1. Snyder, Noel FR, Snyder Helen (2006) Raptors of North America: natural history and conservation. Voyageur Press, McGregor, pp 40–49
2. American Ornithologists’ Union (1983) Check-list of North American Birds, 7th edn. American Ornithologists’ Union, Washington, DC
3. Paterson RL Jr (1984) Wilson Bull 96:467–469
4. Coleman JS, Fraser JD (1987) J Wildl Manage 51:733–739
5. Migratory Bird Treaty Act of 1918, 16 USC 703–712