LB 5-42 - Post-breeding survival of adult and juvenile Bank Swallows in the Great Lakes ecoregion

Background/Question/Methods:

The post-breeding period poses significant threats to young newly fledged birds due to predation, starvation, exposure to inclement weather, and collision risk prior to their first southward migration. To address the gap in knowledge about this period for Bank Swallows (Riparia riparia), we aim to estimate and compare the survival rates of adults and post-fledgling juveniles from lakeshore colonies and inland aggregate pit colonies in southern Ontario. In 2018 (juveniles) and 2021 (juveniles and adults), individuals were captured using mist nets, banded, had morphological measurements taken, and radio tags affixed. Detection data was downloaded from the Motus Wildlife Telemetry System and will be used to generate movement paths and encounter histories for the estimation of post-breeding survival rate in mark-recapture models. Seventy-six juveniles were radio tagged at 23 colonies in 2018, while 76 juveniles and 116 adults were radio tagged at 12 colonies in 2021. Malaise insect traps were set up at four sites for three days on four occasions in 2021 for the estimation and comparison of aerial insect availability between lakeshore and aggregate pit sites.

Results/Conclusions:

Based on initial data exploration, the majority of Bank Swallow remained on the north shore of Lake Erie during the entire detection period (about 90 days), with only 2 juveniles successfully crossing Lake Erie to the south shore. In June 2018, 25 juveniles were radio tagged and 11 were detected. In July 2018, 51 juveniles were radio tagged and 35 were detected. In June 2021, 116 adults were tagged and 74 were detected. In June 2021, 10 juveniles were tagged while 3 were detected. In July 2021, 66 juveniles were tagged while 29 were detected. Based on intertower movements and Motus detections, Bank Swallow juveniles showed higher exploratory movement in the post-breeding period compared to adults. Juveniles and adults remained within a 28 000 km2 study region with good Motus coverage, which supports the development of mark-recapture models to estimate survival. Preliminary analyses also suggest a greater abundance and diversity of insects compared to aggregate pit colonies. Mark-recapture models, which estimate survival while accounting for imperfect detection, will be needed to evaluate whether survival depends on colony location. Results will help determine if Ontario Bank Swallows have age dependent post-breeding survival and if post-breeding survival depends on habitat quality.