Henslow's Sparrow Research Articles

Helping at a Henslow's Sparrow Nest in Wisconsin

We document the first reported observation of helping at the nest of a Henslow's Sparrow (Ammodramus henslowii). Video surveillance recorded two unbanded adults (a presumed male and female) and one banded adult male feeding chicks. No intraspecific aggression among the adults was observed.

Relative effects of litter and management on grassland bird abundance in Missouri, USA

Transect bird surveys were conducted at 43 tallgrass prairies in southwestern Missouri, U.S.A. in mid-June each year from 1992 to 1999. Litter volume on and near the ground was estimated on a nine-point scale during 1994 to 1999. The relative importance of management type (rotational burning, rotational haying, or a combination of both) and litter volume on relative abundance was analysed for three declining grassland songbirds: Henslow's Sparrow Ammodramus henslowii, Grasshopper Sparrow A. savannarum, and Dickcissel Spiza americana. Haying resulted in significantly higher abundance than burning for all species except Dickcissel, for which few significant management effects were detected. Henslow's Sparrow increased in abundance from light to heavy litter, Grasshopper Sparrow peaked in low to intermediate litter, and Dickcissel showed little pattern relative to litter. Litter scores recorded in each management type increased with number of years since last treatment. Although litter profoundly affected bird abundance, independent and equally important was whether that litter was obtained via haying or burning. Greater consistency among years in hayed vegetation structure may help explain these birds' preference for haying over burning or haying + burning. Rotational haying should be employed more than burning in the management of these declining birds, especially for the sharply declining, fire-sensitive Henslow's and Grasshopper Sparrows.

Landscape-level Analyses of Henslow's Sparrow (Ammodramus henslowii) Abundance in Reclaimed Coal Mine Grasslands

Abstract Henslow's sparrow (Ammodramus henslowii) abundance, measured as average number of males at point counts, varied within and among reclaimed mine grasslands of southwestern Indiana. The 19 mine grasslands studied range from about 100 to 3200 ha and vary in landscape structure and composition both within the mines and in relation to the surrounding area. Nevertheless, few landscape-level attributes of mine grasslands were related to Henslow's sparrow abundance. Landscape composition (e.g., percent forest or grassland cover), in particular, had a negligible effect on Henslow's sparrow abundance. Neither habitat patch size nor shape had a significant effect on Henslow's sparrow abundance, but these birds tended to avoid habitat edges. Variation in Henslow's sparrow abundance was, however, influenced by the composition and structure of local vegetation. The relative “landscape insensitivity” of Henslow's sparrows probably reflects the large area of mine grasslands rather than a true lack of landscape-s...

Reclaimed Coal Mine Grasslands and Their Significance for Henslow's Sparrows in the American Midwest

Abstract Present methods of surface coal-mine reclamation in the Midwest produce large grasslands, some of which exceed 2,000 ha in extent. Total “mine grassland” production in southwestern Indiana alone is well in excess of 70 square miles (180 km2). Our work in 19 reclaimed coal mines in southwestern Indiana indicates that mine grasslands harbor many Henslow's Sparrows (Ammodramus henslowii). We base that conclusion on point-count and line-transect surveys that yielded between 200–300 singing male Henslow's Sparrows during the 1997 and 1998 breeding seasons. Those survey results imply an uncorrected population density of ∼0.10 males per hectare, and a corrected density of ∼0.16 males per hectare (correcting for undetected males). Extrapolating this corrected density to total habitat coverage suggests an overall population of a few thousand Henslow's Sparrows in the mine grasslands of southwestern Indiana. Small-scale vegetational surveys suggest that much of the within-mine variation in Henslow's Sparrow abundance reflects local vegetative structure, with males preferring sites typically associated with that species of bird: tall, dense grass-dominated vegetation with a substantial litter layer. Management for this kind of vegetative structure could greatly increase the number of Henslow's Sparrows inhabiting reclaimed mines. Midwestern mine grasslands could play a significant role in stabilizing the populations of Henslow's Sparrows and other grassland birds.

Reclaimed Coal Mine Grasslands and Their Significance for Henslow's Sparrows in the American Midwest

Reclaimed Coal Mine Grasslands and Their Significance for Henslow's Sparrows in the American Midwest

RECLAIMED COAL MINE GRASSLANDS AND THEIR SIGNIFICANCE FOR HENSLOW'S SPARROWS IN THE AMERICAN MIDWEST

Present methods of surface coal-mine reclamation in the Midwest produce large grasslands, some of which exceed 2,000 ha in extent. Total “mine grassland” production in southwestern Indiana alone is well in excess of 70 square miles (180 km2). Our work in 19 reclaimed coal mines in southwestern Indiana indicates that mine grasslands harbor many Henslow's Sparrows (Ammodramus henslowii). We base that conclusion on point-count and line-transect surveys that yielded between 200–300 singing male Henslow's Sparrows during the 1997 and 1998 breeding seasons. Those survey results imply an uncorrected population density of ∼0.10 males per hectare, and a corrected density of ∼0.16 males per hectare (correcting for undetected males). Extrapolating this corrected density to total habitat coverage suggests an overall population of a few thousand Henslow's Sparrows in the mine grasslands of southwestern Indiana. Small-scale vegetational surveys suggest that much of the within-mine variation in Henslow's Sparrow abundance reflects local vegetative structure, with males preferring sites typically associated with that species of bird: tall, dense grass-dominated vegetation with a substantial litter layer. Management for this kind of vegetative structure could greatly increase the number of Henslow's Sparrows inhabiting reclaimed mines. Midwestern mine grasslands could play a significant role in stabilizing the populations of Henslow's Sparrows and other grassland birds.

Grassland Bird Conservation: CP1 vs. CP2 Plantings in Conservation Reserve Program Fields in Missouri

To determine the relative value of different Conservation Reserve Program (CRP) plantings for breeding grassland and winter birds we measured vegetation structure, avian abundance and reproductive success, and estimated fecundity during 1993–1995 on CP1 (cool-season grass) and CP2 (warm-season grass) plantings in 16 fields in northern Missouri. CP1 fields had been planted to cool-season grasses or cool-season grass-legume mixtures and CP2 fields had been seeded with switchgrass (Panicum virgatum). Species richness, abundance and nesting success of grassland birds during the breeding season and total bird use in the winter did not differ between CPs. During the breeding season CP1 fields had higher abundances of grasshopper sparrow (Ammodramus savannarum), eastern meadowlark (Sturnella magna), Henslow's sparrow (Ammodramus henslowii) and American goldfinches (Carduelis tristis), whereas common yellowthroats (Geothlypis trichas) were more abundant in CP2 fields. Fecundity of dickcissels (Spiza americana) and nesting success and fecundity of red-winged blackbirds (Agelaius phoeniceus) were higher on CP2 than on CP1 habitat, but both CPs were likely sinks (λ < 1) for these species. Both CPs were likely source (λ > 1) habitat for grasshopper sparrows, whereas only CP1 habitat was likely a source for eastern meadowlarks and American goldfinches. In winter American goldfinches were more abundant in CP1 fields than CP2 fields. The shorter, more diverse, cool-season grass fields were equal or better habitat than taller, more vertically dense, switchgrass-dominated fields for grassland birds, including several species of high conservation concern. Single-species plantings of warm- or cool-season grasses should be avoided to increase the potential wildlife benefits of CRP and other grassland habitats.

Detecting Area Sensitivity: A Comment on Previous Studies

Abstract Several studies have reported that some grassland birds are area sensitive; they exhibit a nonrandom avoidance of small fields. The methods used to test for area sensitivity, however, differed among studies. Some investigators sampled fields with sampling effort proportional to field size, whereas others used equal sampling effort in all fields. We created a simulation model with the same number of fields and field sizes as those examined in earlier studies to determine if birds that select habitat randomly would display area sensitivity if fields were sampled in proportion to their size. The three species that we modeled to settle randomly, upland sandpiper (Bartramia longicauda), Henslow's sparrow (Ammodramus henslowii) and eastern meadowlark (Sturnella magna), had positive relationships between occurrence and field size when a complete census or proportional sampling was used, and therefore, would have been considered area sensitive by the methods used by some previous authors. When equal-effo...

Nocturnal Singing in Grassland Birds

We conducted unlimited radius point counts from March–July 1999 at sunrise, dusk, and night to document the relative frequency of nocturnal singing by grassland birds at Prairie Ridge State Natural Area, Jasper County, Illinois. Most grassland species were recorded singing at all times of day, but least commonly at night. Short-eared Owls (Asio flammeus) and American Woodcock (Scolopax minor) were only recorded at dusk and night. Sedge Wrens (Cistothorus platensis) and Henslow's Sparrows (Ammodramus henslowii) were most frequently recorded at night and least frequently at sunrise. Only 57% of all the breeding species recorded by our surveys were detected on June sunrise counts corresponding to the timing of the North American Breeding Bird Survey.

Evidence for Edge Effects on Multiple Levels in Tallgrass Prairie

Abstract We tested how edges affect nest survival and predator distribution in a native tallgrass prairie system in southwestern Missouri using artificial nests, natural nests of Dickcissels (Spiza americana) and Henslow's Sparrows (Ammodramus henslowii), and mammal track stations. Survival of artificial nests was lower within 30 m of forest edge. Nesting success of Dickcissels and Henslow's Sparrows was lower within 50 m to a shrubby edge than at greater distances, whereas fates of nests were not related to distances to roads, agricultural fields, or forests. Evidence from clay eggs placed in artificial nests indicated that mid-sized carnivores were the major predators within 30 m of forest edges. Furthermore, mid-sized carnivores visited track stations most frequently within 50 m of forest edges. Because proximity of woody habitat explained more variation in nest survival and mammal activity than did fragment size, it appears that edge effects were more pronounced than area effects. Edge effects appeared to be caused mainly by greater exposure of nests to mid-sized carnivores. We argue that, based on edge avoidance behavior, “grassland-interior” species such as the Henslow's Sparrow respond to edge effects mainly by a decrease in density, whereas habitat generalists such as the Dickcissel are affected mainly by a decrease in nesting success.

Grassland management for the conservation of songbirds in the Midwestern USA

We monitored breeding eastern meadowlarks, dickcissels, Henslow's sparrows, grasshopper sparrows and field sparrows using strip transect surveys in 1995 and 1996. The 473-ha study area was an array of 3-ha management units of burned, mowed, hayed, grazed and undisturbed (>1 year) cool- and warm-season grasses and annual weeds. Management units grouped by habitat type (management regime and grass type) had different ( P<0.05) abundances of each species. Eastern meadowlarks and dickcissels were most frequently observed in grazed warm-season grasses. Observation rates of Henslow's sparrows and field sparrows were highest in undisturbed warm-season grasses, whereas eastern meadowlarks and grasshopper sparrows were observed least often in this habitat type. Grasshopper sparrows were observed most frequently in annual weeds; Henslow's sparrows and field sparrows were not observed in this habitat type. Overall avian abundance was lowest in recently burned cool-season grasses. The low-intensity, late-season grazing system was important for creating a heterogeneous habitat mosaic attractive to the five species studied.

HENSLOW'S SPARROW HABITAT ASSOCIATIONS ON KANSAS TALLGRASS PRAIRIE

We examined macro- and microhabitat characteristics of breeding Henslow's Sparrows (Ammodramus henslowii) on Fort Riley Military Reservation, Kansas during 1995 and 1996. Survey points were identified at the macrohabitat scale as either grassland, savanna, or woodland edge. A military disturbance index was used to quantify the severity of training disturbance to the vegetation at survey and bird use sites. At the large scale, Henslow's Sparrows were associated with grassland habitat last burned in 1993, two or three years previously. Microhabitat at Henslow's Sparrow use sites had lower tree density than random survey points, but neither shrub density nor military disturbance index differed between use sites and survey points during spring. In summer, the military track index was higher on Henslow's Sparrow's use sites. Habitat used by Henslow's Sparrows was consistently tall and dense vegetation with high litter cover during early spring, late spring, and summer whereas the vegetation of random survey points changed in response to vegetation growth. Characteristics of Henslow's Sparrow use sites included high cover by litter and dense, structurally homogeneous vegetation, whereas litter depth and standing dead vegetation, physiognomic diversity, and military disturbance did not differ from random survey points.

EVIDENCE FOR EDGE EFFECTS ON MULTIPLE LEVELS IN TALLGRASS PRAIRIE

Abstract We tested how edges affect nest survival and predator distribution in a native tallgrass prairie system in southwestern Missouri using artificial nests, natural nests of Dickcissels (Spiza americana) and Henslow's Sparrows (Ammodramus henslowii), and mammal track stations. Survival of artificial nests was lower within 30 m of forest edge. Nesting success of Dickcissels and Henslow's Sparrows was lower within 50 m to a shrubby edge than at greater distances, whereas fates of nests were not related to distances to roads, agricultural fields, or forests. Evidence from clay eggs placed in artificial nests indicated that mid-sized carnivores were the major predators within 30 m of forest edges. Furthermore, mid-sized carnivores visited track stations most frequently within 50 m of forest edges. Because proximity of woody habitat explained more variation in nest survival and mammal activity than did fragment size, it appears that edge effects were more pronounced than area effects. Edge effects appeare...

Patterns of Area Sensitivity in Grassland‐Nesting Birds

Abstract: Between 1995 and 1997, we studied breeding birds in fragments of native tallgrass prairie in southwestern Missouri to determine the effect of habitat fragmentation on grassland bird populations. Data on density and nesting success collected in 13 prairie fragments of various sizes revealed three levels of area sensitivity. The most area‐sensitive species, Greater Prairie‐Chicken ( Tympanuchus cupido), was absent from small prairie fragments. An intermediate form of area sensitivity was apparent in only one species, Henslow's Sparrow (Ammodramus henslowii), which occurred in lower densities in small than in large prairie fragments. Based on census (i.e., distributional) data, only those two species were area‐sensitive (i.e., negatively affected by habitat fragmentation) in southwestern Missouri. A species can be sensitive not only on a distributional level, however, but also by having lower nesting success in small than in large prairie fragments. The Dickcissel ( Spiza americana) was the only species that was area‐sensitive on such a demographic level. These data indicate that we cannot rely solely on census data to describe the sensitivity of grassland‐nesting species to habitat fragmentation, but that we also need to investigate demographic data (e.g., nesting success). Whereas it has previously been shown that density measures of forest‐nesting birds do not reliably reflect nesting success in habitat fragments of various sizes, ours is the first study that describes this pattern for grassland‐nesting species.

Correlations in abundance of grassland songbirdsand prairie butterflies

During 1992–1997, transect surveys simultaneously counting three declining grassland songbirds and all butterfly species were conducted at 109 prairie grasslands in Illinois, Iowa, Minnesota, Missouri, North Dakota, and Wisconsin, USA. Pairwise correlations in abundance between a songbird and a butterfly species were performed with the three songbird species—Henslow's sparrow Ammodramus henslowii, grasshopper sparrow A. savannarum, and dickcissel Spiza americana—and 17 butterfly species, chosen because they were the most frequently observed butterflies in each of three ecological groups (prairie specialist, grassland, generalist) or because they were taxonomically close to the prairie specialists in analysis. Butterfly species in the most restrictive ecological group (specialists) significantly and positively correlated most strongly with the three songbirds, especially at the scale of the entire study region and in subregions where both species in the correlation were more abundant. Grassland butterflies (occurring widely in native prairie and old fields) and generalist butterflies were similarly lower than specialists in degree of covariance with the birds. Correlations of the birds as a group with all observed butterfly individuals in each of the three ecological groups showed similar patterns. Other studies have shown that diversities of distantly related animal groups may not correlate well among habitats and regions. But this study suggests that, within a habitat and region, conservation programs benefitting grassland birds can be favorable for co-occurring prairie-specialist butterflies and that certain bird and butterfly species can be effective indicators of each other.

Effects of Habitat Area on the Occurrence of Grassland Birds in Illinois

Abstract We documented the occurrence of 12 bird species within Prairie Ridge State Natural Area, Jasper County, Illinois, a matrix of nine grassland tracts (range 7–120 ha, totaling 489 ha), from 1994 to 1997 and analyzed the presence of these species relative to the area of the nine grassland tracts. Grassland tract area was correlated with the occurrence of greater prairie-chickens (Tympanuchus cupido) (P = 0.016), upland sandpipers (Bartramia longicauda) (P = 0.012), savannah sparrows (Passerculus sandwichensis) (P = 0.009) and Henslow's sparrows (Ammodramus henslowii) (P = 0.005). Minimum area requirements varied from 12 ha for grasshopper sparrows (Ammodramus savannarum), 55 ha for northern harriers (Circus cyaneus), 65 ha for greater prairie-chickens and upland sandpipers, to 75 ha for Henlsow's and savannah sparrows. Therefore, grasslands larger than 60 ha may be required to attract nine breeding grassland bird species. Each grassland tract was divided into 2- to 6-ha management units (mode = 2.8 ...

Habitat Requirements of Henslow's Sparrows Wintering in Silvicultural Lands of the Gulf Coastal Plain

Henslow's Sparrow (Ammodramus henslowii) is one of several grassland bird species that has declined during the last several decades. Although several studies have char- acterized the habitat requirements of breeding Henslow's Sparrows, winter habitat require- ments for the species remain poorly known. The purpose of our study was to identify habitat variables associated with occupancy by Henslow's Sparrow on silvicultural larids in the core of its winter range in the Gulf Coastal Plain. Forty-one study sites were chosen on lands managed for timber production in Baldwin County, Alabama. Henslow's Sparrows selected moist sites that occurred as pitcher plant bogs or as transition areas between wet pitcher plant bogs and drier upland areas. A multiple logistic regression model identified the den- sity of the grass Panicum verrucosum and the density of pitcher plants as the variables best able to explain the presence of Henslow's Sparrows. Sites occupied by Henslow's Sparrows had higher herbaceous vegetation densities and had been disturbed by timber harvest and/ or fire more recently than unoccupied sites. Within occupied sites, Henslow's Sparrows chose areas with higher densities of herbaceous vegetation, especially P. verrucosum. Received 16 October 1997, accepted 9 June 1998.

Management responses of three species of declining sparrows in tallgrass prairie

SummaryThree species of declining grassland songbirds were counted in June transects at 42 south-western Missouri (U.S.A.) prairie preserves managed three different ways: biennial July haying, spring burning on a 1–4 year cycle, and sites both burned and hayed every 2–4 years. Hayed prairies had twice as many Henslow's Sparrows Ammodramus henslowi as burned prairies and 2.5 times as many as sites which had been burned and hayed. Hayed prairies had 59% more Grasshopper Sparrows A. savannarum and 14% more Dickcissels Spiza americana than burned prairies. Fired and hayed sites had 34% higher detection rates of Grasshopper Sparrows than sites only burned and similar numbers of Henslow's Sparrows and Dickcissels as burned sites. The three species summed were 60% more abundant in hayed as in fired or fired and hayed prairies. Henslow's Sparrows increased and Grasshopper Sparrows decreased with time since the last management. Grasshopper Sparrows peaked one year earlier after haying than after burning. Dickcissels did not vary by time since last management. Henslow's Sparrows and Dickcissels were significantly more abundant in larger prairies. Preserve management for these three prairie birds should emphasize biennial to triennial mid-summer haying, instead of burning.

Destruction of Nests by the Short-Billed Marsh Wren

-Short-billed Marsh Wrens (Cistothorus platensis) examined experimentally offered nests of Red-winged Blackbirds, Yellow-headed Blackbirds, Long-billed Marsh Wrens, and conspecifics. They also pecked eggs of Zebra Finches, Long-billed Marsh Wrens, Red-winged Blackbirds, and Cinnamon Teal, and once a male wren also pecked nestling Red-winged Blackbirds. Marsh wrens broke all small eggs, but the largest (teal) eggs survived the wrens' attacks. Results suggested that Short-billed Marsh Wrens attack eggs regardless of their size and color, but can destroy only small eggs. These wrens probably have a significant impact on nesting success of other small sympatric birds, including conspecifics. By destroying nests, Shortbilled Marsh Wrens probably exclude other birds from the vicinity of their activity centers and thereby reduce interference from them. Among all temperate zone passerines, marsh-nesting birds suffer the highest nest mortality rates, mainly through predation (Ricklefs 1969). Predators include raccoons, mink, hawks, owls, jays, crows, and water snakes (Allen 1914, Bent 1958, Robertson 1972). Other studies have shown that one of the most important predators destroying nests of marsh-dwelling passerines in North America is the Long-billed Marsh Wren (Cistothorus palustris; Allen 1914, Orians and Willson 1964, Burt 1970, Verner 1975, Picman 1977a, 1980). Destruction of nests by small passerines appears rare, but has been observed in several species of wrens, including the House Wren (Troglodytes aedon; Kendeigh 1941); Long-billed Marsh Wren (Allen 1914); Cactus Wren (Campylorhynchus brunneicapillus; Anderson and Anderson 1973); and Bewick's Wren (Thryomanes bewickii; Picman, pers. observ.). This indicates that nest-destroying behavior might be a common feature of the wren family. In this study, we investigated nest-destroying behavior of another wren, the Short-billed Marsh Wren (Cistothorus platensis) which breeds on wet sedge and grass meadows adjacent to marshes of eastern and central North America (Bent 1948). This species frequently is sympatric with Redwinged Blackbirds (Agelaius phoeniceus), Long-billed Marsh Wrens, Common Yellowthroats (Geothlypis trichas), Savannah Sparrows (Passerculus sandwichensis), Henslow's Sparrows (Ammodramus henslowii), Swamp Sparrows (Melospiza georgiana), and Song Sparrows (Melospiza melodia; Walkinshaw 1935, Bent 1948, Kroodsma and Verner 1978, this study). Nest destruction by this wren, therefore, might present an important factor reducing reproductive success of these and possibly other marsh-nesting birds. The questions we asked during this study were: (1) Do Short-billed Marsh Wrens normally destroy nests? (2) What kinds of nests and eggs will these wrens attack? (3) Do they attack nestlings? (4) Do affected species interact behaviorally with Shortbilled Marsh Wrens? (5) Why do these wrens attack nests with eggs or young?

Differential Niche Utilization in a Grassland Sparrow

Henslow's Sparrow (Ammospiza henslowii) is a secondary sexually monomorphic breeding bird in meadows, hayfields, prairies, grasslands, and some croplands in eastern North America. Foraging behavior during the nestling period involved no intersexual differences in prey selection, and both sexes were opportunistic in food choice. Sexual spatial partitioning of the feeding niche was accomplished by adults foraging in different directions and at different distances from the nests. Males, which defend the territories alone, forage at greater distances from the nest than females. Females forage closer to the nest and in different areas than males, which enhances survival of young because females do most of the feeding and all brooding of young.