The potential for agri-environment schemes to reverse farmland bird declines is limited for some species by a lack of suitable prescriptions, in particular effective in-field options for species that breed in crops. We assess the provision of alternative nesting habitat for increasing productivity of the Corn Bunting Emberiza calandra. Breeding success was monitored over three years in response to a tailored option that provided extensively managed crops of spring-sown barley, most of which were funded by existing agri-environment schemes and were left unharvested. Corn Buntings nested in both extensively managed crop provisions and conventional intensively managed barley crops. Females that used extensively managed crops for first nesting attempts were almost four times more likely to re-nest, despite their later onset of breeding, than females nesting in conventional crops. The latter rarely produced a second nest and, when they did, usually switched nesting habitat. Extensively managed cereal crops were strongly selected by breeding females and supported a high proportion of the breeding population. A re-nesting model demonstrated that differential re-nesting rates led to 26% higher annual productivity per female in extensively managed cereal crops. Scenario testing illustrated the importance of timely establishment and deferred harvest of these extensively managed cereals. We recommend the provision of unharvested, extensively managed cereal crops as an agri-environment option for Corn Buntings where intensively managed cereal crops are the main nesting habitat.

Costs of reproduction represent a common life-history trade-off. Critical to understanding these costs in migratory species is the ability to track individuals across successive stages of the annual cycle. We assessed the effects of total number of offspring fledged and date of breeding completion on pre-migratory body condition, the schedule of moult and annual survival in a migratory songbird, the Savannah Sparrow Passerculus sandwichensis. Between 2008 and 2010, moult was delayed for individuals that finished breeding later in the breeding period and resulted in reduced lean tissue mass during the pre-migratory period, suggesting an indirect trade-off between the timing of breeding completion and condition just prior to migration. Lean tissue mass decreased as the number of offspring fledged increased in 2009, a particularly cool and wet year, illustrating a direct trade-off between reproductive effort and condition just prior to migration in years when weather is poor. However, using a 17-year dataset from the same population, we found that parents that fledged young late in the breeding period had the highest survival and that number of offspring fledged did not affect survival, suggesting that individuals do not experience long-term trade-offs between reproduction and survival. Taken together, our results suggest that adult Savannah Sparrows pay short-term costs of reproduction, but that longer-term costs are mitigated by individual quality, perhaps through individual variation in resource acquisition.

Winter body condition may play important roles in the life history of migratory birds, but it is difficult to estimate. We used the growth rate of winter-grown tail feathers of Collared Flycatchers Ficedula albicollis as an indicator of winter body condition, comparing this trait between age classes and sexes and relating it to plumage ornamentation (forehead and wing patch sizes). Adults and males were in better nutritional condition during winter, as indicated by their faster tail feather growth rates, than were yearlings and females, respectively, which could indicate differences in individual quality and foraging ability with age, or age- and sex-related winter habitat segregation. However, feather growth rate was related neither to the size of the winter-grown forehead patch nor to the size of the summer-grown wing patch, suggesting weak condition-dependence for the winter-grown ornament and complex life-history consequences for the summer-grown ornament.

To understand population dynamics it is necessary to understand vital rates, which may be affected by a wide range of factors including environmental variables such as weather. Weather conditions can affect birds’ vital rates directly through increased mortality due to impaired conditions, or indirectly via changes in body condition and/or behaviour. Most understanding of direct and indirect effects of weather comes from studies of breeding birds, whereas the situation in non-breeding periods is less clear. Here, we analysed annual survival of non-breeding Mallard Anas platyrhynchos, the most hunted waterfowl species in Europe, and assessed whether survival is related directly to winter harshness and/or indirectly via changes in winter recovery distributions. Recovery data on Mallards, initially marked in southeast Sweden, were analysed with an information-theoretic approach using program mark. Over 10 000 Mallards were marked in two time periods, 1964–1982 and 2002–2008, of which 13.3 and 4.7%, respectively, were later recovered. Mallards had lower annual survival in the early trapping period (0.58–0.63) than in the later period (0.69–0.71), with no clear effects of sex, age or year. Within each study period, winter harshness did not directly correlate with survival. However, milder winters may have contributed indirectly to higher survival in the second period, as winter harshness data were correlated with the distances to recovery positions for females, and also because winter recovery areas have shifted northeast during the past decades, possibly indicating a shortened migratory distance. Migration is costly, and there is therefore a likely linkage between migration behaviour and survival of dabbling ducks, in which direct as well as indirect effects of winter harshness may play a role. Other factors, such as hunting pressure, are also likely to have changed in the past decades, and may also have contributed to improved survival of Mallards in northwest Europe.

Although male age has often been found to predict success in gaining extra-pair paternity, it is unclear whether this gain is associated with an individual’s success in avoiding cuckoldry. We examined the relationship between male age and both within- and extra-pair paternity in passerines using a meta-analytical approach. There was a positive correlation between male age and success in extra-pair paternity but little evidence for an association between male age and within-pair paternity. In addition, effect sizes for male within-pair paternity and male extra-pair paternity were not significantly correlated. Thus, factors that predict success in obtaining extra-pair paternity, such as male age, may not necessarily predict success in avoiding cuckoldry.

Recent improvements in satellite tracking, such as the miniaturization of transmitters, have enabled the study of movements of an increasing number of bird species. The Lesser Kestrel Falco naumanni has been the subject of numerous studies but detailed information on its migration routes and wintering areas is still lacking. Here, we provide a detailed description of migration routes, timing of migration and wintering areas of Lesser Kestrels. Five adults fitted with satellite transmitters in southeastern Spain were tracked during autumn and spring migration journeys and on their wintering grounds. The overall migration duration was longer in spring than in autumn, although birds also showed longer stopovers in this season and hence the number of travelling days was lower. Lesser Kestrels covered longer daily distances in spring due to a higher frequency of nocturnal migration, rather than differences in flight speed, which did not differ between seasons. Wintering areas of Lesser Kestrels from the same breeding colony were widely spaced throughout the western Sahel along the borders of Mauritania, Mali and Senegal, approximately 2800 km from their breeding sites. The autumn migration duration of Lesser Kestrels derived from recent studies using geolocators was underestimated compared with that recorded by satellite telemetry. Given the current rapid habitat loss in the Sahel, a better understanding of migratory routes and wintering areas of other populations of this species would be important to assess its influence on population trends.

In some bird species, the survival of chicks hatching later in the season is lower than those hatched earlier due to increased risk of predation and a seasonal decline in feeding conditions. To reduce these risks, it might be advantageous for late-hatched chicks to grow faster and hence fledge at younger age. In this experimental study, the growth rates of early- and late-hatched Rhinoceros Auklet Cerorhinca monocerata chicks were compared under average and poor food supplies in captivity. Controlling for potentially confounding effects of chick mass at 10 days old, chick age and nest-chamber temperature, late-hatched chicks had higher wing growth rate than early-hatched chicks before attaining the minimum wing length required for fledgling under both average and poor food supplies. After attaining the minimum wing length, however, late-hatched chicks had a lower fledging mass, indicating a potential cost that could diminish the early advantage of fast wing growth.

Parentage studies have shown that alternative reproductive strategies are widespread in many avian taxa that were once thought to be monogamous. Recent anthropogenically mediated habitat change may have disrupted ecological factors, such as breeding density, which have given rise to inter- and intraspecific variation in the frequency of extra-pair fertilization (EPF) and intraspecific brood parasitism (IBP). We used genetic analyses to quantify the incidence of alternative reproductive strategies exhibited within clutches of Canada Geese Branta canadensis maxima nesting in high- and low-density situations in and around urban areas in southern Michigan, USA. We tested the hypothesis that high nesting density would increase the frequency of EPF and IBP. There were no significant differences in rates of EPF and IBP clutches (14 and 26% of clutches, respectively) from nests in high-density (21.7% EPF, 21.7% IBP) vs. low-density (5.3% EPF, 31.6% IBP) areas, although high-density sites had a fourfold higher rate of EPF. Rates of EPF and IBP in high-density urban areas in Michigan were comparable to rates observed in other species nesting under different ecological conditions. Levels of relatedness between host and parasitic females were higher than expected by chance, suggesting that related females are more tolerant of one another and that host females could gain inclusive fitness benefits from rearing parasitic offspring. Our study highlights the importance of understanding the different costs and benefits associated with alternative behavioural repertoires that may vary as habitats and associated selection pressures are increasingly modified by human activities.

Age-related improvement in reproductive success is widely observed in birds, and the mechanisms by which productivity is enhanced have received considerable attention. However, little is known about how parental age affects the loss of eggs or nestlings despite the fact that age effects on nesting success are often reported. We examined parental age effects on reproductive success in relation to the avoidance of nest predation in an island subspecies of the Japanese White-eye, the Daito White-eye Zosterops japonicus daitoensis. Clutch size and annual number of breeding attempts did not differ between parental age classes. Reproductive success was affected only by male age through an increase in nesting success. Nest failure was attributed only to predation in this species and nest concealment and nest height were important nest characteristics promoting successful fledging. Older males built their nests in more concealed and higher positions than first-year birds, regardless of vegetation status around the nest. Analysis of individual birds suggested that by shifting the nest to a safer position, male White-eyes achieved higher nesting success than in the previous year. Of three hypotheses of age-related improvement in reproductive success considered, our data favoured the hypothesis that as individuals grow older, their breeding competence improves.

The effects of visits to nests by researchers interested in quantifying avian nesting success have received considerable attention, as researchers have long been concerned about the possible negative effects of their own activities on the resulting estimates. There is a widely held view that investigator disturbance has an overall negative effect on breeding success by increasing nest predation rates in the nests studied. However, to date no one has statistically assessed the empirical evidence for such a relationship. We undertook a meta-analysis of published results to assess whether researcher activities increase nest predation in birds. We also assessed the variability in this effect in relation to the traits of the study species and the methodology used. These analyses used data from 18 experimental studies involving 25 species from six avian orders. Our results suggest that, contrary to the traditional view, researcher activities do not generally affect the incidence of nest predation. Moreover, this relationship appears inconsistent among avian orders and, surprisingly, nest survival of passerines increased weakly with researcher activities. We also found significant positive effects of researcher activity on nest survival for species breeding on coastal areas and for species nesting on the ground. The possible explanation for these differences among orders and guilds could be due to different nest predator communities. This new perspective on the effect of investigators could have important implications for bird management and conservation, as well as for other fields of study such as ecology and evolution, in which nest survival rates measured in the field are widely used to test and support a range of hypotheses.

Effective DNA extraction methods from bird feathers have facilitated non-invasive sampling, leading to the suggestion that feathers are a great source for genetic studies. However, few studies have assessed whether all feathers can be used or provide equal numbers of useful templates. In this study, feathers collected in various ways from Red Grouse Lagopus lagopus were examined to establish the quality of DNA extracted. Individual samples were classified into two categories according to whether they were collected from shot birds or found in the field. DNA was extracted from all samples and genotyped at 19 microsatellite loci. PCR products were analysed on a MegaBACE 1000. A total of 93% of the ‘shot’ category produced a genotype that was considered successful (i.e. 15 of 18 loci) and 23% of the ‘collected’ category produced successful genotypes under the same criteria. There was a significant difference between shot and collected samples in genotyping success and the observed number of missing loci. Recommendations and best practices are discussed along with the utility of bird feathers as a source of DNA for population and conservation biology.

The levels of haematocrit (Hct) and plasma haemoglobin (Hb) vary markedly through the annual cycle of birds, as well as among individuals at all life-stages (embryos, chicks, adults). It is thus surprising that the functional, fitness-related consequences of this variation are poorly understood. Putative ‘adaptive’ variation in these haematological traits has been associated with varying demands for aerobic capacity and oxygen transport, for example during migration, winter acclimatization, with increasing altitude, or during parental care. It has also been proposed that changes in Hct might reflect ‘costs’ of parental investment, for example during ‘reproductive anaemia’. However, almost all studies to date have been correlative. Here we describe a series of experiments that validate the use of phenylhydrazine hydrochloride (PHZ) for the transient, reversible experimental manipulation of Hct and Hb in birds. A single bolus injection (12.5 μg PHZ/g body weight delivered via intra-muscular injection) caused a rapid decrease in Hct and plasma Hb within 24 h, from pretreatment values of 50–54% to 40–44% in non-breeding Zebra Finches Taenipoygia guttata and European Starlings Sturnus vulgaris, and to 35% in breeding female Zebra Finches, changes within the normal physiological range. Hct and Hb returned to pre-injection levels within 5–10 days of treatment. Changes in plasma Hb paralleled those for Hct. We suggest that PHZ treatment provides a widely applicable technique for use in experimental work to establish relationships between haematological status, aerobic capacity, workload (e.g. migration, parental care, thermoregulation), individual quality (of both adults and chicks) and trade-offs such as costs of reproduction.

Detecting and predicting how populations respond to environmental variability are eminent challenges in conservation research and management. This is particularly true for wildlife populations at high latitudes, many of which demonstrate changes in population dynamics associated with global warming. The Falkland Islands (Southwest Atlantic) hold one of the largest Gentoo Penguin Pygoscelis papua populations in the world, representing c. 34% of the global population. The numbers of breeding Gentoo Penguins at the Falkland Islands have shown a high degree of inter-annual variability since monitoring commenced in 1990. However, proximate causes of annual variability in breeding numbers have not been explored. Here we examine 21 years of Gentoo Penguin breeding surveys from the Falkland Islands and assess whether inter-annual variability in the number of breeding pairs were correlated with proxies of environmental variability. There was a positive correlation between the number of breeding pairs and a broad-scale climatic variation index, the Southern Oscillation Index (SOI). In turn, the SOI was significantly correlated with spring sea surface temperature anomalies, indicating a more immediate atmospherically forced response to El Niño Southern Oscillation variability in the Southwest Atlantic than previously reported. However, we also describe a non-linear response to environmental variability that may highlight foraging plasticity and/or the complexity of regional ecosystem interactions that operate across a range of different scales.

The migrations and winter distributions of most seabirds, particularly small pelagic species, remain poorly understood despite their potential as indicators of marine ecosystem health. Here we report the use of miniature archival light loggers (geolocators) to track the annual migration of Sabine’s Gull Larus sabini, a small (c. 200 g) Arctic-breeding larid. We describe their migratory routes and identify previously unknown staging sites in the Atlantic Ocean, as well as their main Atlantic wintering area in the southern hemisphere. Sabine’s Gulls breeding in northeast Greenland displayed an average annual migration of almost 32 000 km (n = 6), with the longest return journey spanning close to 39 000 km (not including local movements at staging sites or within the wintering area). On their southern migration, they spent an average of 45 days in the Bay of Biscay and Iberian Sea, off the coasts of France, Spain and Portugal. They all wintered in close association with the cold waters of the Benguela Upwelling, spending an average of 152 days in that area. On their return north, Sabine’s Gulls staged off the west African coast (Morocco, Mauritania, Senegal), spending on average 19 days at this site. This leg of migration was particularly rapid, birds travelling an average of 813 km/day, assisted by the prevailing winds. Sabine’s Gulls generally followed a similar path on their outbound and return migrations, and did not exhibit the broad figure-of-eight pattern (anti clockwise in the southern hemisphere and clockwise in the northern hemisphere) seen in other trans-equatorial seabirds in the Atlantic and Pacific oceans.

Studies of migration have revealed multiple trade-offs with other life-history traits that may underlie observed variation in migratory properties among ages and sexes. To assess whether, and to what extent, body size and/or sex-specific differences in competition for resources (e.g. breeding territories or winter food) may shape variation in migration distance and timing of arrival in ecologically and phylogenetically related species, we combined over 30 000 sightings of individually marked, sexually mature males and females of Herring Gulls Larus argentatus and Lesser Black-Backed Gulls Larus fuscus with biometric measurements and phenological observations at a mixed breeding colony. In L. argentatus, larger males migrated further from the breeding colony, whereas migration distance was independent of body size in adult females. In L. fuscus, no relationship between body size and migration distance was apparent in either sex. Mean arrival dates at the breeding colony did not vary with migration distances but differed between males and females of L. argentatus (but not L. fuscus). As allometry at least partly explains sexual segregation in migration behaviour in L. argentatus, but not in L. fuscus, we conclude that the effect of body size on sex-related migratory strategies may vary between closely related, sympatric species despite similar size dimorphism.

Most tropical booby species complete breeding foraging trips within daylight hours, thus avoiding nights at sea. Nazca Boobies Sula granti are unusual in this respect, frequently spending one or more nights away from the nest. We used GPS dataloggers, time-depth recorders, and changes in body weight to characterize foraging trips and to evaluate potential influences on the decisions of 64 adult Nazca Boobies to spend a night at sea, or to return to their chicks on Isla Española, Galápagos, in daylight hours. The tagged birds foraged east of Isla Española, undertaking both single-day (2–15 h, 67% of trips) and overnight trips (28 h–7.2 days, 33%), and executing 1–19 foraging plunge-dives per single-day trip. Birds might forage longer if they are in nutritional stress when they depart, but body weight at departure was not correlated with trip length. Birds might be expected to return from longer trips with more prey for young, but they returned from single-day and overnight trips with similar body weights, consistent with previous indications that Nazca Boobies forage until accumulating a target value of prey weight. Birds with a lower dive frequency during the first 5 h of a trip were more likely to spend the night at sea, suggesting that they might choose to spend the night at sea if prey capture success was low. At night, birds almost never dived and spent most of their time resting on the water’s surface (11.8–12.1 h, > 99% of the time between civil sunset and civil dawn). Thus, the night is an unproductive time spent among subsurface predators under low illumination. The birds’ webbed feet provided evidence of this risk: 24% of birds were missing > 25% of their foot tissue, probably due to attacks by predatory fish, and the amount of foot tissue lost increased with age, consistent with a cumulative risk across the lifespan. In contrast, other tropical boobies (Blue-footed Sula nebouxii and Brown Boobies Sula leucogaster), which do not spend the night on the water, showed no such damage. These results suggest that chick-rearing Nazca Boobies accept nocturnal predation risk on occasions of low prey encounter during a foraging trip’s first day.

Mating between close relatives can have deleterious effects on reproductive success or offspring fitness, which should favour the evolution of active or passive inbreeding avoidance mechanisms. In birds, evidence for active inbreeding avoidance by kin-discriminative mate choice is scarce; many studies describe random mating in relation to kinship and thus support passive inbreeding avoidance by natal dispersal. However, most studies were conducted in island populations of short-lived passerines with fast alternation of generations. In this study, we present inbreeding estimates based on pedigree data from a 16-year study in a coastal colony of Common Terns Sterna hirundo, a long-lived seabird with delayed sexual maturation and low rates of extra-pair paternity. Incestuous mating was rare (four of 2387 pairs), even if partially accounting for incomplete pedigrees. Although the average relatedness of observed pairs was lower than would be expected from random pairing, the inbreeding coefficient did not differ from random mating. Hence, we found no clear evidence for active inbreeding avoidance by kin-discriminative mate choice, and the low level of inbreeding seems to be related to the high immigration rate in the colony and thus to be maintained passively by dispersal.

A detailed knowledge of the habitat requirements of steppe birds living in farmland habitats is necessary to identify agricultural practices compatible with their conservation. The globally threatened Great Bustard Otis tarda is a partial migrant in central Iberia, but factors affecting its winter habitat use have not been identified. We assessed habitat differences between breeding and wintering areas and winter habitat selection of radiotagged migrant female Great Bustards in central Spain. Of 68 tagged females, 35% moved to wintering areas located 64.3 ± 24.0 km south of their breeding areas, and 80% wintered in a single area of c. 236 km². A census of the population in this area identified it as one of the most important wintering areas of this species in the world, holding c. 1500 individuals. There were significant differences between breeding and wintering habitats of individually marked migrant females. Compared with breeding areas, wintering areas of migrant females were located further from roads and urban nuclei, had lower human population densities and area of urban developments, and a higher diversity of land-use types, with less cover of cereals and more vineyards and olive groves. Within this area, radiotracked migrant females preferred sites with more vineyards and a lower land-use diversity. Our results highlight the importance of traditional Mediterranean dry farmland mosaics, and suggest that different conservation strategies are needed for migrant and resident populations in winter to secure the conservation of suitable wintering habitat for Great Bustards in the Iberian Peninsula.

The floodplains of the West-African Sahel region have experienced extensive habitat transformation during the past four decades, coinciding with an impoverishment of raptor populations. We investigated foraging patterns of Palaearctic migratory Eurasian Marsh Harriers Circus aeruginosus, Pallid Harriers C. macrourus and Montagu’s Harriers C. pygargus on a floodplain system in northern Cameroon to assess species, sex- and age-related habitat preferences. Sex and age have rarely been incorporated into general studies of raptor habitat associations, despite clear evidence of intrasexual and age-related differences in foraging strategies and diet composition, potentially carrying strong conservation implications. We found evidence of sexual differences in foraging preference related to land use, particularly in the most sexually dimorphic Pallid Harrier, and evidence that juveniles used different habitats to adults. This constitutes the first quantitative documentation of such differentiation by Palaearctic raptors on African wintering grounds, indicating that general patterns of habitat use in wintering raptors may obscure sex- and age-specific preferences. Contrary to expectations, we found limited evidence for interspecific foraging segregation. Food partitioning by prey mass was related to harrier body mass and facilitated by a diverse availability of prey on human-transformed floodplains. Anticipated further large-scale conversion of floodplain habitat into predominantly desiccated grasslands raises concerns about the survival of wintering harriers.

Spatial and temporal variation in prey abundance have been shown to impact the time of breeding and breeding success of birds. Understanding the ecological requirements of preferred prey can help develop management measures to improve food supply for target species. For the colonial Lesser Kestrel Falco naumanni, mole crickets Gryllotalpa spp. are one of the most important prey items during the mate-feeding period. Lesser Kestrel colonies with higher mole cricket consumption had earlier egg-laying dates, suggesting that differences between individuals in the time of breeding could be caused by differences in the diet. Moreover, the mean number of mole crickets in pellets was significantly correlated with clutch size (in one of the studied years) and egg volume. Thus, the impact of environmental variables and land use on mole crickets is likely to be relevant to Lesser Kestrel conservation. Weekly consumption of mole crickets was higher following an increase in either precipitation or minimum temperature values. Furthermore, mole cricket consumption was higher in colonies surrounded by higher quality soils and in wetter areas and years. Predicted probability of mole cricket occurrence in surveyed watercourse margins suggested a positive relationship between soil penetrability and mole cricket occurrence. Among variables that might be the target of management, the presence of riparian vegetation positively influenced the occurrence of mole crickets, whilst tillage and sowing of streambeds were revealed as the most important threats. We suggest that the maintenance of native vegetation in the margins of watercourses could improve soil resilience to erosion, increase water retention, soil penetrability and fertility, and provide a food supply and shelter for mole crickets. Overall, the implementation of such recommendations is likely to benefit other farmland species known to consume mole crickets, including several endangered species.

Understanding relationships between environmental conditions and reproductive parameters is important when interpreting variation in animal population size. The northwestern North American population of Golden Eagles Aquila chrysaetos canadensis initiates courtship and nesting in early spring when prey diversity is low and weather conditions are severe. Snowshoe Hare Lepus americanus and Willow Ptarmigan Lagopus lagopus, the primary prey of Golden Eagles early in their nesting season in interior Alaska, both exhibit cyclical fluctuations in abundance, providing the opportunity to investigate such relationships. We used Bayesian hierarchical models to explore variation in territory occupancy, nesting rates, nesting success and productivity of Golden Eagles from 1988 to 2010 in Denali National Park and Preserve, Alaska, in relation to annual and site-specific parameters including prey abundance, weather conditions, elevation and human activity. We also investigated the long-term fluctuations of breeding performance over the course of the study. The abundance of Hares influenced both the number of Eagles that laid eggs and the number of Eagles that produced fledglings. The conditions on the breeding ground did not explain observed declines in nesting rates and fledgling production, suggesting that other factors such as change in the age structure of the population, increased intraspecific competition or deterioration of migration and wintering habitat are driving the long-term trends of these parameters.

Poisoning by pesticides is considered one of the primary threats to the Red Kite Milvus milvus. We studied the diet of this raptor in an area of eastern France where the rodenticide bromadiolone is widely used to control Water Vole Arvicola terrestris outbreaks. A high degree of specialization for Water Voles was noted, as their remains were identified in all 119 pellets collected in autumn 2008, whereas other small rodent species and insects occurred in 27 and 9% of pellets, respectively. We estimated that Water Voles constituted 94% of the total biomass ingested by Red Kites under these conditions. Based on these data, the risk of secondary poisoning due to feeding on poisoned voles was assessed. Acute exposure on a single day was not considered a risk for Kites, but exposure to poisoned voles over 1 week represented the maximal risk for the Red Kite; the calculated dose of bromadiolone ingested by a Red Kite was 137 times higher than the toxicological benchmark for birds. A field survey in the studied area detected four dead Red Kites and one moribund bird in autumn 2008 but did not confirm that the cause of death was bromadiolone poisoning. We suggest that professional monitoring is needed to assess the impact of rodenticides on Red Kites in areas where voles are controlled.

Male and female European Robins Erithacus rubecula display their red breasts in year-round territorial contests. Despite the clear signalling role of the red breast, little is known about its sexual dimorphism or trends in size when Robins age. We studied these patterns in resident and migrant Robins in a Mediterranean population. Both male and female first-year Robins had smaller red breasts than second-year individuals. Females, but not males, showed a reduction in badge area after the second year of life, leading to sexual dimorphism in red breast area in the oldest Robins. The grey fringe around the red breast showed a steady increase in width in males when ageing, but not in females, also leading to sexual dimorphism in this trait among oldest Robins. The contrast between the red breast and its surrounding grey fringe was higher than that between the breast and the back at both high and low environmental light intensities. This suggests that the grey fringe could function as a frame to highlight the perimeter of the red breast, and that the Robin’s plumage is equally suited to display in open areas and forest understoreys. Our study suggests that the extent of the red breast and its grey frame could confer information about the age and sex of the birds, and thus be used as a signal in territorial contests and mating decisions.

Yearling birds generally display duller colours than adults. This may be due to selection favouring birds with more intensely coloured plumage or to an increase in colour after the first complete moult. Most research to date on the topic has been carried out on species with structural plumage coloration or with carotenoid-based coloration that is produced by the unmodified deposition of pigments. However, no study has been carried out on species whose carotenoids are metabolically modified before deposition. In this study, we assess age-related changes in the carotenoid-based coloration of European Serins, a species that metabolically processes carotenoids before they can be deposited into feathers. Birds were captured over consecutive years and we carried out both cross-sectional and longitudinal analysis. Adults had significantly greater values of lightness and chroma than yearling birds. However, there were no changes in plumage colour when analysing the same individuals captured in subsequent seasons. Plumage lightness and chroma of adult males after moult were related to body mass, suggesting a role of body condition on plumage coloration. Our results suggest that changes in plumage coloration with age in European Serins are due to a selection process that favours more intensely coloured individuals.

We quantified vigilance during feeding in the Zenaida Dove Zenaida aurita, a tropical species with stable pair-bonds and year-round territoriality. Both males and females decreased the proportion of time spent vigilant by 30% when feeding with their partner compared with when feeding alone. This reduction was achieved through increasing the length of inter-scan duration, while scan duration remained constant. No evidence was found for coordination of vigilance between pair members. The equal investment in vigilance by male and female Zenaida Doves might be related to the mutual benefits of long-term pair-bonding.

The secretive breeding behaviour of petrels makes monitoring their breeding populations challenging. To assess population trends of Cory’s Shearwater Calonectris diomedea, Bulwer’s Petrel Bulweria bulwerii and Macaronesian Shearwater Puffinus baroli in Tenerife from 1990 to 2010, we used data from rescue campaigns that aim to reduce the mortality of fledgling petrels attracted to artificial lights as proxies for trends in breeding population size. Despite increases in human population size and light pollution, the number of rescued fledglings of Cory’s Shearwater and Bulwer’s Petrel increased and remained stable, respectively, whereas numbers of rescued Macaronesian Shearwaters sharply declined. In the absence of more accurate population estimates, these results suggest a worrying decline in the Macaronesian Shearwater’s breeding population.

Male Golden-collared Manakins Manacus vitellinus perform an elaborate courtship display composed of acrobatic jumps between saplings delimiting a court on the forest floor. Males rehearse their displays for hours until they are executed with amazing precision and speed. Here we investigated the plasticity of the display by examining whether males modify their choreography in response to a disturbance, such as when a small branch is placed against one of the saplings. Male Manakins performed displays that were longer and lacked a key element that invites females to copulate, supporting the hypothesis that males learn a specific sequence of moves to build their choreography.

Unmanned aircraft systems (UAS) are remote-controlled devices capable of collecting information from difficult-to-access places while minimizing disturbance. Although UAS are increasingly used in many research disciplines, their application to wildlife research remains to be explored in depth. Here, we report on the use of a small UAS to monitor temporal changes in breeding population size in a Black-headed Gull Chroicocephalus ridibundus colony. This method makes it possible to obtain georeferenced data on nest locations without causing colony disturbance, which would not otherwise be possible via direct ground observations.

Between 2000 and 2009 we studied the diet and breeding success of Egyptian Vultures Neophron percnopterus in southern Spain. Wild species accounted for 74.9% of prey items (n = 1071) with a predominance of mammals (62.3%), followed by birds (20.8%) and reptiles (13.1%). Spatially, the diet was highly varied and not restricted to carcasses of livestock; wild Rabbits Oryctolagus cuniculus accounted for 54% of the overall remains. The spatial variability may reflect regional and local disparity in the availability of main prey. The temporal relationship between variation in trophic diversity and Vulture nesting productivity (both values showing a long-term decrease) might suggest a causal link between variation in diet and reproductive output. We hypothesize that high turnover rates could explain productivity variation as a consequence of the recruitment of less experienced individuals to the breeding population. This could in turn generate covariation between diet and reproductive output.

Survivorship in animals depends on both foraging activities and avoidance of predation, and thus behavioural decisions often reflect a trade-off between predation risk and foraging efficiency. In this experimental study, we compared behavioural responses of free-living adult and juvenile Willow Tits Poecile montanus to a conspecific alarm call in two treatments. The alarm call was played back when a focal bird was either not feeding, or feeding on a sunflower seed on the middle part of a spruce branch. When feeding at the time of the alarm call, juveniles more often stayed motionless or moved shorter distances than adults. Our results suggest that in hierarchical groups, juveniles are forced to take greater risks to maintain access to food or lack experience to optimize between food and safety.

The southern African subspecies of Jacobin Cuckoo Clamator jacobinus serratus is a brood parasite of a range of host species. While Jacobin Cuckoos do not evict host young, previous research has found that host young rarely survive the nestling period. Here we provide the first records of Jacobin Cuckoo parasitism of a new host species, the Southern Pied Babbler Turdoides bicolor. We investigate rates of brood parasitism and the survival of host young. The Southern Pied Babbler is one of the largest recorded hosts for Jacobin Cuckoos and, unusually, we find that host young tend to survive the nestling period and maintain similar body mass to host young in unparasitized broods. However, host young were less likely to survive to independence than young raised in unparasitized nests, suggesting a post-fledging reproductive cost to hosts.

We documented brood parasitism by the poorly studied Large Hawk-Cuckoo on a previously unknown host species, the Chinese Babax. Furthermore, we describe a new egg colour for the Large Hawk-Cuckoo. The parasitism rate of Chinese Babax nests over 4 years was 6.9% (11 of 159 nests), with significant temporal variation. The Large Hawk-Cuckoo laid immaculate white eggs that appeared non-mimetic to the blue Babax eggs, an impression that was confirmed by avian visual modelling. Nevertheless, most Cuckoo eggs were accepted by the host, suggesting that this host–parasite system may be evolutionarily recent.