Songbird Nest Survival in Managed Oak Savannas and Woodlands in the Missouri Ozarks

摘要

Midwestern savannas and woodlands were once dominant transitional communities but are now considered endangered. Savanna and woodland habitat is being restored and managed throughout the central and east-central portions of the United States, but few studies have investigated the effects of management on songbird nest survival. We monitored songbird nests in managed savanna and woodland sites in southern Missouri from 2009 to 2011 to estimate nest survival and to predict the relationships between nest survival and temporal, vegetation structure, and nest site variables. Daily nest survival was generally higher for the four canopy-nesting species, Acadian flycatcher (Empidonax virescens), blue-gray gnatcatcher (Polioptila caerulea), Eastern wood-pewee (Centopus virens), and summer tanager (Piranga nebra) (0.96-0.98), than the four shrub-nesting species, field sparrow (Spizella pusilla), indigo bunting (Passerina cyanea), prairie warbler (Setophaga discolor), and yellow-breasted chat (Icteria virens) (0.92-0.95), for which we estimated survival rates. In general vegetation structure around the nest had little influence on nest survival, except for canopy cover, which occurred in the top model set for four species. Nest survival of yellow-breasted chats was much higher in areas of lower canopy cover, whereas nest survival of Eastern wood-pewees was moderately lower and indigo buntings and summer tanagers peaked at low and intermediate levels of canopy cover, respectively. Therefore. savanna and woodland management, which tends to open the tree canopy, may benefit some bird species in this forested landscape, particularly those associated with low to intermediate canopy cover.