Stable hydrogen isotope measurements of songbird feathers: effects of intra-feather variability and sample processing Abstract Deuterium composition of feathers has been widely applied to establish provenance of birds. Surprisingly, little attention has been paid to the potential sources of unwanted hydrogen isotopic variability that may affect the comparability and replicability of deuterium measurements. Feathers may exhibit hydrogen isotopic differences between distal and proximal sections, as well as between rachis and vane. For this reason, it is recommended to always analyse ground vane from the same section of the feather. However, this protocol may be seriously limiting when working with songbird feathers, which are usually small and light. In this paper, intra-feather hydrogen isotopic variability was studied in four species of songbirds by comparing four sections of the same feather. No difference in hydrogen isotopic composition was found between distal and proximal sections of the vane. This was expected as songbird feathers grow rapidly and individuals avoid geographical movements during moult, favouring a homogeneous source of hydrogen during keratin synthesis. Conversely, as previously demonstrated for other avian species, rachis showed systematically c. 11‰ δ2H more negative values than vane. This is probably a result of their biochemical and ultrastructural differences, which seem strongly conserved across taxa. Such differences imply that we need to describe which feather part was used in the methods of our reports to ensure full comparability and replicability among studies. Nevertheless, vane and rachis δ2H were strongly correlated, demonstrating that rachis can be also used in isotope analyses because its δ2H can be accurately rescaled. This is useful since rachis represents an important fraction of feather mass in songbirds. Values of δ2H from ground and non-ground samples from the same feather were also compared. There was no effect of the processing protocol, suggesting that grinding is unnecessary when working with passerine feathers.

Juvenile dispersal in an uninhabited continent: young Spanish Imperial Eagles in Africa Abstract The Spanish Imperial Eagle (Aquila adalberti) disappeared from Africa as a breeding species in the 1960s coincident with a general decline of their populations in the Iberian Peninsula. Because of a combination of successful conservation actions and a general change in human attitudes, the Spanish Imperial Eagle population has been increasing in Iberia from 103 pairs in 1980 to more than 500 breeding pairs in 2018. As a consequence, the number of juveniles that cross the Strait of Gibraltar into Africa has increased recently. Abundance and distribution of potential prey should affect young eagles’ behaviour and could be a limiting factor for a potential re-colonization of previous North-African populations. Additionally, determination of temporary settlement areas is crucial from a conservation point of view. Conservation actions in these areas, particularly reduction of juvenile mortality, are a priority to facilitate future reestablishment of breeding populations of the species in North Africa. Here we report on the dispersal movements of juvenile Spanish Imperial Eagles marked with GPS-GSM transmitters in Andalusia (southern Spain), some of which crossed the Strait of Gibraltar into north-western Africa, an area that does not have populations of the eagle’s main prey, the European rabbit. We analysed the differences in dispersal patterns and temporary settlement behaviour in the two study areas. We found that dispersal movements were greater, temporary settlement areas were larger, and individuals stayed longer in areas and moved greater distances among them in Africa than in Iberia. We believe that our results are best explained by applying the Marginal Value Theorem, which predicts that individuals will leave a foraging area when the availability of prey drops to similar levels of those of the surrounding environment. We suggest that the increase in the records of the species in Africa could lead to a recolonization of the species in Africa based on birds coming from the “source” Iberian population, but only if the Iberian population continues to increase. We recommend that conservation measures must be established in these temporary settlement areas in Africa.

Dupont’s Lark males start to sing earlier but reduce song rate on full moon dawns Abstract Moon phase affects the ecology and behaviour of animals and may thus affect both circadian and circannual rhythms. Its influence on nocturnal and dawn bird behaviour is known, but fewer studies have examined its effect on passerines’ singing activity, some of which have yielded contradictory findings. With the aim of elucidating whether moon phase affects dawn singing in passerines, we recorded dawn singing activity of the Dupont’s Lark Chersophilus duponti in three mediterranean shrub-steppes, through repeated sampling over three lunar cycles per breeding season in 2 years. Our results corroborate the idea that moon phase affects signalling behaviour of passerines. We found that, on average, dawn singing started 15 min earlier when the moon was full, due to variations in the light intensity, which seems to act as a trigger for singing activity in the Dupont’s Lark. Nonetheless, the dawn chorus finished at the same time regardless of moon phase, maybe due to a low contribution of moonlight as sunrise approaches. As a consequence, performance time increased during full moon nights. However, the total production of songs did not differ between moon phases, and therefore, song rate was lower during full moons. Reduced song rate on full moon nights could be a response of singing males to reduce their predation risk, since singing on bright nights can increase the ability of predators to locate them, but it could be also related to the energetic cost of longer choruses. The consequences of moon phase for mate attraction, reproductive success and behaviour in this and other bird species remain unknown, and thus our research can serve as a starting point from which to develop new studies.

Self-recognition in corvids: evidence from the mirror-mark test in Indian house crows ( Corvus splendens ) Abstract The ability to recognize oneself is separate from recognizing a conspecific. Self-recognition is a higher cognitive function and generally tested by a mirror-mark paradigm, in which the individual recognizes and responds to an inconspicuously placed mark on body from its mirror-reflected image. Although initially suggested to be associated with large-brained mammals, the ability of self-recognition has now been shown in non-mammals, including fish and birds. Hence, studies on many more species might be useful to understand general principles and underlying mechanisms of the evolution of social intelligence. Here, we examined self-recognition ability in Indian house crows (Corvus splendens), by testing them first for mirror-induced responses and then for the mark-directed responses. A circular coloured mark was inconspicuously placed on the throat under the bill where crows could see it only from its mirror-reflected image; a similar black mark placed at identical location which was difficult to be seen served as the control condition. We evaluated how closely crows viewed and inspected the object, and expressed social, contingent and self-directed responses to the mirror and cardboard. Crows exhibited greater preference in response to the mark when in front of the mirror, compared to they were in front of the non-reflective black cardboard. The majority (4/6) crows responded to the mirror-reflected self-image, as evidenced by attempts to remove the coloured mark by using beak or claws; no such response was found in control condition. These results suggest self-recognition by Indian house crows, and support the growing evidence that the ability of self-recognition is more widely present among animals.

Testing for the effect of meteorological conditions on transient dynamics of a reed warbler Acrocephalus scirpaceus population breeding in northern Iberia Abstract Transients can have a severe impact on demographic parameter estimates. For instance, the use of visual counts or number of captures at a ringing station to assess indices of abundance may result in biased over-estimates due to the presence of transients. With the aim of contributing to understand transient dynamics within the Eurasian breeding passerines, we used data collected at a ringing station (2010–2018) in a reed bed area of northern Spain designed to sample breeding reed warblers Acrocephalus scirpaceus. Specifically, we tested for the effect of season on the proportion of transients and explored for correlations of rainfall regimens at both the winter and breeding quarters on annual fluctuations of the proportion of transients. The proportion of transients was not constant across the season; it showed relatively small values until mid-June, coinciding with arrivals from Africa and the peak of the breeding period, and then increased very steeply (means > 60%) already in July, with even ca. 90% of transients captured during the second half of July, coinciding with an influx of birds that would be already passing through the area en route to winter quarters in Africa. Analyses to estimate population trends of breeding reed warblers should take this circumstance into account; otherwise, models may show odd patterns, due to a mixture of local and non-local population that might show dissimilar demographic trends. Limiting data analyses to the breeding sub-period having a lesser amount of transients is recommended. Annual fluctuations in the proportion of transients did not correlate with any of the rainfall values in Africa (winter quarters) or meteorological conditions in Europe (NAO index; rainfall values at a local level), though it might be that we did not choose the appropriate variable/period/location combination. Our data set was relatively small; hence, this may hamper us to detect weak linear trends. Future research should contribute to answer this question and deep into the factors driving transience dynamics in bird populations.

Movements of three alcid species breeding sympatrically in Saint Pierre and Miquelon, northwestern Atlantic Ocean Abstract Among seabirds, alcids are particularly sensitive to bycatch in fisheries and oil pollution, yet their distribution at sea remains scarcely known in most of their breeding areas. GPS telemetry data of fifteen individuals of alcids (5 Razorbills 6 Common Murres and 4 Puffins) were analyzed to determine their distribution during the breeding period of 2016 at Saint Pierre and Miquelon Archipelago (SPM). Two analytical methods (threshold and a switching state-space model) were used to identify behavioral modes and foraging areas. We compared foraging movements and estimated the overlap between the species. Distribution and foraging covered an area located between SPM and Newfoundland. Our results revealed that the three species headed northward of their breeding colony, targeting coastal waters. Nonetheless, the three species differed in their habitat distribution as well as in their space-use sharing. There was limited overlap between the foraging zones of the three species and a gillnet fishery targeting Atlantic salmon. Identifying alcids habitat use is imperative to the successful management and survival of these marine species especially since the distribution areas coincide with fishing pressure.

Habitat structure affects nest predation of the Scaly-crowned Babbler ( Malacopteron cinereum ) by macaques and snakes in a Thai-seasonal evergreen forest Abstract Nest success of forest birds is typically low due to high rates of predation, but little is known regarding how different nest predators affect nest-site selection and nesting success, particularly in the tropics. We studied nest-site selection and nest success of the understory-nesting Scaly-crowned Babbler (Malacopteron cinereum) in a seasonal evergreen forest in northeastern Thailand during four breeding seasons. We identified nest predators using video-monitoring and examined relationships between nest site vegetation structure and nest predation by dominant predators. Based on 71 video-monitored nests, 98.5% of failures were due to predation; 59 predation events from nine predator species were documented including Northern Pig-tailed Macaque (Macaca leonina) (47.5%, n = 28), five avian predator species (32.2%, n = 19), and two snake species (18.6%, n = 11). Nest sites had significantly higher concealment and number of lianas than random sites. Higher concealment may represent selection against visually oriented predators which were responsible for approximately 80% of predation events. Vegetation parameters suggested opposing patterns for macaques versus snakes; nests surrounded by higher density of saplings and lower density of taller stems (5–10 m) were depredated by macaques, whereas snake depredated nests were associated with a lower density of saplings, a higher density of taller stems and a higher density of lianas. Nests depredated by avian predators were not associated with any measured variables. Our data suggest that different vegetation structures perhaps facilitate or impede different predators and different predators may generate conflicting selection pressures for nesting birds within a given habitat. Our data also imply that impacts on nesting success from vegetation disturbance (e.g., logging, road edges, etc.) may be difficult to predict, as these effects are likely to vary among sites and regions depending on the foraging behavior of dominant local predators.

Photography as a tool for avian morphometric measurements Abstract Accurate morphometric measurements of birds are frequently needed in studies to provide an index of body size. However, obtaining these measurements in the field can be challenging and inter-observer repeatability of taking these measurements using calipers has been questioned in the literature. Here we present a method for measuring tarsus length and bill length, width and depth using digital photography with open source software (ImageJ), and we compare the repeatability and handling time of the digital measurements with those traditionally made using calipers. The digital method was more or equally repeatable than manual measurements of bill and tarsus and its repeatability was independent of measurement length, making it especially suited to making shorter measurements. While digital and manual measures were highly correlated for all body measures, the digital method produced slightly higher measurements in all cases meaning digital and manual measurements may not be directly comparable. Morphometric measurements made from digital photographs were possible with a significantly shorter bird handling time, can be completed by less experienced fieldworkers, and create a permanent record that can be later verified, making them a useful alternative to traditional manual measurements of unfeathered skeletal body parts which can be clearly visualized in photographs.

Age-, sex- and tactic-specific kleptoparasitic performance in a long-lived seabird Abstract Kleptoparasitism is an exploitative foraging strategy used across taxa, but factors underlying variation in the foraging performance of individuals using it have not often been addressed. Using longitudinal data on Common Terns stealing food from conspecifics during breeding, we show that variation in the energetic reward of kleptoparasitic behaviour is explained by interactive effects of sex and the attack tactic used by the parasite, as well as by age. Males obtain a higher reward when using an aerial than a terrestrial attack tactic, with decomposition analyses showing that this is due to the energy content of chased after prey items being higher in their aerial attacks. On the other hand, females obtain a higher reward when attacking terrestrially, which is due to their success rate being higher on land than in the air. In addition, the birds show decelerating within-individual improvement with age, which is due to individuals chasing after prey with a higher energy content as they grow older. Our study not only pinpoints factors underlying variation in the foraging performance of kleptoparasites, but also illustrates the importance of modelling individual variation when analyzing foraging performance.

A new Myzomela honeyeater (Meliphagidae) from the highlands of Alor Island, Indonesia Abstract We here describe a new species of Myzomela honeyeater from the Lesser Sunda island of Alor (southeast Indonesia). The new species is phylogenetically most closely related to Myzomela kuehni from the adjacent island of Wetar and most closely resembles that species in plumage. However, it differs in important morphological, bioacoustic and ecological characteristics. The discovery of a new bird species on Alor is of great biogeographic importance and elevates this island to the status of an Endemic Bird Area. The new Alor Myzomela is restricted to montane eucalypt woodland mostly above 900 m elevation and is currently known from few sites across the island. Based on its occurrence records and human population trends in the highlands of Alor Island, we recommend classification under the IUCN threat status endangered.