Migratory behaviour in young individuals is probably developed by using a complex suite of resources, from molecular information to social learning. Comparing the migration of adults and juveniles provides insights into the possible contribution of those developmental factors to the ontogeny of migration. We show that, like adults, juvenile Icelandic Whimbrel Numenius phaeopus islandicus fly non‐stop to West Africa, but on average depart later, follow less straight paths and stop more after reaching land, resulting in slower travel speeds. We argue how the variation in departure dates, the geographical location of Iceland and the annual migration routine of this population make it a good model to study the ontogeny of migration.

Males and females often exhibit different behaviours during mate acquisition, pair‐bonding and parenting, and a convenient label to characterize these behaviours is sex role. The diverse roles that male and female shorebirds (plovers, sandpipers and allies) exhibit in mating and parenting have played a key role in advancing mainstream theories in avian ecology and behavioural biology including sexual selection, sexual conflict and parental cooperation. Recent advances in shorebird research have also highlighted the significance of the social environment in driving sex role behaviours by linking the adult sex ratio with breeding behaviour and population demography. Here we review the key advances in sex role research using shorebirds as an ecological model system. We identify knowledge gaps and argue that shorebirds have untapped potential to accelerate diverse research fields including evolutionary genomics, movement ecology, social networks and environmental changes. Future studies of sex roles will benefit from individual‐based monitoring using advanced tracking technologies, and from multi‐team collaborations that are facilitated by standardized data collection methodologies across different species in the field. These advances will not only contribute to our understanding of reproductive strategies, but they will also have knock‐on effects on predicting population resilience to environmental changes and on prioritizing species for conservation.

Birds display a rainbow of eye colours, but this trait has been little studied compared with plumage coloration. Avian eye colour variation occurs at all phylogenetic scales: it can be conserved throughout whole families or vary within one species, yet the evolutionary importance of this eye colour variation is under‐studied. Here, we summarize knowledge of the causes of eye colour variation at three primary levels: mechanistic, genetic and evolutionary. Mechanistically, we show that avian iris pigments include melanin and carotenoids, which also play major roles in plumage colour, as well as purines and pteridines, which are often found as pigments in non‐avian taxa. Genetically, we survey classical breeding studies and recent genomic work on domestic birds that have identified potential ‘eye colour genes’, including one associated with pteridine pigmentation in pigeons. Finally, from an evolutionary standpoint, we present and discuss several hypotheses explaining the adaptive significance of eye colour variation. Many of these hypotheses suggest that bird eye colour plays an important role in intraspecific signalling, particularly as an indicator of age or mate quality, although the importance of eye colour may differ between species and few evolutionary hypotheses have been directly tested. We suggest that future studies of avian eye colour should consider all three levels, including broad‐scale iris pigment analyses across bird species, genome sequencing studies to identify loci associated with eye colour variation, and behavioural experiments and comparative phylogenetic analyses to test adaptive hypotheses. By examining these proximate and ultimate causes of eye colour variation in birds, we hope that our review will encourage future research to understand the ecological and evolutionary significance of this striking avian trait.

Protected areas are one of the most widespread and accepted conservation interventions, yet population trends of species within protected areas are rarely compared to regional trends to gain insight into their effectiveness. Here, we leverage two long‐term community science datasets, finding mixed effects of protected areas on long‐term bird population trends. We analyzed 31 years of bird transect data recorded by community volunteers across all major habitats of Stanford University's Jasper Ridge Biological Preserve to determine the population trends for a sample of 66 species. We found that nearly a third of species experienced long‐term declines and, on average, species declined by 12%. Further, we averaged species trends by conservation status and key life history attributes to identify correlates and possible drivers of these trends. Observed increases in some cavity‐nesters and declines of scrub‐associated species suggest that long‐term fire suppression may be a key driver, reshaping bird communities through changes in forest and chaparral structure and composition. Additionally, we compared our results to those of the North American Breeding Bird Survey's Central California Coast region (n = 55 species) to place Jasper Ridge in a broader context. Most species experienced similar directional population trends inside and outside of the preserve, and only eight species (14.5%) did better inside this small protected area. Therefore, we must identify relevant management strategies for declining populations and explicitly consider how existing protected areas target and manage each species. Further, this analysis underscores the importance of local and national community science for revealing long‐term bird population trends.

For practical reasons, assessments of species’ vulnerability to rising temperatures are often limited to measuring responses to a single ecological response variable, but this could result in an underestimation of vulnerability. Using the Cape Rockjumper Chaetops frenatus (‘Rockjumper’) we examined the thermal risk to nestling Rockjumpers for lethal (i.e. increased nest predation) and sublethal (i.e. reduced nestling mass gain) consequences of sustained hot weather under both current and predicted future climatic conditions (RCP 8.5). We used a mechanistic approach to examine these risks, first as independent ecological responses and then as combined risk driven by both response variables (mass gain and predation risk). This study revealed that the inclusion of multiple climate‐related responses affected the predicted vulnerability to climate change. Further, our analyses showed that increased vulnerability to climate change will vary within the Rockjumper's habitat. Our results demonstrate the variability in predicted thermal risk depends on which response variable was used, with implications for how and where conservation practitioners direct their already limited resources.

Information on migratory connections provide a basis for effective conservation efforts. The spatial connections between breeding and wintering areas are poorly known for many species. The connections become complicated in species that carry out additional migrations between their breeding and wintering areas. Common Shelducks (Tadorna tadorna, hereafter Shelducks) in western Europe perform an extensive moult migration after the breeding season. In this study, we examined the geographic connections between the breeding and wintering areas to identify ecological patterns, and estimate the influence of moult migration. Possibly patterns would be to winter: (I): in distant and separate areas; (II) in a moulting area; (III) in the vicinity of a moulting area; (IV) near the individual breeding area. Further there might be individuals who breed, moult and winter in the same area (V) Sedentary. We analysed recoveries of ringed Shelducks from the EURING databank and count data from the International Waterbird Census, and tracked 11 individuals from a German breeding population using GPS transmitters. We found evidence of all possible wintering patterns in Shelducks breeding in regions of Europe with long‐term mean January temperatures at least slightly above 0°C. Shelducks from cold parts of Europe always migrated to separate and warmer wintering areas. Shelducks from warmer regions used diverse patterns even within the same breeding populations. Some individuals used wintering areas near or in a moulting area, even if that area was sometimes colder than their breeding area. Our results support the idea that the location of the moulting area influenced the geographic position of the wintering area. Furthermore, the observed low migratory connectivity and high diversity in wintering patterns support the idea that Common Shelducks are able to adapt to changing environmental conditions.

Survival estimates are critical components of avian ecology. In well‐intentioned efforts to maximize the utility of one's research, survival estimates often derive from data that were not originally collected for survival assessments, and such post hoc analyses may include unintentional biases. We estimated the survival of Whimbrels captured and marked at two breeding sites in Alaska using divergent data streams that in isolation were subject to methodological biases. Although both capture sites were chosen to study the migration ecology of Alaska‐breeding Whimbrels, maximizing the conservation value of the data we collected was obviously desirable. We used multi‐year telemetry information to infer survival from one site (Colville River) and mark–resight techniques to estimate survival from a second site (Kanuti River). At Colville River, we could not feasibly include a control group of birds to assess potential survival effects of externally mounted transmitters, and at Kanuti River we were unable to account accurately for potential emigration events because we used resightings alone. We integrated these datasets in a Bayesian hierarchical framework, an approach that permitted insights across sites that moderated methodological biases within sites. Using telemetry enabled us to detect permanent emigration events from breeding sites in two of 10 birds, results that informed estimates for birds without tracking devices. These datasets yielded point estimates of true survival of Whimbrels from Colville River equipped with solar‐powered satellite transmitters that were higher (0.83) than true survival estimates of Whimbrels from Kanuti River marked with leg flags alone (0.74) or equipped with surgically implanted satellite transmitters (0.50), but the 95% credible intervals on these estimates overlapped across groups. For species such as Whimbrels that are difficult and costly to study, combining information from disparate data streams allowed us to derive novel demographic estimates, an approach with clear application to other similar studies.

Museum collections of birds are a key source of data on the colours of ‘soft parts’, e.g. legs, feet, bill (maxilla, mandible), wattles, periocular skin and, our focus here, the iris of the eye. However, subjective descriptions of soft parts' colours have long plagued their use, whether in research or in illustrations of birds. We document a case where reasonable doubt about the accuracy of iris colour recorded more than 50 years ago in several taxonomically important series of specimens of the Australian Spinifex Pigeon Geophaps plumifera is probably unresolvable. This doubt clouds the downstream use of the specimens in a complete understanding of geographical and temporal variation, and taxonomy. We discuss how ornithologists may apply methods now readily available that will enable more rigorous recording of soft parts' colours, despite many valid limitations. This especially applies in situations where existing knowledge dictates care, such as in already known zones of taxonomic intergradation or when colours known to be unusual and unexpected are seen.

During 2021 and 2022 High Pathogenicity Avian Influenza (HPAI) killed thousands of wild birds across Europe and North America, suggesting a change in infection dynamics and a shift to new hosts, including seabirds. Northern Gannets (Morus bassanus) appeared especially severely impacted, but a detailed account of the data available is required to help understand how the virus spread across the metapopulation, and the ensuing demographic consequences. Accordingly, we analyse information on confirmed and suspected HPAIV outbreaks across most North Atlantic Gannet colonies and for the largest colony (Bass Rock, UK), provide impacts on population size, breeding success, and preliminary results on apparent adult survival and serology. Unusually high numbers of dead Gannets were first noted at colonies in Iceland during April 2022. Outbreaks in May occurred in many Scottish colonies, followed by colonies in Canada, Germany and Norway. By the end of June, outbreaks had occurred in colonies in Canada and the English Channel. Outbreaks in 12 UK and Ireland colonies appeared to follow a clockwise pattern with the last infected colonies recorded in late August/September. Unusually high mortality was recorded at 40 colonies (75% of global total colonies). Dead birds testing positive for HPAIV H5N1 were associated with 58% of these colonies. At Bass Rock, the number of occupied nest sites decreased by at least 71%, breeding success declined by ~66% compared to the long‐term UK mean and the resighting of marked individuals suggested that apparent adult survival between 2021 and 2022 could have been substantially lower than the preceding 10‐year average. Serological investigation detected antibodies specific to H5 in apparently healthy birds indicating that some Gannets recover from HPAIV infection. Further, most of these recovered birds had black irises, suggestive of a phenotypic indicator of previous infection. Untangling the impacts of HPAIV infection from other challenges faced by seabirds is key to establishing effective conservation strategies for threatened seabird populations as the likelihood of further epizootics increases, due to increasing habitat loss and the industrialization of poultry production.

When waders gather in mixed‐species flocks to feed on benthic prey, differences in morphological traits, foraging strategies and prey selection may allow different species to optimize their energy intake while reducing competition. As the effect of the fine‐scale spatial distribution of resources on energy intake is unknown, we simulated the foraging performance of two types of waders with contrasting body plans and foraging strategies in a variety of virtual mudflats with different horizontal and vertical prey distribution patterns. Although larger, longer‐billed individuals had higher energy intake rates, smaller individuals with shorter bills maintained higher prey capture rates by relocating if prey was insufficiently available. Shorter‐billed individuals struggled more to meet their energetic demands because they selected smaller prey items and had a more limited capacity to metabolize energy from food. Being able to catch larger, high‐quality prey offered a competitive advantage for longer‐billed individuals, which could be a driving force for the evolutionary lengthening of bills in waders. Interestingly, their performance was more affected by the horizontal than by the vertical prey distribution. Quantifying prey distributions may help explain how some wader species can co‐occur in the field and why some wetland areas are unattractive as foraging areas. The work confirms that the foraging performance of larger, longer‐billed birds is not limited by bill size per se, but by the energetic trade‐offs associated with the ability to catch larger prey items more efficiently, increased handling times and higher absolute energy costs. These trade‐offs may become particularly important in landscapes where prey is scarce and spatially patchy.