The Windy City Rookery: Movement and Activity Patterns of Black‐Crowned Night Herons ( <i>Nycticorax nycticorax</i> ) in a Human‐Dominated Landscape

ABSTRACT As urbanization continues to accelerate, human‐dominated habitats are becoming increasingly important for wildlife as some species of conservation concern move into urban landscapes. In response to the widespread loss or conversion of their preferred wetland habitat, black‐crowned night herons ( Nycticorax nycticorax ; BCNH) frequently nest in urban areas. Despite being the most widely distributed colonial wading bird in the world, BCNH face population declines and have been listed as a special‐status species in 11 U.S. states and Ontario, Canada. The largest remaining BCNH rookery in the Great Lakes region of the U.S. is located at Lincoln Park Zoo in Chicago, Illinois. Although nesting in an urban center is inherently risky, this colony appears to be thriving. We used GPS/GSM satellite transmitters to better understand the home range size, habitat use, and activity patterns of individual birds during the breeding season. We found that BCNH foraged in a wide variety of natural and highly modified waterbodies and exhibited distinct behavioral differences between breeding and non‐breeding birds. Non‐breeding birds' home ranges were on average 18 times larger than those of breeding birds, which primarily foraged within 10 km of the colony, while non‐breeding birds ranged widely but continued to use relatively urban habitats. All birds were active throughout the 24‐h period, but breeding BCNH showed higher activity rates than non‐breeding birds during daytime hours. Understanding the behavior of this declining species within urban landscapes can improve our understanding of this species' ecology and provide valuable insights to inform management and conservation efforts.