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Prescribed fire is used to reverse invasion by woody vegetation on grasslands, but managers often are uncertain whether influences of shrub and tree reduction outweigh potential effects of fire on nest survival of grassland birds. During the 2001–2003 breeding seasons, we examined relationships of prescribed fire and woody vegetation to nest survival of clay-colored sparrow (Spizella pallida) and Savannah sparrow (Passerculus sandwichensis) in mixed-grass prairie at Des Lacs National Wildlife Refuge in northwestern North Dakota, USA.We assessed relationships of nest survival to 1) recent fire history, in terms of number of breeding seasons (2, 3, or 4–5) since the last prescribed fire, and 2) prevalence of trees and tall (>1.5 m) shrubs in the landscape and of low (≤1.5 m) shrubs within 5 m of nests. Nest survival of both species exhibited distinct patterns related to age of the nest and day of year, but bore no relationship to fire history. Survival of clay-colored sparrow nests declined as the amount of trees and tall shrubs within 100 m increased, but we found no relationship to suggest nest parasitism by brown-headed cowbirds (Molothrus ater) as an underlying mechanism. We found little evidence linking nest survival of Savannah sparrow to woody vegetation. Our results suggest that fire can be used to restore northern mixed-grass prairies without adversely affecting nest survival of ≥2 widespread passerine species. Survival of nests of clay-colored sparrow may increase when tall woody cover is reduced by fire. Our data lend support to the use of fire for reducing scattered patches of tall woody cover to enhance survival of nests of ≥1 grassland bird species in northern mixed-grass prairies, but further study is needed that incorporates experimental approaches and assessments of shorter term effects of fire on survival of nests of grassland passerines.

To improve the economic viability of grazed prairie and thus conserve it as wildlife habitat, the Prairie Pothole Joint Venture (PPJV) cost-shares establishment of rotational cattle grazing on privately owned, native rangeland. During 1996 and 1997 we evaluated duck nest density, nest success, and nesting habitat on six PPJV rotational grazed pastures on the Missouri Coteau landform in central and northwestern North Dakota. Each rotational pasture was paired with a traditional, continuous grazed pasture for comparison. We located 444 nests of eight duck species. We detected no differences (P > 0.1) between rotational and continuous grazed pastures in apparent nest density of ducks (x ± SD nests/ha, all species combined, 1996: 0.26 ± 0.09 and 0.31 ± 0.12; 1997: 0.38 ± 0.14 and 0.25 ± 0.12), although a grazing type x year interaction suggested rotational pastures might be more attractive to ducks in a dry spring (1997). No differences in duck nest success were detected between rotational and continuous pastures (% Mayfield estimate, 1996: 27.2 ± 12.6 and 15.5 ± 11.0; 1997: 21.6 ± 10.0 and 16.7 ± 13.7), but varied occurrence of canid species could have obscured differences. We detected no differences in vegetation height-density indices as measured by visual obstruction readings (VORs) between rotational and continuous pastures in 1996. VORs were greater on rotational pastures, however, in the relatively dry spring of 1997. Our findings suggested that rotational grazing systems can serve as a prairie conservation tool on private rangelands without altering habitat values for nesting ducks, and in relatively dry springs might provide more attractive nesting cover for ducks than prairie under continuous grazing.

The long-eared owl (Asio otus) is a secretive, poorly understood species in the Great Plains of the United States and Canada. In North Dakota the long-eared owl has been considered a species of special concern (Petersen 1991), due mainly to lack of information on its occurrence and nesting status. We discovered 39 long-eared owl nests while searching for Cooper's hawk (Accipiter cooperii) nests in northwestern and north central North Dakota during April and May 2000. Long-eared owl nests mainly were observed at J. Clark Salyer and Des Lacs National Wildlife Refuges (NWRs) in the Souris River basin (for study area descriptions see Nenneman et al. 2002) and at Lostwood NWR on the Missouri Coteau landform (Murphy 1993). These 39 nests exceed the total of all state breeding records for the long-eared owl through the early 1970's (Stewart 1975: 159). During 1994 to 1999 we annually found 2 to 12 long-eared owl nests while searching for Cooper's hawk nests in approximately the same area of North Dakota.

Low reproductive success is thought to be a chief cause of the steady decline in numbers of piping plover (Charadrius melodus) that nest in the northern Great Plains. Surprisingly, few reproductive success data are published from alkali lakes in the region, where most breeding pairs of piping plover nest. During 1994 to 1997 we measured nest success and fledging rates of piping plovers at 32 alkali lakes across northwestern North Dakota and northeastern Montana, at the center of the species' breeding range in the Great Plains. Annual nest success and fledging rates averaged 38% (Mayfield estimate; 20 to 66 nests/year) and 0.76 chicks/pair (28 to 76 pairs/year). The mean annual fledging rate we observed approximated that previously projected for the region from a small number of major breeding areas, and was at least 33% below estimated levels needed for population stability. About one-half of the productivity losses occurred during the egg stage, especially near hatching. Our data confirm that reproductive success of piping plovers on alkali lakes probably is less than that needed to sustain the species' Great Plains population.

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.

Ducks (Anserifonnes; Anatinae) are preyed on by red-tailed hawks (Buteo jamaicensis) in the northern Great Plains of North America, yet I found no published, direct observations of captures of wild ducks by red-tailed hawks in the region. I made the following observations in south central Burke County, northwestern North Dakota.