Scientists have long been trying to understand why the Neotropical region holds the highest diversity of birds on Earth. Recently, there has been increased interest in morphological variation between and within species, and in how climate, topography, and anthropogenic pressures may explain and affect phenotypic variation. Because morphological data are not always available for many species at the local or regional scale, we are limited in our understanding of intra‐ and interspecies spatial morphological variation. Here, we present the ATLANTIC BIRD TRAITS, a data set that includes measurements of up to 44 morphological traits in 67,197 bird records from 2,790 populations distributed throughout the Atlantic forests of South America. This data set comprises information, compiled over two centuries (1820–2018), for 711 bird species, which represent 80% of all known bird diversity in the Atlantic Forest. Among the most commonly reported traits are sex (n = 65,717), age (n = 63,852), body mass (n = 58,768), flight molt presence (n = 44,941), molt presence (n = 44,847), body molt presence (n = 44,606), tail length (n = 43,005), reproductive stage (n = 42,588), bill length (n = 37,409), body length (n = 28,394), right wing length (n = 21,950), tarsus length (n = 20,342), and wing length (n = 18,071). The most frequently recorded species are Chiroxiphia caudata (n = 1,837), Turdus albicollis (n = 1,658), Trichothraupis melanops (n = 1,468), Turdus leucomelas (n = 1,436), and Basileuterus culicivorus (n = 1,384). The species recorded in the greatest number of sampling localities are Basileuterus culicivorus (n = 243), Trichothraupis melanops (n = 242), Chiroxiphia caudata (n = 210), Platyrinchus mystaceus (n = 208), and Turdus rufiventris (n = 191). ATLANTIC BIRD TRAITS (ABT) is the most comprehensive data set on measurements of bird morphological traits found in a biodiversity hotspot; it provides data for basic and applied research at multiple scales, from individual to community, and from the local to the macroecological perspectives. No copyright or proprietary restrictions are associated with the use of this data set. Please cite this data paper when the data are used in publications or teaching and educational activities.

In tropical dry areas, rainfall is predicted to be the most important climatic variable influencing bird phenology because it triggers food and foliage production. In addition, because resources are scarce, the moulting and breeding seasons are not expected to overlap. We conducted a 2year study on the phenology of passerine birds at one site in Caatinga, South America's largest dry forest region to: (a) evaluate the contributions of climate, foliage cover, and food abundance to the onset of the breeding and moulting seasons, (b) assess the duration of the breeding and moulting seasons, and (c) measure the frequency of the bird moult-breeding overlap. Birds can use rainfall or humidity as environmental cues to start their breeding seasons. The effects of water availability are mediated by both foliage cover and food abundance, but foliage cover is more important to the onset of the bird breeding season than food abundance. In contrast, both foliage cover and food abundance equally influence the timing of the primary moult. Because we found several cases of moult-breeding overlap, we suggest that some passerine species adapt that strategy to adjust the timing of their life history stages to the relatively short period of abundant resource availability.

Fragmentation is one of environmental degradation and reduction of biodiversity causes, including in bird communities, mainly in Atlantic Forest areas. The aim of this study was to evaluate the differences in richness and functional groups structure in the ornitofauna from a Restinga forest fragment and four areas with different ages of reforestation. We selected five forest fragments in a Restinga area in the state of Paraiba. A native fragment (Control Area-AC) and four fragments that have undergone a mining process and present different ages of reforestation (1989, 1997, 2001 and 2003). The avifauna samples occurred in four expeditions between November 2006 and April 2008 and counted with a total effort of 2700 net.m2 per expedition. Statistical tests verified richness differences between studied areas, as well as the composition of their functional groups. In general, 90 bird species were recorded, and the highest reforestation age area presented the highest richness (n = 51 spp.). The species richness comparisons indicated that the difference in the richness between AC and reforested areas is not statistically significant. The similarity analysis indicates that reforested areas share a large amount of species and AC has a great differentiation in composition. This differentiation is explained by the significant presence of frugivorous, nectarivorous, leaf and understory-insectivorous species. Changes in species richness and composition in degraded areas are expected and reforested areas usually have a smaller number of forest-dependent species due to the deficiency of available resources. The recovery of areas by reforestation are important conservation strategies, however there is need for management measures that promote the enrichment of these areas and the availability of resources for species dependent on environments Forest.