300 



The Great Plains — Our Living Resources 



Table 3. Mean number of inJieal- 

 ed breeding pairs in 128 randomly 

 selected quarter-sections in North 

 Dakota by year, migration strategy, 

 and preferred breeding habitat. 



For further information: 



Lawrence D. Igl 



National Biological Service 



Northern Prairie Science Center 



8711 37th St. SE 



Jamestown, ND 38401 



Fedefal land-retifenient programs (such as 

 the Soil Bank Program in 1967 and the 

 Conservation Reserve Program in 1992-93) 

 may help slow or reverse the declines of some 

 grassland species. For example, between 1982 

 and 1991. the sedge wren {Cistothorus platen- 

 sis) showed a significant decline on Breeding 

 Bird Surveys in North Dakota, Over 5(Wc of 

 sedge wren breeding pairs found in all 3 years 

 were found in these set-aside habitats. 



In contrast, the populations of birds associat- 

 ed with woody vegetation may be less vulnera- 

 ble to climatological factors such as drought. 

 Species associated with woody vegetation have 

 increased dramatically between 1967 and 1992- 

 93 (Tables 2 and 3), In presettlemenl times, fire 

 and grazing pressures played a major role in the 

 fomiation and maintenance of the grassland 

 landscape of the northern Great Plains, The 

 rela.xation and alteration of these pressures 

 resulted in the encroachment of shrubs and trees 

 into grassland habitats. Landscape fragmenta- 

 tion by tree plantings (e.g., farmstead wind- 

 breaks and field shelterbelts) is also suspected 

 in the increase in species associated with woody 



vegetation. These conditions provided wood- 

 land and woodland-edge species with nesting 

 opportunities that did not exist or were quite 

 limited in presettlemenl times. In addition, mat- 

 uration of the woody vegetation in these tree 

 plantings may be attractive to certain species. 

 For example, 14 of 15 species that nest in tree 

 cavities showed increasing or stable populations 

 in this survey. 



Conservation Implications 



Further analysis of habitat changes between 

 1967 and 1992-93 are needed to fully under- 

 stand the changes in bird populations in North 

 Dakota. Many species associated with the 

 increasing amount of woody vegetation are 

 common and have widespread distributions in 

 North America (Johnson et al, 1994), On the 

 other hand, many grassland and wetland species 

 experienced declines and have few habitat alter- 

 natives to the Great Plains. The implication is 

 that preservation of native grassland and wet- 

 land habitats is necessary to support breeding 

 populations of migrants in the northern plains. 



References 



Faanes. C,A,. and R,E, Stewart. 1982. Revised checklist of 

 North Dakota birds. Praine Naturalist 14:81-92. 



Johnson, D.H., R.L. Kreil, G.B. Berkey. R.D. Crawford. 

 D.O. Lambeth, and S.F. Galipeau. 1994. Influences of 

 waterfowl management on nongame birds: the North 

 Dakota experience. Transactions of the North American 

 Wildlife and Natural Resource Conference 59: 293-302. 



Stewart. R.E. 197,5. Breeding birds of North Dakota. Tri- 

 College Center for Environmental Studies. Fargo. ND. 

 295 pp. 



Stewart. R.E., and H.A. Kantrud. 1972. Population estimates 

 of breeding birds in North Dakota. Auk 89:766-788. 



Duck Nest 

 Success in the 

 Prairie 

 Potholes 



by 



Terry L. Shaffer 



Wesley E. Newton 

 National Biological Service 



Since the early 1970"s. the numbers of some 

 waterfowl species such as mallard (Amis 

 platyrhynchos), blue-winged teal (A. discors). 

 and northern pintail (A. acuta) have reached or 

 nearly reached the lowest ever recorded. Low 

 nest success (the proportion of nests in which 

 one or more eggs hatch) in key breeding areas, 

 including the U.S. Prairie Pothole region, is 

 partly responsible for declines in duck numbers 

 (Klett et al, 1988; Johnson et al, 1992). 



Methods 



We examined status and trends of duck nest 

 success for mallard, blue-winged teal, gadwall 

 (A. strepera). northern shoveler (A. clypeata), 

 and northern pintail, for one to four time peri- 

 ods between 1966 and 1989. and for five 

 regions in North and South Dakota and 

 Minnesota (Fig. 1). Nest success data originat- 

 ed from numerous independent studies conduct- 



ed throughout the region. Some data from 1966 

 to 1984 were previously analyzed by Klett et al. 

 ( 1988). We followed the methods of Klett et al., 

 except we considered one additional time peri- 

 od (1985-89) and one additional habitat 

 (Conservation Reserve Program lands). 



Nest Success 



Mallard 



Data for 4,093 mallard nests showed that 

 their nest success ranged from 6% to 20% (Fig. 

 2). Only 3 of 14 nest success estimates reached 

 or exceeded 15%, the level of nest success 

 thought necessary to maintain mallard numbers 

 at a stable level in central North Dakota 

 (Cowardin et al. 1985). These three areas were 

 central South Dakota (1966-74), eastern South 

 Dakota (1985-89). and central North Dakota 

 (1985-89). 



