COSEWIC Assessment and Status Report on the Common Nighthawk in Canada
- Assessment Summary
- Executive Summary
- COSEWIC History, Mandate, Membership and Definitions
- Lists of Figures and Tables
- Species Information
- Population Sizes and Trends
- Limiting Factors and Threats
- Special Significance of the Species
- Existing Protection or Other Status Designations
- Technical Summary
- Acknowledgements and Authorities Consulted
- Information Sources and Biographical Summary of Report Writer
The Common Nighthawk is a medium-sized bird, with a large flattened head, large eyes, a small bill, a large mouth, long slender pointed wings and a long, slightly notched tail. It has dark brown plumage mottled with black, white and buff. In flight, adults have a white patch across the primaries. Seven subspecies are generally recognized in North America.
The breeding range of the Common Nighthawk includes all of North America, Central America and possibly southeastern Colombia. In Canada, the species occurs in all Canadian provinces and territories, except Nunavut. The Common Nighthawk winters throughout South America, primarily in regions in eastern Peru and Ecuador and in southern Brazil.
The breeding habitat of the Common Nighthawk is varied and includes open habitats where the ground is devoid of vegetation, such as sand dunes, beaches, logged areas, burned-over areas, forest clearings, rocky outcrops, rock barrens, prairies, peatbogs and pastures. From the start of European settlement, the Common Nighthawk probably took advantage of newly opened habitats created by massive deforestation in the eastern United States, as well as urban areas where it used flat gravel roofs for nesting. However, since the early 1900s, the quantity of available habitat has been declining due to forest fire suppression, reforestation, the intensive use of agricultural land and the gradual replacement of gravel roofs with tar covered roofs.
Generally, two eggs are laid directly on the ground, from the third week of May to mid-August. Incubation is carried out by the female only, and lasts 16 to 20 days, depending on the region. The nestlings remain in the nest from mid-June to the end of August and become fully developed at between 45 and 52 days. The life span of the Common Nighthawk is usually 4 to 5 years.
Population Sizes and Trends
The current population size for Common Nighthawks in Canada is estimated at 400 000 breeding adults. In Canada, data from the Breeding Bird Survey (BBS) indicate a significant long-term (i.e. 1968-2005) decline of 4.2% per year. In the most recent 10 year period (1995-2005), BBS data show a significant decline of 6.6% per year. This corresponds to a 49.5% decrease in the population. Declines have also been observed along BBS routes in the boreal forest, suggesting that the declines are not limited to southern parts of the range. Declines have also been observed along BBS routes in the boreal forest, suggesting that the declines are not limited to southern parts of the range.
Limiting Factors and Threats
The reasons for the decline in Common Nighthawk populations have not been determined. Reductions in insect prey due to large-scale pesticide use seem likely to have contributed to the decline, given the widespread declines observed in other species of aerial insectivores. Habitat loss and alteration, in particular the reforestation of abandoned agricultural fields and harvested forests, fire suppression, intensive agriculture and the gradual reduction of buildings with flat gravel covered rooftops, may also have contributed to the observed declines.
Special Significance of the Species
The Common Nighthawk is one of the only species of insectivorous, crepuscular birds that uses a wide variety of habitats and is widely distributed in Canada.
Existing Protection or Other Status Designations
In Canada, the Common Nighthawk, its nest and eggs are protected under the Migratory Birds Convention Act, 1994. Globally, NatureServe (2005) considers the species as secure (G5). The species has received NatureServe ranks in Newfoundland and Labrador and Prince Edward Island of S1S2B.
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