29S 



The Great Plains — Our Living Resources 



For lurthtr information: 



Fritz L. Knopf 



National Biological Service 



Midcontinent Ecological 



Science Center 



4512 McMurry Ave. 



Fort Collins, CO 80525 



At one location. Crook, Colorado. 83 species of 

 birds in tiie vicinity included only 6 representa- 

 tives of the Great Plains avifauna, of which only 

 3 species bred locally (Knopf 1986). None of 

 those three species bred in the riparian vegeta- 

 tion. That riparian forest developed since 1900. 

 and almost 90% of the native birds cunently 

 breeding in northeastern Colorado have colo- 

 nized in recent times. 



Causes of Declines Unknown 



Ecological processes driving population 

 trends of North American grassland birds are 

 undescribed. As a group, grassland birds have 

 declined more than birds of other North 

 American vegetative associations. Unlike 

 Neotropical migrants, which have experienced 

 declines primarily in the northeastern deciduous 

 forests (Robbins et al. 1989). declines in grass- 

 land species are occurring at a continental scale. 

 For example, the decline in numbers of the 

 mountain plover. Cassin's sparrow, and lark 



bunting are occumng across their ranges. The 

 lack of understanding of the wintering ecology 

 of grassland birds precludes optimistic projec- 

 tions, especially for these species experiencing 

 widespread, geographic declines. 



References 



Knopf. F.L. 19S6. Changing landscapes and the cos- 

 mopolitism of the eastern Colorado avifauna. Wildlife 

 Society Bull. 14:132-142. 



Knopf. F.L. 1444. Avian assemblages on altered grasslands. 

 Studies in Avian Biology 15:247-257. 



Knopf. F.L., and F.B. Samson. Conserving the hiotic 

 integrity of the Great Plains. In S. Johnson and A. 

 Bouzaher. eds. Conservation of Great Plains ecosystems: 

 cuiTent science, future options. Kluwer Academic Press. 

 Dordrecht. Netherlands. In press. 



Mengel. R.M. 1970. The North American Central Plains as 

 an isolating agent in bird speciation. Pages 280-340 in W. 

 Dort and J.K. Jones, eds. Pleistocene and recent environ- 

 ments of the central Great Plains. University of Kansas 

 Press. Lawrence. 



Robbins, C.S., J.R. Sauer. R.S. Greenberg. and S. Droege. 

 1989. Population declines in North American birds that 

 migrate to the Neotropics. Proceedings of the National 

 Academy of Science 86:7658-7662. 



Migratory 

 Bird 



Population 

 Changes in 

 North Dakota 



by 



Lawrence D. Igl 



Douglas H. Johnson 



National Biological Service 



The status of migratory bird populations in 

 North America has received increased 

 attention in recent years. Much of this consider- 

 ation has been on Neotropical migrants, espe- 

 cially those associated with eastern forests. The 

 status of migratory bird populations in the Great 

 Plains has received far less attention. During the 

 past quarter-century, populations of many 

 species of birds that breed in the northern Great 

 Plains have increased or declined, as indicated 

 by trends from the North American Breeding 

 Bird Survey. 



In 1967 Stewart and Kantrud (1972) con- 

 ducted a survey of breeding bird populations 

 throughout North Dakota. This study offered a 

 rare glimpse of bird populations breeding in the 

 northern Great Plains as well as important base- 

 line data on breeding bird populations. These 

 data help us evaluate relationships between birds 

 and habitat conditions. We repeated the survey 

 to compare bird populations in North Dakota 

 during 1967 with those in 1992 and 1993. 



Study Areas and Methods 



To aid in a direct comparison, the same 130 

 legal quarter-sections (64.7 ha. 160 acres) sur- 

 veyed in 1967 were visited again in 1992 and 

 1993 (Figure). Surveys of breeding birds were 

 conducted as similarly as possible to the meth- 

 ods used by Stewart and Kantrud ( 1972). 



Each bird species was classified into one of 

 three groups according to its migratory strategy: 

 pennanent resident (present in North Dakota 

 year-round), short-distance migrant (winters 

 north of the U.S. -Mexico border), and long-dis- 



Figurc. Distribution of the original 1 30 quarter-sections 

 in North Dakota. 



tance migrant (winters south of the U.S.- 

 Mexico border). In addition, each species was 

 categorized to a prefeired breeding habitat: wet- 

 land/wet meadow, grassland/open habitat, open 

 habitat with scattered trees, woodland/wood- 

 land-edge, shrubland, residential/liabitat gener- 

 alist. and other. Within each group, a mean pop- 

 ulation size was calculated and expres.sed as the 

 number of indicated pairs per 100 ha (247 

 acres). 



Status and Trends 



Data were obtained on 160 breeding bird 

 species within the 128 quarter-sections that we 

 received permission to survey in all 3 years 

 (Table 1 ), including 129 species in 1967, 144 in 

 1992, and 152 in 1993. Thus, about 72% of the 

 known breeding avifauna of North Dakota 

 (Faanes and Stewart 1982) were identified. 

 Songbirds were the most common group. 



