Northern Prairie Wildlife Research Center
Density and Fledging Success of Grassland Birds in Conservation Reserve
Program Fields in North Dakota and West-central Minnesota
by
Rolf R. Koford
Abstract: The Conservation Reserve Program, initiated in 1985,
was designed primarily to reduce soil erosion and crop surpluses. A secondary
benefit was the provision of habitat for wildlife. Grassland bird populations,
many of which declined in the decades prior to the Conservation Reserve Program,
may have benefited from the Conservation Reserve Program if reproduction in
this newly available habitat has been at least as high as it would have been
in the absence of the Conservation Reserve Program. On study areas in North
Dakota and Minnesota, I examined breeding densities and fledging success of
grassland birds in Conservation Reserve Program fields and in an alternative
habitat of similar structure, idle grassland fields on federal Waterfowl Production
Areas. Fields were 10 to 25 hectares in size. The avifaunas of these two habitats
were similar, although brush-dependent species were more abundant on Waterfowl
Protection Areas. The common species in these habitats included ones whose continental
populations have declined, such as Grasshopper Sparrow (Ammodramus savannarum),
Savannah Sparrow (Passerculus sandwichensis), and Bobolink (Dolichonyx
oryzivorus). These ground-nesting species were pooled with other ground
nesters in an analysis of fledging success, which revealed no significant differences
between habitats, between states, or among years (1991-1993). Predation was
the primary cause of nest failure. I concluded that Conservation Reserve Program
fields in this region were suitable breeding habitat for several species whose
populations had declined prior to the Conservation Reserve Program era. This
habitat appeared to be as secure for nests of ground-nesting birds as another
suitable habitat in North Dakota and Minnesota.
Key Words: Bobolink; Conservation Reserve Program; Grasshopper
Sparrow; grassland birds; habitat quality; nest success; North Dakota; Minnesota;
productivity; Savanna Sparrow; Waterfowl Production Areas
This resource is based on the following source (Northern Prairie Publication
1060):
Koford, Rolf R. 1999. Density and Fledging Success of Grassland Birds
in Conservation Reserve Program Fields in North Dakota and West-
central Minnesota. Studies in Avian Biology 19:187-195.
This resource should be cited as:
Koford, Rolf R. 1999. Density and Fledging Success of Grassland Birds
in Conservation Reserve Program Fields in North Dakota and West-
central Minnesota. Studies in Avian Biology 19:187-195.
Jamestown, ND: Northern Prairie Wildlife Research Center Online.
http://www.npwrc.usgs.gov/resource/birds/denfled/index.htm
(Version 02MAR2000).
Table of Contents
Tables
- Table 1 — Numbers seen, estimated
densities, and confidence intervals for density estimates for birds counted
on CRP and WPA fields.
- Table 2 — Estimated fledging success
of grassland birds on CRP and WPA fields.
- Table 3 — Least squares mean Daily
Survival Rates for nests of ground species in CRP and WPA fields.
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