Age Structure of Golden-cheeked Warblers in Areas of Low Abundance

Understanding how habitat use and reproductive performance vary among age classes is important to understanding population structure and viability. Habitat conditions can affect occupancy and productivity of many songbirds, including golden-cheeked warblers (Setophaga chrysoparia). Thus, it is important to know which members of the population are using habitat of varying conditions. Existing demographic literature on golden-cheeked warblers focuses on populations where warblers occur in high abundance. I examined the age structure of golden-cheeked warblers in areas of low abundance to determine if there are patterns of differential habitat use based on age in this species. Over two breeding seasons, I monitored 13 low-density and 10 high-density study sites in central Texas for arrival dates and productivity. Males arrived to low density sites on average 6 days later (11 March) and those that established territories on those sites tended to be younger (62% Second-year, n = 8) than those males that established territories on high density sites (5 March, 32% SY, n = 22) although there were no differences in age structure by territory density. I aged 30 males on my study sites, 26 of which were territorial. Productivity did not vary between low and high-density sites; however, SY males had lower pairing and territory success than After Second-year (ASY) males. Understanding which portions of the warbler population are using patches of varying condition could lead to the detection of potential demographic drivers in habitat selection and could inform future management.