Records of the Henslow's Sparrows in Day and McPherson Counties and the First Nest Record for the Species in South Dakota

Table of Contents

• Historic Breeding Season Records in South Dakota
• Recent Breeding Season Records in South Dakota
• Present Status
• Henslow's Sparrow in CRP
• Day County in 1997
• McPherson County in 2000
• McPherson County in 2001
• Breeding Status in Bordering States
• Conclusions
• Acknowledgments
• Literature Cited

Table

• Table 1 -- Recent (post-1960) records of the Henslow's Sparrow in South Dakota during the breeding season.

Breeding Season Records in South Dakota

Historic Breeding Season Records in South Dakota. — The species' breeding range is frequently purported to include eastern South Dakota (e.g., Roberts 1932, Rising 1996), although there are no published nesting records of Henslow's Sparrows in the state (SDOU 1991, Dowd Stukel and Backlund 1997, D. Tallman, Northern State University, Aberdeen, SD, pers. com.). The breeding history of the species in South Dakota is obscure, and the species' status as a breeder in the state appears to be based on indirect evidence, (i.e., presence of adults or territorial males during the breeding season). One of the earliest references to Henslow's Sparrows in South Dakota during the breeding season came from Brewster (1891), who had three specimens in his collection that were taken in Moody County of the Dakota Territory on or about 16 June 1882. One of those specimens was collected by F. T. Jencks, but it is unclear who collected the other two birds. Brewster (1891) listed Moody County as the type location for a new subspecies named the Western Henslow's Sparrow (Ammodramus henslowii occidentalis). Brewster did not mention nesting, although he suggested that the "habitat" (presumably breeding range) of this subspecies includes the Dakota Territory and other regions along the eastern border of the Great Plains.

Other early (pre-1960) references to Henslow's Sparrows nesting in South Dakota are equally vague or inconclusive. Over and Thoms (1921) indicated that the species nests in South Dakota but did not provide information on nest locations or nesting birds. Agersborg (1885) did not include the Henslow's Sparrow in a list of birds that occur in southeastern South Dakota, whereas Larson (1925) labeled the Henslow's Sparrow as a summer resident and breeder in the Sioux Falls area (Minnehaha County) in southeastern South Dakota, but gave no evidence of nesting. Johnson (1958) indicated that Henslow's Sparrows may be expected to breed in Bon Homme County, although the species had been observed there only during migration. Other early references also noted that the species was a common migrant in South Dakota, but the references did not mention nesting. For example, Visher (1913, 1915) listed the species as only migratory in Sanborn and Clay counties. Although the literature suggests that both the eastern (A. h. susurrans) and western (A. h. henslowii) subspecies of the Henslow's Sparrow once migrated through South Dakota, only the western subspecies was considered to breed in the state (e.g., Graber 1968, Smith 1968). Recently, Vickery and Dunwiddie (1997) questioned whether the eastern subspecies still existed or had become extinct.

Recent Breeding Season Records in South Dakota. — There have been several recent (post-1960) reports of Henslow's Sparrows in South Dakota during the breeding season (Table 1). In 1965, P. F. Springer observed a singing male on 12-13 June and 3 July at Altamont Prairie in Deuel County (Springer 1965, P. F. Springer, pers. com.), and two singing males in Brookings County on 10 July (Springer in Whitney et al. 1978, Springer, pers. com.). J. Harter recorded two Henslow's Sparrows on the Tripp Breeding Bird Survey (BBS) route in Hutchinson County on 27 June 1968 and one Henslow's Sparrow near Ree Heights on the Crow Creek BBS route in Hand County on 30 June 1969 (J. R. Sauer and K. L. Pardieck, U.S. Geological Survey, Laurel, MD, pers. com.). J. D. Bryce (Cumberland, WI, pers. com.) banded a hatching-year bird in a willow (Salix spp.) thicket at LaCreek National Wildlife Refuge (Bennett County) on 13 August 1971. J. Weigle and D. Ewert observed a singing male Henslow's Sparrow at Samuel H. Ordway Memorial Prairie in McPherson County on about 15 June 1984 (Harris 1984). In Sanborn County, J. S. Palmer and R. Rogers observed a singing male Henslow's Sparrow near Forestburg on 25 June 1994 and another near Long Lake on 17-24 June 1997 (Swanson 1996, Palmer 1997, J. S. Palmer, Dakota State Univ., Madison, SD, pers. com.). The Henslow's Sparrow was not recorded during the South Dakota Breeding Bird Atlas project, which occurred between 1988 and 1993 (Peterson 1995).

Present Status. — Whitney et al. (1978) designated the Henslow's Sparrow as a rare summer resident in eastern South Dakota. The South Dakota Ornithologists' Union (1991) reduced the species' status to "casual summer visitor" in the eastern quarter of the state (casual was defined as "out of normal range [one each 2 or 3 years]"). The South Dakota Natural Heritage Program included the Henslow's Sparrow in their list of 197 vertebrates and invertebrates that are considered rare or vulnerable in the state or nation (Dowd Stukel and Backlund 1997).

Henslow's Sparrow in CRP. — The Conservation Reserve Program (CRP) of the 1985 and 1995 Farm Bills of the U.S. Department of Agriculture removed millions of hectares of highly erodible and environmentally sensitive land from crop production and established perennial grassland cover for a 10-year period. Many grassland birds, including the Henslow's Sparrow (Herkert 1997), have benefited from the network of perennial grasslands established by the CRP throughout the Great Plains and the United States (Johnson and Schwartz 1993). The vegetation structure of CRP grasslands in South Dakota is similar to that used by the Henslow's Sparrow elsewhere in the species' breeding range (e.g., see Herkert 1997, 2001). Between 1990 and 2001, staff from The Northern Prairie Wildlife Research Center of the U.S. Geological Survey have conducted annual surveys of breeding birds in over 400 CRP grassland fields in nine counties in Montana, North Dakota, South Dakota, and Minnesota (Johnson and Schwartz 1993, Johnson and Igl 1995, 2001). During this study, I observed Henslow's Sparrows on four different occasions, three of which occurred in northern South Dakota. Here I report my observations of Henslow's Sparrows in CRP fields in Day and McPherson counties, including the first documentation of a Henslow's Sparrow nest in South Dakota.

Day and McPherson County Records

Day County in 1997. — On 11 June 1997, during a survey of breeding birds in a CRP grassland field in northeastern Day County (T124N, R59W), I heard the characteristic hiccup ("tsi-lick") song of a male Henslow's Sparrow. The male was perched on a dead stem of an absinthe wormwood (Artemesia absinthium) plant within the CRP field, about 25 m from a barbed-wire fence. I observed the male for about 15 minutes, and then continued my bird survey. After completing the bird survey, I returned to the site of my original observation. I flushed the male from his original perch and from several other locations. The male remained in a well-defined area about 0.5 ha in size, and often would allow me to approach within 10 m before flying to another perch or dropping into the dense vegetation. The male sang from exposed perches as well as from within the vegetation. He usually returned to his original perch on the wormwood plant after a few flushing attempts. Whitewash on and under the original perch suggested that the bird may have used this perch for several days or perhaps weeks. I did not see or hear any other Henslow's Sparrow in the area, nor did the male exhibit any behaviors (e.g., nervousness, alarm notes, carrying food material) indicative of the presence of a female or nest.

The CRP field was 20.5 ha in size, and was surrounded by CRP, pasture, and cropland. The topography of the field was moderately rolling. Half of the field had been mowed the previous year (1996), but the male's territory was confined to the idle portion of the field. The vegetation in the idle section was about 60 cm tall, and consisted of 40% wheatgrass (Agropyron spp.), 20% alfalfa (Medicago sativa), 30% vegetative litter, and 10% standing dead vegetation. Other bird species in the field included Sedge Wren, Common Yellowthroat, Grasshopper Sparrow, Savannah Sparrow, Clay-colored Sparrow, Bobolink, Brown-headed Cowbird, and Red-winged Blackbird. I surveyed the same field in 1998-2001, at about the same date as in 1997, but did not record any Henslow's Sparrows. This was the first record of a Henslow's Sparrow in this ongoing study (but see Igl 1996 for an observation in a field in Grant County, Minnesota), and the first record of a Henslow's Sparrow in Day County during the breeding season (Table 1).

McPherson County in 2000. — On 13 June 2000, I recorded three male Henslow's Sparrows singing in a CRP grassland field in McPherson County (T128N, R72W). The males appeared to be loosely colonial, as has been described by others for this species (Rising 1996). I observed these males for about 15 minutes, and then continued my bird survey. After the survey, I flushed each male several times to estimate territory size and to evaluate mating status. The males maintained contiguous but non-overlapping territories, each about 0.25 ha or less in size. None of their behaviors suggested that they were mated, and I saw no evidence of nesting, although one of the males was more evasive than the other two. I returned to the site later that day with my two field assistants, J. Doster and K. Andersson, and we observed the three males for an additional 20 minutes, but saw no evidence of females or nesting.

This CRP field was 31.8 ha in size and was surrounded by pasture, CRP, and hayland. The vegetation was about 80 cm tall, and consisted of 60% alfalfa and 40% smooth brome (Bromus inermis). The topography of the field was slightly rolling. Other breeding species in the field included Sedge Wren, Common Yellowthroat, Dickcissel, Grasshopper Sparrow, Le Conte's Sparrow, Savannah Sparrow, Song Sparrow, Clay-colored Sparrow, Bobolink, Brown-headed Cowbird, and Western Meadowlark. There is one previous record of Henslow's Sparrows in McPherson County during the breeding season (Table 1).

McPherson County in 2001. — On 14 June 2001, I returned to that same field in McPherson County and found one male Henslow's Sparrow singing from an exposed perch (standing dead alfalfa) near the location of the previous year's observations. As I approached the male, the male stopped singing, flew about 5 m, dropped into the vegetation, and began chipping emphatically. Within 3 m of the male's original song perch, I flushed a second Henslow's Sparrow (probably a female) from a well-concealed nest, located 6 cm above the ground at the base of a clump of smooth brome and alfalfa.

The nest was cup-shaped, constructed primarily of grass, and lined with very fine grasses and rootlets. The nest was loosely woven around the vertical stems of smooth brome and alfalfa. Matted litter formed a partial dome over the nest, and vegetation height above the nest was about 45 cm. The nest contained one recently hatched nestling that I estimated to be less than one day old. Its eyes were closed, and grayish down covered portions of its head, back, sides, and wings. Henslow's Sparrows typically lay 4-5 eggs (Rising 1996), so I searched the ground within 0.5 m of the nest, but I found no evidence (e.g., eggs, egg shell fragments, dead nestlings) to indicate that the size of the clutch had been reduced (e.g., by a predator). Both adult Henslow's Sparrows were chipping from within the vegetation. I backed off from the nest location and observed the adults for about 15 minutes from distances of 25-35 m. Both adults visited the nest vicinity several times, and on one occasion I noted an adult carrying a green caterpillar to the nest vicinity. I did not return to this field to determine the nest's outcome. R. E. Martin (Minot, ND, pers. com.) visited the site on 26 June, but did not find either of the birds or the nest.

The vegetation in the field was more heterogeneous than the previous year, and included smooth brome (40%), alfalfa (25%), yellow sweet clover (Melilotus officinalis; 15%), field bindweed (Convolvulus arvensis; 5%), and vegetative litter (15%). Vegetation height for the field was about 55 cm. Other breeding species in the field included Bobolink, Grasshopper Sparrow, Clay-colored Sparrow, Common Yellowthroat, Sedge Wren, Savannah Sparrow, Red-winged Blackbird, Brown-headed Cowbird, and Western Meadowlark.

Breeding Status in Bordering States

The breeding status of the Henslow's Sparrow in states bordering South Dakota varies with the state's proximity to the species' primary breeding range. Montana and Wyoming are well outside the species' current range, and there are no published records of Henslow's Sparrows in those states (Montana Bird Distribution Committee 1996, Luce et al. 1999). Nebraska occurs on the western edge of the species' breeding range, and Sharpe et al. (2001) indicated that there were about 75 records of Henslow's Sparrows during the summer season, but no documented nesting records. Johnsgard (2001) credited CRP for recent increases and westward range expansion of Henslow's Sparrows in Nebraska. In Minnesota, the species was formerly widespread, but uncommon in the southern half of the state (Roberts 1932). Most of the recent (post 1960) breeding season records are largely restricted to the southeastern portion of the state (Janssen 1987, Hanson 1994). There is direct evidence of nesting in Hennepin and Winona counties in southeastern Minnesota (Hertzel and Janssen 1998). The species was considered a common breeder in Iowa in the late 1800s (Keyes and Williams 1889), but only a rare summer resident by the late 1900s (Kent and Dinsmore 1996). There were two recent nest records in southwestern Iowa (Melde and Koford 1996). The species' breeding history in North Dakota parallels that of South Dakota. Henslow's Sparrows have been observed several times during the breeding season in North Dakota (e.g., Renken and Dinsmore 1982), and historically the species was considered a breeder in the state (e.g., Larson 1928), but there are no records of nests before 2001, when two nests were found (Dechant et al. in prep.).

Conclusions

Since Brewster (1891) described the western subspecies of the Henslow's Sparrow, there have been only a handful of published observations of the species in South Dakota during the breeding season. Most of the observations occurred between mid- and late June and most have been fairly recent (i.e., post-1960) (Table 1). Because there is little baseline information against which population changes can be assessed, it is difficult to determine whether these apparent increases in Henslow's Sparrow observations are the result of recent changes in the species' distribution or abundance or whether they are the result of increases in observers or coverage in South Dakota in recent years.

Several factors have likely influenced the number of Henslow's Sparrow observations in South Dakota. Since European settlement, the species' breeding population has declined and its breeding range has contracted (Pruitt 1996), largely reflecting changes in the availability of suitable habitat (Kent and Dinsmore 1996, Rising 1996). Even if the species' former breeding range included the tallgrass prairies in eastern South Dakota, Henslow's Sparrow populations likely fluctuated erratically on this edge of the species' breeding range before settlement. Even within the core of the species' breeding range, populations of the Henslow's Sparrow tend to fluctuate from year-to-year in relation to moisture conditions (Herkert and Glass 1999), as has been noted for other Ammodramus sparrows (Wiens 1974, Stewart 1975, Igl and Johnson 1999). Nonetheless, I suspect that, even in recent years, the species occurs annually in South Dakota during the breeding season, but largely goes unnoticed by observers. Cryptic in both song and appearance, Henslow's Sparrows are easily overlooked in their grassland habitat. The male's song is short and insect-like (Rising 1996), and unlike many other passerines, male Henslow's Sparrows sing more frequently at night and less frequently at sunrise (Walk et al. 2000). During the breeding season, the Henslow's Sparrow is extremely secretive, and adults often escape attention by running along the ground or dropping into dense cover rather than flying. The species may be present at a site in some years and absent in others (Hyde 1939). If someone is interested in observing a Henslow's Sparrow during the breeding season in South Dakota, it is important that one is familiar with the species, its song and behaviors, and its breeding habitat. Indeed, all of the recent records of this species in South Dakota during the breeding season were by a few observers, most with multiple observations in more than one year or county (Table 1).

The dearth of earlier records of Henslow's Sparrow nests in South Dakota may reflect only that the species' nests are very well-concealed and notoriously difficult to find, even for the most experienced nest-searchers. Moreover, there are very few observers actively searching for nests in South Dakota (Springer, pers. com.). Given that very few Henslow's Sparrow nests have ever been found for this species (Pruitt 1996), it is not surprising that no nests have been found in South Dakota until 2001.