Baker Sanctuary News By Christopher Murray

Baker Sanctuary

This season the annual 100-acre survey marked its sixth year of data collection since color-banding of territorial males was initiated in the spring of 2011. While 100-acre surveys of various intensities have occurred on the 100-acre plot since its inception in 1999, the presence of color-banded individuals has made data collection more consistent, accurate, and provided the opportunity to compare results across breeding seasons. During the 2016 field season, three additional males were captured and banded for a total of 44 banded individuals over the past six years.

Beginning on March 20 and continuing through May 25, one half of the study plot was formally surveyed by Christopher Murray and the other half by Beth Samuelson. Each week the surveyors would rotate which half of the plot they surveyed in an effort to reduce observer bias. In total, 103 hours were invested in monitoring the Baker 100-acre plot for the 2016 season, still well above the 60 hours per season invested prior to 2011.


Based on compiled observations, including patterns of movement, re-sighted color banded individuals, counter-singing, and the presence of females and fledglings, it is estimated that nine GCWA males established territories primarily within plot boundaries, three males occupied territories partially within the plot, and one male occupied a territory directly adjacent to the plot, yielding an adjusted total of 10.5 territories for the 100-acre study area. While the presence of color banded GCWAs has eliminated some of the guesswork involved with attributing territories to males, some individuals remain unbanded. In the instances where males were not banded, territories were estimated in a conservative fashion to avoid overstating the number of territories associated with the plot.

Golden-cheeked warbler, Baker Sanctuary

Female Golden-cheeked warbler feeds fledgling, by Christopher Murray.

Pairing success for 2016 was similar to that of prior seasons with all territory-holding males being observed with a female. A total of 17 fledglings were detected in eight of the thirteen territories throughout the breeding season. Since no concerted effort was made to locate and monitor nests, it is very likely some fledglings were not detected as they wandered outside of documented territories or occurred on portions of a territory not within the 100-acre plot boundary.

Golden-cheeked Warbler, Baker Sanctuary

2016 Territory map shows locations for Golden-cheeked Warbler locations and individual territory boundaries, by Christopher Murray.

The map displays locations of all Golden-cheeked Warbler observations and estimated territory boundaries for 2016. Polygons surrounding the observations represent approximate boundaries of male territories, with each territory identified by color band combinations or an unbanded (UB) designation. The number of fledglings (f) detected are also indicated within each territory. In addition to clarifying territory and fecundity data, the presence of color-banded individuals also allows recognition of males returning to the plot from previous seasons. The 2016 survey saw four banded individuals (OR/SI:DB/YE, MV/MV:YE/SI, RD/WH:MV/SI, and YE/DG:DG/SI) return to the 100-acre plot area from the 2015 season as well as one individual banded during the 2014 season (BK/SI:OR/BK).