25(1): 95-103

Trop Life Sci Res. August 2014; 25(1): 95–103.

PMCID: PMC4156476

The Numerical Competency of Two Bird Species (Corvus splendens andAcridotheres tristis)

Nor Amira Abdul Rahman,* Nik Fadzly, Najibah Mohd Dzakwan, and Nur Hazwani Zulkifli
Author information  
School of Biological Sciences, Universiti Sains Malaysia, 11800 USM, Pulau Pinang, Malaysia
*Corresponding author: Email: ku.oc.oohay@ycniuqanomar


Numerical knowledge refers to the ability to count objects and to understand the relationship between numbers in small or large amounts. This trait of numerical competence is found only in adult humans and consists of a variety of precise, stimulus-independent, numerical capabilities. Shared numerical competence, however, consists of a variety of approximate, stimulus-dependent, numerical capabilities, and is found in non-human animals, human infants and human adults (Katz 2007).
According to Tennesen (2009), number counting by animals may be an innate ability. Even without using actual numbers, animals can count and sum sets of objects. However, because they do not possess the linguistic sense of numerals, animals are not able to count verbally. Instead, the ability to count may have evolved for territorial animals as a way of determining whether to stay in an area by estimating the time invested to find food versus the amount of food found (Tenessen 2009).
The exact process of counting among non-human animals is still unclear and controversial. Most of the basic calculations for the counting ability of non-human animals follow Weber’s Law. This law states that as numerical magnitude increases, a larger numerical difference is needed to obtain the same level of discrimination (Hunt et al. 2008). For example, most animals could differentiate the magnitude difference between one versus two or two versus three but will have difficulty comparing five versus six or six versus seven. Subitising is a numerical process that allows the observer to rapidly and accurately understand the number of small sets of objects, usually within the range of 1–4 items (Piazza et al. 2002; Balakrishnan & Ashby 1992; Kaufman et al. 1949). Counting is when enumeration is slower and is more prone to errors when more than four items are involved (Egeth et al. 2008; Piazza et al. 2002).
In recent years, the study of counting and other related numerical skills has been investigated across a wide range of non-human species. Studies have shown the potential for numerical discrimination in a variety of species ranging from honey bees (Dacke & Srinivasan 2008) and monkeys (Addessi et al. 2008) to ants (Reznikova & Ryabko 2011). Non-human primates have shown a more advanced numerical skill set compared to other animal species (Tomonaga 2008). Birds are considered promising subjects for the study of numerical competency based upon previous experiments (Shaw & Clayton 2012; von Bayern & Emery 2009; Hunt et al. 2008) that showed they possess abilities that were once considered unique to primates (Scarf et al. 2011).
Because corvids are famous for their intelligence and boldness, they have garnered much attention and interest from the scientific community. For example, corvids are capable of using and making tools to catch prey (von Bayern et al. 2009). Corvids will use sticks (and sometimes even modify a stick) to acquire bugs or other food from crevices and small cracks (Kenward et al. 2006). When necessary, corvids have even been known to successfully bend a piece of wire into a hook to obtain their food (Weir et al. 2002). Some corvid species, such as the common raven (Corvus corax) (Bugnyar et al. 2007), have solved the challenging task of keeping track of a moving object, a skill similar to that observed in human infants. Despite known as a fast-learning and intelligent bird species (Yosef et al. 2012), little is known about the ability of corvids to quantitatively judge inequality, and whether these numerical judgements in wild animals have any adaptive significance is still unclear (Hauser et al. 2000).
Starlings are another bird group considered to be intelligent due to their ability to recognise trees and people in pictures and also due to their vocal identification signalling (Kak 2000). Heptonstall (2010)stated that some species of starlings [in particular, the Common Hill Myna (Gracula religiosa)], also have the ability to mimic human speech as well as other environmental sounds.
Corvus splendens (House Crows) and Acridotheres tristis (Common Myna) are considered nuisance and pest species and are usually associated with a dirty environment and noise pollution. Both of these starling species are found in Malaysia and Pulau Pinang. The main objective of this study was to evaluate the numerical competency in two species of birds, C. splendens (Family: Corvidae) and A. tristis (Family: Sturnidae).


The Common Myna is a small bird species with very distinct features. The body is brown with a greyish-black hood, whitish vent, and a yellow bill and facial skin. The House Crow is slightly bigger than the Common Myna and is black with a sharply contrasting, pale grey collar. The bill of a House Crow is shorter and more slender than other species of crows. The Common Mynas were captured using a mist net around the Universiti Sains Malaysia (USM), Pulau Pinang campus. The House Crows were obtained from the local municipal authority, Taman Tun Sardon, Pulau Pinang.
Our experiments were conducted from April 2012 to June 2012 at the School of Biological Sciences (5°21’N, 100°18’E), USM. A total of six Common Myna and six House Crows were used for the experiments. All of the birds were kept in a custom-made cage with a floor area of 12.6 m2. The cage was divided into three sections with the middle compartment designated as the experimental area and the other two compartments as holding cages. The cage was cleaned regularly to maintain a healthy and clean environment for the birds. Both species were fed with similar food and clean water once a day. Outside of the experimental sessions, the birds were fed with white bread, fruits, rice and mealworms. Experimental trials were conducted three times per week on Mondays, Wednesdays and Fridays and lasted from 1600 to 1800. A one-day gap between experiments was allowed to prevent stress on the birds.
We evaluated the birds’ numerical competency using choice-test experiments with mealworms. Each trial was recorded using a Sony Legria video recorder and followed the protocol described by Hunt et al.(2008). For each trial, only one bird was used at a time and each experiment was repeated three times. At the start of the experiment, a bird was released from the holding cage into the experimental cage. The researcher then showed the mealworms to the bird for five seconds before depositing the mealworms into the container cup. The mealworms were placed in two opaque white cup containers measuring 70 × 50 × 97 (mm). Both cups were placed 50 cm apart on a plastic black board. This process was repeated several times to acclimatise the birds to the food dropping process and to the researcher’s presence. The trial was then recorded when the bird was calm and attentive. Two researchers conducted each trial (one to record the trial and the other to put the mealworms in the container) to reduce recognition bias from the birds. The researchers wore a breathing mask, white gloves and a white lab coat, both for the safety of the researcher and to reduce any facial recognition bias from the birds. We then proceeded to test different proportions of food items in the container cups. Seven food item combinations were presented to all 12 birds: 1 versus 3, 1 versus 4, 2 versus 5, 3 versus 7, 5 versus 8, 6 versus 9, and 8 versus 10. These combinations were tested in a random order to control for observational learning behaviour. The left or right orientation of the different number combinations were also randomised to prevent preference bias and to control for observational learning (Hunt et al. 2008).
Initially, most of the birds would perch at the highest position in the experiment cage and observe the researcher's actions. During the early stages of the trials, both House Crows and Common Myna needed approximately five minutes to choose the food item. However, after several repetitions of these trials, the birds learned to choose a food item within one minute after the trial began. Occasionally, the birds would continue searching for food items in the other cup even after the first selection. House crows produced noisy vocalisation and flew aggressively during the trials, and similar to Medina et al. (2011), they exhibited an agonistic response for the duration of the experiment. However they managed to count or distinguish the number of mealworms in the paper cup. Comparatively, although the Common Myna did produce noisy vocalisations, they were quite passive and calm during the trials. The experimental observations were conducted within a five minutes time frame. If the bird chose the food item with the highest number, it was considered to have made the “correct choice”. The selection of the food item with the lowest number would be considered the “wrong choice”. If the bird did not show any reaction or did not choose any food item after five minutes, the trial was considered a failure and excluded from the analysis. The results were analysed via a binomial test using JMP 10 software (SAS, Petaling Jaya, Kuala Lumpur).


When testing the House Crows, we found that only one (one versus four) out of the seven different food proportion combinations was significantly different, where the birds selected the cup with more mealworms at frequencies above random chance (p = 0.041) (Fig. 1). Overall, the House Crows made successful choices, as shown in Figure 2. These data suggest that the crows are capable of discriminating larger versus smaller numbers because the number of successes exceeded the number of failures (133 successes over 108 failures).
Results for (a) House Crows and (b) Common Myna where the total of number of food items used in each trial is on the x-axis, and the percentage of birds choosing the greater number of food items is on the y-axis.



The number of successes and failures for each food item combination for (a) House Crows and (b) Common Myna.



Our results showed that the Common Myna has a better numerical competency than the House Crow. In four out of the seven food proportion combinations (1 versus 4, 2 versus 5, 6 versus 9 and 8 versus 10), the Common Myna made successful choices at frequencies above random chance (Fig. 1). We found that the Common Myna can easily discriminate a larger quantity over a smaller quantity because the number of successful choices exceeded the number of failures (161 successes over 86 failures) (Fig. 2).
Hunt et al. (2008) stated that most animals can differentiate small quantities, but after training (learning, observing and experiencing), animals are also able to distinguish larger quantities. For example, after extensive training, primates have the ability to discriminate more than four items (Beran 2004). The exact numerosity judgment, which is limited to four countable items, has led to the suggestion that different mechanisms may be responsible for the representation of large versus small number sets (Feigenson et al. 2004). In Yellow Mealworm beetle (Tenebrio molitor) males (Carazo et al. 2009), the numerical competence training involved sequentially presenting items but had a set size limit of four items. Similar numerical competency has also been found in Rhesus macaque (Macaca mulatta) (Hauser et al. 2000).
Even though the House Crows only chose one food proportion combination at a rate above random chance, the House Crows often chose the larger of two quantities (133 successes over 108 failures) (Fig. 2). This is similar to the studies by Brannon and Terrace (2000) and by Gallistel and Gelman (2000) that state that exactness in numerical judgments will decrease with increasing magnitude. In our first trial (using a food combination of one versus three items), the crows made more successful choices but at a rate below chance. Unfamiliarity and lack of learning experience, however, might have affected these early trials and may be the reason that the proportion of successful to failed choices was not significant. According to Werdenich and Huber (2006), this could be attributed to the fear of trying something new (neophobia) in the crows. Our results show that crows did not process information about quantity in an efficient manner and perhaps chose the food item randomly. The House Crows might have developed a preferential selection based upon the orientation of the food cups the first time they encountered the larger food portion. A similar result was observed in a study by Willson and Comet (1993) using adult Northwestern Crows (Corvus caurinus), where the birds exhibited individual preferences for sugar and lipid content and the colour of the food. Another possibility is that the crows remembered the first cup they chose and continued to choose the same cup because of observational spatial memory (Emery & Clayton 2004). The crows also have a tendency to select larger food items but to avoid extra energy and greater handling cost, they may strategically choose the cup with the smaller portion (Hunt et al. 2008). We also speculate that the crows could have simply chosen a cup based upon the fact that they knew both cups contained food and it is more beneficial to select the cup nearest to their perching position.
Comparatively, the Common Myna had an impressive number of successful choices – 161 successes and 86 failures (Fig. 2). This indicates Weber’s Law does not apply for the Common Myna. Similar to the House Crows, unfamiliarity and lack of experience could have affected the earliest test (one versus three). However, unlike the House Crows, the Common Myna managed to adapt and learn within a short period of time. The last two proportions tested (6 versus 9 and 8 versus 10) had a significantly higher success count compared to all the other food item proportions. We speculate that this was due to learning between trials. There are other aspects of learning besides habituation and operant conditioning, which are also considered to be part of instrumental (or observational) learning. This instrumental learning was made possible because the experimental test area and the confinement area for the myna was located next to each other. We observed that the Common Myna had the tendency to perform a successful choice after observing another individual bird select a larger over a smaller quantity of mealworms. A similar situation has been previously observed in ducks, where it was shown that they could learn their tasks by observation (Klopfer 1957). The improvement of the Common Mynas’ numerical capacity could also be attributed to the fact that birds can be trained naturally and have the tendency to develop more advanced numerical abilities over an extended period of time (Hunt et al. 2008). Another possible explanation for the excellent performance of the Common Myna is that extensive experience enhances the formation of analogue numerical representations (Tomonaga 2008).
Even though the House Crow is an invasive species in Malaysia (Nyari et al. 2006), both House Crow and Common Myna species are commonly found in Malaysia and especially in Pulau Pinang. Both species of birds can successfully adapt to any environment, including urban developments. Both species are omnivorous where they feed mainly on insects, fruits and grains. Regularly they have been seen to feed on refuse around human habitation too. The ability of these two species to adapt to a new environment as well as compete with each other for resources is an open debate. Our results show that the Common Myna may be more intelligent than the House Crow in terms of counting ability. The Common Myna made 161 successful selections, while the House Crow only made 133 successful selections (Fig. 2). Although both species of birds selected more food items, the House Crow made wrong choices more often (108 failures) than the Common Myna (86 failures).


From our observation, House Crows are capable of discriminating a large number of items from a smaller number. Although House Crows were long known as intelligent birds, our results indicate that the numerical learning capacity of the House Crows might be lacking. These results also suggest that the House Crows’ total limit for making numerical discriminations is less than four. However, further studies on the numerical competency of House Crows are needed. Our results provide the field with a better understanding of how animals solve mathematical problems. Based on our results, we suggest that the Common Myna uses memory cognition when counting, rather than subitising. This study also provides evidence that the numerical competency of these birds can be improved by observational learning. Future studies should therefore use different procedures, such as operant conditioning, involving both active and passive reinforcement.


The authors thank all the staff from the School of Biological Sciences, USM for their help during the sampling session. This project was funded by USM Short Term Grant 304/PBIOLOGI/6311071.


  • Addessi E, Crescimbene L, Visalberghi E. Food and token quantity discrimination in capuchin monkeys (Cebus apellaAnimal Cognition. 2008;11(2):275–282. [PubMed]
  • Balakrishnan JD, Ashby F. Subitizing: Magical numbers or mere superstition? Psychological Research. 1992;54(2):80–90. [PubMed]
  • Beran MJ. Chimpanzees (Pan troglodytes) respond to nonvisible sets after one-by-one addition and removal of items. Journal of Comparative Psychology. 2004;118(1):25–36. [PubMed]
  • Brannon E, Terrace HS. Representation of the numerosities 1–9 by rhesus macaques (Macaca mulattaJournal of Experimental Psychology: Animal Behavior Processes. 2000;26(1):31–49.[PubMed]
  • Bugnyar T, Stoewe M, Heinrich B. The otogeny of caching in ravens, Corvus coraxAnimal Behaviour. 2007;74(4):757–767.
  • Carazo P, Font E, Forteza-Behrendt E, Desfilis E. Quantity discrimination in Tenebrio molitor: Evidence of numerosity discrimination in an invertebrate? Animal Cognition. 2009;12(3):463–470. [PubMed]
  • Dacke M, Srinivasan MV. Evidence for counting in insects. Animal Cognition. 2008;11(4):683–689. [PubMed]
  • Emery NJ, Clayton NS. The mentality of crows: Convergent evolution of intelligence in corvids and apes. Science. 2004;306(5703):1903–1907. [PubMed]
  • Egeth HE, Leonard CJ, Palomeras M. The role of attention in subitizing: Is the magical number 1?Visual Cognition. 2008;16(4):463–473.
  • Feigenson L, Dehaene S, Spelke E. Core systems of number. Trends in Cognitive Sciences.2004;8(7):307–314. [PubMed]
  • Gallistel CR, Gelman R. Non-verbal numerical cognition: From reals to integers. Trends in Cognitive Sciences. 2000;4(2):59–65. [PubMed]
  • Hauser MD, Carey S, Hauser LB. Spontaneous number representation in semi-free ranging rhesus monkeys. Proceedings of the Royal Society B: Biological Sciences. 2000;267(1445):829–833.[PMC free article] [PubMed]
  • Heptonstall RAE. The distribution and abundance of Myna birds (Acridotheres tristis) and Rimatara Lorikeets (Vini kuhlii) on Atiu, Cook Islands. 2010. MSc. diss., UK: Leeds University.
  • Hunt S, Low J, Burns KC. Adaptive numerical competency in a food-hoarding songbird.Proceedings of the Royal Society B: Biological Sciences. 2008;275(1649):2373–2379.[PMC free article] [PubMed]
  • Kak S. Grading intelligence in machines: Lessons from animal intelligence. In: Meystel A, Messina ER, editors. Measuring the performance and intelligence systems. Proceedings of the 2000 PerMIS Workshop. Washington, DC: The National Institute of Standards and Technology (NIST); 2000. pp. 331–334. Gaithersburg, MD, August 14–16 2000.
  • Katz MA. Numerical competence and the format of mental representation. 2007 PhD diss., University of Pennsylvania.
  • Kaufman EL, Lord MW, Reese W, Volkman J. The discrimination of visual number. The American Journal of Psychology. 1949;62(4):498–525. [PubMed]
  • Kenward B, Rutz C, Weir AAS, Kacelnik A. Development of tool use in New Caledonian crows: Inherited action patterns and social influences. Animal Behaviour. 2006;72(6):1329–1343.
  • Klopfer PH. An experiment on empathetic learning in ducks. American Naturalist.1957;91(856):61–63.
  • Medina FS, Taylor AH, Hunt GR, Gray RD. New Caledonian crows’ responses to mirrors. Animal Behaviour. 2011;82(5):981–993.
  • Nyari A, Ryall C, Peterson AT. Global invasive potential of the house crow, Corvus splendensbased on ecological niche modelling. Journal of Avian Biology. 2006;37(4):306–311.
  • Piazza M, Mechelli A, Butterworth B, Price CJ. Are subitizing and counting implemented as separate or functionally overlapping process? Neurolmage. 2002;15(2):435–446. [PubMed]
  • Reznikova Z, Ryabko B. Numerical competence in animals, with an insight from ants. Behaviour.2011;148(4):405–434.
  • Shaw RC, Clayton NS. Eurasian jays, Garrulus glandarius flexibly switch caching and pilfering tactics in response to social context. Animal Behavior. 2012;84(5):1191–1200.
  • Scarf D, Hayne H, Colombo M. Pigeons on par with primates in numerical competence. Science.2011;334(6063):1664. [PubMed]
  • Tennesen M. Animals by the numbers. Scientific American. 2009;301(3):23–24. [PubMed]
  • Tomonaga M. Relative numerosity discrimination by chimpanzees (Pan troglodytes): Evidence for approximate numerical representations. Animal Cognition. 2008;11(1):43–57. [PubMed]
  • von Bayern AMP, Emery JN. Jackdaws respond to human attentional states and communicative cues in different contexts. Biology. 2009;19(7):602–606. [PubMed]
  • von Bayern AMP, Heathcote RJP, Rutz C, Kacelnik A. The role of experience in problem solving and innovative tool use in crows. Current Biology. 2009;19(22):1965–1968. [PubMed]
  • Weir AAS, Chappell J, Kacelnik A. Shaping of hooks in New Caledonian Crows. Science.2002;297(5583):981. [PubMed]
  • Werdenich D, Huber L. A case of quick problem solving in birds: String pulling in keas, Nestor notabilisAnimal Behavior. 2006;71(4):855–863.
  • Willson MF, Comet TA. Food choices by Northwestern Crows: Experiments with captive, free-ranging and hand raised birds. The Condor. 1993;95(3):596–615.
  • Yosef R, Zvuloni A, Yosef-Sukenik N. House Crow (Corvus splendens) attempt to cooperatively kleptoparasitize Western Osprey (Pandion haliaetusThe Wilson Journal of Ornithology.2012;124(2):406–408.

Bird research highlights this week on PubMed: September 2014 Week 3

PubMed listing for 'bird' OR 'songbird' excluding references to influenza and flu - September 2014 Week 3

1. PLoS One. 2014 Sep 12;9(9):e107341. doi: 10.1371/journal.pone.0107341. eCollection 2014.

Repeatability of Feather Mite Prevalence and Intensity in Passerine Birds.

Diaz-Real J1, Serrano D2, Pérez-Tris J, Fernández-González S, Bermejo A, Calleja JA, De la Puente J, De Palacio D, Martínez JL, Moreno-Opo R, Ponce C, Frías O, Tella JL, Møller AP, Figuerola J, Pap PL, Kovács I, Vágási CI, Meléndez L, Blanco G, Aguilera E, Senar JC, Galván I, Atiénzar F, Barba E, Cantó JL, Cortés V, Monrós JS, Piculo R, Vögeli M, Borràs A, Navarro C, Mestre A, Jovani R1.
Author information:
1Estación Biológica de Doñana (CSIC), Sevilla, Spain; Departamento de Ecoloxía e Bioloxía Animal. Universidade de Vigo, Campus As Lagoas Marconsende, Vigo, Pontevedra, Spain.


Understanding why host species differ so much in symbiont loads and how this depends on ecological host and symbiont traits is a major issue in the ecology of symbiosis. A first step in this inquiry is to know whether observed differences among host species are species-specific traits or more related with host-symbiont environmental conditions. Here we analysed the repeatability (R) of the intensity and the prevalence of feather mites to partition within- and among-host species variance components. We compiled the largest dataset so far available: 119 Paleartic passerine bird species, 75,944 individual birds, ca. 1.8 million mites, seven countries, 23 study years. Several analyses and approaches were made to estimate R and adjusted repeatability (Radj) after controlling for potential confounding factors (breeding period, weather, habitat, spatial autocorrelation and researcher identity). The prevalence of feather mites was moderately repeatable (R = 0.26-0.53; Radj = 0.32-0.57); smaller values were found for intensity (R = 0.19-0.30; Radj = 0.18-0.30). These moderate repeatabilities show that prevalence and intensity of feather mites differ among species, but also that the high variation within species leads to considerable overlap among bird species. Differences in the prevalence and intensity of feather mites within bird species were small among habitats, suggesting that local factors are playing a secondary role. However, effects of local climatic conditions were partially observed for intensity.
PMID: 25216248 [PubMed - as supplied by publisher]

2. Science. 2014 Sep 12;345(6202):1343-6. doi: 10.1126/science.1254610.

Loss of avian phylogenetic diversity in neotropical agricultural systems.

Frishkoff LO1, Karp DS2, M'Gonigle LK3, Mendenhall CD4, Zook J5, Kremen C3, Hadly EA6, Daily GC7.
Author information:
1Department of Biology, Stanford University, Stanford, CA 94305, USA. Center for Conservation Biology, Stanford University, Stanford, CA 94305, USA.
2Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720, USA. Nature Conservancy, Berkeley, CA 94705, USA.
3Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720, USA.
4Department of Biology, Stanford University, Stanford, CA 94305, USA. Center for Conservation Biology, Stanford University, Stanford, CA 94305, USA.
5Unión de Ornitólogos de Costa Rica, Apartado 182-4200, Naranjo de Alajuela, Costa Rica.
6Department of Biology, Stanford University, Stanford, CA 94305, USA.
7Department of Biology, Stanford University, Stanford, CA 94305, USA. Center for Conservation Biology, Stanford University, Stanford, CA 94305, USA. Woods Institute for the Environment, Stanford University, Stanford, CA 94305, USA. Global Economic Dynamics and the Biosphere, Royal Swedish Academy of Sciences, SE-104 05 Stockholm, Sweden. Stockholm Resilience Center, University of Stockholm, SE-106 91 Stockholm, Sweden.


Habitat conversion is the primary driver of biodiversity loss, yet little is known about how it is restructuring the tree of life by favoring some lineages over others. We combined a complete avian phylogeny with 12 years of Costa Rican bird surveys (118,127 detections across 487 species) sampled in three land uses: forest reserves, diversified agricultural systems, and intensive monocultures. Diversified agricultural systems supported 600 million more years of evolutionary history than intensive monocultures but 300 million fewer years than forests. Compared with species with many extant relatives, evolutionarily distinct species were extirpated at higher rates in both diversified and intensive agricultural systems. Forests are therefore essential for maintaining diversity across the tree of life, but diversified agricultural systems may help buffer against extreme loss of phylogenetic diversity.
Copyright © 2014, American Association for the Advancement of Science.
PMID: 25214627 [PubMed - in process]

3. Poult Sci. 2014 Sep 11. pii: PS4207. [Epub ahead of print]

Effects of probiotics and application methods on performance and response of broiler chickens to an Eimeria challenge.

Ritzi MM1, Abdelrahman W2, Mohnl M3, Dalloul RA4.
Author information:
1Avian Immunobiology Laboratory, Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg 24061.
2BIOMIN Holding GmbH, 3130 Herzogenburg 3130, Austria Faculty of Veterinary Medicine, Suez Canal University, Ismailia, Egypt 41522.
3BIOMIN Holding GmbH, 3130 Herzogenburg 3130, Austria.
4Avian Immunobiology Laboratory, Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg 24061


Coccidiosis is an inherent risk in the commercial broiler industry and inflicts devastating economic losses to poultry operations. Probiotics may provide a potential alternative to the prophylactic use of anticoccidials in commercial production. This study evaluated the effects of probiotic applications (feed and water) on bird performance and resistance to a mixed Eimeria infection in commercial broilers. On day of hatch, 1,008 commercial male broilers (Cobb 500) were assigned to 1 of 6 treatments (8 replicate floor pens; 21 birds/pen), including noninfected negative control (NEG), Eimeria-infected positive control (POS), anticoccidial control (0.01% salinomycin, SAL), intermittent high-dose water-applied probiotic (WPI), continuous low-dose water-applied probiotic (WPC), and feed-supplemented probiotic (FSP). On d 15, all birds except those in NEG were challenged with a mixed inoculum of Eimeria acervulina, Eimeria maxima, and Eimeria tenella. Measurements were taken on d 7, 15, 21, 28, 35, and 42. Fecal samples were collected from d 20 to 24 for oocyst counts, and lesion scores were evaluated on d 21. Data were analyzed using the Fit Model platform in JMP Pro 10.0 (SAS Institute Inc.). Differences in experimental treatments were tested using Tukey's honestly significant difference following ANOVA with significance reported at P ≤ 0.05. Overall, NEG birds outperformed all other groups. For performance, the probiotic groups were comparable with the SAL-treated birds, except during the 6 d immediately following the Eimeria species challenge, where the SAL birds exhibited better performance. The WPC birds had lower duodenal and jejunal lesion scores, indicating a healthier intestine and enhanced resistance to Eimeria species compared with POS. Birds in the WPI treatment shed fewer oocysts in the feces, although this was not a trend for all of the probiotic treatment groups. The results of this study suggest probiotic supplementation without anticoccidials can enhance performance and help alleviate the negative effects of a mixed Eimeria infection.
Poultry Science Association Inc.
PMID: 25214558 [PubMed - as supplied by publisher]

4. J Exp Biol. 2014 Sep 11. pii: jeb.107573. [Epub ahead of print]

The intensity threshold of colour vision in a passerine bird, the blue tit.

Gomez D1, Grégoire A2, Del Rey Granado M2, Bassoul M2, Degueldre D2, Perret P2, Doutrelant C2.
Author information:
1CNRS MNHN, Brunoy, France;
2CEFE, CNRS, Montpellier, France.


Many vertebrates use colour vision for vital behaviours. Yet, their visual performance in dim light is largely unknown. The light intensity threshold of colour vision is only known in humans, horses and two parrot species. Here, we first explore this threshold in a passerine bird, the blue tit (Cyanistes caeruleus). Using a classic conditioning of colour cues to food rewards in three individuals, we find a threshold ranging from 0.05 to 0.2 cd.m-2. Results are comparable to the two previously tested bird species. For tits, nest light conditions likely exceed that threshold, at least after sunrise. These first results shed new light on the lively debate questioning cavity-nesters visual performance, and the evolutionary significance of egg and chick coloration. Although this needs proper testing, it is possible that blue tits exploit both colour and brightness cues when viewing their eggs, chicks or conspecifics in their nests.
PMID: 25214487 [PubMed - as supplied by publisher]

5. Trop Life Sci Res. 2014 Aug;25(1):95-103.

The Numerical Competency of Two Bird Species (Corvus splendens and Acridotheres tristis).

Rahman NA, Fadzly N, Dzakwan NM, Zulkifli NH.
Author information:
School of Biological Sciences, Universiti Sains Malaysia, 11800 USM, Pulau Pinang, Malaysia.


We conducted a series of experiments to test the numerical competency of two species of birds, Corvus splendens (House Crow) and Acridotheres tristis (Common Myna). Both species were allowed to choose from seven different groups of mealworms with varying proportions. We considered the birds to have made a correct choice when it selected the food group with the highest number of mealworms. Our overall results indicated that the Common Myna is able to count numbers (161 successful choices out of 247 trials) better than House Crows (133 successful choices out of 241 trials). We suspect that House Crows do not rely on a numerical sense when selecting food. Although House Crows mostly chose the cup with more mealworms (from seven food item proportions), only one proportion was chosen at rate above random chance. The Common Myna, however, were slow performers at the beginning but became increasingly more capable of numerical sense during the remainder of the experiment (four out of seven food proportion groups were chosen at a rate above random chance).
PMID: 25210590 [PubMed]

6. PLoS One. 2014 Sep 11;9(9):e106366. doi: 10.1371/journal.pone.0106366. eCollection 2014.

Mapping seabird sensitivity to offshore wind farms.

Bradbury G1, Trinder M2, Furness B2, Banks AN3, Caldow RW3, Hume D4.
Author information:
1Wildfowl & Wetlands Trust (Consulting) Ltd., Slimbridge, United Kingdom.
2MacArthur Green, Glasgow, United Kingdom.
3Natural England, Exeter, United Kingdom.
4Marine Management Organisation, Newcastle, United Kingdom.


We present a Geographic Information System (GIS) tool, SeaMaST (Seabird Mapping and Sensitivity Tool), to provide evidence on the use of sea areas by seabirds and inshore waterbirds in English territorial waters, mapping their relative sensitivity to offshore wind farms. SeaMaST is a freely available evidence source for use by all connected to the offshore wind industry and will assist statutory agencies in assessing potential risks to seabird populations from planned developments. Data were compiled from offshore boat and aerial observer surveys spanning the period 1979-2012. The data were analysed using distance analysis and Density Surface Modelling to produce predicted bird densities across a grid covering English territorial waters at a resolution of 3 km×3 km. Coefficients of Variation were estimated for each grid cell density, as an indication of confidence in predictions. Offshore wind farm sensitivity scores were compiled for seabird species using English territorial waters. The comparative risks to each species of collision with turbines and displacement from operational turbines were reviewed and scored separately, and the scores were multiplied by the bird density estimates to produce relative sensitivity maps. The sensitivity maps reflected well the amassed distributions of the most sensitive species. SeaMaST is an important new tool for assessing potential impacts on seabird populations from offshore development at a time when multiple large areas of development are proposed which overlap with many seabird species' ranges. It will inform marine spatial planning as well as identifying priority areas of sea usage by marine birds. Example SeaMaST outputs are presented.
PMID: 25210739 [PubMed - in process]

Icon for Public Library of Science

Thursday, 11 September 2014

The Condor: August 2014; Volume 116, Issue 3

The Condor

Published by: Cooper Ornithological Society

Table of Contents

August 2014 : Volume 116, Issue 3 


Demographic heterogeneity among individuals can explain the discrepancy between capture–mark–recapture and waterfowl count results Full Access

Matthieu Guillemain, Roger Pradel, Olivier Devineau, Géraldine Simon, and Michel Gauthier-Clerc
pg(s) 293–302
Demographic heterogeneity has long been considered within wildlife populations, but only the modern development of capture–mark–recapture methods allows this to be easily tested and quantified. It is now possible to rapidly assess whether the modeling of heterogeneous populations, in which categories of individuals differ in survival rate, performs better than traditional approaches, in which all individuals are considered equivalent within a sex and age class. Using long-term banding data for 4,703 adult female Green-winged Teal (Anas crecca) from the Camargue, southern France, we show that a heterogeneous model outperformed a homogeneous model. Individuals from the high survival category had a ∼60% annual survival rate, whereas birds in the second category had a survival rate reduced by a factor of 0.76–0.80, depending on the model (i.e. <50%). We could not demonstrate that individuals within the high survival category were larger or heavier. The link between survival rate and potential differences in individual morphometrics or individual behavioral strategies thus remains to be established. Previous studies in which a Green-winged Teal population was modeled as homogeneous suggested it should decline (population growth rate <1), which we also found when using demographic parameters obtained from a homogeneous model. This finding contradicts waterfowl surveys that show a long-term population increase in this flyway. Modeling the population as heterogeneous led to growth rates of 1.03–1.05 (a 3–5% annual increase), numbers consistent with the growth rate inferred from duck counts and that also partly explain how species such as Green-winged Teal can increase in numbers despite large hunting harvest, sustaining harvest to some extent.
Abstract & References : Full Text : PDF (273 KB) 

A multiscale assessment of tree avoidance by prairie birds Full Access

Sarah J. Thompson, Todd W. Arnold, and Courtney L. Amundson
pg(s) 303–315
In North America, grassland bird abundances have declined, likely as a result of loss and degradation of prairie habitat. Given the expense and limited opportunity to procure new grasslands, managers are increasingly focusing on ways to improve existing habitat for grassland birds, using techniques such as tree removal. To examine the potential for tree removal to benefit grassland birds, we conducted 446 point counts on 35 grassland habitat patches in the highly fragmented landscape of west-central Minnesota during 2009–2011. We modeled density of four grassland bird species in relation to habitat composition at multiple scales, focusing on covariates that described grass, woody vegetation (trees and large shrubs), or combinations of grass and woody vegetation. The best-supported models for all four grassland bird species incorporated variables measured at multiple scales, including local features such as grass height, litter depth, and local tree abundance, as well as landscape-level measures of grass and tree cover. Savannah Sparrows (Passerculus sandwichensis), Sedge Wrens (Cistothorus platensis), and Bobolinks (Dolichonyx oryzivorus) responded consistently and negatively to woody vegetation, but response to litter depth, grass height, and grassland extent were mixed among species. Our results suggest that reducing shrub and tree cover is more likely to increase the density of grassland birds than are attempts to improve grass quality or quantity. In particular, tree removal is more likely to increase density of Savannah Sparrows and Sedge Wrens than any reasonable changes in grass quality or quantity. Yet tree removal may not result in increased abundance of grassland birds if habitat composition is not considered at multiple scales. Managers will need to either manage at large scales (80–300 ha) or focus their efforts on removing trees in landscapes that contain some grasslands but few nearby wooded areas.
Abstract & References : Full Text : PDF (384 KB) 


Using patch occupancy models to estimate area of crevice-nesting seabird colonies Full Access

Joel H. Reynolds and Heather M. Renner
pg(s) 316–324
Crevice-nesting seabirds are notoriously difficult to monitor. We present a survey design and analysis that estimates both colony area and geographic extent, using indirect evidence to determine whether a cell is “occupied.” The approach is to define a grid of cells across potential habitat and randomly sample small plots within each cell, surveying for signs of occupancy. Visiting ≥1 plot cell−1 provides a basis for mapping geographic extent. Occupancy models are used to estimate colony area, probability of detection for an occupied cell, and standard errors for all estimated parameters (allowing for statistical comparisons across surveys or colonies). We estimated the area of a colony of Least Auklets (Aethia pusilla) and Crested Auklets (A. cristatella) on Segula Island, Aleutian Archipelago, Alaska, in 2006, and use this as an example of how to adapt the survey design to the logistical constraints common in seabird colony surveys. Surveying only a handful of sample plots of ∼16 m2 in each ∼2,500-m2 cell in the grid was adequate to estimate the detection bias from spatial subsampling, correcting a >50% underestimate of colony area due to plots without evidence having been interpreted as unoccupied cells.
Abstract & References : Full Text : PDF (264 KB) 


Variation in home-range size of Black-backed Woodpeckers Full Access

Morgan W. Tingley, Robert L. Wilkerson, Monica L. Bond, Christine A. Howell, and Rodney B. Siegel
pg(s) 325–340
The Black-backed Woodpecker (Picoides arcticus) is a species of conservation concern that is strongly associated with recently burned forests. Black-backed Woodpeckers are known to have variable home-range sizes, yet the ecological factors related to this variation have not been adequately explored and may hold insights into the natural history of the species and the management of its habitat. During 2011 and 2012, we radio-tracked Black-backed Woodpeckers nesting in 3 forested areas of California that burned between 2 and 5 years before the initiation of tracking. Among 15 individuals with robust tracking data, we found that home-range size varied by an order of magnitude, from 24.1 to 304.1 ha, as measured by movement-based kernel estimation. Using an information-theoretic approach, we evaluated the functional relationship between snag basal area—an a priori key resource—and home-range size, additionally controlling for sex, age, and years since fire as covariates. We found that snag basal area alone best predicted home-range size, explaining 54–62% of observed variation. As snag basal area increased, home-range sizes exponentially decreased. This relationship held true both with and without the inclusion of 3 individuals that nested in burned forest yet foraged predominantly outside the fire perimeter in unburned forest. Snag basal area, unlike other potential influences on home-range size, is an attribute that forest managers can directly influence. We describe a quantitative relationship between home-range size and snag basal area that forest managers can use to predict Black-backed Woodpecker pair density in burned forests and assess the likely population consequences of specific harvest treatments. Given that the birds in our study, foraging primarily in burned forest, all had home ranges with an average snag basal area ≥17 m2 ha−1, this may represent a benchmark for minimum habitat needs in postfire stands.
Abstract & References : Full Text : PDF (1512 KB) 

Landscape alterations influence differential habitat use of nesting buteos and ravens within sagebrush ecosystem: Implications for transmission line development Full Access

Peter S. Coates, Kristy B. Howe, Michael L. Casazza, and David J. Delehanty
pg(s) 341–356
A goal in avian ecology is to understand factors that influence differences in nesting habitat and distribution among species, especially within changing landscapes. Over the past 2 decades, humans have altered sagebrush ecosystems as a result of expansion in energy production and transmission. Our primary study objective was to identify differences in the use of landscape characteristics and natural and anthropogenic features by nesting Common Ravens (Corvus corax) and 3 species of buteo (Swainson's Hawk [Buteo swainsoni], Red-tailed Hawk [B. jamaicensis], and Ferruginous Hawk [B. regalis]) within a sagebrush ecosystem in southeastern Idaho. During 2007–2009, we measured multiple environmental factors associated with 212 nest sites using data collected remotely and in the field. We then developed multinomial models to predict nesting probabilities by each species and predictive response curves based on model-averaged estimates. We found differences among species related to nesting substrate (natural vs. anthropogenic), agriculture, native grassland, and edge (interface of 2 cover types). Most important, ravens had a higher probability of nesting on anthropogenic features (0.80) than the other 3 species (<0.10), and the probability of nesting near agriculture was greatest for ravens (0.55) followed by Swainson's Hawk (0.28). We also describe changes in nesting densities over 4 decades at this site as related to natural and anthropogenic disturbances. Since the 1970s, the composition of the raptor and raven nesting community has drastically changed with anthropogenic alterations and loss of continuous stands of sagebrush (Artemisia spp.), favoring increased numbers of nesting ravens and fewer nesting Ferruginous Hawks. Our results indicate that habitat alterations, fragmentation, and forthcoming disturbances anticipated with continued energy development in sagebrush steppe ecosystems can lead to predictable changes in raptor and raven communities.
Abstract & References : Full Text : PDF (347 KB) 

Radar analysis of fall bird migration stopover sites in the northeastern U.S. 

Jeffrey J. Buler and Deanna K. Dawson
pg(s) 357–370
The national network of weather surveillance radars (WSR-88D) detects flying birds and is a useful remote-sensing tool for ornithological study. We used data collected during fall 2008 and 2009 by 16 WSR-88D radars in the northeastern U.S. to quantify the spatial distribution of landbirds during migratory stopover. We geo-referenced estimates based on radar reflectivity, of the density of migrants aloft at their abrupt evening exodus from daytime stopover sites, to the approximate locations from which they emerged. We classified bird stopover use by the magnitude and variation of radar reflectivity across nights; areas were considered “important” stopover sites for conservation if bird density was consistently high. We developed statistical models that predict potentially important stopover sites across the region, based on land cover, ground elevation, and geographic location. Large areas of regionally important stopover sites were located along the coastlines of Long Island Sound, throughout the Delmarva Peninsula, in areas surrounding Baltimore and Washington, along the western edge of the Adirondack Mountains, and within the Appalachian Mountains of southwestern Virginia and West Virginia. Locally important stopover sites generally were associated with deciduous forests embedded within landscapes dominated by developed or agricultural lands, or near the shores of major water bodies. Preserving or enhancing patches of natural habitat, particularly deciduous forests, in developed or agricultural landscapes and along major coastlines could be a priority for conservation plans addressing the stopover requirements of migratory landbirds in the northeastern U.S. Our maps of important stopover sites can be used to focus conservation efforts and can serve as a sampling frame for fieldwork to validate radar observations or for ecological studies of landbirds on migratory stopover.

Acoustic monitoring of nocturnally migrating birds accurately assesses the timing and magnitude of migration through the Great Lakes 

Claire E. Sanders and Daniel J. Mennill
pg(s) 371–383
Tracking the movements of migratory songbirds poses many challenges because much of their journey takes place at night. One promising technique for studying migratory birds relies on microphones to record the nocturnal flight calls produced by birds on the wing. We compared recordings of night flight calls with bird-banding data in a southern Great Lakes ecosystem. We collected >6,200 hr of nocturnal recordings at 7 locations around Lake Erie. We detected >60,000 flight calls from migratory birds and classified 45,775 calls to species level or to a bioacoustic category comprising several species with similar calls. We compared these acoustic data with records of 5,624 birds captured in mist nets. We found that acoustic recordings accurately quantified the magnitude of migration; comparison with mist-net data revealed significant positive correlations between the number of acoustic detections and the number of mist-net detections across species. We also found that acoustic recordings accurately quantified the timing of migration; we found significant positive correlations between the date of passage of the 10th, 50th, and 90th percentiles of the populations of up to 25 groups of passage migrant species in the acoustic data and mist-net data. A careful examination of 6 species with distinctive flight calls revealed only subtle seasonal differences between peak detections via acoustic monitoring and mist netting, at both daily and weekly timescales. This research enhances our understanding of the role that acoustic sampling can play in monitoring migratory birds, providing important empirical support for the validity of night-flight-call monitoring.

Density, habitat use, and opportunities for conservation of shorebirds in rice fields in southeastern South America Full Access

Rafael Antunes Dias, Daniel E. Blanco, Andrea P. Goijman, and María Elena Zaccagnini
pg(s) 384–393
Worldwide, shorebirds are a major component of rice field avian biodiversity. Rice fields in Argentina and southern Brazil hold large numbers of shorebirds and have been recognized as important areas for migrating or wintering species. To develop successful shorebird conservation strategies, we need to understand geographic variation in shorebird abundance in rice fields as well as how bird use of rice fields varies over the rice growing cycle. We surveyed shorebirds in November and December in the main rice cultivation regions of interior Argentina and coastal Brazil to estimate shorebird densities using distance sampling and to evaluate densities of individual species at different stages of the rice cycle. We detected >7,000 shorebirds in rice fields, including a variety of Nearctic migrants. Density of resident species was generally low and showed no differences between countries. Densities of migratory taxa were higher and varied between Brazil and Argentina. Pectoral Sandpiper (Calidris melanotos) and Lesser Yellowlegs (Tringa flavipes) were the most common species in Argentina, but White-rumped Sandpiper (Calidris fuscicollis) and American Golden-Plover (Pluvialis dominica) were the most common species in Brazil. Pectoral Sandpiper density was nearly 8 times higher in Argentina than in Brazil; densities of the White-rumped Sandpiper and American Golden-Plover were 33 and 25 times higher in Brazil than in Argentina. Shorebird density was highest in lightly flooded paddies with rice height <20 cm. Our findings confirm the importance of rice paddies for shorebirds in southeastern South America and emphasize the need for detailed assessments to ensure that agricultural chemical and water management practices are biodiversity friendly.
Abstract & References : Full Text : PDF (640 KB) 

Factors influencing nest survival and renesting by Piping Plovers in the Great Lakes region Full Access

Andrea H. Claassen, Todd W. Arnold, Erin A. Roche, Sarah P. Saunders, and Francesca J. Cuthbert
pg(s) 394–407
Renesting is an important breeding strategy used by birds to compensate for nest failure. If birds renest, clutch removal for captive rearing can be used to augment endangered populations; however, not all individuals renest following nest loss, and later nesting attempts may have lower survival rates and clutch sizes. We investigated variation in nest initiation date, clutch size, daily nest survival, renesting propensity, and renesting intervals of federally endangered Great Lakes Piping Plovers (Charadrius melodus) from 1993 to 2010. We also compared productivity under hypothetical clutch removal for captive rearing vs. non-removal scenarios. Nest initiation date was earlier for older adults and was more strongly affected by female than male age. Clutch size and nest survival decreased with later nest initiation, and nest survival increased with male age and nest age until close to hatching. Overall, Piping Plovers replaced 49% of failed nests. Renesting propensity decreased with later date, increased with each successive nesting attempt, and varied according to cause of failure; probability of renesting was highest following flooding and lowest for inviable clutches. Renesting intervals increased with age of the previous nest and averaged 4.2 days longer for birds that changed mates. Results also indicated that, compared to leaving eggs in situ, clutch removal for captive rearing would produce 43% fewer 1-year-old recruits, partly because renesting does not fully offset clutch removal; therefore, efforts to increase fledging success in this endangered population should focus on proactively protecting nests in situ rather than relying on collection of eggs for captive rearing.
Abstract & References : Full Text : PDF (431 KB) 


The persistent problem of lead poisoning in birds from ammunition and fishing tackle 

Susan M. Haig, Jesse D'Elia, Collin Eagles-Smith, Jeanne M. Fair, Jennifer Gervais, Garth Herring, James W. Rivers, and John H. Schulz
pg(s) 408–428
Lead (Pb) is a metabolic poison that can negatively influence biological processes, leading to illness and mortality across a large spectrum of North American avifauna (>120 species) and other organisms. Pb poisoning can result from numerous sources, including ingestion of bullet fragments and shot pellets left in animal carcasses, spent ammunition left in the field, lost fishing tackle, Pb-based paints, large-scale mining, and Pb smelting activities. Although Pb shot has been banned for waterfowl hunting in the United States (since 1991) and Canada (since 1999), Pb exposure remains a problem for many avian species. Despite a large body of scientific literature on exposure to Pb and its toxicological effects on birds, controversy still exists regarding its impacts at a population level. We explore these issues and highlight areas in need of investigation: (1) variation in sensitivity to Pb exposure among bird species; (2) spatial extent and sources of Pb contamination in habitats in relation to bird exposure in those same locations; and (3) interactions between avian Pb exposure and other landscape-level stressors that synergistically affect bird demography. We explore multiple paths taken to reduce Pb exposure in birds that (1) recognize common ground among a range of affected interests; (2) have been applied at local to national scales; and (3) engage governmental agencies, interest groups, and professional societies to communicate the impacts of Pb ammunition and fishing tackle, and to describe approaches for reducing their availability to birds. As they have in previous times, users of fish and wildlife will play a key role in resolving the Pb poisoning issue.
Abstract & References : Full Text : PDF (1319 KB) 


Considering the switch: Challenges of transitioning to non-lead hunting ammunition 

Clinton W. Epps
pg(s) 429–434
In this issue of The Condor: Ornithological ApplicationsHaig et al. (2014) summarize negative impacts of lead ammunition and fishing tackle on birds and discuss strategies for mitigating risks to wildlife and human health. Their Review raises an important set of questions for hunters, wildlife managers, and conservation scientists. Effective mitigation will require careful understanding of technical, economic, and social dimensions of the problem. Here, I focus on challenges specific to adopting non-lead ammunition for hunting, particularly for large game animals. I discuss limitations of using the ban on lead ammunition for waterfowl hunting as an analog for reducing lead use for other types of hunting, explain important technical considerations in design and use of non-lead ammunition, and point out areas where effective non-lead alternatives are still lacking. I suggest that currently available economic analyses of the cost of non-lead alternatives are inadequate and do not recognize wide variation in hunter behavior. These considerations have strong implications for designing effective outreach and predicting responses of hunters asked to consider non-lead alternatives. Enforcing outright bans on using lead ammunition for all types of hunting, as recently enacted in California, may prove even more challenging than similar restrictions for waterfowl hunting. Despite this, I propose that major reductions in exposure of wildlife and people to lead bullet fragments are achievable, particularly through outreach and incentive programs that focus on the most commonly used types of firearms for big game hunting—high velocity modern rifles. Bullets from these widely used rifles typically produce the most lead fragments and have the best selection of effective non-lead options available at this time. Efforts to change hunter behavior must recognize the true costs and challenges of changing to non-lead ammunition. Likewise, hunters should recognize and accept their important role in wildlife conservation and work to embrace effective alternatives to lead as they become available.
Abstract & References : Full Text : PDF (189 KB) 


Stable occupancy by breeding hawks (Buteo spp.) over 25 years on a privately managed bunchgrass prairie in northeastern Oregon, USA Full Access

Patricia L. Kennedy, Anne M. Bartuszevige, Marcy Houle, Ann B. Humphrey, Katie M. Dugger, and John Williams
pg(s) 435–445
Potential for large prairie remnants to provide habitat for grassland-obligate wildlife may be compromised by nonsustainable range-management practices. In 1979–1980, high nesting densities of 3 species of hawks in the genus Buteo—Ferruginous Hawk (Buteo regalis), Red-tailed Hawk (B. jamaicensis), and Swainson's Hawk (B. swainsoni)—were documented on the Zumwalt Prairie and surrounding agricultural areas (34,361 ha) in northeastern Oregon, USA. This area has been managed primarily as livestock summer range since it was homesteaded. Unlike in other prairie remnants, land management on the Zumwalt Prairie was consistent over the past several decades; thus, we predicted that territory occupancy of these 3 species would be stable. We also predicted that territory occupancy would be positively related to local availability of nesting structures within territories. We evaluated these hypotheses using a historical dataset, current survey and habitat data, and occupancy models. In support of our predictions, territory occupancy of all 3 species has not changed over the study period of ∼25 yr, which suggests that local range-management practices are not negatively affecting these taxa. Probability of Ferruginous Hawk occupancy increased with increasing area of aspen, an important nest structure for this species in grasslands. Probability of Swainson's Hawk occupancy increased with increasing area of large shrubs, and probability of Red-tailed Hawk occupancy was weakly associated with area of conifers. In the study area, large shrubs and conifers are commonly used as nesting structures by Swainson's Hawks and Red-tailed Hawks, respectively. Availability of these woody species is changing (increases in conifers and large shrubs, and decline in aspen) throughout the west, and these changes may result in declines in Ferruginous Hawk occupancy and increases in Swainson's Hawk and Red-tailed Hawk occupancy in the future.
Abstract & References : Full Text : PDF (434 KB) 

Apparent survival of adult Burrowing Owls that breed in Canada is influenced by weather during migration and on their wintering grounds Full Access

Troy I. Wellicome, Ryan J. Fisher, Ray G. Poulin, L. Danielle Todd, Erin M. Bayne, D. T. Tyler Flockhart, Josef K. Schmutz, Ken De Smet, and Paul C. James
pg(s) 446–458
Understanding factors that influence the survival of endangered migratory species is critical for making informed management decisions, yet this understanding relies on long-term recapture datasets for species that are, by definition, rare. Using 3 geographically widespread (Saskatchewan, Alberta, and Manitoba, Canada) and long-term (6–15 yr) mark–recapture datasets, we quantified spatial and temporal variation in apparent annual survival and recapture probabilities of Burrowing Owl (Athene cunicularia), an endangered species that breeds in Canada. We then examined how large-scale weather patterns during migration (storms) and on the wintering and breeding grounds (precipitation), in addition to prey irruptions on the breeding grounds, influenced apparent survival of Burrowing Owls. Female Burrowing Owls had lower apparent survival than males in all 3 study areas. Storms during fall migration and above-average precipitation on the wintering grounds were associated with reduced apparent survival of Burrowing Owls in the longest-running study area, Saskatchewan; in Alberta and Manitoba, there were few correlations between apparent survival of Burrowing Owls and weather or prey irruptions. Increases in stochastic events such as storms during migration or precipitation on the wintering grounds could have adverse consequences on the already small Burrowing Owl population in Canada. Local management actions that focus solely on improving adult apparent survival within Canada are likely insufficient for mitigating susceptibility of adults to inclement weather or other factors outside the breeding season, underscoring the need for management of this species across multiple jurisdictions within North America.
Abstract & References : Full Text : PDF (406 KB) 

Response of avian communities to invasive vegetation in urban forest fragments Full Access

Sarah C. Schneider and James R. Miller
pg(s) 459–471
Proliferation of invasive plants in forest understories throughout North America has prompted restoration efforts focused on removal of invasive vegetation. Although the negative impacts of invasives on native plant communities are well documented, effects on forest bird communities remain largely unknown. To address this issue, we examined the response of avian communities to invasive plants in forest fragments across 4 counties in northeastern Illinois, a region characterized by extensive urbanization. We surveyed breeding bird communities in 46 forest plots representing a gradient in abundance of invasive woody plants. We quantified vegetation structure and composition within plots, as well as landscape context. Exotic trees and shrubs were present on all but 3 plots. Although native trees were common, native species represented <7% of total stem density of shrubs. Measures of invasion were weakly correlated with those representing urbanization, yet broad-scale measures of urbanization such as building density and urban cover were strongly associated with avian community structure. At finer scales, measures of invasion were important predictors of the relative abundance of birds in several nesting and foraging guilds. Shrub nesters showed a positive response to invasive vegetation, whereas the relative abundance of aerial salliers and ground nesters decreased with increased proportions of invasive trees. Because restoration strategies aimed at the complete removal of invasive shrubs could diminish habitat quality for some species, thinning of understory vegetation or the removal of invasive trees may confer the greatest benefits to avian communities when few native understory plants are present.
Abstract & References : Full Text : PDF (322 KB) 

No evidence of displacement due to wind turbines in breeding grassland songbirds Full Access

Amanda M. Hale, Erin S. Hatchett, Jeffrey A. Meyer, and Victoria J. Bennett
pg(s) 472–482
Projected global growth in wind energy development has the potential to negatively affect wildlife populations, and yet the indirect effects of wind turbines on wildlife (e.g., displacement from otherwise suitable habitat) remain largely understudied, compared with investigations of direct effects (e.g., collision mortality). Thus, over a 3-yr period (2009–2011), we used 2 alternative survey methods to study displacement in breeding grassland songbirds at an operational wind facility in the southern Great Plains, USA. Using a line transect method in 2009 and 2010, we estimated the densities of Dickcissels (Spiza americana), Eastern Meadowlarks (Sturnella magna), and Grasshopper Sparrows (Ammodramus savannarum) within 500 m of wind turbines. Dickcissel density was positively related to vegetation structure and was highest 301–400 m from wind turbines in both years; however, this relationship was confounded by fence lines bisecting transects within this single distance bin. By contrast, we found no such relationships in Eastern Meadowlarks or Grasshopper Sparrows. Using a plot-based method in 2011, we estimated Dickcissel and Grasshopper Sparrow densities within 750 m of wind turbines. Again, we found a strong positive relationship between Dickcissel density and vegetation structure. With the change in survey method, however, the confounding effect of fence lines was removed and the relationship between distance to turbine and Dickcissel density disappeared. Variation in Grasshopper Sparrow density in 2011 was not explained by any variable we measured. In summary, we found no evidence of displacement within 500–750 m of wind turbines in the 3 most abundant breeding grassland songbirds at our site. We caution that it may be difficult to isolate the effect of distance to turbine from other factors that covary with distance (e.g., presence of fence lines) when using a line transect method to study displacement at operational wind facilities.
Abstract & References : Full Text : PDF (774 KB) 

Habitat use and population status of Yellow-billed and Pacific loons in western Alaska, USA Full Access

Joshua H. Schmidt, Melanie J. Flamme, and Johann Walker
pg(s) 483–492
Effective conservation of sympatric avian populations depends on unbiased estimates of population size, distribution, and habitat use. For populations of Yellow-billed Loons (Gavia adamsii) and Pacific Loons (G. pacifica) co-occurring in Arctic wetland communities in Alaska, USA, such data are limited and difficult to obtain, hindering population assessments and decision making. The Yellow-billed Loon is also under consideration for additional protections under the Endangered Species Act due to small global population size, specific habitat requirements, and low fecundity, further increasing the need for information at the landscape scale. To help evaluate the population status and habitat use of both species, we used repeated aerial surveys and a dynamic multistate occupancy modeling approach to jointly estimate 1) probability of lake use and 2) probability of use for nesting for Yellow-billed and Pacific loon populations at the landscape scale on the Seward Peninsula and Cape Krusenstern, Alaska, in 2011 and 2013. We also estimated state-specific transition probabilities and degree of interspecific competition to assess population stability and degree of species interactions. We found that probability of site reuse (ϕYellow-billed = 0.73 [0.44–0.94]; ϕPacific = 0.86 [0.72–0.98]) or reuse for nesting (ϕYellow-billed = 0.72 [0.46–0.97]; ϕPacific = 0.59 [0.38–0.85]) in 2013 was high, as was overall use of lakes >7 ha by loons (>80%). These results suggested that lake habitats may have been saturated, and that populations of both species were stable over the two-year interval between surveys. Our estimates indicated that nesting populations in western Alaska were much larger than previously thought for both Yellow-billed (∼2.5 times larger) and Pacific loons (∼1.5–2.0 times larger). Together our results indicate that Arctic wetlands in western Alaska are important for both species and that loon populations in this area warrant additional consideration for conservation.

Minimal changes in heart rate of incubating American Oystercatchers (Haematopus palliatus) in response to human activity Full Access

Tracy E. Borneman, Eli T. Rose, and Theodore R. Simons
pg(s) 493–503
An organism's heart rate is commonly used as an indicator of physiological stress due to environmental stimuli. We used heart rate to monitor the physiological response of American Oystercatchers (Haematopus palliatus) to human activity in their nesting environment. We placed artificial eggs with embedded microphones in 42 oystercatcher nests to record the heart rate of incubating oystercatchers continuously for up to 27 days. We used continuous video and audio recordings collected simultaneously at the nests to relate physiological response of birds (heart rate) to various types of human activity. We observed military and civilian aircraft, off-road vehicles, and pedestrians around nests. With the exception of high-speed, low-altitude military overflights, we found little evidence that oystercatcher heart rates were influenced by most types of human activity. The low-altitude flights were the only human activity to significantly increase average heart rates of incubating oystercatchers (12% above baseline). Although statistically significant, we do not consider the increase in heart rate during high-speed, low-altitude military overflights to be of biological significance. This noninvasive technique may be appropriate for other studies of stress in nesting birds.