SURVIVORSHIP OF PERMANENT-RESIDENT BIRDS IN A FRAGMENTED FORESTED LANDSCAPE

Few studies have examined survivorship of animals in forest fragments differing in size, and none has used appropriate mark–recapture analysis techniques taking into account probability of recapture. Using Program MARK, a flexible mark–recapture software package, we estimated annual survival rates of four permanent-resident woodland bird species over a 5-yr period in a fragmented landscape. For Carolina Chickadees, White-breasted Nuthatches, and Downy Woodpeckers, the probability of survival was related to site, with survival being highest in large woodlots, low in small woodlots, and either intermediate or lower in riparian woodlands. The presence of supplemental food had a positive influence on survivorship. Survivorship of the Tufted Titmouse was lower in years with heavy snow cover. There was some evidence for an age difference in apparent survival, with adult birds having higher survival rates. Overall, however, these age-specific estimates had large variances or the differences disappeared when models were averaged, except in the chickadee, where young birds appeared to survive less well in forested river corridors. This last result was quite likely due, at least in part, to age-specific dispersal, suggesting that river corridors function as important dispersal routes for young, transient birds of permanent-resident species. These results suggest a strong additional cost of fragmentation: increased mortality. This cost has not been previously documented using modern mark–recapture analytical techniques.