Southwestern Willow Flycatcher (Empidonax traillii extimus) surveys in San Diego County, California, 2021

Data presented are results of surveys in 2021 for Southwestern Willow Flycatcher (Empidonax traillii extimus) in San Diego County, California. Surveys were conducted at the 2016-19 nest monitoring locations (Cleveland National Forest, Rey River Ranch, and Vista Irrigation District) and at Lake Henshaw along the Upper San Luis Rey River. Surveys were conducted along multiple sections of the river where permission to access properties could be obtained. Locations were surveyed using a standardized protocol three to four times between 15 May and 31 July. The number, age (adult or juvenile), sex, banding status (color banded or not, and if so, color combination), and breeding status (paired, undetermined, or transient) of all willow flycatchers was recorded.