To investigate whether the cumulative years of treatment had an impact on vireo reproductive effort, we looked at the effects of the Treatment Index on reproductive parameters. Results from generalized linear models indicated that treatment did not have an effect on vireo nesting effort or the number of vireo fledglings per pair produced in 2020.
Twenty-eight adult vireos were banded with a unique color combination, and 143 nestlings were banded with a single dark blue numbered federal band on the left leg. Between 2006 and 2020, survivorship of males (67±10 percent) was consistently higher than females (59±11 percent). First-year birds from 2006 to 2020 had an average over-winter survivorship of 17±5 percent. First-year dispersal in 2020 averaged 2.9±2.9 kilometers (km), with the longest dispersal (13.5 km) by a female that was recaptured at Las Flores Creek, MCBCP. From 2007 to 2012, most returning first-year vireos returned to the Project Area, whereas from 2013 to 2017, the majority of returning birds dispersed to areas outside of the Project Area. In 2018, the trend shifted, and most first-year vireos returned to the Project area. This trend continued in 2020 with most first-year vireos returning to the Project Area; 77 percent of all re-encountered first-year birds returned to the Project Area and 23 percent dispersed to areas outside of the Project Area (upstream to the middle San Luis Rey River and to drainages on MCBCP).
|Title||Least Bell's Vireos and Southwestern Willow Flycatchers at the San Luis Rey flood risk management project area in San Diego County, California—Breeding activities and habitat use—2020 annual report|
|Authors||Alexandra Houston, Lisa D. Allen, Ryan E. Pottinger, Barbara E. Kus|
|Publication Subtype||USGS Numbered Series|
|Series Title||Open-File Report|
|Record Source||USGS Publications Warehouse|
|USGS Organization||Western Ecological Research Center|