Reduced feather growth rates of two common birds inhabiting central Amazonian forest fragments

Forest fragmentation may negatively affect populations typically found with in continuous forest tracts Some effects, such as absence from small fragme nts, are obvious, but other effects may be subtle and easily overlooked. We evaluated the hypothesis that forest birds dwelling in fragments, where mi croclimatic conditions have been shown to be hotter, and drier than in cont inuous forest, may be in poorer physiological condition than those in the f orest interior We studied two bird species, the Wedge-billed Woodcreeper (G lyphorynchus spirurus) and the White-crowned Manakin (Pipra pipra), common to the fragmented landscape north of Manaus, Brazil We analyzed feather gro wth rates in Pipra and Glyphorynchus captured in 1-, 10-, and 100-ha forest fragments and continuous forest. Mean daily feather growth rates of the ou ter right rectrix of birds captured in fragments were significantly slower than feather growth rates of birds captured in continuous forest. Based on recapture data, Wedge-billed Woodcreepers probably grew their feathers in s ites where they were first captured. White-crowned Manakins, however were h ighly mobile and were recaptured rarely. Although ute cannot conclusively s how that fragmentation caused birds to be in poorer physiological condition , the data indicate that birds in poorer physiological condition were more likely to be captured in fragments than in continuous forest. Thus our data suggest that forest fragmentation may have subtle but important effects on species that are relatively common after landscape alteration.