| Popis: |
Predation is typically the primary cause of nest failure for songbirds, even within unfragmented forested landscapes. In recent years, video cameras have been used to study causes and patterns of nest failure in a variety of habitats and regions. However, surprisingly few video camera studies have been performed in forests of northeastern North America. Over 5 years, we monitored Veery (Catharus fuscescens) nesting success in a mature forest landscape in northeastern Pennsylvania and used video cameras at a subset of nests to identify the predator assemblage and to describe relevant patterns of predation. Overall, we located 289 nests and recorded 67 of these nests with video cameras. Annual nest survival rates varied substantially across years (0.17–0.44) with this variation driven primarily by the dominant source of nest mortality: predation. Video cameras recorded 40 predation events by 12 predator species. Mammals (7 species), birds (4 species), and snakes (1 species) accounted for 75%, 20%, and 2.5% of predation events recorded, respectively. Predation events occurred during the day more often than expected by chance. Logistic exposure analyses indicated that both camera presence and nest age affected nest survival by influencing predation rates, but date did not. The diverse predator community observed depredating Veery nests led to low nesting success in some years, but also demonstrated that causes of nest failure vary by year and cannot be attributed to any single predator species or group. A greater apparent predation rate at nests with cameras likely resulted from a more frequent visitation rate to these nests by researchers compared to those without cameras and suggests a potential bias with artificially decreased nest survival estimates in years in which cameras were used. |
