PARENT SESSION
Oral Session 2: Avian Ecology I: Habitat and Disturbance.
Presiding: D Miles and C Lepczyk
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room A 106.
Modeling occupancy of nest cavities in recently burned forests.
Saab, Victoria *,1, Dudley, Jonathan2, Thompson, William3, 1 Rocky Mountain Research Station, Bozeman, MT, USA2 Rocky Mountain Research Station, Boise, ID, USA3 National Park Service, Anchorage, AK, USA
ABSTRACT- Recently burned forests in western North America provide nesting habitat for many species of cavity-nesting birds. Little is understood about the time frame in which these forests are beneficial and the variables affecting occupancy of post-fire habitats by cavity-nesting birds. We studied factors influencing the occupancy of nest cavities from 1 – 7 years after fire in two burned sites of western Idaho during 1994 –1999. Tree cavities were used for nesting by 12 species of cavity nesters that were classified by the original occupant (strong, weak, or non-excavator) of 385 nest cavities. We used logistic regression to model cavity occupancy by strong excavators (n = 575 trials) and weak excavators (n = 206 trials). Year after fire had the greatest influence on occupancy of nest cavities for both groups, whereas site of the burn was primarily important in predicting cavity occupancy by strong excavators. Predicted probability of cavity occupancy was highest during the early years (1 – 4) after fire, declined over time (5 – 7 years after fire), and varied by site, with a faster decline in the smaller burn with a greater mosaic of unburned forest. In combination with time and space effects, the predicted probability of cavity occupancy was positively affected by tree and nest heights. Patterns in occupancy of nest cavities in recently burned forests were likely affected by food availability and nest predator access. We provide evidence that early post-fire forests play a critical role in the long-term persistence of cavity-nesting birds that rely on fire-maintained systems.
Key words: cavity-nesting birds, burned forests, ponderosa pine forests