Seasonal variation in tropical and subtropical systems can have different effects on bird species depending on the resources they use and how they use them. However, despite recent research advances, knowledge of the drivers of the presence and abundance of species in different seasons is still limited for most tropical bird species. In these poorly understood systems, examining seasonal changes in species composition from the perspective of traits related to resource use can provide insight into what resources may be driving bird movements between areas throughout the year and what types of species are more subject to seasonality. Here, we explore bird community seasonality in three forest types (dense, semi‐deciduous and mixed rainforests) subjected to different climatic conditions in one of the world's biodiversity hotspots, the Atlantic Rainforest. We investigated differences between summer and winter in species richness and in the composition of resource‐related species traits (diet, foraging strata and substrates) obtained from the literature. The seasonal differences (summer and winter) between forest types were explored in terms of species and trait composition. We found that the main changes that occurred in bird composition between seasons in the southern Atlantic Rainforest were related to species traits such as diet and foraging strata. In general, the proportion of invertivores was higher in winter than in summer, and in the mixed forest, the forest type exposed to the coldest winters, the proportion of frugivores was lower in winter. Furthermore, species with a more varied diet were better represented in the summer. In general, more generalist species were better represented in the forest type subjected to higher seasonal variations in rainfall. Our results revealed seasonal changes in bird community structure that are related to niche occupation and that were more strongly apparent in the forest type subjected to colder winters.

Targeted management actions to boost key demographic rates can help to restore rare and localized populations but are increasingly required to stabilize or reverse declines of formerly common and widespread species. Many breeding wader populations across Europe are declining because of unsustainably low rates of productivity, and the conservation tools designed to boost wader breeding productivity have been most effectively used for semi‐colonial species within protected areas. Targeted management for wader species that breed at low densities across human‐modified landscapes, such as the rapidly declining Eurasian Curlew Numenius arquata, is likely to be more challenging. Here, we quantify variation in Curlew nest survival to explore how management could be targeted to boost this key component of breeding productivity. Up to 80 pairs of Eurasian Curlew were monitored annually between 2019 and 2021 in eight locations across Breckland, eastern England, where nesting densities range from <1 to c 0.7 pairs/km2. For 136 nests across grassland‐ and arable‐dominated sites, the majority of failures (86%) were caused by (primarily nocturnal) predation and the mean probability of surviving incubation (PSI) for all hatched or predated nests (127) was c. 0.25. Nest survival showed little annual or seasonal variation but did vary slightly between sites; however, this spatial variation was not clearly related to management conditions or nest concealment at these sites. Fencing to exclude mammalian nest predators can be effective for waders, but too few Eurasian Curlews currently nest within fenced areas in Breckland to produce observable effects. Fencing the few sites with high nesting densities could potentially double the number of chicks hatched each year within the study area, but landscape‐scale actions to reduce predator impacts on nests and chicks are likely to be needed to maintain breeding numbers in the wider countryside.

Population‐level estimates of offspring sex ratios in birds typically approximate parity whereas biased ratios within nests are not uncommon. In sexually dimorphic raptors, the costs and relative fitness benefits of rearing male and female progeny vary with changing environmental circumstances. This may lead to substantial deviations from balanced investment in offspring of a particular sex by individual parents. Based on a 13‐year dataset for breeding MerlinsFalco columbariusin Saskatoon, Canada, we used a model selection approach to assess the influence of parents, nest‐mates and nesting area on brood sex ratio during the nestling phase. The best model for predicting brood sex ratio included age of the breeding male and brood size for each nest (n = 127); nests with older male breeders and smaller brood sizes had more female young. The population‐level annualized average proportion of male offspring was 0.472 ± 0.017 (mean ± standard error), but tended towards greater production of female young during an initial period of population growth (8 years, 10–21 pairs; proportion male 0.435 ± 0.031) versus a period when the population fluctuated around a presumed carrying capacity (11 years, 24–33 pairs; proportion male 0.500 ± 0.017). Energetics appears to be a finely tuned mechanism driving sex ratio allocation in Merlins at both brood and population levels. Provisioning food for young in the nest represents the male's ability to successfully capture prey, reflecting his age and/or experience, as well as the availability of prey to the male. Confounding this mechanism to determine sex ratio allocation are the pressures created by population dynamics that dictate competition for resources both within the nest (brood size) and external to the nest (population density).

Many bird species produce low‐amplitude acoustic signals, known as soft songs, which are widely believed to function primarily in aggressive interactions. However, there are surprisingly few experimental studies that have examined whether soft songs are reliable signalling strategies for escalating aggressive interactions. Here, we investigate the functions of soft song in a colour‐marked population of the Plain Laughingthrush Pterorhinus davidi, using playback experiments combined with specimen‐based simulated territory intrusions. We found that playback of male soft song provoked quicker response and stronger aggressive intent by territorial pairs compared with playback of male broadcast song. Responses by territorial pairs to male soft song playback were significantly stronger compared with responses to broadcast song playback, with a greater number of flights over the speaker, more time spent within 1 m of the speaker and closer approaches to the speaker. Furthermore, closer approach with the production of soft song by focal males was the best predictor of aggressive intent in combined playback and specimen intrusion experiments. Our results suggest that male soft song is used as an aggressive signal in the Plain Laughingthrush, and represents the first evidence of such for a monogamous temperate duetting species.

Electrocution can pose a serious threat to large birds, particularly threatened species with low population sizes. However, few studies have focused on the impacts of electrocution on large parrots such as the Endangered Lear's Macaw Anodorhynchus leari, endemic to the Brazilian Caatinga. Here, we compile and describe 31 electrocution events, as reported by villagers, indicating that electrocution may be an important threat to Lear's Macaw. We suggest a research and monitoring agenda to better understand the spatial and temporal patterns of this impact and recommend some immediate mitigation measures for decreasing electrocutions.

A detailed analysis of fatty acid (FA) profiles and their properties relating to fuelling strategy can improve understanding of avian migration. The study aimed to understand whether and how FA composition differs among several passerine species which migrate using different fuelling strategies (constant fuelling, gradual fuelling, early fuelling or late fuelling). We found evidence for differential FA composition among migratory species according to their fuelling strategies: early fuellers presented higher n‐3 polyunsaturated FA and gradual fuellers higher mono‐unsaturated FA, which can be directly related to their differential migratory strategies to maximize energy use.

Many animals, including shrikes (Laniidae), are known to store food. This behaviour ensures food availability during inclement weather, for rearing nestlings or signalling territory quality. Unlike most other shrike species, which accumulate food before breeding, Red‐backed Shrikes Lanius collurio store food in larders, mainly during the nestling and fledgling periods. If this is an adaptive behaviour, variation in this behaviour should affect either or both the number and condition of nestlings, which may benefit from such larders. We assessed the haematological condition of Red‐backed Shrike nestlings in east‐central Poland in 2021 using a suite of blood parameters relating to sites where shrikes did or did not store food. Haemoglobin concentrations were positively correlated with larders, being significantly higher in nestlings of pairs that stored prey compared with those whose parents did not do so. White blood cell counts were lower in nestlings whose parents kept larders. Red blood cell counts and glucose concentrations in nestlings were not related to whether parents had larders. Food storage probably ensures a more constant access to food, which results in a superior haematological condition in nestlings.

Understanding how climatic and environmental changes, as well as human activities, induce changes in the distribution and population size of avian species refines our ability to predict future impacts on threatened species. Using multilocus genetic data, we show that the population of a threatened New Zealand endemic open‐habitat specialist, the Black‐fronted Tern Chlidonias albostriatus – in contrast to forest specialists – expanded during the last glacial period. The population has decreased subsequently despite the availability of extensive open habitat after human arrival to New Zealand. We conclude that population changes for open habitat specialists such as Black‐fronted Terns in pre‐human New Zealand were habitat‐dependent, similar to Northern Hemisphere cold‐adapted species, whereas post‐human settlement populations were constrained by predators independent of habitat availability, similar to other island endemic species.

Hybridization occurs between numerous bird species, with some of them capable of producing backcrosses. However, little information is available concerning mating between pairs of hybrids. In this case study, a mixed pairing is reported between hybrids of Syrian and Great Spotted Woodpeckers, Dendrocopos syriacus and Dendrocopos major, respectively. Mixed phenotypic and genotypic traits were found in the male, the female and their offspring. The possible consequences of hybridization and its effect on the Syrian Woodpecker, which is protected under the Bird Directive of the European Union, are discussed.