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Friday, 8 July 2016

Journal of Ornithology; Volume 157, Issue 3, July 2016

Journal of Ornithology

Volume 157, Issue 3, July 2016


Original Articles

No short-term effects of geolocators on flight performance of an aerial insectivorous bird, the Barn Swallow (Hirundo rustica)

Piotr Matyjasiak, Diego Rubolini, Maria Romano, Nicola Saino

Miniaturized light-level geolocators are becoming increasingly popular devices for the study of avian migration. However, the effects of these devices on birds’ flight behaviour, and hence fitness components, are poorly known. We investigated the effect of miniaturized geolocators on flight performance of the Barn Swallow (Hirundo rustica), which may be especially susceptible to geolocator deployment as it is a small (~20 g), aerially insectivorous, long-distance migratory species. We tested whether miniaturized geolocators (~3.5 % of body mass) affected short-term flight performance traits of breeding males by comparing flight manoeuvrability, velocity and acceleration of geolocator-equipped versus control (handled only) birds in flight tunnels. We used a robust experimental design wherein the within-individual change in flight performance was compared between geolocator-equipped birds (after allowing for a period of acclimation) and control birds (that were also tested twice). We found no statistically significant evidence that short-term flight performance traits were affected by geolocator deployment. Here we discuss the implications of our findings for the deployment of geolocators in studies of migratory behaviour of small birds.

Combining stable hydrogen (δ2H) isotopes and geolocation to assign Scaly-sided Mergansers to moult river catchments

Diana Solovyeva, Keith A. Hobson, Natalia Kharitonova, Jason Newton, James W. Fox, Vsevolod Afansyev, Anthony D. Fox


Scaly-sided Mergansers Mergus squamatus breed on freshwater rivers in Far East Russia, Korea, and China, wintering on similar habitat in China and Korea, but information on their post-breeding moulting habitats remains elusive. We combined analysis of stable hydrogen isotope ratios (δ2H) in flight feathers from nesting females equipped with geolocators to test whether we could correctly identify their use of moulting rivers (which show a strong north–south gradient in river water δ2H characteristics) based on feather δ2H values. The results are the first ever to demonstrate a strong positive correlation (r 2 = 0.91) between measured river catchment water δ2H and feather δ2H from birds of known moulting location (from geolocation) in an avian piscivorous species. Furthermore, our δ2H results overwhelmingly supported previous determinations based on feather δ13C and δ15N measurements from the same individuals confirming that most Scaly-sided Mergansers of both sexes moulted on freshwater, although four non-breeding and failed breeding females (out of 21) and one male (out of six) apparently undertook moult migration to brackish and marine waters. The single case where the δ2H results contradicted previous isotopic evidence was likely due to birds eating migratory fish of marine provenance that migrate up freshwater rivers. These results confirm the potential power of feather δ2H to assign piscivorous birds to specific river catchment moult sites and the utility of using multiple stable isotopes to assign birds to moult habitat and location in potentially complex estuarine and brackish situations or where migratory prey may be used by birds in freshwater habitats.

Migration routes and timing in a bird wintering in South Asia, the Common Rosefinch Carpodacus erythrinus

Robert Stach, Cecilia Kullberg, Sven Jakobsson, Kåre Ström, Thord Fransson


Only few bird species from Western Europe migrate eastward to wintering areas in South Asia, and little is known about this migratory flyway. The Common Rosefinch has in the past century expanded its breeding range westward to include Western Europe and migrate along this flyway to wintering sites in South Asia. This is the first study describing the migration routes of Common Rosefinches between Europe and Asia in detail, revealed by light level geolocators. The rosefinches showed loop-migration with more northerly routes in autumn than in spring, possibly in order to shorten the flight over the Central Asian deserts, which are very inhospitable at this time of the year. In spring the deserts are less dry and richer in vegetation, which may have supported the more southerly routes. During autumn migration the birds used several staging sites in Central Asia for prolonged periods. Although the birds passed over mountain regions at this time, which potentially act as barriers to them, the length of the stops seem unrealistically long for only fuel deposition. Instead, this suggests that the birds temporarily suspended migration to take advantage of abundant and predictable food sources in this region. During spring migration the birds made a few longer stops while still in north India or Central Asia, before migrating at fast speeds towards the breeding grounds. The birds covered 4–5000 km with only very short stopovers and thus most of the fuel used on spring migration must have been accumulated in Asia. Our results thus indicate that Central Asia, and north India, are important staging areas for this species in both autumn and spring. During winter, birds used two sites located several hundred kilometres apart, and relocation was probably a response to local food availability.

Spring and fall migration phenology of an Arctic-breeding passerine

Emily A. McKinnon, C. M. Macdonald, H. G. Gilchrist, O. P. Love


Understanding patterns in avian migration phenology and the proximate mechanisms for such patterns is important for assessing behavioural responses of individuals or populations to climate change. Among songbirds, protandry in spring is a common pattern; phenology in fall is less well described. Using tracking data collected from geolocators deployed at a breeding site, and capture data from banding stations, we assessed fall and spring migration phenology of an Arctic-breeding passerine, the Snow Bunting (Plectrophenax nivalis), by sex and age. We measured migration timing, speed, and distance, as well as duration of migration stopovers to test proximate mechanisms for observed sex and age differences in spring and fall migration phenology. During fall migration, hatch-year birds preceded adults, and adult males tended to precede adult females; however, there remained extensive variation by year. Males and females tracked directly arrived at winter sites at approximately the same time. During early spring migration, Snow Buntings exhibited moderate protandry, where after-second-year males preceded all other age-sex classes by ~6 days, on average. Surprisingly, protandry was not apparent at late spring migration or at breeding arrival. Instead, arrival dates by sex and age appeared highly variable between years. The winter site arrival date was predicted by fall migration departure date, total number of stopover days, migration speed, and migration distance. The breeding site arrival date was similarly predicted by spring migration departure date, total stopover days, and migration speed. Our results provide key baseline data for monitoring ongoing changes in migration phenology of this important Arctic-breeding songbird, as climate change effects become more pronounced across temperate and Arctic regions.

Contrasting annual cycles of an intratropical migrant and a tropical resident bird

André C. Guaraldo, Jeffrey F. Kelly, Miguel Â. Marini


Throughout their annual cycle, migrants often adopt different foraging and microhabitat usage strategies. Previous studies treat migrants as niche-trackers/niche-followers, i.e., they track similar niches along their annual cycle, almost exclusively based on food resource availability, which is inferred based on the climate at either the wintering or breeding grounds. An alternative approach is the use of such techniques as stable isotope analyses that allow researchers to more directly infer a migrant’s niche across seasons. While the use of carbon isotopes enables an assessment of microhabitat traits, that of nitrogen isotopes provides information on a bird’s trophic level. In the study reported here, we performed comparative analyses of stable carbon and nitrogen isotope ratios in tissues of the resident Plain-crested Elaenia and the intratropical migrant Lesser Elaenia to evaluate their year-round ecological niches. Our data suggest that both residents and migrants were consistent in their use of similar microhabitats throughout the year, which indicates a niche-tracking behavior on the part of migratory individuals. Migrants often fed at higher trophic levels than residents, but both species exhibited similar trophic level shifts through the year, feeding on higher trophic levels during breeding and on the lowest ones while wintering. The observed patterns could be due to several factors, including differential energetic demand needed for the migratory journey, species-specific nutritional needs during each stage of the year, and/or the use of multiple wintering grounds by migrants.

Survival and dispersal of the Cyprus wheatear Oenanthe cypriaca, an endemic migrant

Marina Xenophontos, Will Cresswell


Many populations of European migrant bird species are declining and this may be driven by survival rates; however, there are few studies that can estimate true survival rates. Cyprus wheatears Oenanthe cypriaca are an endemic migrant that winter in East Africa: populations are probably not declining but are annually variable. We recorded territory occupation and reoccupation in a colour-ringed population of 45–69 pairs over a 4-year period (2010–2013) from April to August to measure apparent survival and determine how it varied with sex, age, breeding productivity and year. We then estimated true survival by correcting apparent survival for dispersal by recording territory shifts and how this also varied by sex, age, breeding productivity and year. Apparent annual survival rate varied significantly by sex, age and year (males 2011, 2012, 2013: 0.70, 0.50, 0.62; females: 0.56, 0.34, 0.47; chicks: 0.35, 0.19, 0.28) but was not affected by the productivity of a territory. An average of 1.1 % of males and 8.2 % of females were lost during breeding, where 5/7 lost females were found depredated during incubation. Adults did not usually change territories between years (87 % were resident and 99 % moved less than four territories between years) regardless of sex, productivity or year; chicks, independent of their sex, moved on average three territories away from their natal territory. After correcting apparent survival for the probability of dispersal, males had the highest true minimum annual survival compared to females which were very similar to chicks (males 2011, 2012, 2013: 0.77, 0.50, 0.65; females: 0.65, 0.35, 0.50; chicks: 0.64, 0.34, 0.49). The results indicate a very high survival rate for a small passerine migrant, although they are probably sufficiently annually variable to profoundly affect annual population dynamics. If females have a lower survival rate, the sex ratio at birth may be female-biased to compensate; alternatively, females may have longer range dispersal than we could measure, particularly if they respond to their mates not returning by moving territories, leading to underestimation of their true survival. A high survival rate may be due to the rarity of sparrowhawks on Cyprus and the wheatears relatively short distance migration.

Reproductive success and productivity of the Cyprus Wheatear Oenanthe cypriaca, a migratory, island endemic

Marina Xenophontos, Will Cresswell


Population dynamics of annually breeding bird species depend crucially on productivity, and so this variation can help us understand the causes of declines in migrant birds. We investigated variation in annual productivity 2010–2012 in the Cyprus Wheatear Oenanthe cypriaca, a small endemic migrant passerine at the National Forest Park (NFP) of Troodos. Clutch size for first nests was usually five, although 0.40 eggs lower in 2011. Nest survival did not vary with year, nesting attempt, or clutch initiation date, but was significantly higher in the chick (0.96; 0.88–0.98, 95 % CI) versus the egg stage (0.74; 0.62–0.83, 95 % CI). The number of chicks fledged from a successful nest varied with nest type—with first nests and second nests after failure being similar producing ~3–4.5 chicks dependent on year, and with second nests after success producing ~2 chicks, independent of year. There were only weak positive or negative effects of clutch initiation date dependent on year, controlling for nest type, and no effects of male age on productivity. After fledging, chicks had a >95 % chance of surviving the first month, but with a greater probability of one or rarely two chicks per brood dying if fledged later in the season. Renesting rate was significantly different in all years (26, 48, and 78 % renesting): 2010 had a much lower renesting rate after success with very few second broods (29 versus 76 % and 73 % in 2011 and 2012, respectively). Overall productivity per territory did not vary with year with 3.96 ± 0.09 SE chicks alive 1 month after fledging. Cyprus Wheatears showed several unusual breeding parameters including a highly variable renesting probability, high nestling, and very high fledgling survival, resulting in exceptionally high productivity. This may be because renesting is constrained by high mid-summer temperatures and low abundance of chick predators.

Patterns of nest attendance by female Greater Prairie-Chickens (Tympanuchus cupido) in northcentral Kansas

Virginia L. Winder, Mark R. Herse, Lyla M. Hunt, Andrew J. Gregory, Lance B. McNew, Brett K. Sandercock


Nest attendance behavior is a critical component of avian ecology that influences nest survival and population productivity. Birds that provide uniparental care during incubation and brood-rearing must balance the benefit of reproductive success with the costs of physiological needs and predation risk. We used miniature nest cameras to record 5904 h of video footage at 33 nests of Greater Prairie-Chickens (Tympanuchus cupido) during 2010 and 2011 in northcentral Kansas. We quantified the timing and duration of incubation bouts to address alternative hypotheses about physiological requirements and predation risk as drivers of incubation behavior. We also identified nest predators and determined timing of predation events, and tested for effects of nest attendance and monitoring technique on nest survival (video vs. telemetry). Female prairie chickens exhibited high incubation constancy per day (~95 %) and typically took two ~40-min recesses per day: one after sunrise and one before sunset. Mesocarnivores were responsible for 75 % (18 of 24) of nest losses, and most nest predation events occurred during crepuscular or overnight hours. Controlled comparisons provided no evidence that video surveillance attracted predators to nests. Variation in nest attendance had a minimal effect on nest survival compared to height of vegetative cover at the nest site. Timing of recesses did not indicate avoidance of predator activity in our study system. The bimodal pattern of incubation breaks observed in most grouse species is likely driven by physiological requirements of the female rather than predation pressure. Female Greater Prairie-Chickens appear to prioritize their metabolic needs and future reproductive potential over current nest survival.

Comparative breeding ecology, nest survival, and agonistic behaviour between the Barred Warbler and the Red-backed Shrike

Marcin Polak

The majority of studies have demonstrated that the Barred Warbler Sylvia nisoria (BW) and the Red-backed Shrike Lanius collurio (RBS), where they occur sympatrically in central Europe, inhabit similar niches and are not averse to nesting in each other’s vicinity. The present work compares the reproductive parameters, nest survival, and behavioural interactions between these two ecologically similar species. The study was carried out in eastern Poland in two types of habitat: a river valley and farmland. Inter-habitat analysis showed both species to have similar reproductive parameters, although nest survival of the RBS was greater in farmland than in the river valley. Interspecific comparison revealed that the BW built smaller nests, laid fewer and smaller eggs than the RBS, but the production of offspring was similar in both species. In comparison to the other populations from Europe, both the BW and RBS in eastern Poland experienced good breeding parameters, and this is likely to be related to the region's extensive agriculture management and abundant food resources. The main factor reducing breeding success in both species was the plundering of their broods by raptors. Analysis using the MARK program indicated that habitat parameters significantly affected brood survival in the RBS to a relatively constant extent throughout the season. While habitat factors were less decisive in BWs, the fate of this species’ broods was strongly dependent on the phase of the reproductive cycle, and its nests were least likely to survive in the middle of the breeding season. The level of aggression between the BW and RBS was low, as demonstrated by experiments with stuffed models; this was a factor in favour of their nesting in close proximity to one another.

Effect of nestbox type on the breeding performance of two secondary hole-nesting passerines

Javier Bueno-Enciso, Esperanza S. Ferrer, Rafael Barrientos, Juan José Sanz

The use of nestboxes to study secondary cavity nesting avian species has greatly improved the knowledge related to many fields of environmental sciences. The aim of this study has been to compare the breeding performance of Great Tits (Parus major) and Blue Tits (Cyanistes caeruleus) in two types of nestboxes that differ with regard to their shape and thermal properties. Both nestbox types were placed in the same area to avoid confounding factors. There were significant differences between the extreme values of temperature and relative humidity obtained for the two nestbox types, and this was also the case in their daily patterns. Secondary hole-nesting birds appear to prefer breeding in woodcrete nestboxes. Nest predation was, however, significantly greater in woodcrete nestboxes. The nest height was significantly higher in woodcrete nestboxes, as was the danger distance between the nest cup and the entrance hole, which could account for the fact that Great Tits prefer this type of nestbox. The laying date was earlier in woodcrete boxes, but nestbox type did not influence clutch size. However, the eggs of both species were significantly smaller in woodcrete boxes. Breeding success was worse in woodcrete nestboxes. Nestbox type also affected the incubation pattern in both species, and attentiveness was significantly diminished in woodcrete nestboxes. This study reinforces the idea that the type of nestbox used in avian studies is not a trivial issue and may have strong biological effects on avian populations. It is important to take this into account when nestboxes are used as management measures for bird conservation.

Breeding biology of Magellanic Penguins (Spheniscus magellanicus) at the Beagle Channel: interannual variation and its relationship with foraging behaviour

Gabriela Scioscia, Andrea Raya Rey, Adrián Schiavini

Interannual variation in seabird foraging or reproductive behaviour may reflect fluctuations in marine resources. In this study, we evaluated different foraging and breeding parameters of Magellanic Penguins (Spheniscus magellanicus) from Martillo Island in the Beagle Channel, and the relationships between these parameters at different stages within the season (incubation, early and late chick-rearing) over three consecutive breeding seasons (2006–2007, 2007–2008 and 2008–2009). In 2007, we observed greater adult foraging effort (longer foraging trip duration and vertical travel distance, VTD) and lower chick feeding frequency, together with a slower growth rate and later fledging date of chicks, which we suggest was linked to lower food availability near the colony that year. The increased foraging effort appeared to be compensated by enhanced feeding activity (e.g., number of wiggles per dive). However, this increase did not coincide with a larger amount of food load brought to colony, which may have been due to a change in the type or size of prey consumed by the penguins. Magellanic Penguins from Martillo Island showed great plasticity in foraging behaviour, as evidenced by changes in consumed prey type or increased foraging effort and feeding activity when the consumption of their main prey item, Sprattus fuegensis, seemed to decrease. Moreover, during this particular breeding season, although the growth rate of chicks was lower, the breeding success remained constant throughout the study period, suggesting that the penguins managed to compensate for the apparent decrease in Fuegian sprat.

Variable decline of Alpine Rock Ptarmigan (Lagopus muta helvetica) in Switzerland between regions and sites

Roman Furrer, Michael Schaub, Andreas Bossert, Res Isler, Hannes Jenny, Tobias Jonas, Christian Marti, Lukas Jenni

Alpine species adapted to mountain climate are particularly vulnerable to environmental changes and have recently come under multiple environmental pressures, such as climate change associated with habitat loss (e.g. upward shift of the treeline) and unfavourable weather, as well as increasing human recreation activities. A prime example is the Alpine Rock Ptarmigan (Lagopus muta helvetica), a subspecies restricted to the Alps. We analysed counts of territorial males from 40 sites in the Swiss Alps since 1995 with state-space models including various environmental variables. Over the 18 study years, population growth rate (as deduced from territorial males) was negative overall (−13 %), but varied greatly between different regions of the Swiss Alps (from −50 to +6 %) and between sites, with some declining drastically and others doing well. Overall and within regions, growth rates showed little evidence for synchrony between local study sites. We did not find an overall factor which explained variation in population growth rates, except for a curvilinear effect of July temperature. It thus seems that various factors act locally to different degrees, such as upward shift of the treeline, unfavourable weather, and perhaps local increase in winter and/or summer tourism and unsustainable hunting. Together with a predicted shrinkage of the distribution area in the future due to global warming, the observed decrease of this isolated subspecies is of conservation concern. A better understanding of the different causes of decline and possibly different management strategies will be essential for the conservation of Alpine Rock Ptarmigan in Switzerland.

No short-term effects of climate change on the breeding of Rock Ptarmigan in the French Alps and Pyrenees

Claude Novoa, Guillelme Astruc, Jean-François Desmet, Aurélien Besnard

In the last decades, the effects of climate warming have been particularly marked in high mountain areas. High-altitude species adapted to cold temperatures are consensually held to be particularly vulnerable to climate warming. Among these species at risk, alpine birds like the Rock Ptarmigan (Lagopus muta) are expected to exhibit a strong negative response, particularly at the southern margins of their ranges in the northern hemisphere. In this study, conducted from 1998 to 2011, we investigated whether variations in the local climate affected the breeding biology of Rock Ptarmigan in the French Alps and Pyrenees. The median hatching date did not significantly advance in either massif, suggesting that Rock Ptarmigan did not breed earlier during this period. The date of snowmelt and spring temperatures influenced the onset of breeding but not consistently in both sites. In the Alps, the median hatching date was significantly correlated with the date of snowmelt, but this correlation was less clear in the Pyrenees. Unlike woodland grouse which inhabit lower elevations, the onset of breeding in Rock Ptarmigan may be related to both date of snowmelt and spring temperatures. Reproductive success varied greatly over the years and among sites. On average, the number of young per adult in the Pyrenean population was greater than that recorded in the two populations in the Alps. A significant positive trend of reproductive success over the period of 2000–2009 was detected in the Pyrenees but not in the Alps. The model that best explained annual variation in reproductive success included the additive effects of site, date of total snowmelt and rainfall after hatching. The estimates from this model showed that for all sites, reproductive success was much lower when snowmelt was late, and rainfall after hatching was high. We did not detect any altitudinal changes in locations of either breeding females or nests, suggesting that the breeding habitat of the species has not shifted upward from 1998 to 2011. To conclude, although the Rock Ptarmigan is generally considered a potential sentinel species for indicating temperature-induced changes in alpine avifauna, our study did not show a short-term effect of climate change on the breeding biology of the southern populations of this species.

Effects of habitat and land use on breeding season density of male Asian Houbara Chlamydotis macqueenii

M. A. Koshkin, R. J. Burnside, N. J. Collar, J. L. Guilherme, D. A. Showler, P. M. Dolman

Landscape-scale habitat and land use influences on Asian Houbara Chlamydotis macqueenii (IUCN Vulnerable) remain unstudied, while estimating numbers of this cryptic, low-density, over-hunted species is challenging. In spring 2013, male houbara were recorded at 231 point counts, conducted twice, across a gradient of sheep density and shrub assemblages within 14,300 km2 of the Kyzylkum Desert, Uzbekistan. Four sets of models related male abundance to: (1) vegetation structure (shrub height and substrate); (2) shrub assemblage; (3) shrub species composition (multidimensional scaling); (4) remote-sensed derived land cover (GLOBCOVER, 4 variables). Each set also incorporated measures of landscape rugosity and sheep density. For each set, multi-model inference was applied to generalised linear mixed models of visit-specific counts that included important detectability covariates and point ID as random effects. Vegetation structure received strongest support, followed by shrub species composition and shrub assemblage, with weakest support for the GLOBCOVER model set. Male houbara numbers were greater with lower mean shrub height, more gravel and flatter surfaces, but were unaffected by sheep density. Male density (mean 0.14 km−2) estimated by distance analysis differed substantially among shrub assemblages, being highest in vegetation dominated by Salsola rigida, high in areas of S. arbuscula and Astragalus, respectively, lower in Artemisia and lowest in Calligonum. The study area was estimated to hold 1824 males (CI 1645–2030). The spatial distribution of relative male houbara abundance, predicted from vegetation structure models, had the strongest correspondence with observed numbers in both model calibration and the subsequent year’s data. We found no effect of pastoralism on male distribution, but potential effects on nesting females are unknown. Density differences among shrub communities suggest extrapolation to estimate country- or range-wide population size must take into account vegetation composition.

Stress response varies with plumage colour and local habitat in feral pigeons

Hélène Corbel, Ariane Legros, Claudy Haussy, Lisa Jacquin, Julien Gasparini, Battle Karimi, Adrien Frantz

Bird populations exposed to different extrinsic conditions often differ in the responsiveness of the hypothalamo–pituitary–adrenal (HPA) axis and thus in corticosterone response that individuals mount when facing stressful events. However, the contribution of genetic variation to among-individual variability in HPA axis responsiveness across different environmental conditions is poorly understood. Melanin-based coloured types provide reliable phenotypic markers of alternative genotypes underlying stress coping styles. Large variations in melanin-based colouration are heritable in feral pigeons. We tested whether melanin-based colouration is associated with variation in corticosterone stress response in feral pigeons. To this end, we examined how corticosterone response varies both within and between differently coloured individuals across different environmental conditions. Differently coloured individuals produced different stress-induced corticosterone levels in relation to their environmental conditions: dark pigeons exhibited a higher corticosterone when originating from rural habitats, while this was not observed in pale pigeons. This suggests that among-population variation in stress response is higher in dark pigeons, this variation possibly reflecting adjustment and/or (epi)genetic adaptation to environmental conditions. In addition, corticosterone response increased with the degree of melanin-based colouration in pigeons originating from rural habitats but not in pigeons originating from more urbanized populations, resulting in the coexistence of alternative stress responses in some populations, but not in others. Our results suggest that species with melanin-based variation in differently urbanized populations along rural–urban gradients are potentially good candidate systems for studying stress coping styles under alternative selective regimes.

Excretion patterns of coccidian oocysts and nematode eggs during the reproductive season in Northern Bald Ibis (Geronticus eremita)

Didone Frigerio, Lara Cibulski, Sonja C. Ludwig, Irene Campderrich, Kurt Kotrschal, Claudia A. F. Wascher

Individual reproductive success largely depends on the ability to optimize behaviour, immune function and the physiological stress response. We have investigated correlations between behaviour, faecal steroid metabolites, immune parameters, parasite excretion patterns and reproductive output in a critically endangered avian species, the Northern Bald Ibis (Geronticus eremita). In particular, we related haematocrit, heterophil/lymphocyte ratio, excreted immune-reactive corticosterone metabolites and social behaviour with parasite excretion and two individual fitness parameters, namely, number of eggs laid and number of fledglings. We found that the frequency of excretion of parasites’ oocysts and eggs tended to increase with ambient temperature. Paired individuals excreted significantly more samples containing nematode eggs than unpaired ones. The excretion of nematode eggs was also significantly more frequent in females than in males. Individuals with a high proportion of droppings containing coccidian oocysts were more often preened by their partners than individuals with lower excretion rates. We observed that the more eggs an individual incubated and the fewer offspring fledged, the higher the rates of excreted samples containing coccidian oocysts. Our results confirm that social behaviour, physiology and parasite burden are linked in a complex and context-dependent manner. They also contribute background information supporting future conservation programmes dealing with this critically endangered species.

Seasonal and daily patterns of nocturnal singing in the Field Sparrow (Spizella pusilla)

Antonio Celis-Murillo, Kirk W. Stodola, Brian Pappadopoli, Jessica M. Burton, Michael P. Ward

Nocturnal singing in diurnal birds is poorly described in the literature and is not well understood. Most research has been limited to the documentation of the behavior, with little information regarding the patterns and function of nocturnal song. We used autonomous acoustic recording units and automated detection and classification algorithms to examine the seasonal and nocturnal patterns of song in the Field Sparrow, Spizella pusilla, a diurnal songbird. We used a generalized linear mixed model to investigate the patterns in the probability of recording each of the two song types described for the species (simple and complex) at night from 7938 10-min recordings from 14 different individuals singing in six different grassland patches. We fit different models investigating the influence of date within the season and time period during the night, and compared models using the Bayesian information criterion. Male Field Sparrows sang both simple and complex songs during the early stages of territory settlement and mate acquisition. However, as the breeding season progressed, we detected fewer instances of simple song, while the occurrence of complex song increased, reaching its peak during the height of reproductive activity. The seasonal pattern of simple and complex songs suggests that they may have a similar function at night and during the day, with simple songs used for inter-sexual interactions and complex songs used for intrasexual functions. Consequently, the role and function of nocturnal song may be more important for reproductive activities than previously assumed.

Genetic and morphological sex identification methods reveal a male-biased sex ratio in the Ivory Gull Pagophila eburnea

Glenn Yannic, Thomas Broquet, Hallvard Strøm, Adrian Aebischer, Christophe Dufresnes, Maria V. Gavrilo, H. Grant Gilchrist, Mark L. Mallory, R. I. Guy Morrison, Brigitte Sabard, Roberto Sermier, Olivier Gilg

Sex identification of birds is relevant to studies of evolutionary biology and ecology and is often a central issue for the management and conservation of populations. The Ivory Gull Pagophila eburnea (Phipps, 1774) is a rare high-Arctic species whose main habitat is sea ice throughout the year. This species is currently listed Near Threatened by the IUCN, because populations have drastically declined in part of the species distribution in the recent past. Here we tested molecular sexing methods with different types of samples. Molecular sexing appeared to be very efficient with DNA extracted from muscle, blood, and buccal swabs, both for adults and young chicks. We also performed morphological analyses to characterize sexual size dimorphism in Ivory Gulls sampled in three distinct regions: Greenland, Svalbard, and Russia. Males were larger than females for all morphometric measurements, with little overlap between sexes. Discriminant analysis based on six morphometric variables correctly classified ~95 % of the individuals, even when using two variables only, i.e., gonys height and skull length. Therefore, both molecular and biometric methods are useful for sexing Ivory Gulls. Interestingly, our results indicate a male-biased sex ratio across all Ivory Gull populations studied, including two samples of offspring (67.8 % males).

Sexual size dimorphism and discriminant functions for predicting the sex of Atlantic Puffins (Fratercula arctica)

Alexander L. Bond, Rebecca A. Standen, Antony W. Diamond, Keith A. Hobson

Assortative mating is an important aspect of mate choice, especially in species where both sexes express ornamentation. Such ornaments could function as signals of individual quality and could result in individuals mating with partners of similar quality. We tested for assortative mating by measuring 63 pairs of Atlantic Puffins (Fratercula arctica) at two Canadian colonies (Gull Island, Witless Bay, Newfoundland and Labrador; and Machias Seal Island, New Brunswick), and constructed a function to predict the sex of puffins from Witless Bay. Male and female puffins have similar plumage, and both sexes have fleshy rosettes at the base of their bill, which are supposedly ornaments. We also examined changes in measurements over time in 5–30-year-old puffins recaptured at Machias Seal Island. Our discriminant function correctly predicted the sex of 88 % of puffins from Witless Bay. Overall, males were larger than females in all measurements, but within pairs, some females were larger in 4–27 % of individual measurements. We found no evidence of positive assortative mating or of assortative mating by rosette size, and rosette area did not increase with age. The importance of puffins’ rosettes as indicators of quality requires further investigation.

A stem falconid bird from the Lower Eocene of Antarctica and the early southern radiation of the falcons

Marcos Cenizo, Jorge I. Noriega, Marcelo A. Reguero

Antarctoboenus carlinii nov. gen. nov. sp. is a large-sized falconiform bird from the La Meseta Formation (Lower Eocene) at Seymour (Marambio) Island, West Antarctica. The holotypical tarsometatarsus was originally assigned to Falconidae and its affinities to Polyborinae were pointed out. Detailed osteological and comparative analyses of the Antarctic specimen allowed recognition of the new taxon as a member of stem group Falconidae, i.e. it is supposed to belong to the early radiation of the falconiform lineage. Antarctoboenus carlinii is distinguished from members of crown group Falconidae by having a very shallow sulcus extensorius, a large foramen vasculare distale, an undistinguishable tendinal attachment for the m. adductor digiti II, and short trochlea metatarsi II, among its main diagnostic characters. Purported phylogenetic relationships between A. carlinii and Polyborinae are based on plesiomorphic characters retained in the tarsometatarsus of the latter clade. Our conclusions reinforce the hypothesis about the Neotropical or Austral origin of Falconidae supported by previous molecular phylogenies.

Year-round spatiotemporal distribution of the enigmatic Semi-collared Flycatcher Ficedula semitorquata

Martins Briedis, Johan Träff, Steffen Hahn, Mihaela Ilieva, Miroslav Král, Strahil Peev, Peter Adamík

We examined migration routes and non-breeding sites of a poorly studied long-distance migrant, the Semi-collared Flycatcher Ficedula semitorquata, by tracking adult birds with geolocators from an eastern European breeding population across two subsequent years. All 11 birds migrated in a clockwise loop fashion where autumn migration routes lay east from the spring migration routes. Non-breeding sites were located in Eastern-Central Africa, i.e. Uganda, Tanzania, Burundi, Rwanda, and east DR Congo, where birds spent on average 128 days. Non-breeding sites of two birds were located outside of the currently estimated species’ non-breeding range.

Migration routes of Eurasian Curlews (Numenius arquata) resting in the eastern Wadden Sea based on GPS telemetry

Philipp Schwemmer, Leonie Enners, Stefan Garthe

The Wadden Sea is an important resting site on the East Atlantic Flyway for Eurasian Curlews (Numenius arquata). However, there is currently little information regarding the connectivity between breeding, staging, and over-wintering sites. We equipped four Curlews with GPS-data loggers and recorded their migration patterns during 2014–2015. Curlews left the Wadden Sea during April and migrated to their breeding grounds in (north-) eastern Russia within 2–4 days. All individuals remained in the breeding area for 51–53 days, and then returned to the same place in the Wadden Sea where they had been caught, indicating high site fidelity.

Female and male Blue Tits (Cyanistes caeruleus) sing in response to experimental predator exposition

Katharina Mahr, Carlo L. Seifert, Herbert Hoi

Female song is recognized to serve a similar function as male song and underlies sexual selection processes; yet certain patterns of the expression of female singing behaviour are not in line with traditional explanations known from male songbirds. In particular, in northern hemisphere songbirds, female singing behaviour is regarded to occur only rarely, and; therefore, studies investigating it are sparse. Within the framework of an experimental study on nest defence behaviour, we observed female singing in a common European passerine, namely, the Blue Tit (Cyanistes caeruleus). Females expressed singing behaviour when a dummy of a Sparrow Hawk was exposed to the nest, raising the idea that song might be multifunctional in this species.

Phylogenetic position of the Wallcreeper Tichodroma muraria

Min Zhao, Per Alström, Urban Olsson, Yanhua Qu, Fumin Lei

The Wallcreeper Tichodroma muraria is usually placed in a monotypic family or subfamily within the superfamily Certhioidea, with assumed close relationships to Certhia (treecreepers), Sitta (nuthatches) and Salpornis (spotted creepers). Previous studies have suggested that Tichodroma is most closely related to Sitta, alternatively to Salpornis. We analysed the relationships of Tichodroma using two mitochondrial and five nuclear loci. The tree based on concatenated sequences strongly supported a sister relationship between Tichodroma and Sitta, as well as between Salpornis and Certhia. However, species tree analysis (MP-EST) was unable to resolve these relationships, and although the concatenation tree remains the best hypothesis, more data are needed to corroborate this.

No genetic structure in a mixed flock of migratory and non-migratory Mallards

Robert H. S. Kraus, Jordi Figuerola, Katharina Klug

Mallards do not show genetic differentiation into migratory populations across typical flyways. It is also known that some Mallard populations are non-migratory. The aim of this study was to test if genetic structure exists between migratory and non-migratory Mallards in an area where they occur sympatrically, in Doñana, Spain. After quality filtering we analysed 350 single nucleotide polymorphism markers (SNPs) from 104 migratory and non-migratory Mallards. No genetic structure was evident from our data. We conclude that the lack of large-scale genetic structure of the global Mallard population remains valid when specifically testing potential differentiation between migratory and non-migratory Mallards.

“Shortest-distance” method is more accurate than conventional method in estimating flight initiation distances for close, perched birds

Kent B. Livezey, Daniel T. Blumstein

The conventional method to determine avian flight initiation distance (the distance at which birds exposed to an approaching human activity initiate escape behavior) overestimates this distance for perched birds because it uses the distance between the bird and the ground at the person’s feet rather than the distance between the bird and the part of the person’s body closest to the bird. Here, we introduce an alternative “shortest-distance” method that more accurately estimates flight initiation distance, especially for close, perched birds.

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