Amazonian Forest Disturbance Shows Reduced Breeding Activity and Recruitment of Young Birds

Abstract

The Biological Dynamics of Forest Fragments Project (BDFFP) in the central Amazon rainforest has been studying the effects of fragmentation for over 40 years. Forest fragmentation negatively impacts biodiversity, but it is not known how it affects different life stages of animals, thus we assess the impact on the breeding activity and the recruitment of young birds, predicting that both will be negatively impacted. Before and after the forest was isolated, understory birds were caught in mist nets and identified to species level, age, and assessed for signs of breeding activity. Mist netting occurred in 1ha, 10ha, 100ha, fragments and secondary, and primary forest. There were 418 fewer birds actively breeding and 48 fewer young after fragment isolation compared to before isolation. Primary forests had almost 4 times as many breeding birds and young as secondary forest and 8 times as many as forest fragments..More specifically, insect eating birds were negatively impacted more than other species, which provides evidence for the global decline in these birds. For example, the insect eating birds' young declined by 61% and their breeding activity by 74%, where as frugivore and nectivore young increased and breeding activity was largely unchanged. We demonstrated, for the first time, breeding activity and the recruitment of young are a bottle neck for species growth in forest fragments, and in second growth forest.