AUTHORS: Sarah Slayton, University of Illinois, Urbana-Champaign; Henry Adams, Urban Wildlife Institute, Lincoln Park Zoo; Michael Ward, University of Illinois, Urbana-Champaign; Michael Avara, University of Illinois, Urbana-Champaign; Brad Semel, Illinois Department of Natural Resources
ABSTRACT: Black-crowned Night-herons (BCNH) (Nycticorax nycticorax) are a colonial wading bird facing notable declines in the Great Lakes region of the U.S. due to wetland habitat loss and degradation. Although BCNH are globally distributed, they are a special-status species in 11 states including Illinois, where the species has been listed as endangered since 1977. The last major rookery in the state is located at the Lincoln Park Zoo (LPZ) near downtown Chicago. Despite the inherent risks associated with nesting in an urban center the colony appears to be flourishing, with over 300 pairs of birds fledging over 400 chicks in 2024. However, little research has been conducted on how birds are acquiring resources and utilizing city habitat to cope with the environmental pressures posed by urban living. BCNH’s cryptic nature and nocturnal lifestyle have made them challenging to study solely using traditional field methods, making them ideal to study using advanced tracking technologies. During the 2023 and 2024 breeding seasons, we deployed 16 GPS/GSM transmitters on BCNH from this colony to identify critical foraging grounds in the Chicago area. So far, these transmitters have illuminated that birds are utilizing a wide variety of natural and manmade waterbodies throughout the breeding season, some of which are hydrologically influenced by Lake Michigan while others are managed by state and local agencies. They have also revealed unexpected patterns in post-breeding movements, migration routes, and wintering ground habitat use. These insights will help inform conservation efforts for this species in Illinois, and beyond.
