Fish Crows: Overnight Winter Roost

Jan. 27, 2025: According to Dr. Kevin J. McGowan, the leading expert on Fish Crows in the United States, Fish Crows form large roosts outside the breeding season, sometimes exceeding 45,000 birds. They gather in pre-roosting areas and may mix with American Crows. Typically roosting in trees, they have also been found in willows, marshes, urban settings, rural areas, and offshore islands. They sometimes share roosts with herons, egrets and other wading birds.

For years, members of the Crow Patrol have been dedicated to identifying a significant winter Fish Crow (Corvus ossifragus) roost in Florida, an aspect of their ecology that remains largely undocumented. Despite the ubiquity of Fish Crows in the Southeast United States, there are very few known videos or imaging records of a winter roost, and McGowan has recognized that little research exists on their behavior outside the breeding season. In late 2024, we observed large winter roost flight streams in Jupiter, Florida, offering a rare opportunity to document and analyze these birds using pioneering regular and thermal aerial imaging technology—an approach never before applied to a winter Fish Crow roost.

From early November 2024 to late February 2025, an estimated 4,000 to 4,500 Fish Crows arrived many evenings, streaming in primarily from the south and converging over and into trees on a small island in a waterway within a private residential community. Nearby pre-roost staging sites included estuarine shorelines, small islands, trees, power lines, and rooftops. The roosting flight typically lasted between 15 and 35 minutes, with peak movement occurring 18 to 37 minutes after sunset time, at times reaching an influx of over 250 crows per minute. Birds flew in at heights of 25 to 45 meters, often higher than wading birds sharing the same area. Unlike previous observations, we noted frequent vocalizations, including unique calls, which may signal social interactions, hierarchical structuring, or kinship recognition.

In his monograph on Fish Crows for “Birds of the World“, McGowan has noted the lack of detailed studies on Fish Crow populations in winter months, their seasonal movements, vocal communications, and maintaining social bonds. Our dedicated count in February 2025 of approximately 4,100 birds suggests a very stable midwinter population. This new study provides rare insights into Fish Crow winter roosting behavior, their migration patterns, and the social dynamics within large aggregations. The use of regular and thermal aerial imaging tools to document the roost activity marks a groundbreaking step in understanding the nocturnal behaviors of this understudied species. Continued monitoring and expanded research efforts are essential to fully grasp the complexities of Fish Crow winter ecology.

Reference: McGowan, K. J. (2020). Fish Crow (Corvus ossifragus), version 1.0. In Birds of the World (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA