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A trapping program was implemented along the upper San Luis Rey River (uslr) and Pamo Valley (pv) in San Diego County, California, to protect nesting southwestern willow flycatchers (Empidonax trail/ii extimus, flycatcher, swfl), least Bell's vireos ( Vireo bellii pusillus, vireo, lbvi), and riparian cohabitants from brood parasitism by the brown-headed cowbird (Molothrus ater). Four traps were operated in each location (8 total) from 1 April to 30 June 2001. We removed 284 cowbirds (68 males, 42 females, and 1j 11veniles at 11slr; 103 males, 60 females, and 10juveniles at pv). In addition, 290 individuals of 8 non-target species were captured (47 at uslr, 243 at pv), of which all but 2 (0.7%) were released unharmed. Topical protection from cowbird parasitism allows targeted populations of host species to increase annual productivity and to grow, but does not affect the regional cowbird population (Griffith and Griffith 2000).

A trapping program was implemented along the upper San Luis Rey River (uslr) and Pamo Valley (pv) in,San Diego County, California, to protect nesting southwestern willow flycatcher (Empidonax traillii extimus, flycatcher, swfl), least Bell's vireo ( Vireo bellii pusillus, vireo, lbvi), and their riparian cohabitants from brood parasitism by the brown-headed cowbird (Molothrus ater). Four traps were operated in each location (8 total) from 1 April to 30 June 2003. We removed 207 cowbirds (54 males, 38 females, and 0 juveniles at uslr; 61 males, 48 females, and 6 juveniles at pv). In addition, 330 individuals of 8 non-target species were captured (79 at uslr, 251 at pv), of which all but 6 (l.8%) were released unharmed. Topical protection from cowbird parasitism allows targeted populations of host species to increase annual productivity and to grow between years, but does not affect the regional cowbird population (Griffith and Griffith 2000).

Surveys for Harbison’s dun skipper adults were conducted to assess year to year variation in population size and to collect non-lethal genetic samples. Field visits were also used to document plants used for nectar sources. The 2017 counts were generally low, and there was not a clear relationship between the 2016 and 2017 counts as some were higher and some lower. We were able to collect 16 genetic samples including the first from Santa Margarita Trail, a second from Fox Springs, and samples three and four from Pamo Valley. Efforts were focused on sites with small populations and few previous samples, likely the reason for the low number of 2017 samples. While past years have been dry, the 2016-2017 winter had several rainstorms, each with several inches of precipitation. Soil and vegetation, including San Diego sedge, were removed in locations, altering the skipper’s habitat within the oak woodlands. It was also commonly observed that the sedge leaves were knocked down by water. Removal of sedge by high water flow is clearly a threat to the skipper, but it is unknown if short-term flooding of the sedge is a threat to the larvae. To provide a complete report, we included all 2017 Harbison’s dun skipper survey data, including our surveys not funded by this project.