The Henslow’s Sparrow’s inconspicuous presence in grasslands of eastern North America has declined dramatically in some areas, while increasing in western portions of its range in recent decades. The faint song of the Henslow’s Sparrow can hardly be considered musical, and its rather specific habitat requirements make its distribution very localized throughout its range.
The well concealed nest of the Henslow’s Sparrow, and its cryptic habits of often running rather than flying through dense grass when pursued, make studying its breeding ecology difficult. Female Brown-headed Cowbirds manage to find some nests to parasitize, although parasitism rates are relatively low.
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Description of the Henslow’s Sparrow
The Henslow’s Sparrow has a dark back patterned with much rufous, rufous wings, an olive-greenish cast to much of the head and nape, a white eye ring, a buffy breast with dark streaking, and a white belly. Like all Ammodramus sparrows, its short tail is evident in flight. Length: 5 in. Wingspan: 6 in.
Seasonal change in appearance
Juveniles are similar but duller. Different facial pattern, browner with less dark on the face.
Henslow’s Sparrows inhabit tallgrass prairies with little woody vegetation, reclaimed surface mines, and moist, weedy fields.
Henslow’s Sparrows eat insects and seeds.
Henslow’s Sparrows forage on the ground.
Henslow’s Sparrows breed locally across parts of the eastern U.S., Midwest, and eastern Great Plains. They winter in the southeastern U.S. The population has declined in some areas, but has increased in the western portions of its range.
When flushed from prairie grasses, Henslow’s Sparrows typically make only short flights.
Periodic fire or other disturbances are needed to control brush in Henslow’s Sparrow habitat, but disturbances that are too intensive or too frequent do not leave behind enough thick, grassy cover for the species to occupy.
Henslow’s Sparrows nests are difficult to locate, because the female often runs some distance before flushing from the nest.
The song consists of a short, two-note “ts-lick.” A high “tik” call is given as well.
The LeConte’s Sparrow has an orange supercilium.
Savannah Sparrows are heavily streaked below.
The Henslow’s Sparrow’s nest is a cup of grasses and is lined with finer materials. It is placed on or near the ground, well hidden in vegetation.
Number: Usually lay 3-5 eggs.
Color: Whitish with darker markings.
Incubation and fledging:
The young hatch at about 10-11 days, and fledge at about 10-11 days, though remaining dependent on the adults for some time.
Bent Life History of the Henslow’s Sparrow
Published by the Smithsonian Institution between the 1920s and the 1950s, the Bent life history series of monographs provide an often colorful description of the birds of North America. Arthur Cleveland Bent was the lead author for the series. The Bent series is a great resource and often includes quotes from early American Ornithologists, including Audubon, Townsend, Wilson, Sutton and many others.
Bent Life History for the Henslow’s Sparrow – the common name and sub-species reflect the nomenclature in use at the time the description was written.
PASSERHERBULUS HENSLOWII SUSURRANS Brewster
The Atlantic coastal race of the Henslow’s sparrow, described by William Brewster in 1919 from Falls Church, Va., is slightly darker than the nominate western form, has buffier underparts, more yellow at the bend of the wing, and a much stouter bill.
Henslow’s sparrow is a shy and retiring little inhabitant of open fields and grasslands, where it associates with the far more obvious and familiar bobolinks, meadowlarks, Savannah and grasshopper sparrows. While occasionally found in dry and in cultivated uplands, it shows a preference for old weedy fields and swales, especially wet or damp ones. In most instances thick vegetation seems a basic requirement of its habitat, which is in keeping with its custom of skulking or running mouselike through the grass at the approach of an intruder. Its scurrying through the undercover is so characteristic that Robert F. Mason, Jr., suggested in a letter to Mr. Bent that “mouse sparrow” might be a more appropriate name for it. It seldom flies when disturbed, and when it does take wing, it is often for only a short distance, so short that N. C. Brown (1879) calls its flights little more than ”respectable jumps over the grass.”
Because of its secretiveness and of the security afforded by the thick vegetation it prefers to live in, the habits and behavior of the Henslow’s sparrow are rather poorly known. Those of the eastern race apparently differ little, if at all, from those of the more fully studied western form, as described in detail in the next account.
Range: New York and central New England to Florida.
Breeding Range: The eastern Henslow’s sparrow breeds from central New York (Jefferson County, intergrading with P. A. henslowii), southern Vermont (Bennington), southern New Hampshire (Wonalancet), and northeastern Massachusetts (West Newbury) south to extreme eastern West Virginia (Morgan and Berkeley counties), central and southeastern Virginia (Lynchburg, Princess Anne County), and east central North Carolina (Chapel Hill).
Winter Range: Winters on the Atlantic Coastal Plain from South Carolina (Horry County) and Georgia (Sapelo Island, Athens) to south central Florida (Glades County). Casual in New York (Patchogue) and Bermuda.
Migration: T he data apply to the species as a whole. Early dates of spring arrival are: Florida: Lake Jackson, March 5. Alabama: Autaugaville, March 11. North Carolina: Raleigh, March 18. Virginia: Blacksburg, April 21. District of Columbia, March 25 (average of 31 years, April 18). Maryland: Baltimore County, March 16; Laurel, March 24 (median of 9 years, April 16). Pennsylvania: Philadelphia and State College, April 20. New Jersey: Salem, April 12; Carney’s Point, April 13. New York: Bronx County, April 4; Binghamton, Cayuga, and Oneida Lake basins, April 14 (median of 20 years, April 25). Connecticut: Litchfield, April 27. Rhode Island: Charlestown, April 24. Massachusetts: Huntington, April 28. Vermont: Bennington, May 1. New Hampshire: Tilton, April 17. Arkansas: Monticello, April 8. Tennessee: Nashville, March 26. Kentucky: Bowling Green, March 25. Missouri: Shannon County, March 19. Illinois: Chicago Region, March 16 (average of 14 years for Chicago, April 18) ; Urbana, April 13 (median of 6 years, April 14). Indiana: Tippecanoe County, April 7; Wayne County, April 11 (median of 12 years, April 23). Ohio: Cleveland, April 5; Buckeye Lake, April 6 (median of 40 years for central Ohio, April 21). Michigan: Battle Creek, April 10 (average of 33 years, April 27). Ontario: London, May 1. Iowa: Grinnell, March 28. Wisconsin: Madison, April 3. Minnesota: Minneapolis and Cambridge, April 25 (average of 8 years for southern Minnesota, May 6). Kansas: northeastern Kansas, April 14. Nebraska: Lincoln, April 22. South Dakota: Vermilion and Sioux Falls, April 29 (average for Sioux Falls, May 9). North Dakota: Red River Valley, April 30. Oregon: Corvallis, April 12.
Late dates of spring departure are: Florida: Tallahassee and St. Marks Light, April 21. Alabama: Birmingham, May 4. Georgia: Denton, April 22. South Carolina: Horry County, April 13. North Carolina: Raleigh, May 3. Vermont: Rutland, May 12. Louisiana: Cameron, May 15. Tennessee: Nashville, May 21. Kentucky: Bowling Green, May 16; Missouri: St. Louis, May 8. Illinois: Chicago, May 21 (average of 14 years, May 5). Ontario: London, May 14. Iowa: Hudson, May 22. South Dakota: Vermilion, May 6. North Dakota: McKenzie County, May 27.
Early dates of fall arrival are: South Dakota: Faulkton, September 1. Illinois: Chicago, October 3. Missouri: St. Louis, October 5. Kentucky: Bowling Green, September 21. Arkansas: Monticello, October 20. Louisiana: Baton Rouge, October 24. Georgia: Fitzgerald, October 21. Alabama: Birmingham, October 31. Florida: Tallahassee, October 24.
Late dates of fall departure are: North Dakota: McKenzie County, October 29. South Dakota: Faulkton, November 1. Nebraska: Papillion, October 9. Kansas: northeastern Kansas, October 15. Minnesota: Minneapolis, September 2. Wisconsin: Racine, November 29; Dane County, November 14. lowa: Blakesburg, October 27. Ontario: Point Pelee, October 15. Michigan: Birmingham, October 25. Ohio: central Ohio, October 25 (median, October 3). Illinois: Chicago region, November 12. Missouri: St. Louis, November 19. Kentucky: Bowling Green, November 4. New Hampshire: New Hampton, October 23. Massachusetts: Osterville, November 6. Rhode Island: Charlestown, October 14. Connecticut: West Haven, October 27. New York: Shelter Island, November 20; Cayuga and Oneida Lake basins, October 30 (median of 12 years, October 19). New Jersey: Island Beach, October 13. Pennsylvania: State College and Centre Furnace, October 8. Maryland: Baltimore County, November 21; Laurel, October 29. District of Columbia: November 16 (average of 6 years, October 11). Virginia: Charlottesville, October 30.
Egg dates: Maryland: 5 records, May 18 to June 26.
New Jersey: 6 records, May 22 to July 7.
WESTERN HENSLOW’S SPARROW
PASSERHERBULUS HENSLOWII HENSLOWII (Audubon)
Contributed by JEAN W. GRABER
Henslow’s sparrow is a grassland species occupying meadows or marshy openings in the woodlands of central and eastern United States and southern Canada. A shy, unobtrusive, and secretive little bird that tends to run when disturbed instead of flying, it is consequently bard to find and difficult to observe in the field. When Audubon discovered the first specimen in Kentucky just across the Ohio River it from Cincinnati in 1820, he painted the bird and named (1829) for his friend the Reverend John Steven Henslow, professor of botany at Cambridge University, England.
The nominate western subspecies dilTers from the Atlantic coastal race, su~urrans, in being generally lighter, with less yellow at the wing bend, heavier black streakings and less chestnut on the back and scapulars, and a thinner bill. The Appalachian mountain chain may have been the isolating mechanism in the formation of the two races, each of which has apparently expanded its range since the opening of North America by man. As A. Sidney Hyde (1939) points out. “The primeval forests which extended almost unbroken from western Indiana to the salt marshes of the Atlantic coast must have originally offered little to induce colonization by this bird. * * * Widespread clearing of the forests has made more habitat available** *~ Recent marked increases in abundance are reported from Ohio, southern Michigan, and Ontario. * * * many of the known breeding colonies are so situated as to lead to the belief that watercourses serve as important migration highways for the species. In the Appalachian highlands the valleys of the Merrimac, Connecticut, Hudson, Delaware and Susquehanna rivers appear to have a more than casual relationship to the locations of colonies reported from northern New England, New York, and Pennsylvania.~~ Throughout its summer range the western Henslow’s sparrow occupies weedy prairies and meadows, and neglected grassy fields and pasturelands, which are often dotted with low shrubs or bushes. The vegetation it inhabits may be rather irregular in height and density, or fairly uniform; the ground cover is usually quite dense and at least a foot or two high. In northeastern Kansas the species occupies the lower, moister depression in upland, mid-grass prairie. hyde (1939) notes the dominant plants in its southern Michigan habitat to be cord grass (Spartina pectincta) and shrubby cinquefoil (Potentilla fruticosa). It seems to prefer low-lying, damp situations, but it may also be found in drier upland fields. Though drainage of lowlands and intensive cultivation appear recently to have reduced its breeding area and numbers in parts of Iowa, Wisconsin, and Illinois, the bird has adapted to man’s agricultural practices by occupying unmowed timothy-clover hayfields in Ohio, Illinois, Wisconsin, and possibly elsewhere. Smith (1963) states that Henslow’s sparrows abandon a field when the grass is cut.
Some of the birds commonly found nesting in the same environment with the western Henslow’s sparrow are: marsh hawk, ring-necked pheasant, bobolink, meadowlark, red-winged blackbird, dickcissel, and grasshopper and Savannah sparrows. Other species that frequently nest near by and associate with it occasionally include: greater prairie chicken, upland plover, horned lark, short-billed marsh wren, Traill’s flycatcher, yellow warbler, yellowthroat, and song and swamp sparrows.
Spring: The western Henslow’s sparrows usually leave their southern wintering grounds in late March or early April. The latest southern records are: South Carolina, March 28; Georgia, March 29; Florida, April 11; Alabama, May 4; and Louisiana, May 15. Milton Trautman (1956) observed a mass migratory flight of the species at South Bass Island, Ohio, on April 21: 22; the birds were moving in company with juncos, and Savannah, swamp, song, chipping, field, and fox sparrows.
The earliest arrival dates in the north are: Shannon County, Mo., March 19; DuPage County, Ill., March 28; and Sauk, Wis., April 7. The following average arrival dates are given in the literature: Oberlin, Ohio, April 29;Saginaw, Mich., April 22; Dane County, Wis., April 23; Minnesota May 6; and South Dakota May 9. There are Nebraska first records from April 22 to May 9. No data are available as to when the bulk of the breeding population arrives in any area. Lynds Jones (1892) noted that in Iowa “The first arrivals * * * are always found in the underbrush skirting native woods. Later they move out to their prairie homes.”
Territory: Henslow’s sparrows tend to live in loosely formed colonies. They seem to establish territories within these colonies, but the boundaries are not too rigid and may be violated occasionally. Hyde (1939) observed fighting males “bowing to each other beak to beak, like fighting roosters.” He adds: “The fighting was apparently not vicious; one bird flew at the other. Then they both disappeared in the grass; shortly thereafter both birds separated and began singing: one fifty feet south of blind, the other from a tall weed not more than twenty feet east of it.”
He thus described the population density of the colonies he studied in southern Livingston County, Mich.: In fields inhabited by colonies of Henslow’s Sparrows the numbers of birds an acre may run rather high, but over any extensive area, taken as a whole, the population will be low because of the large amount of uninhabited land. In one nineacre field (Field 3) at Anderson four pairs nested in 1934. In 1936 it was estimated that seven males had their territories in this field, in which four nests (one deserted) were found before June 10. In field 6 there were about 40 acres of habitable territory, which held about thirty to forty singing males in 1934. A similar density is reported from Mahoning County, Ohio, by Vickers (1908: 150: 52), who found from nine to twelve males in a fourteen-acre field. Hennessey (1916: 115) found from forty to sixty birds (be does not say pairs) in an area of about 160 acres in southern Michigan, near Albion. A record for density is reported from Iowa by Anderson (1907: 317) on the authority of G. H. Berry, who reported ten pairs breeding in a field of hazel and blackberry of about one-half acre in extent.
Sutton (1928a) found about a dozen pairs in a 10-acre area of dense grass in Pymatuning Swamp in northwestern Pennsylvania.
Courtship: Little has been observed of the courtship of this rather secretive species. Hyde (1939) writes of it as follows:
Aside from the increasing frequency and volume of song, the first courtship behavior was noted on the afternoon of May 9, 1936. A singing bird that had been changing his perch frequently, dropped to the ground and was joined by another individual as the call of intimacy was uttered. Presently the male was seen with a piece of dry grass in his mouth, hopping among the hummocks. He soon dropped the grass and began singing feebly from the ground. The female remained concealed, except at intervals when one bird closely following another flitted above the grass for an instant and then dropped back, the actions being punctuated with frequent renditions of the call of intimacy. No trace of a nest could be found.
Early the next morning at the same place a singing male with a mouthful of dried grass alighted on a hummock near another bird. Dropping the grass and fluttering his wings continually the male proceeded over and among the hummocks. He appeared to be taking the female on a tour of the area, indicating to her each possible nesting site by violently fluttering into it.
A male was seen copulating with a female perching in open view on a bush, and holding dead grass in her bill, on July 23, 1934. After the second union both birds dropped into the grass. The male appeared again, flying with rapid vibrations of the wings characteristic of many birds just subsequent to copulation.
A pair of birds were apparently mating under concealment of the grass on July 11, 1934. The male, at first singing, began to chase the other bird, and both disappeared in the vegetation. Whenever they reappeared their wings were fluttering or vibrating characteristically. Finally the female ate a caterpillar she had been holding all the time, and the male began singing in a subdued voice.
Though the species is essentially monogamous, Hyde observed copulation between a mated female of one territory and the male of an adjacent territory.
Nesting: The well-concealed nest is always placed on or near the ground. A few nests have been found actually sunk into depressions in the ground. Usually it is built at or near the base of a thick clump of grass with its bottom two or three inches above the ground. The grass often arches over the nest so as to form a partial roof. Some nests are attached to vertical sterns of grass and herbs from 6 to 20 inches above the ground; these lack the roof of arching vegetation.
Usually the nest is a deep cup, though Hyde (1939) found one that was merely a shallow open saucer and poorly concealed. The nest cup measures about 2 inches in inside diameter, 3 inches in outside diameter, and has a depth of 1 to 2 inches. The nest is made of coarse grasses and dead weed leaves and lined with finer grasses and sometimes with hair.
Nest material is gathered near the nest site, within 50 feet of one nest Hyde watched. The nest building is done chiefly if not entirely by the female. Hyde reports (1939) the male of one pair sang softly nearby while the female was at work; when she stopped working be became more vociferous. The male of a pair observed by J. T. Southard (pers. comm.) was seen carrying blades of grass twice while the female worked at nest building. Hyde watched one female bring nesting material from 9:08 to 9:50 am, at the rate of once every 3.3 minutes; she spent 0.7 of a minute arranging it at the nest before leaving for more supplies.
Nest building activity seems to be most intense during early morning, but may occur throughout the day until dusk. The nest is built in 4 to 5 days. Hyde reports that one pair, after its nest was destroyed, chose a new site and completed a new nest in 5 to 6 days.
Eggs: Henslow’s sparrow usually lays from 3 to 5 eggs. They are ovate and slightly glossy. The ground is creamy white or pale greenish white, with speckles, spots, and occasional large blotches of reddish browns such as “russet,” “hazel,” “auburn,” “Rood’s brown,” and “tawny,” with undermarkings of “light purplish gray” or “light neutral gray.” The eggs of this species are not so heavily marked as those of the sharp-tailed or seaside sparrows, but resemble more the pattern of those of the grasshopper sparrow. The spottings are concentrated toward the large end where they often form a wreath. The spots may be either sharp and distinct or dull and clouded. The measurements of 55 eggs average 18.3 by 14.1 millimeters; the eggs showing the four extremes measure 20.3 by 15.2, 16.7 by 13.8, and 18.8 by 13.0 millimeters.
The finding of many nests with eggs in Michigan in July and of four eggs laid in one nest between August 12 and 16, and of young still in the nest in Wisconsin in September suggests that some pairs may be double-brooded.
Young: Incubation is entirely by the female. While she incubates the male sings from various perches nearby. She has been observed to respond to his singing by twittering softly from the nest. Hyde (1939) determined that incubation starts with the laying of the last or the next to last egg and takes about 11 days.
Both parents brood and feed the young. Food was brought to one nest Hyde was watching about one hour after the first egg hatched. As he saw no egg shells carried away from the nest, he assumed the parents ate them. During their first day of life the young are fed about once ever 2 hours. Feedings increase as the young grow to as many as 10 per hour at the age of 7 to 8 days. The adults carry away fecal sacs at irregular intervals and sometimes eat them. The young leave the nest on the 9th or 10th day after hatching.
Plumages: The natal down which Dwight (1900) calls smoke gray, Hyde (1939) terms “pale huffy gray.” He found it distributed on a bird 4 hours old in “A superciliary patch of about two tufts on each side; a patch on the back of the head; one on the middle of the back; one lateral to the femur; a humero-scapular tract of two tufts; and a patch on the posterior margin of the ulna. * * * At four days of age down was still prominent. At six days the superciliary and alar tracts retained conspicuous tufts.” He describes a 6-day-old nestling whose juvenal “feathers were almost completely unsheathed, except on the forehead, the crown, and underneath the eye” as follows:
“Sides of crown black, center of crown and nape all around light olive-brown, contrasting with the pale rufous back feathers, which have black centers; edge of wing sulphur; remiges fuscous, the primaries very narrowly margined along outer edges and tips with pale light brown, the secondaries similarly margined with a slightly deeper brown; tertials black, broadly margined with pale cinnamon; scapulars and wing coverts fuscous margined with pale rufous. Upperparts sulphur yellow, sides strongly washed with vinaceous. The feathers of the anterior part of the sides of the breast have narrow fuscous streaks.”
Birds in the completed juvenal plumage also show a characteristic “fused” barring (present also on some adults) on the tail feathers, which are shorter than those of adults. This plumage is replaced in a post-juvenal molt by the first winter plumage, in which the birds are similar to adults but have deeper buff-colored underparts. The post-juvenal molt and the complete post-nuptial molt of the adults appear to be essentially finished on the breeding grounds before migration. Kumlein and Hollister (1951) thus vividly describe the molting adults: “During the latter part of August and September the adults especially are in a condition of such extreme moult as to be almost unable to fly, there being many days when not an individual can boast of even a single tail feather.”
Dwight (1900) states that both the first and the adult nuptial plumages are “acquired probably by a partial prenuptial moult confined chiefly to the head and chin.” This still needs verification for, as Dwight continues, “In species so much affected by wear it is not easy to be sure of a moult without specimens which actually show it. The freshness of many feathers in spring indicate it.”
Food: From 17 stomachs (12 adult, 5 immature) Hyde (1939) collected between April and October, he determined the food to be 82 percent animal matter by bulk and 18 percent vegetable matter. Orthoptera comprised 36.47 percent of the August: September food, Coleoptera 19.3, ileteroptera 12.2, Lepidoptera 3.3, and Hymenoptera 1.8 percent. Additional items of animal matter included Diptera, Neuroptera, spiders, unidentified arachnids, myriapods, and gastropods.
The Orthoptera eaten were crickets (especially Nemobius sp.), grasshoppers, and katydids; the Coleoptera were weevils (mostly), chrysomelids, carabids, scarabaeids, and histerids; the Heteroptera were. lygaeids, pentatomids, and a few others; the Lepidoptera included caterpillars of dutworms (noctuids); and the Hymenoptera were andrenids (chiefly), ants, ichneumonids, tenthredinids, and chalcids. All the insects were species found on or near the ground in the vegetation in which the bird lives.
Seeds of grasses constituted 6.2 percent of the total food; ragweed 9.2 percent (75 to 85 percent in two specimens taken in October); Pologonaceae 1.6; and sedges less than 0.5 percent. Hyde adds: “It is nearly certain that if fall, winter, and early spring specimens had been examined in proportion to those collected in the summer, the percentage of vegetable matter would have been much higher.”
The principal food brought to day-old nestlings was smooth noctuid caterpillars. These and soft abdomens of Orthoptera (katydids, tree crickets, and grasshoppers) were the chief items fed to young birds the first 3 days after hatching. After the third day the parents brought a greater variety of insect food, though caterpillars and Orthoptera still predominated. Other items Hyde saw fed to the nestlings included sawflies (Qimbex), a large garden spider (Argiope), and a firefly (lampyrid).
Voice: “More often heard than seen” describes Henslow’s sparrow. Unless the bird happens to be singing, its presence is easily overlooked. Though its unobtrusive song has been described (Peterson, 1947) as “one of the poorest vocal efforts of any bird, * * * a hiccoughing ‘tsi-lick’,” it is characteristic and readily identifies the singer. It is sometimes given from concealment in the grass, but more usually from a weed stem or bush just above the level of the surrounding vegetation.
Though the song is generally heard as two short buzzy notes, often described as ‘ftee-sic,” an audiospectrographic analysis of tape reeordings by Borror and Reese (1954) revealed that it actually consists of six separate notes, the last three of which are the ones usually heard and described. The flee is the lowest, loudest, and fourth note in the song, while the sic is actually two notes, the fifth and sixth, the fifth being slightly higher in pitch than the sixth.
In addition to this characteristic song which the male gives from singing perches atop a weed or stalk of grass, Jouy (1881) described a six-noted flight song, “sis-r-r-rit-sril-srit,” which Sutton (1 928a) thought Joiiy may have attributed to the wrong species, as it is an excellent rendition of the flight song of the grasshopper sparrow, and in his studies of Henslow’s sparrow Sutton “never once heard the birds utter this song.” Nor does Hyde (1939) mention hearing it. However, R. R. Graber tells me he has heard Henslow’s sparrow give this flight song in Illinois.
Hyde (1939) describes what he terms the “call of intimacy,” heard only during the height of the breeding season, as a series of intense, high-pitched, sibilant, descending whistles. It may be given by birds of either sex in situations of high emotional intensity, as during courtship, combat, or when warning off an intruding male. Hyde continues:
“The hunger call of the young is a nasal whistle, ‘kee,’ pitched like the monosyllabic ‘pee’ of the Wood Pewee, but less sharp. The usual alarm note is a sharp ‘tsip’ similar to that of the Chipping and Savannah Sparrows. A higher pitched, more penetrating ‘tsip’ is used as a warning when a hawk appears.”
George M. Sutton has written me of a variety of calls given by juveniles he kept in captivity. He decribes the food call of the young as “a high, clear yeee-eee,” a call given by the young to parent birds as “reee,” a call given when caught in the hand as a loud “jeer” or “djeer,” and a “lonely” call as a “thin, very high note, not exactly a cheep,” which is hard to hear. He heard well-fed captives singing “little whisper songs” 11 days after leaving the nest, at an age of about 20 days.
The birds are in song when they arrive on the breeding grounds. Their singing increases in vigor and frequency during the courtship period. After the young hatch it decreases noticeably, presumably because the males are then busy helping feed the young. A second period of less intensive singing in late July and early August is terminated when the adults start undergoing their postnuptial molt. They are then heard to sing no more, though they may remain on the breeding grounds into October.
Song begins at dawn and sometimes continues all night. One male Hyde (1939) watched closely for 529 minutes in early July while his mate was incubating spent 80 of them in song. He found that the average interval between individual songs during singing periods increased from 4.19 seconds on June 17 to 8.7 seconds on August 9.
Sutton reported singing peaks at sunrise and early evening, but Hyde found singing lessened toward evening.
W. E. Saunders (MS.) reports that Henslow’s sparrows sang intermittently throughout the night of July 20: 21, 1935, at Morpeth, Ontario, and that not more than 15 minutes elapsed without a song being heard. Other observers have had similar experiences. The species has also been observed singing incessantly when rain was pouring. down. Perhaps lessened light intensity stimulates singing, and in this respect the bird seems crepuscular.
Behavior: This small sparrow spends much of its time concealed in the grass and dense vegetation in which it lives. During the breeding season it does not move far from its nest, which is often hard to locate because it is so well concealed and because the female usually runs some distance from it before flushing, and returns to it on foot as well. When not singing, it is seldom noticed unless it is flushed from the cover. It is difficult to flush, for it apparently places great reliance on its marvelously concealing coloration, and either runs through the grass from the intruder or remains motionless in hiding until almost stepped upon. When it does flush, it seldom flies more than a few yards before dropping back into the vegetation. It evidently has a strong game effluvium, as bird dogs often point it, to the annoyance of their quail-hunting masters.
Sutton (1928a) describes its flight as being more erratic and undulating than that of the grasshopper sparrow. The wing beat usually alters just after the bird takes flight, and the tail and rump are twisted in a peculiar and characteristic manner.
Field marks: The Henslow’s is confused mainly with the grasshopper and Le Conte’s sparrows, which frequently share its habitat, particularly in winter. The best field marks are its distinctly reddish wings and the olive-green nape (rufous-brown in the Le Conte’s). The ilenslow’s streaked breast and flanks distinguish it from the clearbreasted adult grasshopper sparrow.
Enemies: Although nests of Ilenslow’s sparrow are occasionally victimized by the brown-headed cowbird, the species appears to escape heavy parasitism, possibly because the nests are so ~vell hidden. No data are available on the percentage of nests parasitized (which is apparently low), or as to whether the presence of a cowbird nestling precludes successful fledging of the young Henslow’s sparrows in the nest. J. T. Southard writes me of finding nests of this species containing two cowbird eggs in addition to three or four host eggs.
Snakes are probably the foremostpredatorsof the species. In Pennsylvania, Henslow’s sparrows and their eggs were found to constitute 12 percent of the diet of specimens of the blue racer (Coluber constrictor) examined by Ruthven et al. (1928). hawks also prey on this sparrow.
Stoddard (1931) found remains of a Henslow’s sparrow in a marsh hawk from a winter roost in Leon County, Fla., and Sutton (1928b) reports one from the stomach of a sharp-shinned hawk in Pennsylvania. Skunks, minks, weasels, raccoons, and foxes are all potential predators, and opossums and ground squirrels probably devour eggs when they find them, though no examples are recorded in the literature.
Hyde (1939) reports one nestful of young destroyed by cattle trampling. Mowing of hayfields must also result in some losses.
Ectoparasites reported by Hyde include red mites or chiggers (Trombiciila bisignata) found on the skin, particularly about the ears and anus, and mallophaga (unidentified). He notes the species “seems to be relatively free from lice.” He also notes one nest of three young destroyed by “cool weather and a heavy infestation of nest mites.”
Fall: Hyde (1939) comments: “lii August * * * there seems to be a tendency for the birds, at least the immature ones, to venture into new territory. ** * From late August on, the birds have a tendency to make longer flights when disturbed. If flushed several times in succession they frequently fly to the edge of a thicket or into a low tree. Such behavior presages the reactions of the birds during the migrating period. Nearly all of the definitely migrating birds seen by me in Kansas, Illinois, and New Jersey were along hedgerows or at the edges of similar shrubby places.”
The migratory exodus begins in September and by late October or November the birds have left the breeding grounds.
Winter: Benslow’s sparrow winters in the southeastern United States from South Carolina, Georgia, and Florida westward to southeastern Texas. In South Carolina, Alexander Sprunt, Jr., and E. Burnliam Chamberlain (1949) consider it a “Fairly common winter resident, October 21 to March 28, probably throughout most of the State” and notes that “The western race of the Henslow’s Sparrow seems to be, so far as it is possible to determine from specimens examined, about as numerous in South Carolina as the eastern race.” Arthur T. Wayne (1910) says the bird varies greatly in abundance in South Carolina from year to year.
In Georgia, however, Thomas Burleigh (1958) considers the western Henslow’s sparrow “A scarce and local resident in the southern part of the state.” He lists less than a dozen specimen records assignable to it, and considers the eastern subspecies the predominant form there.
In Florida, Sprunt (1954) again considers “the eastern and western forms about equal in distribution.” The specimen record, however, shows the western subspecies predominant in the “Panhandle” and southward along the west coast to the Tampa region. Though Sprunt (1954) states it frequents “old fields, roadsides, and thick, rather wet growth,” its principal habitat in Florida is the open longleaf pine flatwoods, where it lives on the damp ground in the wire-grass (Aristida strieta), which grows thickly in the wet acid soil in clearings and where the tree growth is sparse, providing the birds ideal cover. Francis Weston wrote Hyde (1939) that “the birds are so difficult to flush in their winter home that it is very hard accurately to judge their abundance.”
Imhof (1962) writes: “North of the Fall Line in Alabama, this sparrow is rare in winter and on migration. In the Coastal Plain it is uncommon in winter but undoubtedly more numerous than recorded because it is difficult to flush and identify. * * * The species frequents weedy, rank growths like other sharp-tailed sparrows, but also occurs in open, wet, shrubby areas. On or near the coast, it usually lives in broomsedge or other grasses in boggy places in the pine flats.”
In Louisiana, George Lowery (1955) says “it is often found in the same broom sedge situations [as the LeConte’s sparrow] but it appears to be less numerous there. It is most common in the grass of the ‘pine flats’ particularly in the Florida Parishes. * * * Henslow Sparrows arrive in Louisiana in late October. They are usually gone by the end of March.”
Range: Eastern South Dakota, Wisconsin, and southern Ontario south to Texas and the Gulf Coast.
Breeding Range: The western Henslow’s sparrow breeds from eastern South Dakota (Moody County), central Minnesota (Grant and Isanti counties), southern and northeastern Wisconsin (Dane and Oconto counties), casually north to central Michigan (Mackinaw City) and southern Ontario (Barrie, Carlsbad Springs) south to central Kansas (Cloud County), northeastern Texas, Central Missouri (Hickory and St. Louis counties), southern Illinois (iRichland County), northern Kentucky (Jefferson County), and central southern West Virginia (Monroe County).
Winter Range: Winters from north central Texas, Louisiana (Monroe, New Orleans), and southern Mississippi (Saucier) to western and northern Florida (Ean Gallie), southeastern Georgia (Tifton, Sapelo Island), and South Carolina (Chester, Aiken, and Charleston counties); casually in southern Illinois and southern Indiana (Jackson County).
Casual records: Casunl in northwestern North Dakota (Kenmare). Accidental in Massachusetts (Osterville).
Egg dates: Illinois: 20 records, May 20 to July 4; 10 records, June 19 to June 26. Iowa: 9 records, May 18 to June 29. Michigan: 30 records, May 28 to August 16. Missouri: 1 record, May 26.
Ontario: 2 records, both August 14. Wisconsin: 4 records, May 23 to June 12.