Bat monitoring at the Crossroads at Big Creek Preserve, Door County, Wisconsin: 2021

We surveyed three locations for bats at the Crossroads at Big Creek Preserve during the 2021 maternity season (June–July, when bats are breeding) utilizing a zero crossing ultra-sonic acoustic recorder. Analyses of acoustic data indicated that three species were common: Big Brown Bat, Hoary Bat and Little Brown Bat. Both Big Brown and Little Brown bats are state Threatened Species. We also confirmed three additional species as present and possibly breeding: Eastern Red Bat, Silver-Haired Bat and Tricolored Bat (or Eastern Pipistrelle). Tricolored Bat is also a state Threatened Species. Of the latter three species Silver-Haired Bat showed the greatest activity and is most likely to be breeding at the Crossroads Preserve. We recommend that surveys continue for additional years to collect more comprehensive baseline data from additional sampling sites and habitats during the maternity season, as bat populations vary annually based on weather and insect availability. We also recommend that full spectrum recorders and analyses be performed in order to improve statistical confidence of automated species identifications from acoustic data. Several habitat management recommendations are made to improve bat roosting and nesting features, improve flying insect production as forage for bats, and to follow avoidance guidance for listed species.