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Thursday, 19 March 2015

Journal of Ornithology. April 2015, Volume 156, Issue 2

Journal of Ornithology

Volume 156, Issue 2, April 2015



Morphological and behavioural adaptations to feed on nectar: how feeding ecology determines the diversity and composition of hummingbird assemblages
Stefan Abrahamczyk, Michael Kessler

Hummingbirds are the most specialised nectarivorous birds and show close ecological relationships to their food plants. Their small body size, bright colors, and unique behaviour have fascinated generations of naturalists. In this review, we investigate the morphological and behavioural adaptations of hummingbirds to feed on nectar and arthropods, and explore their diffuse co-evolution with their food plant species. Further, a list of plant genera including species mainly pollinated by hummingbirds is presented. Summarising the existing knowledge on hummingbird feeding ecology, we find that much of the variability in morphology and behaviour of hummingbirds is determined by their unique feeding mode and the constraints set by their food plants. Based on the existing literature, we developed a hierarchical system explaining how different environmental factors have shaped the current richness of hummingbirds, and their morphological and behavioural diversity. We propose that climatic stability within and between seasons and days determines the constancy of food availability, which in turn is the most important factor for species richness in hummingbird assemblages. However, the assemblage composition of hummingbirds is also influenced by phylogenetic factors, especially under harsh environmental conditions. Unsurprisingly, the highest morphological and behavioural diversity is observed in the most species-rich assemblages. This diversity may have at least partly evolved to reduce inter- and intraspecific competition. Independently of which morphological character we consider, the 360 different hummingbird species have evolved a large morphological variability to adapt to their individual feeding niches.

Original Articles

Dispersal in an extensive continuous forest habitat: Marsh Tit Poecile palustris in the Białowieża National Park
Tomasz Wesołowski

Dispersal is one of the least understood features in the life-history of organisms. Theoretical work concentrates on explaining dispersal of organisms in patchy and heterogeneous landscapes, but there are few predictions of dispersal patterns in stable, spatially extensive and largely homogenous landscapes, such as large forests. It is expected that we should observe short-distance dispersal in such places, that, to avoid competition with parents and siblings and incestuous mating, offspring should leave natal patches (natal dispersal), disperse independently in different directions, and move over distances that efficiently minimise the probability of meeting a sibling. Breeding dispersal should be very limited, site tenacity should prevail. To explore these ideas, I use observations of Marsh Tits Poecile palustris (a small passerine specialist of mature forests) made in the strictly protected part of the Białowieża National Park (Poland) over 21 years. The birds largely followed expectations: all fledglings left their natal territories and dispersed in different directions, and males moved shorter distances than females (median = 570 vs. 1,720 m). Apart from this difference, no influence of population density, fledgling time or family size was observed. No parent–offspring pairing occurred, with just one case of sibling–sibling pairing. After first breeding, individuals remained site-tenacious, as breeding dispersal distances were very short (median ca. 100 m). Such behaviour renders Marsh Tit poorly adapted to cross barriers and undertake long-distance movements, and this is actually observed in fragmented landscapes. Understanding dispersal patterns of organisms from extensive environments would be thus of value for basic and conservation science alike.

Phylogenetic relationships and taxonomic status of the endemic Socorro Warbler (Setophaga pitiayumi graysoni)
Edward L. Evans III, Juan E. Martínez-Gómez… 

The Socorro Warbler (Setophaga pitiayumi graysoni) is currently classified as a subspecies of the Tropical Parula. This bird is endemic to Socorro Island, and due to the island’s distance from mainland Mexico and likely low levels of gene flow for this non-migratory species, we expected this form to exhibit significant divergence from its mainland counterparts. Here, we analyzed the phylogenetic position of the Socorro Warbler and examined its taxonomic status. Using blood samples from four individual Socorro Warblers, we performed phylogenetic analyses using the nuclear genes rhodopsin intron 1 (RDPSN) and transforming growth factor beta-2 (TGFB2), and the mitochondrial genes ATPase and cytochrome b. Bayesian inference, maximum-likelihood, and maximum parsimony analyses were employed to determine the genetic relationship of the Socorro Warbler to its mainland counterparts. Results reveal significant genetic divergence and a basal position of the Socorro Warbler relative to its mainland counterparts. Based on its distinct phylogenetic placement and geographical isolation, we recommend returning the Socorro Warbler to its original specific status, Setophaga graysoni, based on its taxonomic history. This case illustrates the importance of preserving island habitats to save unique island biodiversity that otherwise could pass unnoticed.

Blood parasite prevalence in the Bluethroat is associated with subspecies and breeding habitat
Aleš Svoboda, Gunnhild Marthinsen, Václav Pavel, Bohumír Chutný… 

Long-distance migratory birds are potentially exposed to a range of blood sucking arthropods that transmit avian blood parasites. Because of differential vector exposure, the parasite fauna may vary in different habitat types, among populations, or even within populations where individuals travel to different areas during migration. We applied PCR-based molecular techniques to determine patterns of blood parasite occurrence in adults of seven geographically isolated Bluethroat populations, belonging to three distinct subspecies differing in habitat preferences and wintering areas (Luscinia svecica svecica, L. s. cyanecula, L. s. namnetum). Moreover, to elucidate potential transmission of blood parasites on breeding sites, we tested adults of the relatively sedentary White-throated Dipper (Cinclus cinclus) from a Norwegian population. Across populations, we detected infection of at least one blood parasite genus in 68.5 % (139/203) of adult Bluethroats. The most common parasite genus was Plasmodium (10 lineages, 33.5 % of surveyed individuals), present in all seven populations, followed by Leucocytozoon (four lineages, 31.5 %) and Haemoproteus (two lineages, 4.9 %). We recorded multiple infections in 26.1 % of individuals. Leucocytozoon was found only in svecica inhabiting mountainous/subalpine areas with high abundance of blackflies, the main vector for this parasite. In Plasmodium, two lineages (BT6 and GRW4) were confined to specimens from svecica populations. In contrast, Lineage SGS1 was dominated by southern birds of the subspecies cyanecula and namnetum. Our data suggest transmission of Leucocytozoon on the breeding grounds in Norway as the same lineages were found in relatively sedentary White-throated Dippers as in migratory Bluethroats. We discuss these results in light of the ecological differences between the host populations, affecting their exposure to potential blood parasite vectors.

Spatio-temporal variation in nestling sex ratio among the Black Stork Ciconia nigra populations across Europe
Annika Konovalov, Katrin Kaldma, Andriy Bokotey, Paul Brossault… 

Sex ratio is an indicator of population health as unexpected biases may indicate potential threats. We studied nestling sex ratio in Black Stork Ciconia nigra populations in order to check potential biases and differences along east–west and north–south gradient across its distribution range in Europe. We also studied variation between years, and checked potential correlations with weather variables. The overall sex ratio of nestlings in Europe was nearly equal with a non-significant deficiency (47.1 %) of males, the larger sex. Although yearly fluctuations in sex ratio were detected, no significant effect of the year alone was found, only simultaneously with population and brood size. There was a tendency to have a higher proportion of female nestlings in larger broods, but the pattern was probably scattered by the effect of reduction of largest broods. Compared to Western and Eastern Europe, a significant deficiency of male nestlings was found in Central Europe (Poland), whereas no differences were found along the north–south gradient. We did not find any effect of temperature, but rainfall during the incubation period was negatively correlated with the proportion of male nestlings in Central (Poland) and Western Europe (France) whereas in North-Eastern Europe (Latvia) the same effect of the precipitation in pre-breeding period was found.

Shortening day length as a previously unrecognized selective pressure for early breeding in a bird with long parental care
Marcin Podlaszczuk, Zbigniew Wojciechowski, Patrycja Podlaszczuk… 

Several different selective pressures have been suggested to explain an intense competition for early return to breeding grounds in birds. In this study we hypothesized that shortening day length during summer months may constitute additional selective force acting towards early breeding in avian species with long parental care. To test this hypothesis, we studied time budget and foraging activities of early-nesting and late-nesting white storks Ciconia ciconia from the Central-European population. We found that duration and distance of foraging trips increased significantly over the course of the reproductive season. The relative frequency of foraging trips increased at the expense of other activities, such as resting, plumage maintenance, and nest maintenance. Mean daily foraging duration increased with increasing day length in the early part of the season, with 0.68 h of foraging per individual per 13.16 h of day length in mid-April increasing to 7.42 h of foraging per individual during solstice (16.61 h of day length). Afterwards, mean foraging duration continued increasing in spite of decreasing day length, reaching 11.63 h of foraging per individual per 14.92 h of day length at the end of the season in mid-August, when storks were forced to continue foraging after sunset in order to meet energy requirements of fledglings. The results suggest that shortening day length during summer months may constitute a serious time constraint on food delivery rates to offspring for late-breeding pairs of white stork.

Contrasting population trends at seabirds colonies: is food limitation a factor in Norway?
Emeline Pettex, Robert T. Barrett, Svein-Håkon Lorentsen… 

Norwegian Northern Gannet Morus bassanus populations exhibit contrasting trends on a regional scale, with several colony extinctions having occurred in recent decades. In an attempt to understand the ecological drivers of such variability, we tested whether resource availability is a factor limiting the current development of gannetries in the Lofoten/Vesterålen area. Between 2007 and 2010, we recorded arrival and departure times of breeding Northern Gannets from two colonies from regions showing contrasting population growth rates during the past two decades. We also recorded the duration of joint attendances by Northern Gannet parents at the nest, performed opportunistic diet sampling and counted numbers of occupied nests. Finally, we compiled ring recoveries over a 30-year period to assess inter-colony movements. Norwegian Gannet parents spent more time together, attending their chick, and performed shorter foraging trips than those in British and French colonies of similar size. This suggests that, despite some annual variations, their foraging effort was relatively low. Diet samples from both colonies mainly constituted fish of high energetic value, such as large herring Clupea harengus, mackerel Scomber scombrus, and saithe Pollachius virens, prey that are relatively abundant within the study area. Data from ringed birds revealed a northward movement of adults ringed as breeding birds and chicks from extinct Lofoten colonies that established a growing colony close to the North Cape. Recorded foraging features (trip duration, joint attendance and prey quality) during our study does not indicate food availability as a limiting factor explaining successive extinctions and re-colonisations of breeding sites in Lofoten/Vesterålen. White-tailed Eagles Haliaeetus albicilla are known to predate opportunistically on Northern Gannet adults or chicks and their populations are growing in the Lofoten area. Their potential impact on the Norwegian Northern Gannet population dynamics should be further investigated.

Microclimate and microhabitat selection by the Alpine Rock Ptarmigan (Lagopus muta helvetica) during summer
Linda Visinoni, Claire Agnès Pernollet, Jean-François Desmet… 

The Alpine Rock Ptarmigan (Lagopus muta helvetica)—which is adapted to arctic and alpine environments—is suspected to be vulnerable to climate warming, but direct evidence is limited. Microclimates within a landscape may allow species to exist in regions where the general climate appears to be unsuitable for them. We therefore investigated the diversity of microclimates in alpine habitats used by the Alpine Rock Ptarmigan in summer, and we examined whether Alpine Rock Ptarmigan select places with a microclimate that facilitates heat dissipation during summer days. The study was done in the Haute-Savoie (northern French Alps), where ptarmigan have been equipped with radio transmitters, thus allowing direct observations. We measured the three microclimate variables which determine the thermal environment of an animal: ambient temperature (ground and air temperature), which defines the temperature gradients between the animal and the environment; wind speed, which determines convection; and solar radiation, which determines radiation uptake. Additional measurements at four contrasting microtopographic sites at five locations and at two random sites in July and August showed that the typical habitat of the Alpine Rock Ptarmigan offered a wide variety of microclimates over very short distances, particularly on hot summer days. Compared with control sites at 5 m and 30 m, Alpine Rock Ptarmigan selected places with a particular microtopography and microclimate: slightly cooler places in the shade that were protected from the wind; often small, north-facing depressions with a medium amount of rocks and diverse ground cover. The places selected by ptarmigan during hot summer days conformed well to the requirements of both heat dissipation and predator avoidance, and also offered food.

Male pheomelanin pigmentation and breeding onset in Barn Swallows Hirundo rustica gutturalis
Emi Arai, Masaru Hasegawa, Masahiko Nakamura, Kazumasa Wakamatsu 

Plumage color is a composite trait and each component can provide information regarding individual quality. Melanin-based color is one of the most common plumage coloration in birds. This color comprises two types of melanin pigments: eumelanin (black pigment) and pheomelanin (yellow-reddish pigment), and it is affected by several post-molting processes such as UV damage, staining, and preen oils. In some birds, pheomelanin-based plumage color is related to several measures of sexual selection; however, pheomelanin is almost always expressed together with eumelanin and affected by post-molting processes. Therefore, it is still unclear whether (and to what extent) pheomelanin can explain the observed relationship between plumage color and the measure of sexual selection. Here we examined the melanin (both eumelanin and pheomelanin) concentration in relation to breeding onset, as a fitness component associated with sexual selection in male Barn Swallows (Hirundo rustica gutturalis). We found that throat feathers in males contained more pheomelanin than those in females. The amount of pheomelanin, but not eumelanin, declined throughout the sampling period, indicating that pheomelanin pigmentation conveys different information than eumelanin. Even after correcting for depigmentation of melanin, males with more pheomelanin bred earlier than the others. Together with the results from previous studies, these findings indicate that pheomelanin-based coloration may have evolved via sexual selection for pheomelanin pigmentation in Barn Swallows.

The relationship between parasites and spleen and bursa mass in the Icelandic Rock Ptarmigan Lagopus muta
Ute Stenkewitz, Ólafur K. Nielsen, Karl Skírnisson… 

The spleen and bursa of Fabricius in birds are organs that play an important role in fighting parasite infections. The size of these organs can be used by ecologists as a measure of immune investment, with larger size implying greater investment. The bursa only occurs in juvenile birds during the development of the B cell repertoire, whereas the spleen, which is the main site of lymphocyte differentiation and proliferation, is present in both juveniles and adults. We investigated spleen and bursa mass in relation to parasite measures for 541 Rock Ptarmigan Lagopus muta collected in northeast Iceland during October from 2007 to 2012. Of these 541birds, 540 carried at least one parasite species. Juveniles had heavier spleens than adults, and adult females had heavier spleens than adult males, but there were no sex differences in juveniles. Spleen mass increased from 2007 to 2009, then decreased up to 2011, before slightly increasing again in 2012. Spleen and bursa mass in juveniles increased with improved body condition, but decreased in adults, and this effect differed significantly among years. Spleen mass in juveniles was positively associated with parasite species richness and abundance, in particular endoparasite abundance, with coccidian parasites being the main predictors. Bursa mass was negatively associated with elevated ectoparasite abundance, with two chewing lice being the main predictors. These two immune defense organs appeared to relate to different stimuli. Mean annual spleen mass of juveniles changed in synchrony with Ptarmigan body condition and population density over the years of this study. The only parasite measure that showed any relation to density was coccidian prevalence in juvenile birds, with an approximately 2-year time-lag, suggesting that factors other than parasites are probably more important in triggering changes in spleen mass.

Skeletal morphology of the middle Eocene swift Scaniacypselus and the evolutionary history of true swifts (Apodidae)
Gerald Mayr 

New specimens of Scaniacypselus szarskii, a stem group representative of the Apodidae (true swifts) from the middle Eocene Messel oilshale in Germany, are described. These fossils show that Scaniacypselus differs from crown group Apodidae in a number of distinct and previously unrecognized osteological features. Notably, the sternum of Scaniacypselus is shorter than that of extant true swifts, the ulna proportionally longer, the carpometacarpus shorter, and the internal index process on the proximal phalanx of the major wing digit less developed. In details of its humerus morphology, Scaniacypselus is distinguished from all extant apodiform birds. Scaniacypselus further has a much shorter tarsometatarsus than most crown group Apodidae. It is hypothesized that short legs are plesiomorphic for Apodidae as a total group (stem group and crown group representatives), but that crown group Apodidae primitively have an elongated tarsometatarsus as an adaptation for clinging to vertical surfaces. The less specialized wing and pectoral girdle morphology suggests that Scaniacypselus was probably not as aerial as extant Apodidae. The differences in foot morphology indicate that it was more arboreal than its living relatives and had different breeding and roosting habits. Crown group Apodiformes probably diverged well after the middle Eocene, and the derived nesting behavior may have contributed to their evolutionary success.

Resident but not transient Eurasian Siskins reduce body mass in response to increasing predation risk: a natural experiment
Jordi Pascual, Juan Carlos Senar 

The body mass of birds is the result of a trade-off between predation and starvation risks. According to the mass-dependent predation hypothesis, birds reduce their body mass when predation risk increases. Many studies have supported this hypothesis, but it has rarely been possible to investigate the mass-dependent predation risk response by comparing individuals of the same species foraging simultaneously at the same location, in the field and facing a real (not simulated) risk of predation. Wintering Siskins (Carduelis spinus) are divided in two subpopulations: residents, which stay in a foraging area for several weeks or months, and transients, which only remain a few hours or days. In this paper, we present a natural experiment by comparing the body mass variation of resident and transient Siskins between a period of the wintering season without avian predators and another period with a Sparrowhawk (Accipiter nisus) that was hunting regularly. We found that resident Siskins reduced their body mass with the presence of the hawk, while transients did not. Since in a previous study with no avian predators at the study area it was found that the difference in body condition between residents and transients did not vary throughout the wintering season, we can confidently say that the reduction in body mass observed in this study was directly linked to the presence of the hawk. We additionally found that this reduction was not associated with the dominance of residents over transients. We discuss the advantages of residence related to the knowledge of actual predation risk. Our results strongly support the mass-dependent predation hypothesis.

Non-native spruce plantations represent a suitable habitat for Tengmalm’s Owl (Aegolius funereus) in the Czech Republic, Central Europe
Markéta Zárybnická, Jan Riegert, Karel Št’astný


Anthropogenic activity can lead to deforestation and subsequent dramatic impacts on forest-dwelling animal species. In this study, we investigated the habitat use of a forest raptor (Tengmalm’s Owl Aegolius funereus) in an air-polluted area of the Ore Mountains (Czech Republic) that has been restored by non-native spruce. Based on a 14-year Tengmalm’s Owl nest-box breeding dataset, we found that the percentage of native Norway Spruce forest was higher for occupied nest boxes than for unoccupied ones within close surroundings of the nest (buffer radius of 25 m). Meanwhile, the percentage of non-native Blue Spruce (originally from Northern America) was higher for occupied nest boxes than for unoccupied ones within the home-range breeding area (buffer radius of 750 m). Moreover, the surroundings of non-predated nests (radius of 750 m) showed a higher percentage of Blue Spruce and a lower percentage of deciduous trees than surroundings of nests predated by Pine Martens. Although small mammal availability was not affected by habitat categories, we found a positive correlation between the percentage of Apodemus mice in the diet of owls and the percentages of both Blue Spruce and open forest area within the foraging area radius (750 m). We suggest that adult owls and young fledglings use remnants of tall, old-growth Norway Spruce forests as a safe refuge against avian predators, while secondary stands of non-native Blue Spruce are suitable for hunting both main prey types (Apodemus mice and Microtus voles), and also ensure good protection against nest predation by Pine Martens.

The roles of environmental and geographic variables in explaining the differential wintering distribution of a migratory passerine in southern Europe
Juan Arizaga, Gerard Bota, David Mazuelas, Pablo Vera 

In birds, spatial segregation between age or sex categories during the non-breeding period is a common phenomenon. The main single-factor hypotheses that have been stated to explain this are: (1) body-size variations (that result in more or less cold tolerance) interact with local climate, which promotes age- or sex-associated distributional optima; (2) the dominant age or sex monopolizes high-quality areas; and (3) the age or sex overwintering closer to breeding quarters does so due to the benefits of earlier arrival at the breeding quarters. Southern European countries host millions of birds from northern Europe during the winter period each year. In this work, we aimed to determine the ultimate causes (geographic location and distance to obligate migratory pathways, temperature and land use as a surrogate for food availability) explaining spatial segregation of Reed Buntings (Emberiza schoeniclus) by age and sex in winter. We used data from 38 sampling points across Iberia during the winter of 2011–2012. Reed Bunting abundance did not fit any of our possible models better than the null model, so we were unable to predict bird numbers across Iberia. Moreover, males were found to be predominant at sites close to presumably obligate migratory pathways (western/eastern Pyrenees). Body mass was higher in first-year birds and males, and tended to increase with distance to obligate migratory pathways, land use (in particular with a decreasing proportion of open habitats and urban areas), increasing minimum temperature, and decreasing mean temperature. Our data suggest that the increase in the proportion of males close to obligate migratory pathways is associated with the advantage to males in wintering as close as possible to breeding quarters.

Is it possible to acoustically identify individuals within a population?
Michał Budka, Lucyna Wojas, Tomasz S. Osiejuk 

Acoustically identifying individuals may be a helpful technique when it is necessary to monitor animal populations over space and time. Previous studies have largely focused on the theoretical exploitation of vocal individuality or have looked at a small number of individuals. Here, we examined whether vocal individuality can be used to track the movement of individuals within a population (in this case when the number of individuals is greater than 100) and unknown beforehand. As a model species, we used the Corncrake (Crex crex)—a highly secretive bird whose calls are characterized by an individual-specific feature: pulse-to-pulse duration (PPD). When we performed classical discriminant function analyses on PPD, we correctly identified a high percentage of individuals (>98 %), even when sample size was larger than 100. However, a comparison of PPD similarity within and between individuals showed that, while birds can be correctly discriminated, unambiguous identification is impossible when the number of individuals is unknown beforehand. Therefore, we were only able to assess the probability that two calls belonged to the same individual. The results of this study show that acoustic identification in the Corncrake, and probably in other animal species, is mainly useful in detecting general behavioral patterns within populations. For instance, we discovered that more than 50 % of males change territories during the breeding season, probably to find females. Physical marking methods seem to be more reliable to tracking specific individuals. However, those methods usually consider limited numbers of individuals. Therefore, generalizing results to the population scale can also be misleading.

Tree-cavity availability and selection by a large-bodied secondary cavity-nester: the Military Macaw
Sylvia Margarita de la Parra-Martínez, Katherine Renton… 


Large-bodied secondary cavity-nesters are constrained to use cavities of sufficient size to permit access, while also selecting characteristics to reduce predation. However, no information exists on nest-site availability for large-bodied secondary cavity-nesters in tropical forests. We located 12 tree-cavity nests of the threatened Military Macaw (Ara militaris) in tropical dry semi-deciduous forest in Jalisco, Mexico. For each nest, we determined cavity characteristics, and compared the structure of nest-trees with nearest-neighbor trees. We also established four 100 × 50 m transects in each of deciduous, semi-deciduous, and oak forest to determine tree-cavity availability over 6 ha. Military Macaw nest-sites occurred most frequently in cavities of live Enterolobium cyclocarpum trees. Nest-trees had significantly larger diameter and ramification height than the four nearest-neighbor trees, indicating that macaws selected tall emergent trees as nest-sites. Cavities used as nest-sites by Military Macaws were also in significantly larger trees, at a greater height, and had larger entrance diameter and depth than all accessible cavities. Height above the ground was the main criteria predicting nest-cavity selection, possibly to reduce predation risk. There was also a negative correlation of nest-cavity height with depth, suggesting a trade-off in which Military Macaws may select a nest-cavity high above the ground regardless of depth, but when using lower cavities these tend to be deeper. We found a low density of cavities with characteristics suitable for nesting, and these were concentrated in semi-deciduous forest. Our results demonstrate that the Military Macaw exhibits species-specific selection of nest-cavities, with a low density of cavities suitable for large-bodied secondary cavity-nesters in tropical forests.

Time use and foraging behaviour in pre-breeding dabbling ducks Anas spp. in sub-arctic Norway
Céline Arzel, Johan Elmberg 

We studied time budgets and foraging methods in pre-breeding Mallard Anas platyrhynchos, (Eurasian) Teal Anas crecca, Wigeon Anas penelope, Pintail Anas acuta, Shoveler Anas clypeata and Gadwall Anas strepera in subarctic Norway in May. Among all six species studied, foraging accounted for the most common use of time, ranging from 19 % in male Pintail to 40–60 % in female Mallard, Teal, Pintail and Gadwall. Comfort behaviours amounted to 20–34 % of the time budget, and interaction and disturbance were marginal. Vigilance time ranged from 8 % in female Mallard to 20 % in male Pintail. Movement amounted to some 20 % of the time in most species and sexes. In Wigeon, sexes did not differ in time use, whereas in Mallard, Pintail and, in particular, Teal, females foraged more and engaged less in vigilance and interactions than did males. In addition, Teal and Mallard males engaged in the riskier foraging methods less than females, but more in those permitting vigilance. Although overlap in feeding methods was large among these species, Mallard and Teal were generalists, feeding at all depths, Wigeon foraged mainly in shallow water and Pintail foraged essentially in deep water. Our results support the income/capital breeder hypothesis with respect to males only; compared to lighter species, heavier species allocated less time to foraging but more to vigilance. We found no support for the hypothesis that long-distance migrants forage more to compensate for energy loss due to migratory flight. Foraging time in females was related to breeding phenology; early nesters spent more time feeding than later nesters.

Solar/Argos PTTs contradict ring-recovery analyses: Woodcocks wintering in Spain are found to breed further east than previously stated
Juan Arizaga, Ariñe Crespo, Ibon Telletxea, Rubén Ibáñez…

The development of increasingly small devices for the satellite tracking of small birds allows us to explore aspects of avian migration that have never been studied before. Here, we provide the results of using 12- and 9.5-g platform transmitter terminals (PTTs) to track game birds of 300–385 g. Attaching PTTs to 20 Woodcocks (Scolopax rusticola), wintering in Spain from 2006 to 2012, allowed us to explore (1) migration strategies (timing, velocity and stopovers), (2) the identity of the breeding grounds; (3) inter-year site fidelity to wintering grounds. We provide details of the route, speed and timing of migration and the location of remote breeding sites that were unknown prior to this study. The departure from winter quarters (median date) was completed by 20 March. The spring migration period lasted 40 days, and our birds were found to travel from >5,000 to >10,000 km, with a mean total migratory speed (i.e., including stopovers) of 170 km/day. Woodcocks followed fairly direct routes of migration. Stopover duration tended to be shortened when birds were closer to their breeding areas, which were located further east than previously stated. The only bird that provided long-term data (>1 year) was observed to return to the same wintering area, suggesting high winter site fidelity. The use of small PTTs opens new research lines related to the study and management of small to medium-sized migratory birds.

Bill size correlates with telomere length in male American Redstarts
Frédéric Angelier, Carol M. Vleck, Rebecca L. Holberton… 

Telomere length (TL) has been shown to be a potential predictor of survival in wild vertebrates, and, as a consequence, there is growing interest in understanding the causes of inter-individual variability in TL. In that context, developmental conditions deserve a specific attention because they are thought to be a major driver of telomere shortening. Because poor developmental conditions can accelerate telomere shortening and impair growth (resulting in a small adult size), a positive correlation between TL and body size is expected. However, and surprisingly, the relationship between body size and telomere length has rarely been described in wild vertebrates. Here, we specifically examined this question in hatch-year (HY) and after hatch-year (AHY) male wintering American Redstarts (Setophaga ruticilla). Although tarsus size was not related to TL, we found a significant positive correlation between bill size and TL in HY male Redstarts, therefore supporting the idea that determinants of some components of individual size are also important determinants of TL in young birds. Moreover, this positive relationship between bill size and TL was also found for AHY birds, suggesting that adult TL may be, at least partly, explained by the telomere dynamics that occurred during the developmental phase.

Geographic variation in the calls of the Common Cuckoo (Cuculus canorus): isolation by distance and divergence among subspecies
Chentao Wei, Chenxi Jia, Lu Dong, Daiping Wang, Canwei Xia… 


Studies on the pattern of geographic variation in bird vocalizations can facilitate the understanding of the evolutionary history of species and species differentiation. The Common Cuckoo (Cuculus canorus) is a non-passerine widely distributed in Eurasia, and its calls are not acquired through learning. Revealing the geographic pattern of Common Cuckoo calls may help our understanding of the relationship between environment, genetic differentiation, and vocal differentiation. In the present study, geographic variation in the calls of the Common Cuckoo was investigated throughout Eurasia for the first time. Calls of different subspecies of the Common Cuckoo were compared, and the correlations between differences in calls, geographic distance, climatic differences, and altitude differences were determined in order to evaluate the influence of subspecies differentiation, isolation by distance and environmental differences on call differentiation. The results showed there to be significant differences in the calls of different subspecies of the Common Cuckoo. Discriminant function analysis was able to correctly identify 81.7 % of individuals to their original subspecies, and 98 % of individuals of subspecies subtelephonus were correctly assigned. Differences in calls both within and between subspecies were found to be significantly correlated with geographic distance, while environmental differences have no important effect. Our study stressed the effect of isolation by distance on geographic variation of non-passerine vocalization, and we infer that the great divergence in calls between different Common Cuckoo subspecies may be a hint of cryptic species.

Short Notes

Increasing protandry in the spring migration of the Pied Flycatcher (Ficedula hypoleuca) in Central Europe
A. Harnos, Á. Nóra, Sz Kovács, Zs Lang, T. Csörgő 

Sexual selection theory suggests that the degree of protandry in spring migration should increase when earlier males benefit from better mating opportunities. Western European studies failed to show differences in sex-specific arrival dates for the Pied Flycatcher. However, different climatic conditions and other constraints may affect its phenology in continental Europe. Here, we present evidence that sex-related phenological changes have occurred over the past 25 years (between 1989 and 2013) in Central Europe (Ócsa Bird Ringing Station, Hungary). The spring arrival of male flycatchers shifted to earlier dates whereas female arrival showed no change, implying an increasing degree of protandry.

Summit metabolic rate exhibits phenotypic flexibility with migration, but not latitude in a neotropical migrant, Parkesia noveboracensis
Keely R. Corder, Paul J. Schaeffer 

Physiology–life history interactions suggest that birds living with a fast ‘pace-of-life’ should have higher metabolic capacity to provision higher reproductive activity. Previous work supports this, but does not consider migration. We measured summit metabolism (TeX) in Northern Waterthrush (Parkesia noveboracensis) while wintering in the Republic of Panama, migrating northwards through eastern North America, and while breeding in northeastern North America. TeX is similar between breeding and overwintering (non-migratory) and is significantly elevated in migration. These data suggest that migration is a driver of phenotypic flexibility in these birds and that migration, like winter survival, may be an important determinant of connections between life history and physiology.

Heterospecific intrusions, synchronous fleeing, and nest attendance in a weaverbird colony
Bobby Habig, David C. Lahti 

Synchronous fleeing (i.e. “dreads” or “panic flights”) is a frequently observed but rarely quantified behaviour in colonial birds. Here we analyse video recordings to assess synchronous fleeing behaviour in a Village Weaver (Ploceus cucullatus) colony. Our results indicate that intrusions by heterospecific avian species are frequent and create significant daily differences in female nest attendance. Overall, different sizes, masses and species of intruding heterospecifics appear to affect weaver nesting similarly. Our findings suggest that in colonial birds, with the advantage of “many eyes”, a rapid response to a potential threat nevertheless comes at the apparent cost of many “false alarms”.

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