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Characteristics and Range The Black-crowned Night Heron is the most widespread heron in the world. Some populations are migratory and others sedentary. In North America, the species occurs across central and southern regions, north to the Canadian Prairies (Hothem et al. 2010). Most northern breeders migrate south to overwinter, but some birds remain quite far north, including in the Fraser River delta, where British Columbian birders are familiar with the species because small numbers have overwintered annually since 1982 at the Reifel Migratory Bird Sanctuary (Campbell et al. 1990). The species is largely crepuscular and nocturnal, so can be hard to find by day because it spends much if its time roosting motionless.

Distribution, Abundance, and Habitat There are two British Columbian breeding records, both from Reifel Migratory Bird Sanctuary on Westham Island in the Fraser River delta, in 1973 and 1975 (Campbell et al. 1990).

During the Atlas, two breeding season records were noted, both in July, one in 2008 and one in 2010, in the Fraser River delta, but away from Westham Island. One was in dense riparian habitat near the confluence of Como Creek and the Fraser River, a location which also supported a pair of breeding Green Herons. Subsequently, this site was intensively cleared of invasive plant species, and in 2009 neither Green nor Black-crowned Night herons were re-observed. The other Atlas observation was of a bird flying over potentially suitable habitat near the Nikomekl River. On Westham Island, potential breeding habitat at Reifel Migratory Bird Sanctuary and adjacent Alaksen National Wildlife Area was extensively searched during the Atlas, but no adult night-herons were found outside of their normal August to April overwintering period.

Black-crowned Night-Herons make stick platform nests in trees, usually in colonies. The nearest known colonies to southwest British Columbia are in the Columbia River valley of Washington (British Columbia Waterfowl Society 2014). Preferred nesting habitat in this part of the range is wetlands or brackish sloughs surrounded by tall willow (Salix), alder (Alnus) and birch (Betula) tree species (British Columbia Conservation Data Centre 2015).

Conservation and Recommendations Continued searches of suitable riparian habitat in the Fraser River delta may yield further breeding season records. Loss of potentially suitable riparian habitat to urban and agricultural development is an ongoing issue.

Peter J.A. Davidson and George F. Clulow

Recommended citation: Davidson, P.J.A. and Clulow, G.F. 2015. Black-crowned Night-Heron in Davidson, P.J.A., R.J. Cannings, A.R. Couturier, D. Lepage, and C.M. Di Corrado (eds.). The Atlas of the Breeding Birds of British Columbia, 2008-2012. Bird Studies Canada. Delta, B.C. http://www.birdatlas.bc.ca/accounts/speciesaccount.jsp?sp=BCNH&lang=en [05 Oct 2024]