Density and nest survival of golden‐cheeked warblers: Spatial scale matters

Abstract

ABSTRACTConservation and management plans often rely on indicators such as species occupancy or density to define habitat quality, ignoring factors that influence reproductive success, and potentially limiting conservation achievements. We examined relationships between predicted density and nest survival with environmental features at multiple spatial scales for the golden‐cheeked warbler (Setophaga chrysoparia) in a large preserve within an urbanizing landscape. Larger‐scale features of the forest and landscape composition best predicted density, whereas small‐scale vegetation features best predicted nest success. Predicted warbler density was more influenced by vegetation structure at the forest (100‐m) and landscape (1‐km) scales than at the plot (5–11.3‐m) scale. Predicted warbler density increased with greater woodland cover (100‐m), average canopy height (100‐m), and mixed woodland cover (1‐km). Average predicted density derived from distance sampling models fit to count data across 1,506 points surveyed during 2011–2014 was 0.21 males/ha (95% CI = 0.20–0.22). Nest survival (n = 610 nests) was strongly correlated with vegetation and terrain characteristics at the plot scale. Period nest survival decreased 28% and increased 36% and 21% across the range of slope, woody understory, and juniper basal area, respectively. Daily nest survival averaged 0.97 (0.96–0.98) but declined throughout the breeding season and varied annually (2011–2015). We recommend management for a high percentage of closed‐canopy, tall mixed juniper (Juniperus ashei)‐oak (Quercusspp.) woodland at the forest and landscape scales to support high densities of warblers. We also recommend protecting upland woodlands with a well‐developed woody understory and greater basal area of junipers because these characteristics were associated with greater nest success. © 2017 The Wildlife Society.