296 



The Great Plains — Oi(r Livini; Resources 



numbers. For example, native grassland birds 

 iiave shown steeper, more consistent, and more 

 geographically widespread declines than any 

 other avian group, including Neotropical 

 migrants (Knopf, this section). Species such as 

 mallard {Anas plaTyrhynchos). blue-winged teal 

 (/4. discors). and northern pintail {A. acuta) are 

 now at or near the lowest numbers ever record- 

 ed (Shaffer and Newton, this section). The pri- 

 mary reason for these declines in numbers is 

 low nest success due to predation by common 

 species such as red fox { Viilpes viilpes: Shaffer 

 and Newton, this section). In other species, such 

 as American coot (Ftdica aineiicana). drainage 

 of wetlands compounded by severe drought 

 may have played a role in depressing popula- 

 tions (Igl and Johnson, this section). In contrast 

 to waterfowl, the coyote {Canis latrans) is 

 increasing its range. Historical and recent trends 

 in coyote populations and diet may reflect a 

 response to land-use changes, especially agri- 

 cultural changes and shifts in human popula- 

 tions on the Great Plains (Gipson and Brillhail. 

 this section). 



The Great Plains are becoming increasingly 

 rural because of emigration of people and a shift 



of human populations away from farms to urban 

 centers. Although the Great Plains encompass 

 about 20% of the land mass of the lower 48 

 states, the population is only about 2% of the 

 U.S. total. Federal agricultural land-retirement 

 programs, such as the Soil Bank Program and 

 the Conservation Reserve Program (CRP). 

 devised to mediate tluctuations in the farm 

 economy, may also help slow or reverse the 

 declines of some grassland species. For exam- 

 ple, recent field surveys have shown that sever- 

 al grassland birds that had declined in the Great 

 Plains are much more common on CRP habitat 

 than in cropland (Johnson and Koford, this sec- 

 tion). In recent years numerous small to medi- 

 um tracts of native grassland have been desig- 

 nated as preserves. These areas plus changes in 

 agricultural practices that promote natural 

 resource conservation (e.g.. CRP) are important 

 to protect the remaining biodiversity of the 

 Great Plains. 



References 



Klopatek. E.V.. R.J. Olson. C.J. Emerson, and J.L. Jones. 

 1 979. Landuse conflicts with natural vegetation. 

 Environmental Conservation 6:191-200. 



Declining 



Grassland 



Birds 



by 



Fritz L. Knopf 

 National Biological Senice 



Native grasslands represent the largest vege- 

 tative province of North America. Almost 

 1.5 million km- (0.6 million mi-) of grasslands 

 historically occurred on the Great Plains. 

 Although the Great Plains played a inajor role 

 in the evolution of North American forest birds 

 (Mengel 1970). the grassland avifauna itself is 

 relatively poor with only 5% of all North 

 American bird species believed to have evolved 

 within the Great Plains. That group includes 12 

 species of birds that are considered endemic 

 (i.e., evolved specifically within) to the grass- 

 lands, along with 20 others that have centers of 

 evolution on the grasslands but range more 

 widely into contiguous vegetative provinces. 



The landscape of the Great Plains has under- 

 gone significant alteration from descriptions 

 provided in early accounts. The influences have 

 been varied with many (e.g.. urbanization, min- 

 eral exploration, and defense installations) hav- 

 ing primarily local effects on the native birds. 

 Activities with more universal effects on the 

 landscape have included transformation of the 

 native grazing community, cultivation of grains 

 and tame grasses, draining of wetlands, and 

 woody development in the form of tree plant- 

 ings in the dry central and western Great Plains 

 (Knopf and Samson, in press). Also, ecological 

 invasions following fire suppression in the east- 

 em and central plains and water developments 

 in the western plains have drastically altered 

 historical landscapes. 



Of the 435 bird species breeding in the 

 United States. 330 have been recorded on the 

 Great Plains. Current avian assemblages on the 

 grasslands reflect two broad patterns of change 

 that have occurred in the last century: native 

 endemic species have declined in numbers 

 (Table) while simultaneously (and rather inde- 

 pendently) alien species have expanded their 

 ranges (Knopf 1994). 



Methods 



Information on the annual status of endemic 

 grassland birds was obtained through the 

 Breeding Bird Surveys (1966-91). which are 

 conducted annually during the bird breeding 

 season at numerous sites across the nation. 



Status and Trends 



During the last 25 years, grassland species 

 have shown steeper, more consistent, and more 

 geographically widespread declines than any 

 other behavioral or ecological guild of North 

 American birds, including Neotropical 

 migrants. Continental population trends of 

 many indiv idual species of grassland birds also 

 declined. Excluding the wetland-associated 

 marbled godwit (Limosa fedoa) and Wilson's 

 phalarope (Phalarapus tricolor), 7 of the 10 

 endemic grassland species showed population 



