Richness, composition and trophic groups of an avian community in the Pernambuco Endemism Centre, Alagoas, Brazil

In northeastern Brazil, the reduction of the natural forest cover to a series of small, isolated fragments has had negative consequences for the local avian fauna, in particular, a loss of the more specialized species, while the populations of some generalists have tended to increase. The present study focuses on the composition and trophic groups of a bird community on a farm in the northeastern Brazilian state of Alagoas. Monthly surveys were conducted between November 2008 and October 2009, based on mist-netting and systematic observations. Overall, 112 species were recorded, of which 76 were associated with the two forest fragments surveyed, while all the others were observed exclusively in the surrounding matrix of pasture and orchards. The bird community presented a predominance of insectivorous species, followed by omnivores. However, specialized trunk-creeping and understory insectivores accounted for only around 15% of the species in this feeding category. The reduced diversity of other guilds and species with more specialized diets, and the complete absence of sensitive species such as large parrots and raptors, reflects the severe fragmentation and degradation of the local forests, which has greatly reduced the availability of dietary resources and breeding sites.

在巴西东北部地区，原生林被砍伐并分割为一系列小型孤立片段的行为，已对当地鸟类区系造成负面影响：其中更为特化的鸟类物种多样性出现下降，而部分广适性物种的种群数量则呈上升趋势。本研究聚焦于巴西东北部阿拉戈斯州（Alagoas）某农场内鸟类群落的组成与营养类群特征。调查于2008年11月至2009年10月间开展月度监测，采用雾网采样（mist-netting）与系统观测法相结合的方式。本次调查共记录到112种鸟类，其中76种与本次调研的两处森林片段相关联，剩余物种则仅在周边的牧场与果园生境基质中被观测到。该鸟类群落以食虫鸟类占绝对优势，其次为杂食性鸟类。然而，特化的树干爬行类与林下层食虫鸟类仅占该摄食类群物种总数的约15%。其他功能群以及食性更为特化的物种种群多样性降低，且完全缺失大型鹦鹉、猛禽等敏感物种，这一现状反映出当地森林已遭受严重的片段化与退化，大幅缩减了鸟类可获取的食物资源与繁殖位点。