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North Dakota Bird Life:

Tracking Changes Over a Quarter Century

Population Changes Varied by Habitat

Increases or decreases in populations between 1967 and 1992-93 varied by preferred habitat of each species. Many birds that use wooded habitats increased, likely due to planting and maturation of shelterbelts and windbreaks, and encroachment of woody vegetation into grassland. For example, western kingbirds nearly doubled in number, and brown thrashers and song sparrows more than doubled between the two surveys. Species associated with humans and the structures they build also tended to increase. House sparrows and American robins nearly doubled in number, as did cliff swallows and barn swallows.

GIF-Wilson's phalarope JPG-WetlandsGIF-Mallards

Species associated with wetlands tended to decline from 1967 (a year of about average wetland conditions) to 1992 (a very dry year). Many wetland species bounced back in 1993, which was wetter than average. Mallards, for example, decreased from 212 observed pairs in 1967 to 113 pairs in 1992, but rebounded to 200 pairs in 1993.

Not all wetland species followed the same pattern, however. The marsh wren was more common in 1992 (113 pairs) than in 1967 (51 pairs) and even more numerous in 1993 (153 pairs). The increase probably reflects greater abundance of cattails and other emergent wetland vegetation this bird favors. The Wilson's phalarope, however, with 30 pairs in 1992 and 36 pairs in 1993, had not recovered to 1967 levels, when 73 pairs were observed. Wilson's phalaropes may not have responded to improved water conditions in 1993 because their favored nesting habitat, the wet meadow zone surrounding many wetlands, has been reduced in area by cultivation.

Many grassland birds followed a pattern somewhat similar to wetland birds. Chestnut-collared longspurs fell in number from 1,129 observed pairs in 1967 to 602 pairs in 1992, and then increased to 755 pairs in 1993. Savannah sparrows decreased from 516 observed pairs to 134, and then increased to 276 pairs in 1993. The lark bunting, however, which prefers more semi-arid habitats, increased from 604 pairs in 1967 to 679 pairs in 1992, and then dropped to 298 pairs in the wet year, 1993.

GIF-Upland sandpiperJPG-GrasslandsGIF-Chestnut-collared longspur

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