Response of Cerulean Warblers to different forest treatment: Are estimators of relative abundance and reproductive success good predictors?

by

Kamal Islam

Department of Biology, Ball State University, Muncie, IN 47306-0440. To contact, call 765-285-8847/8820 or email kislam@bsu.edu

Abstract – Abstract - Monitoring responses of mature forest-dependent migratory songbirds to different forest treatments is needed to establish informed management decisions. This information is especially important for species with precipitous declines in populations, such as the Cerulean Warbler (Setophaga cerulea), a long-distance Neotropic-Nearctic migrant songbird. For the past five decades, populations of S. cerulea have declined by 70% based on annual Breeding Bird Surveys. S. cerulea breed in mature deciduous forests in northeastern and midwestern United States, and southern Ontario, Canada, and winter along the eastern slopes of the Andes in northern South America. Since 2007, we have monitored populations of S. cerulea at nine study sites in southern Indiana as part of a long-term study, the Hardwood Ecosystem Experiment. Three sites received uneven-aged treatments (single and patch/group cuts), 3 sites received even-aged treatments (shelterwood and clear-cuts), and 3 sites served as control (no harvests). Initially, S. cerulea populations responded positively to even-aged treatments and negatively to uneven-aged treatments, two years post-harvest. Since 2010, populations of S. cerulea have leveled off to pre-treatment levels at even-aged and control sites but continue to decline at uneven-aged sites. In 2012, we initiated a reproductive study. Reproductive success was higher at control sites than at the 2 treatments sites. However, larger sample sizes are needed from control sites to fully assess the effects of forest treatments on reproduction. Our results stress the importance of studying the long-term effects of forest treatments in songbird populations to account for inter-year variation in relative abundance estimates and reproductive output.