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

Abstract

Studies 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.

Retirement investment theory explains patterns in songbird nest-site choice

“…Males establish nesting territories, nearly all of which include forest edge and extend more than 40 m on either side of the edge, such that they include both forest and shrubland [38]. The edge, or boundary between forest and shrubland, was generally abrupt and clearly defined at our study sites owing to its origin in forest harvest.…”

Variables associated with nest survival of Golden-winged Warblers (Vermivora chrysoptera) among vegetation communities commonly used for nesting

“…We also aggregated states into two distinct and possibly disjunct segments of the Goldenwinged Warbler's breeding range (Roth et al 2012): the Great Lakes (Minnesota and Wisconsin) and Appalachian Mountains population segments (North Carolina, New York, Pennsylvania, Tennessee, and West Virginia). The Great Lakes population segment has a larger population size (Roth et al 2012), greater territory density (Streby et al 2012, Frantz et al 2015, and slower rates of population decline (Sauer et al 2014) than the Appalachian Mountains population segment, which we hypothesized to be in part a consequence of greater DSR in the Great Lakes population segment.…”

Using a natural reference system to evaluate songbird habitat restoration

“…The 250 m scale was chosen to represent the territory + immediate surrounding area, approximating the male home-range (Frantz et al 2016). Finally, we included 500 m because several other studies have suggested forest cover type at the scale is important to Golden-winged Warblers (Streby et al 2012. Around each point count location, we created 150, 250, and 500 m radius buffers in ArcGIS.…”