Spot‐mapping underestimates song‐territory size and use of mature forest by breeding golden‐winged warblers in Minnesota, USA

Abstract

AbstractStudies of songbird breeding habitat often compare habitat characteristics of used and unused areas. Although there is usually meticulous effort to precisely and consistently measure habitat characteristics, accuracy of methods for estimating which areas are used versus which are unused by birds remains generally untested. To examine accuracy of spot‐mapping to identify singing territories of golden‐winged warblers (Vermivora chrysoptera), which are considered an early successional forest specialists, we used spot‐mapping and radiotelemetry to record song perches and delineate song territories for breeding male golden‐winged warblers in northwestern Minnesota, USA. We also used radiotelemetry to record locations (song and nonsong perches) of a subsample (n = 12) of males throughout the day to delineate home ranges. We found that telemetry‐based estimates of song territories were 3 times larger and included more mature forest than those estimated from spot‐mapping. In addition, home ranges estimated using radiotelemetry included more mature forest than spot‐mapping‐ and telemetry‐based song territories, with 75% of afternoon perches located in mature forest. Our results suggest that mature forest comprises a larger component of golden‐winged warbler song territories and home ranges than is indicated based on spot‐mapping in Minnesota. Because it appears that standard observational methods can underestimate territory size and misidentify cover‐type associations for golden‐winged warblers, we caution that management and conservation plans may be misinformed, and that similar studies are needed for golden‐winged warblers across their range and for other songbird species. © 2012 The Wildlife Society.