Seasonal and Nightly Activity Patterns of Migrating Silver-Haired Bats (Lasionycteris noctivagans) Compared to Non-Migrating Big Brown Bats (Eptesicus fuscus) at a Fall Migration Stopover Site

Migrating temperate bats travel hundreds and perhaps thousands of kilometers, which necessitates making use of stopover sites. Migratory birds use stopover sites to rest and refuel for subsequent migratory flights, but it isn't clear what bats do during their comparatively brief stopovers. We used acoustic monitoring to compare activity patterns of migrating silver-haired bats (Lasionycteris noctivagans) and resident big brown bats (Eptesicus fuscus) at Long Point, Ontario, Canada. From September 1 to October 31 2020 we recorded 4,333 echolocation passes from our two focal species and quatified feeding buzzes in those recordings. Migratory L. noctivagans passed through in two waves, one of which had been identified by previous study, and a second suggesting that the migratory period may be longer than previously identified. Eptesicus fuscus was primarily active only in the early and late parts of the night, in contrast to the activity pattern of L. noctivagans which were similarly active and foraging at dusk and dawn, but also during the middle parts of the night. Our acoustic monitoring data complement previous data collected from bat captures and radiotelemetry to provide further insight into stopover behaviors and ecology of temperate migratory bats.