January 4, 2024
Bird-Banding Research at Stone Lakes National Wildlife Refuge
By Zachary Zeillmann, Biological Technician
The mixed riparian
, and wetland habitats at Stone Lakes National Wildlife Refuge (SLNWR) serve as a seasonal or permanent home for over two hundred different bird species. As the primary goal of the Refuge is to manage and restore habitats for these birds, an important component of this work has been surveying what species of songbirds are using the mixed riparian habitat that often borders the wetlands and grasslands. These studies allow for up close analysis of migrant and resident songbirds and provide records of the populations’ health that allows Refuge staff to track trends going back nearly three decades.
Stan Wright, a professor and licensed bander from Sacramento City College, implemented the banding program in 1996. Refuge staff, partners, and biological students have been assisting these efforts over the years. The typical banding day starts before sunrise to get the nets fully deployed just as the sun and temperatures have started to rise. The team leaves the nets open for a period of 4 hours and check them in scheduled runs every half hour. Once the runners find birds in the net, they carefully extract the birds and place them in soft cloth bags, then carry the bags back to the banding station for examination. Examination involves taking multiple measurements of the birds’ bodies to determine relative health. Data points of interest include the wing and tail length, age, weight, body fat reserves, and breeding status. They also place a metal band with a unique serial number on each bird’s ankle. This band is recorded into a national database and helps to identify the same individual if it is captured again later by Stan’s team or any other banding group.
This program has been extremely helpful for the refuge, as demonstrated by two extensive research projects studying the captured songbirds. The first study summarized banding data and analyzed trends of bird captures over a 17-year period. During that time, banders captured over 24,000 birds covering 122 species. Stan and the Refuge staff also used the study to quantify what the top 30 most captured species were on the Refuge and even tracked the average weight by month of three species of interest. This study validated the importance of the Refuge as a breeding ground, rest stop, and wintering ground for many migratory species. The second study involved tracking the spread of West Nile Virus (WNV) through captured birds by testing for the presence of WNV antibodies. Three species of interest in this study were the Wrentit, House Finch, and California Scrub-Jay. The study tracked declines in the three bird populations due to the virus and how widely spread the antibodies became among birds that survived the infection. The heavy decline of the Scrub-Jays gave the Wrentits and House Finches opportunities to recover faster since they not only developed greater resistance to the virus, but also experienced less brood predation from the jays.
It’s thanks to partners like Stan and his many supporters and biological students that have kept interest in the banding program alive and well for so many years. The information this monitoring program provides on the health of the avian community and tracking songbird migrations has helped support management decision for maintaining the mixed riparian, wetland, and grassland habitats.