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Thursday, 3 April 2014

Journal of Ornithology: Contents and Abstracts - Volume 155(2) April 2014

Journal of Ornithology - Volume 155(2)




Table of Contents, Abstracts and Links




Review

Feather structure, biomechanics and biomimetics: the incredible lightness of being
Theagarten Lingham-Soliar

Abstract
Millions of years of biological evolution have produced efficient materials and structures that are a source of inspiration to engineers. The paper reviews the overall design principles in the feather rachis and elaborates upon recent functional interpretations. It concentrates on recent findings that shed new light on feather microstructure and on how keratin fibres in a protein matrix are arranged in intricate ways to achieve specific combinations of stiffness and strength on the one hand and flexibility and elasticity on the other. This includes the syncitial barbule cells of the rachis and barb cortex, the crossed-fibre architecture of the epicortex (lateral walls of the cortex), and the foam-like structure of the medullary pith. Discussion of the biomechanics of feather microstructure uses engineering principles for a better understanding of the functional ramifications. Further research is proposed with respect to feather micro- and macrostructure in trying to expand our knowledge on bird flight, behaviour and ecology in different species. The discussion also considers the validity of a study purporting to use quantitative methods and engineering principles to show that the iconic fossil bird Archaeopteryx was incapable of flapping flight.


Original Article
Vocal behaviour of the island-endemic Cozumel Wren (Troglodytes aedon beani): song structure, repertoires, and song sharing
J. Roberto Sosa-López & Daniel J. Mennill

Abstract
Documenting the diversity of vocal behaviour across different avian taxa is key to understanding the ecology and evolution of complex behaviours. Unique to Cozumel Island in the Mexican Caribbean Sea, the Cozumel Wren (Troglodytes aedon beani) provides an opportunity to investigate how isolation influences complex cultural traits. Most aspects of the biology, natural history, and taxonomy of Cozumel Wrens are unknown. In an attempt to better understand the Cozumel Wren’s biology, we provide the first description of the songs and the vocal behaviour of this island-endemic bird. Based on more than 700 h of recordings, including more than 36,000 songs, we describe the fine structural characteristics of male Cozumel Wrens songs, and explore patterns of repertoire organization and song sharing. Cozumel Wrens sing songs composed of highly variable syllables, with prominent trills at the end of each song. Each bird has a limited repertoire of songs, which they create by recombining a restricted number of syllable and trill types. They repeat a song type several times before switching to a different one, with some variation in the number of times they repeat specific elements. Cozumel Wrens share more song types with neighbours than distant individuals. Syllable sharing, however, is equivalent between neighbours and distant individuals. Our results provide important data for future research on the ecology, evolution, and behaviour of this island-endemic songbird, and for helping to clarify the taxonomic status of Cozumel Wrens.


Original Article
Rediscovery of an enigmatic Chinese passerine, the Blackthroat Calliope obscura: plumage, vocalizations, distribution, habitat choice, nesting and conservation
Gang Song , Per Alström , Yongwen Zhang , Xuebin Gao , Huisheng Gong , Paul I. Holt , Qing Quan , Zuohua Yin & Fumin Lei

Abstract
The Blackthroat (or Blackthroated Blue Robin) Calliope obscura (previously Luscinia obscura) is one of the world’s rarest “robins”. It is extremely poorly known, with only a handful of records since it was firstly described in the 1890s. In 2011–2012, a series of field investigations were carried out in nature reserves in the Qinling Mountains, Shaanxi Province, China. During these surveys, a total of 14 males were found in 2011 and 24 males and 2 females in 2012 in the national nature reserves of Foping and Changqing. Based on these observations, we here describe the Blackthroat’s vocalizations and habitat choice and review its distribution and conservation status. We also provide some notes on the plumage, especially of the female, and the nesting behaviour of this species. The present report confirms that the Blackthroat breeds on the southern slope of the Qinling Mountains in large, dense expanses of dwarf bamboo with scattered coniferous and broadleaved trees above 2,100 m. Our observations suggest that it is more numerous than previously believed, although it appears to be highly localized. The locally dense populations found in 2011 and 2012 and the vast expanses of suitable habitat suggest that the breeding population might be healthy.


Original Article
Is the effect of farming practices on songbird communities landscape dependent? A case study of olive groves in southern Spain
J. C. Castro-Caro , I. C. Barrio & F. S. Tortosa

Abstract
Extensive farming practices and landscape heterogeneity promote biodiversity in agroecosystems. However, the effect of such practices might be landscape dependent; specifically, the effect might be greatest where the loss of heterogeneity has been the largest. In recent decades, agricultural intensification and landscape simplification have dramatically affected the Mediterranean region, where olive groves are one of the predominant crops. For instance, in Spain from 1996 to 2008, the amount of land dedicated to olive groves increased by 300,000 ha (12 %). In conventional olive farming, herbicides are applied intensively to minimize competition between crops and swards for water; however, to prevent erosion, many farmers are maintaining swards within crops. This practice likely benefits farmland biodiversity, although the heterogeneity of the surrounding landscape might influence the extent of these effects. This study assessed the effects of herbaceous cover on the abundance and species richness of songbird communities in six matched pairs of olive groves (ground cover or bare ground) in homogeneous and heterogeneous landscapes over a 3-year period. We predicted that (1) the presence of ground cover and landscape heterogeneity would have a positive effect on songbird communities, and (2) the effect would be greatest in homogeneous environments. Although bird community composition differed among landscape types and farming practices in the olive groves in southern Spain, the effect of ground cover was not landscape dependent. The presence of ground cover had a positive effect on the abundance and richness of songbirds, including sensitive species, but landscape heterogeneity did not have an effect. This study underscores the important role of agricultural practices in preserving farmland bird communities, while it also suggests that landscape heterogeneity might not be very important in Mediterranean perennial farming systems. The positive effects of ground cover can be important for preserving the wintering quarters of numerous European bird species, including species of conservation concern.


Original Article
Small range and distinct distribution in a satellite breeding colony of the critically endangered Waved Albatross
Jill A. Awkerman , Sebastian Cruz , Carolina Proaño , Kathryn P. Huyvaert , Gustavo Jiménez Uzcátegui , Andres Baquero , Martin Wikelski & David J. Anderson

Abstract
To determine the proximate consequences of the limited breeding distribution of the critically endangered Waved Albatross (Phoebastria irrorata), we present continuous breeding season GPS tracks highlighting differences in behaviour, destinations, and distances travelled between three distinct colonies: two in Galápagos and one closer to the South American continent on Isla de la Plata, where a small number of pairs nest. Accelerometer data paired with GPS locations allowed operational classifications of Waved Albatross behaviour. All birds from Galápagos travelled eastward to the continental shelf and foraged southward along the Peruvian coast. Birds from Isla de la Plata made more and shorter foraging trips and used habitat north of the destinations of Galápagos birds. La Plata birds foraged in areas through which Galápagos birds commuted, and had slower average flight speeds and shorter commutes. Overall, albatrosses from La Plata might operate under a consistently lower return but they also incur lower costs compared to birds from Galápagos, which take fewer trips involving longer time investment. Galápagos birds may be able to forage more effectively based on more abundant or more profitable food patches in those highly productive areas. Foraging destinations of birds from the two Galápagos colonies were similar and overlapped areas that presented localized mortality risk from artisanal fisheries in previous years. This study, performed across the species’ breeding range, reveals the different foraging distribution of La Plata albatrosses and the potential conservation value of this small colony in terms of maintenance of spatial diversity and behavioural plasticity.


Original Article
Foraging behaviour and habitat use of chick-rearing Australasian Gannets in New Zealand
Gabriel E. Machovsky-Capuska , Mark E. Hauber , Mariela Dassis , Eric Libby , Martin C. Wikelski , Rob Schuckard , David S. Melville , Willie Cook , Michelle Houston & David Raubenheimer

Abstract
Patchily distributed marine pelagic prey present considerable challenges to predatory seabirds, including Gannets (Morus spp.) departing from large breeding colonies. Here, for the first time, we used GPS data loggers to provide detailed spatial, temporal, and habitat metrics of chick-rearing Australasian Gannets (Morus serrator) foraging behaviours from two distant colonies in New Zealand. Our goal was to examine the extent to which Gannet foraging tactics vary across disparate habitats, and determine whether the observed differences are consistent with predictions derived from foraging studies of other gannet species. Foraging trip performance was highly consistent between colonies, and sexes, and no significant differences in any of the variables analyzed were observed. However, Gannets from Farewell Spit (FS) dove in shallower waters (0–50 m) than birds from Cape Kidnappers (CK, >50 m), which is consistent with previous dietary studies suggesting that FS Gannets feed mainly on coastal prey, whereas CK birds feed on species with a more oceanic distribution. Diving frequencies were similar in the two colonies suggesting that Gannets were foraging in habitats with similar levels of food availability. Further studies are needed to understand the relationship between prey availability, oceanography and geographic features, to better interpret foraging tactics of Australasian Gannets.


Original Article
Male viability is positively related to multiple male ornaments in Asian Barn Swallows
Masaru Hasegawa , Emi Arai , Mamoru Watanabe & Masahiko Nakamura

Abstract
The European Barn Swallow Hirundo rustica rustica is a model system for studying female mate choice for indirect benefits, as the long tail of males, the target of female mate choice, is positively related to male viability. However, situations may differ in other subspecies where male ornaments other than tail length are prominent and seem to be the targets of female choice. In this study, similar to previous studies on European populations, we determined the relationship between male viability and male ornaments, including tail length, in a Japanese population of the Asian Barn Swallow H. r. gutturalis, which have short tails, a whitish ventral plumage, and a large red throat patch. We observed that males with longer tails and larger and more colored (i.e., lower saturation values) throat patches were more likely to return to the study area than other males, independent of their age. Of these ornaments, information on viability of male tail length partially overlapped the information on viability by throat coloration. Because females choose mates, either directly or indirectly, based on their throat coloration, female mate preference for tail length had few benefits for the choosers. This may explain why female mate preference for tail length was not observed in this population. In addition, differing from a previous study in a European population, male throat patch size may serve as a good indicator of male viability, independent of tail length and throat coloration in this population. We discuss the possible explanations for the observed patterns.


Original Article
Extensive post-breeding movements of Adriatic Yellow-legged Gulls Larus michahellis
J. Kralj , S. Barišić , D. Ćiković , V. Tutiš & N. Deans van Swelm

Abstract
The Yellow-legged Gull Larus michahellis is generally considered to be sedentary and dispersive, with long-distance dispersal of young birds developing after the 1970s. In this paper, we present the analysis of the movement of the Yellow-legged Gulls from the eastern Adriatic coast based on observations of colour-ringed birds marked between 1999 and 2011. A total of 4,114 sightings of 1,559 Yellow-legged Gulls marked as chicks were analysed. Our results showed a clear preference in the direction of the movement of Yellow-legged Gulls and significant differences in the directions of movements and the longitude of the observation sites of birds from different colonies. During summer and autumn, the majority of gulls moved towards the north, to the Baltic and North Sea coasts. Maximum distances covered (1,958 km for juveniles and 1,380 km for adults) were much greater than for the other studied populations of the Yellow-legged Gull. We found no difference between the directions of the movement among age classes, while distances decreased with age. Three important features: long-distance movements, migratoriness of adults and differences in movements between colonies, do not support the theory that post-breeding movements of the Yellow-legged Gull have been recently developed as the result of population increase. We presume that the recent pattern of movements reflects the evolutionary history of the Yellow-legged Gulls and might be inherited or result from experience and have been transferred by learning between generations among birds from the same colony.


Original Article
Nest predation in Afrotropical forest fragments shaped by inverse edge effects, timing of nest initiation and vegetation structure
Toon Spanhove , Tom Callens , Caspar A. Hallmann , Petri Pellikka & Luc Lens

Abstract
High levels of nest predation influence the population dynamics of many tropical birds, especially when deforestation alters nest predator communities. The consequences of tropical forest fragmentation on nest predation, however, remain poorly understood, as natural predation patterns have only been well documented in a handful of tropical forests. Here, we show the results of an extensive study of predation on natural nests of Cabanis’s Greenbul (Phyllastrephus cabanisi) during 3 years in a highly fragmented cloud forest in SE Kenya. Overall predation rates derived from 228 scrub nests averaged 69 %, matching the typical high predation level on tropical bird species. However, predation rates strongly varied in space and time, and a model that combined timing effects of fragment, edge, concealment, year and nest was best supported by our data. Nest predation rates consistently increased from forest edge to interior, opposing the classic edge effect on nest predation, and supporting the idea that classic edge effects are much rarer in Afrotropical forests than elsewhere. Nest concealment also affected predation rates, but the strength and direction of the relationship varied across breeding seasons and fragments. Apart from spatial variation, predation rates declined during the breeding season, although the strength of this pattern varied among breeding seasons. Complex and variable relationships with nest predation, such as those demonstrated here, suggest that several underlying mechanisms interact and imply that fixed nesting strategies may have variable—even opposing—fitness effects between years, sites and habitats.


Original Article
The earliest European record of a Stone-curlew (Charadriiformes, Burhinidae) from the late Oligocene of France
Vanesa L. De Pietri & R. Paul Scofield

Abstract
We describe novel material of a small fossil burhinid (Stone-curlew, thick-knee; Aves: Charadriiformes) from the late Oligocene (ca 23 Ma) of Coderet-Bransat in the Allier Basin of central France. This site is one of the renowned Saint-Gérand-le-Puy fossil localities, which have yielded thousands of fossil bird specimens. This is the first record of the Burhinidae to be described from Paleogene and Neogene deposits of Europe, and, together with the late Oligocene–early Miocene burhinid from Australia, are the earliest records worldwide. Although Genucrassum bransatensis gen. et sp. nov. differs from extant burhinids in some presumably plesiomorphic features of the humerus and carpometacarpus, we show that the postcranial elements considered here are remarkably uniform within Burhinidae even in late Oligocene taxa.


Original Article
Directional shifts in migration pattern of rollers (Coracias garrulus) from a western European population
Tamara Emmenegger , Patrick Mayet , Olivier Duriez & Steffen Hahn

Abstract
Individual migrants often fly detours when travelling between breeding and non-breeding sites, resulting in specific changes in flight directions along a migratory leg. Western European populations of the European Roller (Coracias garrulus), the only member of the roller family of birds to breed in Europe, differ substantially in their predicted flight directions, leading to different hypotheses being suggested for passage areas and non-breeding destinations. In this study we have tested the hypotheses on a western or eastern detour and different crossings of the Sahara desert by tracking European Rollers breeding in southern France using light-level geolocators. After the departure from the breeding site between mid and end July, the three European Rollers which were tracked crossed the Mediterranean and the Sahara desert heading in straight southern direction. When arriving in the Sahelian zone they abruptly changed their direction eastwards to circumvent the Gulf of Guinea and reached the western Lake Chad basin, where they made a final direction shift to reach the non-breeding sites in western Angola. Our findings support the hypothesis of a straight north–south Sahara crossing with subsequent directional shifts. Whether western Africa serves as the non-breeding residence of European Rollers from the Iberian Peninsula and northern Africa remains to be elucidated.


Original Article
The vocal behavior of the Brown-throated Wren (Troglodytes brunneicollis): song structure, repertoires, sharing, syntax, and diel variation
J. Roberto Sosa-López & Daniel J. Mennill

Abstract
Empirical descriptions of vocal behaviour are important for understanding avian biology. In this study, we provide the first detailed analysis of the vocal behaviour of the Brown-throated Wren (Troglodytes brunneicollis), a neotropical songbird found in oak forests in the highlands of Mexico and the southwestern United States. We quantify the fine structural characteristics of the song, and describe the size and structure of the song repertoire. Further, we describe diel variation, analyze song-sharing patterns among neighbors, and explore whether this species uses syntactical rules for creating their songs. Our analyses reveal that Brown-throated Wrens have complex songs and simple calls. They sing with eventual variety, repeating songs many times before switching to a new song type. Males combine syllables into phrases to create songs. We show that song repertoire size is not fixed; birds recombine their syllables to produce highly variable song types. Brown-throated Wrens sing with high vocal output after sunrise and song activity declines throughout the morning. Song sharing shows no variation with distance among our sampled individuals. We divide the syllables in Brown-throated Wren songs into 13 categories; birds sing some syllables more frequently than others, and some syllables are more likely to be found at the beginning, middle, or end of the song. Transitions between syllable categories deviate significantly from random chance, and most males analyzed follow similar patterns of syllable transitions, revealing syntactical structure. This research, which provides the first empirical study of Brown-throated Wren song, expands our knowledge of the behaviour of this poorly-studied taxon, and contributes insight into the organization and composition of song in tropical birds.


Original Article
Abdominally implanted satellite transmitters affect reproduction and survival rather than migration of large shorebirds
Jos C. E. W. Hooijmeijer , Robert E. Gill , Daniel M. Mulcahy , T. Lee Tibbitts , Rosemarie Kentie , Gerrit J. Gerritsen , Leo W. Bruinzeel , David C. Tijssen , Christopher M. Harwood & Theunis Piersma

Abstract
Satellite telemetry has become a common technique to investigate avian life-histories, but whether such tagging will affect fitness is a critical unknown. In this study, we evaluate multi-year effects of implanted transmitters on migratory timing and reproductive performance in shorebirds. Shorebirds increasingly are recognized as good models in ecology and evolution. That many of them are of conservation concern adds to the research responsibilities. In May 2009, we captured 56 female Black-tailed Godwits Limosa limosa limosa during late incubation in The Netherlands. Of these, 15 birds were equipped with 26-g satellite transmitters with a percutaneous antenna (7.8 % ± 0.2 SD of body mass), surgically implanted in the coelom. We compared immediate nest survival, timing of migration, subsequent nest site fidelity and reproductive behaviour including egg laying with those of the remaining birds, a comparison group of 41 females. We found no effects on immediate nest survival. Fledging success and subsequent southward and northward migration patterns of the implanted birds conformed to the expectations, and arrival time on the breeding grounds in 2010–2012 did not differ from the comparison group. Compared with the comparison group, in the year after implantation, implanted birds were equally faithful to the nest site and showed equal territorial behaviour, but a paucity of behaviours indicating nests or clutches. In the 3 years after implantation, the yearly apparent survival of implanted birds was 16 % points lower. Despite intense searching, we found only three eggs of two implanted birds; all were deformed. A similarly deformed egg was reported in a similarly implanted Whimbrel Numenius phaeopus returning to breed in central Alaska. The presence in the body cavity of an object slightly smaller than a normal egg may thus lead to egg malformation and, likely, reduced egg viability. That the use of implanted satellite transmitters in these large shorebirds reduced nesting propensity and might also lead to fertility losses argues against the use of implanted transmitters for studies on breeding biology, and for a careful evaluation of the methodology in studies of migration.


Original Article
The Whiskered Tern Chlidonias hybrida expansion in Poland: the role of immigration
Mateusz Ledwoń , Jacek Betleja , Tadeusz Stawarczyk & Grzegorz Neubauer

Abstract
The Whiskered Tern population in Poland has rapidly increased from 40 breeding pairs in 1990 to over 1,600 in 2007, with strongest local population in the Upper Vistula River Valley. Owing to rather low pre-breeding and adult apparent survival rates estimated for this population (0.54 and 0.80, respectively) and a delay in accession to reproduction (recruitment completed at age 3), matrix modelling indicated an intrinsic growth rate of λ calc = 1.02. Observed growth rates of both the Polish and the Upper Vistula River Valley populations was λ obs = 1.29. Using the deterministic population projection matrix including immigrant class, we estimated that, on average, 44 immigrants should enter the Upper Vistula River Valley population annually to match the observed growth. With survival rates increased (Φ P = 0.63, Φ B = 0.90) as to mimic no emigration and reduced dispersal, the estimated number of immigrants was only eight, indicating that substantial emigration rates are likely. A majority of the breeding sites were recorded in man-made water bodies. Colonisation has started in the southeast and proceeded towards the northwest. The strong, stable population in western Ukraine may explain high numbers of immigrants that could originate from there. Other factors favouring quick colonisation of Poland include availability of suitable breeding sites, the wide flexibility of the species with respect to breeding habitat, plentiful food, and high breeding success in the Upper Vistula River Valley. It also seems likely that westward shifts in both breeding and wintering ranges could add to the strong population increases in Eastern Europe.


Original Article
Land use factors determining occurrence of Red-necked Spurfowl (Pternistis afer) in the Drakensberg Midlands, South Africa
Tharmalingam Ramesh & Colleen T. Downs

Abstract
Conservation of forest associated birds depends on appropriate prediction of habitat change effects on their distribution patterns. We investigated a variety of land use gradients in an attempt to determine which factors influence site occupancy and detection of Red-necked Spurfowl (Pternistis afer) on farmland in the Drakensberg Midlands, South Africa. We used presence/absence data from 44 camera traps to estimate proportion of area occupied by the study species during October 2012–January 2013. Average occupancy rate of Red-necked Spurfowl was 0.42 ± 0.10 with a low detection probability 0.29 ± 0.04. Commercial forestry plantation influenced their presence positively while the index of human abundance negatively influenced the proportion of area occupied. Model selection indicated that cropland cultivation area had a strong negative effect on the detection probability of Red-necked Spurfowl while availability of indigenous forest patch and natural grassland influenced their detection positively. In the absence less presence of natural forest, commercial plantation forestry might have provided the next best possible habitat for this forest associated species where indigenous forest patches covering a small part of the landscape have extensively fragmented. These findings detailed the influence of land use variables as fragmentation and conversion of indigenous forest and grassland ecosystems into agricultural and human dominated areas affect the distribution of species that are highly selective towards forested habitats.


Original Article
Latitudinal variation in day length and working day length has a confounding effect when comparing nest attentiveness in tropical and temperate species
Phil Shaw & Will Cresswell

Abstract
During incubation, tropical passerines have been shown to have lower levels of nest attentiveness than their counterparts at north temperate latitudes, spending a higher percentage of daylight time off the nest. This difference has been interpreted as evidence of parental restraint; tropical birds allocate more time to daily self-maintenance, perhaps preserving their higher annual survival rates and future breeding potential. But such comparisons are susceptible to the confounding effects of day length variation, because a given amount of time spent off the nest will account for a greater percentage of daylight time near to the equator than at high latitudes during spring and summer. Based on a pattern of increasing day length between 0° and 70°N, we show that the impact of this bias is likely to be small where sites are separated by less than 30°–40° of latitude, but should increase substantially both with latitudinal span and distance from the equator. To illustrate this effect, we compared nest attentiveness in two congeners breeding at 1°S and 52°N. During incubation, Stripe-breasted Tits Parus fasciiventer in Uganda had a shorter working day (time from emerging to retiring) than north temperate Great Tits P. major, and spent a higher percentage of daylight time off the nest (32 %) than Great Tits in the UK (24 %). However, this difference was almost wholly explained by the latitudinal difference in day length; the amount of time spent off the nest differed by just 10 min day−1 (<1 % of the 24-h cycle). We show that this effect may be moderated by the change in working day length, which increased less rapidly (in relation to latitude) than day length. Although these effects can thus confound latitudinal comparisons of nest attentiveness, accentuating a pattern predicted by life-history theory, they are avoidable if attentiveness is expressed as the percentage of time or the number of minutes spent incubating per 24 h.


Original Article
Is nest predation an important selective pressure determining fecal sac removal? The effect of olfactory cues
Juan Diego Ibáñez-Álamo , Francisco Ruiz-Raya , Gianluca Roncalli & Manuel Soler

Abstract
The removal of nestling feces by adults is a common parental behavior in birds. However, this behavior is still poorly understood despite being an important component of parental care, especially in altricial bird species. The threat of nest predation is a major factor that influences many parental activities at the nest and, therefore, it could also be an important selective pressure determining fecal sac removal. To date, this ‘Nest Predation Hypothesis’ has not been tested despite being proposed more than a century ago. Furthermore, it is important to determine whether it is the olfactory and/or visual components of fecal sacs that attract predators. In this study, we have manipulated the presence of real droppings of Common Blackbird (Turdus merula) nestlings in active nests by hiding fresh fecal sacs (experimental), mud (control) or nothing (manipulation control) in a commercial Canary nest attached below natural nests. Our results showed that the presence of fecal sacs did not reduce the daily survival rate of experimental nests in comparison with the other two treatments. It would therefore appear that predation risk is not a selection pressure that maintains feces removal in nests of the Common Blackbird, at least in relation to the olfactory component of the feces. To date, all evidence suggests that this aspect of parental behavior could be affected by other selective pressures (i.e. parasitism) rather than nest predation. Nevertheless, the effect of the visual cues produced by fecal sacs should be further investigated before the Nest Predation Hypothesis is completely discarded.


Original Article
Lack of correlation between sex ratio and food supply or other biotic variables in nestlings of Tengmalm’s Owl Aegolius funereus
Ortwin Schwerdtfeger & Michael Wink

Abstract
Tengmalm’s Owls (Aegolius funereus) (TO) exhibit a pronounced sexual size dimorphism in which females are bigger than males, which have to provide food for the breeding female and for the brood. Clutch size and breeding success are strongly influenced by food supply, especially by the abundance of small rodents. Since 1979, the breeding ecology of TO has been studied in a nest box population in the Harz Mountains. In this study, the influences of food supply and other variables on sex allocation of young TO were analysed. Between 2001 and 2011, all 758 nestlings from 176 broods were sampled. Their sex was determined by DNA analysis (PCR amplification of DNA markers on the sex chromosomes). The mean sex ratio was male-biased with 53.4 % male offspring with yearly variations between 43.3 and 66.7 %. Nestling mortality was independent of sex. Food abundance changed between good and bad years. No correlation could be established between food supply by individual fathers and offspring sex ratio. Neither seasonal variation of hatching dates, the hatching order within a clutch nor individual fitness characters of parents had a significant influence on sex ratios. Yearly sex ratios did not diverge significantly from 50 %. The sex ratio fluctuated to the same degree in 5 good years and in 4 bad years. These results are in contrast to a study in Sweden, where an influence was detected within a 3-year vole cycle of food supply on offspring sex ratio. There, the sex ratio was male-biased in the good year, unbiased in the subsequent year and female-biased in the bad year.


Original Article
Habitat use and diet of Skylarks (Alauda arvensis) wintering in an intensive agricultural landscape of the Netherlands
Flavia Geiger , Arne Hegemann , Maurits Gleichman , Heiner Flinks , Geert R. de Snoo , Sebastian Prinz , B. Irene Tieleman & Frank Berendse

Abstract
In recent decades, Skylark (Alauda arvensis) populations in Europe have declined sharply due to agricultural intensification. Insufficient reproduction rates are one reason. Increased winter mortality may also be important, but studies outside the breeding season are scarce and mostly limited to the UK. We studied habitat selection of wintering Skylarks in an agricultural area in the Netherlands. We monitored Skylarks between November 2008 and March 2009 on 10 survey plots including 77 different arable fields and permanent grasslands and covering in total 480 ha. We simultaneously measured food availability, vegetation structure and field boundary characteristics. We also analysed 158 faecal pellets collected on potato and cereal stubble fields to relate Skylark diet to seasonal changes in food availability and foraging habitat. We show that cereal stubble fields larger than 4.3 ha, surrounded by no or low boundary vegetation and a density of dietary seeds of more than 860 seeds m−2, were most suitable for wintering Skylarks. Skylark group densities were low on permanent grasslands and on maize stubble fields. Densities of dietary seeds were highest in soils of potato stubble fields followed by cereal stubble fields, grasslands and maize stubble fields. Skylarks showed a strong preference for cereal grains, but their proportion in the diet fell sharply at the end of November, indicating that cereal grains were depleted and birds had to switch to less profitable food sources, such as weed seeds and leaves. We conclude that Skylarks wintering in agricultural landscapes possibly suffer from a lack of energy-rich food sources and only a few fields provide sufficient food. Conservation measures should strive to improve the wintering situation by creating food-rich habitats such as over-winter stubble with a rich layer of weeds on large fields and localised in open areas.


Original Article
Tracking devices attached with harnesses influence behaviour but not body mass of Princess Parrots Polytelis alexandrae
Ashley Herrod , Meaghan King , Dean Ingwersen & Rohan H. Clarke

Abstract
The use of tracking devices to monitor the movements of parrots can benefit conservation and management efforts in species for which there is scant information on their habitat use and distribution. Before such studies can proceed, there is a clear need to assess the efficacy of tag attachment so as not to create welfare issues for the target individuals or negate the scientific value of subsequent tracking results. We developed a harness and trialled it as a method of attaching 5-g non-operational satellite tags to captive Princess Parrots Polytelis alexandrae. The influence of the harness package on the parrots’ activity budgets and body mass was investigated, and comparisons were made with control individuals not fitted with harness packages. The attachment of harness packages led to an initial increase in preening rates at the expense of resting and foraging behaviour, but did not affect the duration of eating and drinking behaviours. Despite an initial difference between the behaviours of tagged parrots and control parrots, after 3 weeks the rates of behaviour of tagged parrots matched those of the controls, suggesting they were more accepting of the harness and satellite tag by this time. The harness package had no effect on body mass; a similar pattern was observed for mean weight change per fortnight between tagged and control parrots. Three-quarters of all harness packages were worn by the tagged parrots for the full captive trial (98 days) without harness damage. The harness design tested here is likely transferable to other bird species that display similar structure and wing-loadings, and as such is a valuable contribution to avian tracking studies.


Original Article
Social cues are preferred over resource cues for breeding-site selection in Barn Swallows
Monamie Ringhofer & Toshikazu Hasegawa

Abstract
To maximize fitness, animals choose habitats by using a combination of direct resource cues, such as the quality and quantity of safe breeding sites or food resources, and indirect social cues, such as the presence or breeding performance of conspecifics. Many reports show that nest predation leads to reduced fitness. However, it remains unclear how birds assess predation risk and how it affects breeding-site selection. In this study, we analyzed the relationship between predation risk and breeding-site selection in Barn Swallows (Hirundo rustica). We assessed the cues that swallows use in their selection. We used nest-site characteristics related to predation and foraging sites as direct resource cues, number of breeding pairs, and breeding success in the previous year as indirect social cues, and number of old and undamaged old nests as direct resource and/or indirect social cues. Breeding-site preference was assessed using the arrival date of males. We showed that only the number of undamaged old nests was used for breeding-site selection. When comparing effects at two spatial scales, nest-site and home-range, the effect of the number of undamaged old nests occurred at the home-range scale only, suggesting that these nests are used as an indirect social cue rather than a direct resource cue to reduce the energy or time-consuming costs of nest building. We suggest that undamaged old nests may indicate the presence and breeding performance of conspecifics for several previous years. Because Barn Swallows are migratory birds, undamaged old nests may be a reliable indirect social cue and may reduce the time required to sample information at breeding sites.


Original Article
Corticosterone in territorial male Swainson’s Thrushes varies in relation to forest age but not vegetation cover
James W. Rivers , Andrea L. Liebl , Lynn B. Martin & Matthew G. Betts

Abstract
Glucocorticoids are thought to be related to habitat quality and may provide information about the relative health of individuals. We used a model selection approach to test whether plasma glucocorticoid levels of the Swainson’s thrush (Catharus ustulatus) were associated with two attributes that may reflect breeding habitat quality in coniferous plantation forests: stand age and vegetation cover. For baseline corticosterone, the top model included stand age with limited support for models that included vegetation cover. Mean baseline corticosterone for territorial male thrushes sampled in mature stands was 78.2 % higher than territorial males sampled in early seral stands. For handling-induced corticosterone, there was limited separation among candidate models, and only one model, containing stand age and Julian day, was better supported than the null model. Despite previous research that has shown hardwood cover is an important component of breeding habitat quality for thrushes, our investigation found limited evidence that vegetation cover was associated with either baseline or handling-induced corticosterone levels. Given that early seral and mature conifer forests are characterized by markedly different habitat features, we hypothesize that the observed differences in baseline corticosterone represent either reduced fitness of male thrushes in mature stands or an adaptive adjustment of glucocorticoid levels to match local environmental conditions that equalize fitness across stands of different ages.


Short Note
Shorebird low spillover risk of mosquito-borne pathogens on Iberian wetlands
Sara Pardal , José A. Alves , Líbia Zé-Zé , Hugo Osório , Afonso Rocha , Ricardo J. Lopes , Pete Potts , Fátima Amaro , Francisco Santiago-Quesada , Juan M. Sanchez-Guzman , José Masero , Maria J. Alves , Javier Pérez-Tris , Jaime A. Ramos & Luísa Mendes

Abstract
Migratory shorebirds are exposed to a wide range of pathogens along their migratory flyways, but their capacity to acquire or spread pathogens beyond endemic areas is poorly known. We focused on the spillover and acquisition of mosquito-borne pathogens such as haemosporidians and West Nile virus (WNV) on key-staging Iberian wetlands during different seasons. We screened seven shorebird species (447 individuals), and detected low haemosporidian prevalence (0.6 %). Furthermore, no WNV infections could be detected, though 6.2 % revealed antibodies against flaviviruses. Although Iberian wetlands congregate numerous shorebirds of different species and origins, the potential introduction of foreign pathogens is not a common event.


Short Note
Multi-year surveillance of selected avian pathogens in the migrant shorebird Red Knot (Calidris canutus rufa) at its main stopover site in Patagonia, Argentina
Verónica L. D’Amico , Patricia M. González , Allan J. Baker , Deborah M. Buehler & Marcelo Bertellotti

Abstract
To investigate possible reasons for recent declines in Red Knot (Calidris canutus rufa) populations we surveyed for selected pathogens in Red Knots captured in San Antonio Bay, Argentina, on their northward migration during the period 2006–2011. Blood, cloacal swabs and faeces were analysed for bacteria [Salmonella sp., Shigella sp., enteropathogenic Escherichia coli (N = 42) and other coliforms (N = 35)], viral agents [responsible for avian influenza (N = 239), St. Louis encephalitis (N = 51) and Newcastle disease (N = 239)] and avian malaria parasites [Plasmodium sp. and Haemoproteus sp. (N = 284)]. All 698 samples taken from 303 individuals were negative, providing no evidence that Red Knots sampled at this stopover site were infected with these pathogens at the time of sampling.


Technical Note
One hundred new universal exonic markers for birds developed from a genomic pipeline
Kevin C. R. Kerr , Alison Cloutier & Allan J. Baker

Abstract
The functional constraint imposed on exonic sequences increases marker universality and improves sequence alignment accuracy, yet introns have been favoured recently in Avian Tree of Life studies because of the increased sequence coverage that would be required to yield similar resolving power with exons. In this study, we address this shortcoming by developing a pipeline to identify a large number of exonic markers from five avian genomes. Markers were targeted to maximize phylogenetic informativeness and to exclude multi-copy genes. We demonstrate the universality of these markers by testing a portion of them on a taxonomically diverse assemblage of avian specimens.



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