US Fish & Wildlife Service


Date of this Version



Published in The Prairie Naturalist 28(2): June 1996. Used by permission.


Nesting chronology of raptors is sparsely documented in North Dakota. During 1981-94, we determined hatching dates at 298 nest attempts by eight species of raptors on and within 10 km of Lostwood National Wildlife Refuge, northwestern North Dakota. Mean hatching dates for most common species were 17 April for great horned owl (Bubo virginianus)(SD = 8.4 days, n = 70 nests), 1 June for red-tailed hawk (Buteo jamaicensis)(7.3, 99), 19 June for northern harrier (Circus cyaneus)(11.1, 37), 24 June for Cooper's hawk (Accipiter cooperii)(4.6, 19), and 27 June for Swainson's hawk (B. swainsoni)(6.8, 45). For six of eight species examined, egg or nestling dates were earlier or later than previously recorded in North Dakota. Overall, a relatively late chronology was suggested.