Recovery of understory bird movement in post-pasture Amazonia

Abstract

I sought to understand how forest fragmentation and secondary growth affect avian movement at the Biological Dynamics of Forest Fragments Project (BDFFP) near Manaus, Brazil. When deforested areas are abandoned, secondary forests regenerate, allowing rainforest animals to gradually recovery their ability to use formerly inhospitable habitat. My colleagues and I captured 2773 understory birds of ten foraging guilds along the edges of primary forest fragments and variable secondary forest. Age of secondary forest along edges was the most important variable driving capture rates on primary/secondary edges. Mean recovery to pre-isolation capture rates was 26 years after abandonment, but terrestrial insectivores took far longer to recover than other guilds, ¡Ý 54 years. I radio-tracked 73 understory insectivores of three species in variable landscapes to uncover patterns in avian movement in secondary growth¡ªspecifically evaluating space use (home range, movement rate, etc.), edge responses and habitat transition probabilities. Space use varied widely as secondary growth recovered, with species showing vastly different spatiotemporal strategies in returning to forest. Woodcreepers Glyphorynchus spirurus and Xiphorhynchus pardalotus recovered to primary-forest-level edge responses and transition probabilities after 11¨C15 and 15¨C20 years, respectively. En route to recovery, both woodcreepers increased home range sizes and movement rates in young secondary forests. Formicarius colma, a common terrestrial insectivore, had a far more rigid strategy, avoiding young secondary forest, then using space in older secondary forest similarly to the way it used space in primary forest. With bird ages pooled, F. colma showed a return to no edge response about 28¨C30 years after land abandonment, with some evidence for an edge response by young birds even 27¨C31 years post-abandonment. Further, through habitat transition probabilities, I showed that F. colma preferred primary forest over 27¨C31 year-old secondary forest (the oldest at the BDFFP), indicating that even after 27¨C31 years, secondary forest had not recovered for movements of this terrestrial insectivore. By quantifying how land-use patterns affect avian movement, connectivity, and community dynamics, we will be generating the understanding necessary to manage heterogeneous landscapes for biodiversity conservation in the 21st century and beyond.