During a continuing investigation in the northern Great Plains, we documented substantial increases of the Le Conte\u27s Sparrow (Ammodramus Leconteii) in Conservation Reserve Program (CRP) fields in 1994 compared with 1990-93. The most dramatic increases occurred in Eddy County, North Dakota, and Sheridan County, Montana. The changes in habitat associated with the drought from 1989 to early 1993 and above-normal precipitation from mid-1993 through mid-1994 likely produced favorable breeding conditions for this species in CRP fields in 1994

Igl, Lawrence D

Johnson, Douglas H

English

UNL | Libraries

University of Nebraska - Lincoln 
DigitalCommons@University of Nebraska - Lincoln 
USGS Northern Prairie Wildlife Research Center US Geological Survey 
1995 
Dramatic Increase of Le Conte's Sparrow in Conservation Reserve 
Program Fields in the Northern Great Plains 
Lawrence D. Igl 
USGS Northern Prairie Wildlife Research Center, ligl@usgs.gov 
Douglas H. Johnson 
USGS Northern Prairie Wildlife Research Center, Douglas_H_Johnson@usgs.gov 
Follow this and additional works at: https://digitalcommons.unl.edu/usgsnpwrc 
 Part of the Other International and Area Studies Commons 
Igl, Lawrence D. and Johnson, Douglas H., "Dramatic Increase of Le Conte's Sparrow in Conservation 
Reserve Program Fields in the Northern Great Plains" (1995). USGS Northern Prairie Wildlife Research 
Center. 170. 
https://digitalcommons.unl.edu/usgsnpwrc/170 
This Article is brought to you for free and open access by the US Geological Survey at DigitalCommons@University of 
Nebraska - Lincoln. It has been accepted for inclusion in USGS Northern Prairie Wildlife Research Center by an 
authorized administrator of DigitalCommons@University of Nebraska - Lincoln. 
89 
Dramatic Increase of Le Conte's Sparrow 
in Conservation Reserve Program Fields 
in the Northern Great Plains. 
LAWRENCE D. IGL and DOUGLAS H. JOHNSON 
National Biological Service, Northern Prairie Science Center, 8711 37th Street 
SE, Jamestown, ND 58401 
Abstrac:t-During a continuing investigation in the northern Great Plains, we documented substantial 
increases of the Le Conte's Sparrow (Ammodramus Lecontei!) in Conservation Reserve Program (CRP) 
fields in 1994 compared with 1990-93. The most dramatic increases occurred in Eddy County, North 
Dakota, and Sheridan County, Montana. The changes in habitat associated with the drought from 1989 
to early 1993 and above-normal precipitation from mid-1993 through mid-1994 likely produced 
favorable breeding conditions for this species in CRP fields in 1994. 
Key words: Le Conte's Sparrow ,Ammodramus Leconteii, distribution, Conservation Reserve Program, 
northern Great Plains 
The Conservation Reserve Program (CRP) of the 1985 Food Security Act 
(Fann Bill) removed millions of hectares of highly erodible and marginal land from 
crop production and established perennial grassland in its place (Young and Osborn 
1990). Many breeding bird species have benefitted from the grassland habitats 
established by this federal land retirement program (King 1991; Johnson and 
Schwartz 1993a,b; Kantrud 1993; Patterson 1994; Reynolds et al. 1994). During an 
ongoing study of breeding bird communities in CRP fields, we observed dramatic 
increases in the number of breeding pairs of the Le Conte's Sparrow (Ammodramus 
leconteil) using CRP fields in the northern Great Plains in 1994 compared with the 
previous four years. 
STUDY AREAS AND METHODS 
Our study areas included CRP fields in nine counties in Montana, North 
Dakota, South Dakota, and Minnesota (Fig. 1), including 240 fields (4,654 ha) in 
1990,335 fields (6,181 ha)in 1991,371 fields (6,904 ha) in 1992,354 fields (7,243 
ha) in 1993, and 359 fields (7,042 ha) in 1994. Once fields were selected, we 
surveyed them in subsequent years unless permission to access a field was denied. 
Many areas in the northern Great Plains experienced drought from 1989 to 
early 1993 and above-normal precipitation from mid-1993 through mid-1994 
(National Oceanic and Atmospheric Administration 1989-1994) (Table 1). Most 
CRP fields remained relatively idle during the study period, although some fields 
were released for emergency haying and grazing because of drought in 1988, 1989, 
90 Prairie Naturalist 27(2): June 1995 
NO DE 
~ 
MN MT 
SO 
Figure 1. Counties selected for surveys of breeding birds in Conservation 
Reserve Program fields. North Dakota: E-Eddy, K-Kidder, H-Hettinger; 
Montana: S-Sheridan, F-Fallon; South Dakota: B-Butte, M-McPherson, D-
Day; Minnesota: G-Grant 
Table 1. Long-term (1961-1990) average precipitation in centimeters (May of 
previous year to April of current year) and annual deviations from the average, 
1990-1994, taken at the nearest national weather station 
Long-term Deviations from the lon~-term avera8e 
County average 1989-90 1990-91 1991-92 1992-93 1993-94 
Eddy, NO 45.72 +0.58 -2.11 +3.71 -8.33 +22.81 
Kidder, NO 41.10 -13.87 +6.45 +1.83 -7.67 +21.54 
Hettinger, NO 41.88 -13.44 -11.68 -9.35 -16.41 +20.04 
Sheridan, MT 32.39 -8.36 +1.57 +10.26 -6.38 +24.92 
Fallon,MT 36.60 -14.38 -7.90 +1.60 -5.38 +16.69 
Butte, SO 42.67 -1.65 -4.83 -13.31 +5.00 +14.38 
McPherson, SO 40.18 -10.41 +12.57 -9.02 +18.03 +39.29 
Oay, SO 53.49 +3.91 +1.40 + 12.12 -6.30 +30.10 
Grant, MN 64.72 -3.40 +3.38 +5.61 -137 +0.25 
Igi and Johnson: Le Conte's Sparrow in CRP 91 
1990, and 1992, and flooding in 1993 and 1994. These disturbances occurred after 
birds were surveyed each year. 
We surveyed breeding birds using a minor modification of the strip transect 
procedures used by Stewart and Kantrud (1972). This method allows a fairly rapid 
assessment of the breeding bird community of a field. Fields were surveyed once 
each year by one or two observers on foot We tallied all indicated breeding pairs, 
based on singing or calling males, females, observed pairs, or presence of an active 
nest Small fields were surveyed by a single observer; large fields were surveyed 
by two observers, each covering about half. The number and configuration of 
transects varied depending upon field size and shape. Care was taken to avoid 
double-counting birds. Surveys began about dawn and continued until midafternoon. 
Surveys extended beyond the time of most active bird vocalization, but Stewart and 
Kantrud (1972) concluded that activities of open-country birds are not appreciably 
affected by time of day other than early morning and late evening. Surveys were 
conducted from late May to early July each year, during the peak breeding season 
of the LeConte's Sparrow (StewartandKantrud 1972, Stewart 1975). Counts were 
avoided in adverse weather conditions (precipitation or strong winds). 
Some breeding birds were likely missed in our single survey (e.g., J~inen 
andLokki 1978) ofCRP fields. The same technique was used in each year, however, 
so any bias should be consistent. 
In each year of the bird surveys, we visually estimated the areal coverage of 
the most common plant taxa in each field. In the northern Great Plains, most CRP 
land is planted to a mixture of grasses and legumes, although vegetation varies 
considerably among fields and counties (Johnson and Schwartz 1993b). 
RESULTS AND DISCUSSION 
Within the area of our study (Fig. I), the Le Conte's Sparrow regularly breeds 
in northwestern Minnesota (Janssen 1987) and in east and central North Dakota 
(Stewart 1975). Le Conte's Sparrows were present in CRP fields in five of the nine 
counties surveyed in 1990-94 (Table 2). Day County, South Dakota, and Grant 
County, Minnesota, are on the southern edge of the species' breeding distribution 
(Janssen 1987, South Dakota Ornithologists' Union 1991). There is one recent 
breeding record of Le Conte's Sparrow in Day County, South Dakota (Skadsen 
1987). Skaar et al. (1985) reported that there was only circumstantial evidence to 
indicate breeding of Le Conte's Sparrow in the region of Sheridan County, 
Montana. The presence of 52 breeding pairs in 1994 suggests that the Le Conte's 
Sparrow may breed commonly in this region in certain years. The remaining four 
counties (Fallon Co., MT; Butte Co., SD; McPherson Co., SD; Hettinger Co., NO) 
are generally considered outside of the species' normal breeding range. 
Information on the breeding biology of the Le Conte's Sparrow is limited 
(Ehrlich et al. 1988). The species primarily breeds in moist grass or sedge meadows 
(American Ornithologists' Union 1983). In North Dakota, the Le Conte's Sparrow 
92 Prairie Naturalist 27(2): June 1995 
Table 2. Number of breeding pairs and density (pairs/1 00 hal of Le Conte's 
Sparrows observed in Conservation Reserve Program fields in the northern 
Great Plains, 1990-1994 
Number of breeding pairs Density 
County 1990 1991 1992 1993 1994 1991-93 1994 
Eddy, ND 0 1 0 0 206 0.03 21.47 
Kidder, ND 0 0 0 1 26 0.03 2.74 
Hettinger, ND 0 0 0 0 0 0 0 
Sheridan, MT 0 0 8 0 52 0.30 7.76 
Fallon,MT 0 0 0 0 0 0 0 
Butte, SD 0 0 0 0 0 0 0 
McPherson, SD 0 0 0 0 0 0 0 
Day, SD 0 0 0 0 2 0 0.23 
Grant, MN 0 0 0 2 4 0.09 0.76 
favors wet habitats (Murray 1969), and Stewart (1975) considered the optimal 
habitat for this species to be the hummocky vegetation of fens. Less commonly, the 
species breeds in other grassland habitats such as tallgrass prairie, hayfields, and 
retired cropland (Stewart 1975). In this study, we found no breeding pairs in 1990, 
one in 1991, eight in 1992, three in 1993, and 290 in 1994 in the perennial grasslands 
established by the CRP. The changes in habitat associated with the increase in 
precipitation between 1989-93 (drought conditions) and 1993-94 (wet conditions) 
likely produced favorable breeding conditions for this species in 1994 (Table 1). In 
this context, Stewart (1975) commented that local populations of the Le Conte's 
Sparrow fluctuate annually in North Dakota and that the species "reaches peak 
numbers during wet years, while during dry years it may be scarce or absent" Many 
of the breeding pairs observed in CRP fields in 1994 were found in damp and low-
lying areas within the fields, although breeding pairs in dry, upland areas were not 
uncommon. In 1994, Le Conte's Sparrows also were common in other grassland-
like habitats (e.g., hayland, native grassland, etc.) in North Dakota (G.B. Berkey, 
Minot State Univ., NO, pers. commun.). 
The most dramatic increase in Le Conte's Sparrows occurred in Eddy County, 
North Dakota (Table 2). In 1994, we found Le Conte's Sparrows in 27 of 43 (63%) 
CRP fields, totalling 206 indicated breeding pairs. Of the 27 fields containing Le 
Conte's Sparrows, the average density was 35.37 (SD= 19.72) pairs per l00ha, with 
arangeof2.41 to 73.20 pairs per l00ha. In 15 of the 27 fields, Le Conte's Sparrow 
populations surpassed or equalled those of the next most abundant species. In strong 
contrast, we found only one pair in CRP fields in Eddy County during the previous 
four years. 
In Eddy County, wheatgrasses (Agropyron elongatum, A. smithii, or A. 
intermedium) dominated the vegetation cover (average: 41%) of CRP fields 
supporting Le Conte's Sparrows, followed by smooth brome (Bromus inermis; 
Igi and Johnson: Le Conte's Sparrow in CRP 93 
20%) and alfalfa (Medicago sativa; 8%). In Saskatchewan, Hartley (1994) found 
that the Le Conte's Sparrow was the most common breeding bird in grasslands 
managed for waterfowl production and dominated by wheatgrass, smooth brome, 
and alfalfa. 
The rapid colonization of CRP fields by Le Conte's Sparrows in 1994 
suggests that CRP fields may be an important breeding habitat for this species only 
under certain (i.e., wet) conditions. Moreover, the current practice of releasing CRP 
fields for emergency mowing and grazing during extreme wet or dry years may 
negatively impact species that breed in CRP fields only under these conditions. 
Murray (1969) suggested that the changes in litter associated with annual mowing 
in North Dakota would eliminate Le Conte's Sparrows from hay fields. Kantrud 
(1981) found that Le Conte's Sparrow populations were reduced or extirpated by 
heavy grazing. Conversely, some species may respond positively to the changes in 
vegetation and residual cover produced from infrequent mowing (e.g., Frawley and 
Best 1991, Herkert 1991). The influence of emergency mowing and grazing ofCRP 
fields on breeding bird populations remains poorly understood. 
ACKNOWLEDGMENTS 
We appreciate the cooperation of the numerous land-owners and -operators 
who allowed access to their property, the Agricultural Stabilization and Conserva-
tion Service (ASCS) state directors, and the executive directors and staffs of county 
ASCS offices who provided information on CRP fields. We also acknowledge C.J. 
Johnson, RL. Manson, K.L. Richardson, M.D. Schwartz, C.M. Shoemaker, J.M. 
Steiner, and K.A. Ward for considerable assistance in the field. G.B. Berkey, H.A. 
Kantrud, J.T. Lokemoen, J. Price, M.D. Schwartz, J.L. Zimmerman, and one 
anonymous reviewer provided constructive comments on the manuscript. 
LITERATURE CITED 
American Ornithologists' Union. 1983. Check-list of North American birds. Allen 
Press, Lawrence, KS. 
Ehrlich, P.R., D.S. Dobkin, and D. Wheye. 1988. The birder's handbook: a field 
guide to the natural history of North American birds. Simon and Schuster 
Inc., New York. 
Frawley, B.J., andL.B. Best 1991. Effects of mowing on breeding bird abundance 
and species composition in alfalfa fields. Wildt. Soc. Bull. 19:135-142. 
Hartley, MJ. 1994. Passerine abundance and productivity indices in grasslands 
managed for waterfowl nesting cover in Saskatchewan, Canada. M.S. 
Thesis. Louisiana State Univ., Baton Rouge. 
Herkert, J.R. 1991. An ecological study of the breeding birds of grassland habitats 
within Illinois. Ph.D. Thesis, Univ. Illinois, Urbana-Champaign. 
Janssen, R.B. 1987. Birds in Minnesota. Univ. Minnesota Press, Minneapolis. 
94 Prairie Naturalist 27(2): June 1995 
Jarvinen, O. and J. Lolli. 1978. Indices of community structure in bird censuses 
based on a single visit effect of variation in species efficiency. Ornis Scand 
9:87-93. 
Johnson, D.H., and M.D. Schwartz. 1993a. The Conservation Reserve Program 
and grassland birds. Conserv. BioI. 7:934-937. 
Johnson, D.H., and M.D. Schwartz. 1993b. The Conservation Reserve Program: 
habitat for grassland birds. Great Plains Research 3:273-295. 
Kantrud, H.A. 1981. Grazing intensity effects on breeding avifauna of North 
Dakota native grasslands. Can. Field-Nat. 95:404-417. 
Kantrud, H.A. 1993. Duck nest success on Conservation Reserve Program land in 
the prairie pothole region. J. Soil Water Conserv. 48:238-242. 
King,J.W. 1991. Effects of the Conservation Reserve Program on selected wildlife 
populations in southeast Nebraska M.S. Thesis. Univ. Nebraska, Lincoln. 
Murray, B.G., Jr. 1969. A comparative study of the Le Conte's and Sharp-tailed 
Sparrows. Auk 86:199-231. 
National Oceanic and Atmospheric Administration. 1989-1994. Climatological 
Data for Minnesota, Montana, North Dakota, and South Dakota. U.S. 
Department of Commerce, Ashville, NC. 
Patterson, M.P. 1994. Bird species abundance, composition and vegetation 
characteristics, and bird productivity in Conservation Reserve Program land 
in central Iowa. M.S. Thesis. Iowa State Univ., Ames. 
Reynolds, R.E., T L. Shaffer, J.R. Sauer, and B.G. Peterjohn. 1994. Conservation 
Reserve Program: benefit for grassland birds in the northern plains. Trans. 
N. Am. Wildi. Nat Resour. Conf. 59:328-336. 
Skaar, D., D. Flath, and L.S. Thompson. 1985. P.D. Skaar's Montana bird 
distribution. Montana Aead. Sei., Monogr. 3. 
Skadsen, D. 1987. LeConte's Sparrow breeding in Day County. South Dakota Bird 
Notes 39:13-14. 
South Dakota Ornithologists' Union. 1991. The birds of South Dakota. Northern 
State Univ. Press, Aberdeen, SD. 
Stewart, R.E. 1975. Breeding birds of North Dakota. Tri-College Center for 
Environmental Studies, Fargo, ND. 
Stewart, R.E., and H.A. Kantrud. 1972. Population estimates of breeding birds in 
North Dakota. Auk 89:766-788. 
Young, E.C., and C.T. Osborn. 1990. Costs and benefits of the Conservation 
Reserve Program. J. Soil Water Conserv. 45:370-373. 
Received 23 January 1995. Accepted 19 April 1995. 


Dramatic Increase of Le Conte\u27s Sparrow in Conservation Reserve Program Fields in the Northern Great Plains

DigitalCommons@University of Nebraska

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln USGS Northern Prairie Wildlife Research Center US Geological Survey 1995 Dramatic Increase of Le Conte's Sparrow in Conservation Reserve Program Fields in the Northern Great Plains Lawrence D. Igl USGS Northern Prairie Wildlife Research Center, ligl@usgs.gov Douglas H. Johnson USGS Northern Prairie Wildlife Research Center, Douglas_H_Johnson@usgs.gov Follow this and additional works at: https://digitalcommons.unl.edu/usgsnpwrc  Part of the Other International and Area Studies Commons Igl, Lawrence D. and Johnson, Douglas H., "Dramatic Increase of Le Conte's Sparrow in Conservation Reserve Program Fields in the Northern Great Plains" (1995). USGS Northern Prairie Wildlife Research Center. 170. https://digitalcommons.unl.edu/usgsnpwrc/170 This Article is brought to you for free and open access by the US Geological Survey at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in USGS Northern Prairie Wildlife Research Center by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. 89 Dramatic Increase of Le Conte's Sparrow in Conservation Reserve Program Fields in the Northern Great Plains. LAWRENCE D. IGL and DOUGLAS H. JOHNSON National Biological Service, Northern Prairie Science Center, 8711 37th Street SE, Jamestown, ND 58401 Abstrac:t-During a continuing investigation in the northern Great Plains, we documented substantial increases of the Le Conte's Sparrow (Ammodramus Lecontei!) in Conservation Reserve Program (CRP) fields in 1994 compared with 1990-93. The most dramatic increases occurred in Eddy County, North Dakota, and Sheridan County, Montana. The changes in habitat associated with the drought from 1989 to early 1993 and above-normal precipitation from mid-1993 through mid-1994 likely produced favorable breeding conditions for this species in CRP fields in 1994. Key words: Le Conte's Sparrow ,Ammodramus Leconteii, distribution, Conservation Reserve Program, northern Great Plains The Conservation Reserve Program (CRP) of the 1985 Food Security Act (Fann Bill) removed millions of hectares of highly erodible and marginal land from crop production and established perennial grassland in its place (Young and Osborn 1990). Many breeding bird species have benefitted from the grassland habitats established by this federal land retirement program (King 1991; Johnson and Schwartz 1993a,b; Kantrud 1993; Patterson 1994; Reynolds et al. 1994). During an ongoing study of breeding bird communities in CRP fields, we observed dramatic increases in the number of breeding pairs of the Le Conte's Sparrow (Ammodramus leconteil) using CRP fields in the northern Great Plains in 1994 compared with the previous four years. STUDY AREAS AND METHODS Our study areas included CRP fields in nine counties in Montana, North Dakota, South Dakota, and Minnesota (Fig. 1), including 240 fields (4,654 ha) in 1990,335 fields (6,181 ha)in 1991,371 fields (6,904 ha) in 1992,354 fields (7,243 ha) in 1993, and 359 fields (7,042 ha) in 1994. Once fields were selected, we surveyed them in subsequent years unless permission to access a field was denied. Many areas in the northern Great Plains experienced drought from 1989 to early 1993 and above-normal precipitation from mid-1993 through mid-1994 (National Oceanic and Atmospheric Administration 1989-1994) (Table 1). Most CRP fields remained relatively idle during the study period, although some fields were released for emergency haying and grazing because of drought in 1988, 1989, 90 Prairie Naturalist 27(2): June 1995 NO DE ~ MN MT SO Figure 1. Counties selected for surveys of breeding birds in Conservation Reserve Program fields. North Dakota: E-Eddy, K-Kidder, H-Hettinger; Montana: S-Sheridan, F-Fallon; South Dakota: B-Butte, M-McPherson, D-Day; Minnesota: G-Grant Table 1. Long-term (1961-1990) average precipitation in centimeters (May of previous year to April of current year) and annual deviations from the average, 1990-1994, taken at the nearest national weather station Long-term Deviations from the lon~-term avera8e County average 1989-90 1990-91 1991-92 1992-93 1993-94 Eddy, NO 45.72 +0.58 -2.11 +3.71 -8.33 +22.81 Kidder, NO 41.10 -13.87 +6.45 +1.83 -7.67 +21.54 Hettinger, NO 41.88 -13.44 -11.68 -9.35 -16.41 +20.04 Sheridan, MT 32.39 -8.36 +1.57 +10.26 -6.38 +24.92 Fallon,MT 36.60 -14.38 -7.90 +1.60 -5.38 +16.69 Butte, SO 42.67 -1.65 -4.83 -13.31 +5.00 +14.38 McPherson, SO 40.18 -10.41 +12.57 -9.02 +18.03 +39.29 Oay, SO 53.49 +3.91 +1.40 + 12.12 -6.30 +30.10 Grant, MN 64.72 -3.40 +3.38 +5.61 -137 +0.25 Igi and Johnson: Le Conte's Sparrow in CRP 91 1990, and 1992, and flooding in 1993 and 1994. These disturbances occurred after birds were surveyed each year. We surveyed breeding birds using a minor modification of the strip transect procedures used by Stewart and Kantrud (1972). This method allows a fairly rapid assessment of the breeding bird community of a field. Fields were surveyed once each year by one or two observers on foot We tallied all indicated breeding pairs, based on singing or calling males, females, observed pairs, or presence of an active nest Small fields were surveyed by a single observer; large fields were surveyed by two observers, each covering about half. The number and configuration of transects varied depending upon field size and shape. Care was taken to avoid double-counting birds. Surveys began about dawn and continued until midafternoon. Surveys extended beyond the time of most active bird vocalization, but Stewart and Kantrud (1972) concluded that activities of open-country birds are not appreciably affected by time of day other than early morning and late evening. Surveys were conducted from late May to early July each year, during the peak breeding season of the LeConte's Sparrow (StewartandKantrud 1972, Stewart 1975). Counts were avoided in adverse weather conditions (precipitation or strong winds). Some breeding birds were likely missed in our single survey (e.g., J~inen andLokki 1978) ofCRP fields. The same technique was used in each year, however, so any bias should be consistent. In each year of the bird surveys, we visually estimated the areal coverage of the most common plant taxa in each field. In the northern Great Plains, most CRP land is planted to a mixture of grasses and legumes, although vegetation varies considerably among fields and counties (Johnson and Schwartz 1993b). RESULTS AND DISCUSSION Within the area of our study (Fig. I), the Le Conte's Sparrow regularly breeds in northwestern Minnesota (Janssen 1987) and in east and central North Dakota (Stewart 1975). Le Conte's Sparrows were present in CRP fields in five of the nine counties surveyed in 1990-94 (Table 2). Day County, South Dakota, and Grant County, Minnesota, are on the southern edge of the species' breeding distribution (Janssen 1987, South Dakota Ornithologists' Union 1991). There is one recent breeding record of Le Conte's Sparrow in Day County, South Dakota (Skadsen 1987). Skaar et al. (1985) reported that there was only circumstantial evidence to indicate breeding of Le Conte's Sparrow in the region of Sheridan County, Montana. The presence of 52 breeding pairs in 1994 suggests that the Le Conte's Sparrow may breed commonly in this region in certain years. The remaining four counties (Fallon Co., MT; Butte Co., SD; McPherson Co., SD; Hettinger Co., NO) are generally considered outside of the species' normal breeding range. Information on the breeding biology of the Le Conte's Sparrow is limited (Ehrlich et al. 1988). The species primarily breeds in moist grass or sedge meadows (American Ornithologists' Union 1983). In North Dakota, the Le Conte's Sparrow 92 Prairie Naturalist 27(2): June 1995 Table 2. Number of breeding pairs and density (pairs/1 00 hal of Le Conte's Sparrows observed in Conservation Reserve Program fields in the northern Great Plains, 1990-1994 Number of breeding pairs Density County 1990 1991 1992 1993 1994 1991-93 1994 Eddy, ND 0 1 0 0 206 0.03 21.47 Kidder, ND 0 0 0 1 26 0.03 2.74 Hettinger, ND 0 0 0 0 0 0 0 Sheridan, MT 0 0 8 0 52 0.30 7.76 Fallon,MT 0 0 0 0 0 0 0 Butte, SD 0 0 0 0 0 0 0 McPherson, SD 0 0 0 0 0 0 0 Day, SD 0 0 0 0 2 0 0.23 Grant, MN 0 0 0 2 4 0.09 0.76 favors wet habitats (Murray 1969), and Stewart (1975) considered the optimal habitat for this species to be the hummocky vegetation of fens. Less commonly, the species breeds in other grassland habitats such as tallgrass prairie, hayfields, and retired cropland (Stewart 1975). In this study, we found no breeding pairs in 1990, one in 1991, eight in 1992, three in 1993, and 290 in 1994 in the perennial grasslands established by the CRP. The changes in habitat associated with the increase in precipitation between 1989-93 (drought conditions) and 1993-94 (wet conditions) likely produced favorable breeding conditions for this species in 1994 (Table 1). In this context, Stewart (1975) commented that local populations of the Le Conte's Sparrow fluctuate annually in North Dakota and that the species "reaches peak numbers during wet years, while during dry years it may be scarce or absent" Many of the breeding pairs observed in CRP fields in 1994 were found in damp and low-lying areas within the fields, although breeding pairs in dry, upland areas were not uncommon. In 1994, Le Conte's Sparrows also were common in other grassland-like habitats (e.g., hayland, native grassland, etc.) in North Dakota (G.B. Berkey, Minot State Univ., NO, pers. commun.). The most dramatic increase in Le Conte's Sparrows occurred in Eddy County, North Dakota (Table 2). In 1994, we found Le Conte's Sparrows in 27 of 43 (63%) CRP fields, totalling 206 indicated breeding pairs. Of the 27 fields containing Le Conte's Sparrows, the average density was 35.37 (SD= 19.72) pairs per l00ha, with arangeof2.41 to 73.20 pairs per l00ha. In 15 of the 27 fields, Le Conte's Sparrow populations surpassed or equalled those of the next most abundant species. In strong contrast, we found only one pair in CRP fields in Eddy County during the previous four years. In Eddy County, wheatgrasses (Agropyron elongatum, A. smithii, or A. intermedium) dominated the vegetation cover (average: 41%) of CRP fields supporting Le Conte's Sparrows, followed by smooth brome (Bromus inermis; Igi and Johnson: Le Conte's Sparrow in CRP 93 20%) and alfalfa (Medicago sativa; 8%). In Saskatchewan, Hartley (1994) found that the Le Conte's Sparrow was the most common breeding bird in grasslands managed for waterfowl production and dominated by wheatgrass, smooth brome, and alfalfa. The rapid colonization of CRP fields by Le Conte's Sparrows in 1994 suggests that CRP fields may be an important breeding habitat for this species only under certain (i.e., wet) conditions. Moreover, the current practice of releasing CRP fields for emergency mowing and grazing during extreme wet or dry years may negatively impact species that breed in CRP fields only under these conditions. Murray (1969) suggested that the changes in litter associated with annual mowing in North Dakota would eliminate Le Conte's Sparrows from hay fields. Kantrud (1981) found that Le Conte's Sparrow populations were reduced or extirpated by heavy grazing. Conversely, some species may respond positively to the changes in vegetation and residual cover produced from infrequent mowing (e.g., Frawley and Best 1991, Herkert 1991). The influence of emergency mowing and grazing ofCRP fields on breeding bird populations remains poorly understood. ACKNOWLEDGMENTS We appreciate the cooperation of the numerous land-owners and -operators who allowed access to their property, the Agricultural Stabilization and Conserva-tion Service (ASCS) state directors, and the executive directors and staffs of county ASCS offices who provided information on CRP fields. We also acknowledge C.J. Johnson, RL. Manson, K.L. Richardson, M.D. Schwartz, C.M. Shoemaker, J.M. Steiner, and K.A. Ward for considerable assistance in the field. G.B. Berkey, H.A. Kantrud, J.T. Lokemoen, J. Price, M.D. Schwartz, J.L. Zimmerman, and one anonymous reviewer provided constructive comments on the manuscript. LITERATURE CITED American Ornithologists' Union. 1983. Check-list of North American birds. Allen Press, Lawrence, KS. Ehrlich, P.R., D.S. Dobkin, and D. Wheye. 1988. The birder's handbook: a field guide to the natural history of North American birds. Simon and Schuster Inc., New York. Frawley, B.J., andL.B. Best 1991. Effects of mowing on breeding bird abundance and species composition in alfalfa fields. Wildt. Soc. Bull. 19:135-142. Hartley, MJ. 1994. Passerine abundance and productivity indices in grasslands managed for waterfowl nesting cover in Saskatchewan, Canada. M.S. Thesis. Louisiana State Univ., Baton Rouge. Herkert, J.R. 1991. An ecological study of the breeding birds of grassland habitats within Illinois. Ph.D. Thesis, Univ. Illinois, Urbana-Champaign. Janssen, R.B. 1987. Birds in Minnesota. Univ. Minnesota Press, Minneapolis. 94 Prairie Naturalist 27(2): June 1995 Jarvinen, O. and J. Lolli. 1978. Indices of community structure in bird censuses based on a single visit effect of variation in species efficiency. Ornis Scand 9:87-93. Johnson, D.H., and M.D. Schwartz. 1993a. The Conservation Reserve Program and grassland birds. Conserv. BioI. 7:934-937. Johnson, D.H., and M.D. Schwartz. 1993b. The Conservation Reserve Program: habitat for grassland birds. Great Plains Research 3:273-295. 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Conservation Reserve Program: benefit for grassland birds in the northern plains. Trans. N. Am. Wildi. Nat Resour. Conf. 59:328-336. Skaar, D., D. Flath, and L.S. Thompson. 1985. P.D. Skaar's Montana bird distribution. Montana Aead. Sei., Monogr. 3. Skadsen, D. 1987. LeConte's Sparrow breeding in Day County. South Dakota Bird Notes 39:13-14. South Dakota Ornithologists' Union. 1991. The birds of South Dakota. Northern State Univ. Press, Aberdeen, SD. Stewart, R.E. 1975. Breeding birds of North Dakota. Tri-College Center for Environmental Studies, Fargo, ND. Stewart, R.E., and H.A. Kantrud. 1972. Population estimates of breeding birds in North Dakota. Auk 89:766-788. Young, E.C., and C.T. Osborn. 1990. Costs and benefits of the Conservation Reserve Program. J. Soil Water Conserv. 45:370-373. Received 23 January 1995. Accepted 19 April 1995. 

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Dramatic Increase of Le Conte\u27s Sparrow in Conservation Reserve Program Fields in the Northern Great Plains

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