Studying North Dakota Colonial Waterbirds to Guide their Conservation


Eastern North Dakota currently is the northern limit of the Cattle Egret’s normal breeding range. During this survey, Cattle Egret were documented breeding in eight colonies. Photo by Nancy Drilling.

Last year, Bird Conservancy led an exciting new effort to survey and inventory colonial waterbird populations in North Dakota. No systematic inventories or monitoring of waterbird colonies had yet been conducted in North Dakota, impeding the ability of conservationists to manage for this vulnerable group of birds. Therefore, the objective of the North Dakota Colonial Waterbird Inventory Project was to compile an up-to-date list or inventory of waterbird breeding sites throughout the state.


Eleven Black-crowned Night-heron colonies were discovered; 10 of these were at key waterbird sites. Most colonies were marsh colonies but most nests were in trees, i.e., tree colonies were more uncommon but larger. Photo by Nancy Drilling.

Colonial waterbirds prefer to breed in high-density groups in a relatively small number of locations, favoring predator-free habitats such as flooded timber, islands, and marsh reed beds. However, this ‘all eggs in one basket’ breeding strategy makes these species vulnerable to natural or man-made catastrophic events that could wipe out a large portion of the breeding population. In addition, populations are in decline because of wetland loss, bio-accumulation of toxins, and degradation of wintering habitat. Thus, many of these species are the focus of conservation efforts throughout North America.

During the North Dakota Colonial Waterbird Inventory Project biologists confirmed 21 colonial waterbird species breeding in the state including herons, night-herons, egrets, grebes, gulls, terns, ibis, American White Pelican, Double-crested Cormorant, and several shorebird species. While conducting the surveys, field technicians also collected data on population size at each site. The majority of sites had fewer than 50 pairs. However, 32 sites were identified as being key sites for breeding colonies of waterbirds. These “key sites” are defined as having more than 500 total breeding pairs or more than five breeding species.


The American White Pelican is a Level I Species of Conservation Priority because a large proportion of the state’s population breeds in just one colony. In addition, they nest in high densities, making them susceptible to single detrimental events (weather, predators) and disease outbreaks.  Photo by Nancy Drilling.

The inventory and associated population information produced from this project will provide baseline data for future monitoring efforts, as well as contribute to regional and national waterbird conservation efforts.

In Colorado, there are many ways to support long-term conservation of colonial waterbirds. One way is to participate in Bird Conservancy’s Colony Watch citizen science program. This program uses data collected by volunteers to inform resource managers of best practices and ensure the continuation of waterbird species. To learn more or get involved please contact Jason Beason, Special Monitoring Projects Coordinator, (970) 310-5117.


attachment ND Natural Resources Trust

Funding for this project came from a State Wildlife Grant, administered by the North Dakota Department of Game and Fish, and the North Dakota Natural Resources Trust.

Click here to download the full North Dakota Colonial Waterbird Inventory Project report.