An improved survey method for monitoring population trends of Golden‐winged Warblers and other patchily distributed birds

Abstract

Conventional surveys designed to monitor common and widespread species may fail to adequately track population changes of rare or patchily distributed species that are often of high conservation concern. We evaluated the performance of a new monitoring approach that employs both a spatially balanced sampling design and a targeted survey protocol designed to estimate population trends of one such patchily distributed species, the Golden‐winged Warbler (Vermivora chrysoptera), in the Appalachian Mountains Bird Conservation Region (BCR 28), USA. Our spatially balanced survey consisted of 105 sample quads (one‐quarter Delorme Atlas pages) across the current range of Golden‐winged Warblers within BCR 28, each with five sample points located in early successional habitat. From 2009 to 2013, collaborators visited each sample point once per year during the peak breeding season and conducted a 17‐min survey consisting of passive observation and playback of conspecific songs and mobbing vocalizations. We used multi‐season, single‐species occupancy models to estimate probability of quad occupancy, detection probability, and occupancy dynamics for Golden‐winged Warblers and closely related Blue‐winged Warblers (Vermivora cyanoptera). Our survey protocol resulted in high estimates of detection probability for Golden‐winged (92%) and Blue‐winged (79%) warblers, with 47% and 56% of quads estimated to be initially occupied, respectively. Derived population trend estimates (λ) indicated an average decline in population of 6% for Golden‐winged Warblers and 7% for Blue‐winged Warblers, resulting in estimated 21% and 22% declines, respectively, in quad occupancy after 5 yr. Our results demonstrate that coupling a spatially balanced survey design in appropriate habitat with a playback protocol to increase detection rates is a viable strategy for tracking populations of Golden‐winged Warblers in the Appalachian Mountains BCR. Similar survey methods should be considered for other rare, declining, or patchily distributed bird species that require targeted monitoring.

Breeding season space use and habitat selection by Blue-winged Warblers in managed shrublands

“…We revisited locations of territorial males starting the first week of May and used 30 mm mist-nets and a playback lure of Vermivora spp. songs and calls to capture males (Wood et al 2017). After recording weight (g) and age (ASY or SY), we fitted each male weighing ≥ 8 g with a 0.35 g VHF radio-transmitter tag (Blackburn Transmitters, Nacogdaches, TX).…”

“…To understand species-habitat relationships, it is important to (1) accurately delineate the spatial scale of interest (i.e., individual core and total home ranges ;Johnson 1980) and (2) quantify habitat features at a scale that matches individual resource selection behaviors (Kirol et al 2012, Farallo andMiles 2016). Both of these can be difficult to achieve for small songbirds occupying structurally complex early successional communities where visual detections can be challenging (Wood et al 2017). However, radio telemetry has provided insight regarding breeding season space use and habitat selection of birds in early successional communities at spatial and temporal resolutions that were previously unobtainable (King et al 2006, Anich et al 2009, Vitz and Rodewald 2011, Frantz et al 2016.…”