Mapping the black-crowned night heron: Uncovering the colony dynamics, hidden movements, and activity patterns of North America’s stealthiest wading bird

Despite being the most widely distributed colonial wading bird in the world, Black-crowned Night Herons (Nycticorax nycticorax; BCNH) face substantial population declines and have been listed as a special-status species in 11 U.S. states. Amidst widespread loss or conversion of their preferred wetland habitat, this species has shown remarkable flexibility in its breeding habitat selection, nesting in a variety of natural and anthropogenic landscapes. In Illinois, the last major BCNH rookery in the state is located at the Lincoln Park Zoo near downtown Chicago. Although nesting in an urban center is inherently risky, this colony appears to be thriving. However, little research has been conducted on how these birds acquire resources and use city habitats to cope with the environmental pressures posed by urban living. To better understand patterns in their colony site preferences, I conducted a nationwide review of historical and extant BCNH colonies to explore trends in their geographical and biological characteristics. While BCNH were recorded nesting in nearly every U.S. state, in over 50 species of vegetation, and with over 30 different species of colonial wading or non-wading waterbirds, there were clear patterns in their colony composition. I also studied the movements of individual birds during the breeding season in Chicago using GPS/GSM satellite transmitters. These trackers have shown that BCNH forage in a wide variety of natural and highly modified waterbodies and revealed unexpected patterns in behavior between breeding and non-breeding birds in terms of their home range size, habitat selection, and activity patterns. This investigation of both fine scale and broader trends in BCNH habitat requirements during the breeding season will inform conservation efforts for this declining species in Illinois and beyond.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Natural Res & Env Sciences

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Slayton, Sarah

Contributors dc:contributor

• Ward, Michael P.
• Benson, Thomas J
• Van Doren, Benjamin M.

• Movement Ecology
• Bird
• Conservation
• Chicago

Statement dc:rights

• Copyright 2025 Sarah Slayton

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/129305

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F129305