Original description: Emberiza Henslowii Audubon 1831
Taxonomic history in AOU/AOS Check-list
AOU 1 (1886): Henslow’s Sparrow, Ammodramus henslowii
AOU 2 (1895): Henslow’s Sparrow, Ammodramus henslowii; Western Henslow’s Sparrow, Ammodramus henslowii occidentalis
AOU 3 (1910): Henslow’s Sparrow, Passerherbulus henslowi henslowi; Western Henslow’s Sparrow, Passerherbulus henslowi occidentalis
AOU 4 (1931): Eastern Henslow’s Sparrow, Passerherbulus henslowi susurrans; Western Henslow’s Sparrow, Passerherbulus henslowi henslowi
AOU 5 (1957): Henslow’s Sparrow, Passerherbulus henslowii susurrans, Passerherbulus henslowi henslowi
AOU 6 (1983): Henslow’s Sparrow, Ammodramus henslowii
AOU 7 (1998): Henslow’s Sparrow, Ammodramus henslowii
IUCN Conservation Status: Of least concern
Habitat: Breeders are found in damp grasslands and weedy overgrown fields; small, widely scattered bushes and other forbs are an important element, providing perches for singing males, but this species abandons fields with too many woody shrubs. In the old midwest of Pennsylvania, Ohio, and Indiana, re-vegetated strip mines substitute for the native prairie this species historically inhabited. Breeding occurs only in fairly extensive patches of grassland, with some studies suggesting that 160 acres is near the minimum size.
Migrating Henslow Sparrows use the same habitats, though they also occur unpredictably in wet brushy or wooded areas, even urban parks and orchards. Extremely inconspicuous when it is not singing, this species may well use a wider range of habitats in migration than suspected.
Behavior: Among the quietest and least conspicuous of North America’s land birds, the Henslow Sparrow is rarely seen excetp when the male climbs a flimsy stem or dried stalk to issue his short, stuttering son. With “a wonderful faculty for worming [their] way through the grass,” feeding birds stay on or very near the ground, crouching and walking haltingly, tail down, over and through the thick, matted litter they prefer. The grass cover at feeding sites is typically four to seven inches high, generally shorter than that immediately surrounding the nest, which is concealed in the ground litter or at the base of a dense clump of grass.
If disturbed by humans or another potential predator, Henslow Sparrows often run rather than take flight, skittering into even deeper cover and remaining motionless and invisible. A bird flushed from the feeding site or nest flies straight away, snipe-like, usually no more than thirty or forty feet, before disappearing and “threading its way through the grass with the nimbleness of a mouse.” As this species appears to be a nocturnal migrant, sustained flight is almost never observed. On flushing, Henslow Sparrows often rock or tilt the body and tail, increasing their resemblance to a tiny, very dark snipe.
Voice: Henslow Sparrows are usually silent in flight. Nervous birds utter a very short, thin tipt; like most such calls, this one is difficult for the human observer to localize, its brevity protecting the calling bird while simultaneously alerting others to the presence of a predator. A whistled chaatter may be exchanged between the members of a pair or competing males.
This species is most famous, if famous at all, for its song–or rather for the memorably ungenerous descriptions of that song published over the years. In naming the male’s territorial vocalization “one of the poorest vocal efforts of any birds,” Roger Tory Peterson stood in a long tradition of disparagement, reaching back even then fifty years or more. Jones, relating his 1881 experiences in Connecticut, determined that “the musical performance of this bird has very little to commend it,” a judgment in which Samuel Rhoads wholeheartedly concurred on making the acquaintance of this species in coastal New Jersey in 1902:
“In the whole class of singing birds known to me the song of this species ranks lowest in all respects. It is essentially lacking in strength, volume, length, melody or variety. Its one redeeming quality is repetition. To offset its many deficiencies the humble vocalist chants night and day… The song of its kinsman the Grasshopper Sparrow, so named because of the insectile character of its voice, is vastly superior.”
Following Peterson, the Henslow Sparrow’s song is today almost invariably styled a “hiccough,” a description that conceals more than it communicates and may indeed have made it harder over the decades for new birders to learn this vocalization. The accounts of the species’ song give a far clearer idea of its distinctive tone and rhythm, accurately and evocatively comparing the simple tse-tlick to the metallic, slightly squeaky flight call of a Horned Lark or American Pipit.
Male Henslow Sparrows sing most frequently from the dried stems and stalks of forbs in their breeding territories. They occasionally perch on a higher shrub or even take to a treetop to sing; at other times, the song proceeds from an invisible male perched near or on the ground beneath the vegetation. While singing, the bird depresses the tail, stands high on the tarsi, and throws the head back at an almost alarming angle, opening the large bill wide.
Though technical analyses have revealed that the song of this species “really” comprises four to six buzzy phrases, the human ear discerns only two, or at very close range three, notes. Their tone is simultaneously buzzy and squeaky–thoroughly un-hiccough-like–and the rhythm accelerating, as if the singer were rushing to get from the short first note (or two notes) to the slightly longer, usually higher-pitched, and noticeably more emphatic final note. As Rhoads noted, the song can be given at any time of day or night.
The Henslow Sparrow has sometimes been said to perform in flight as well, giving a longer song that “may fairly be represented by the syllables sis-r-r-rit-srit-srit, with the accent on the first and last parts. This song is often uttered while the bird takes a short flight upwards, it then drops again into the tangled weeds and grasses.” Jouy’s description applies perfectly to the long reeling flight song of the Grasshopper Sparrow, and most authorities now believe that Henslow Sparrows do not have any similar vocalization.
Detailed descriptions and measurements drawn from standard references works
Adult: Rusty brown tail feathers narrow and sharply pointed, the inner pairs more reddish and much longer than the outer pairs. Rump and upper tail coverts rusty brown with long black shaft streaks. Mantle feathers chestnut, with large black centers and extensive white edges; chestnut scapulars with large black centers and smaller white or gray edges. Primaries gray brown, secondaries extensively reddish, tertials chestnut with wide black edges. Greater coverts chestnut with silver-gray edges and black teardrops, largest on the inner coverts. Median coverts with blurry black shaft streaks. Marginal coverts of under wing yellow, creating yellow wing flash. Nape dull greenish with fine black streaks. Underparts white with buffy wash to under tail coverts, flanks, breast, and sometimes throat. The fine black streaking of the flanks continues across the breast as a broad, neat band. Throat white or pale buffy, separated by fine black lateral throat stripe from green-brown jaw stripe. Chin sometimes faintly spotted blackish. Jaw stripe bordered above by black. Green-brown ear coverts bordered above by short black line or spot, at rear by spot. White eye ring usually conspicuous. Very broad supercilium green, poorly set off from auriculars by short black line behind eye. Lore yellow-green. Crown mostly black, with neat central stripe dull white to greenish, with variable fine black streaking towards nape. Large bill dull pink, darker on upper mandible, especially on culmen. Long tarsi and toes pink.
The eastern susurrans is paler above and clearer white below, with less chestnut on the back and wings.
Juvenile: Duller and more buffy above, with scattered blackish streaking and spotting. Pale yellow buff below, with light streaking restricted to the flanks and sides of the breast. Buffy throat usually without obvious lateral throat stripe; remainder of head pattern similar to that of adult, but tyhe ground color brown-yellow rather than green. Supercilium brightest above the lore, tending to yellow. Large bill dark orange brown, blackish on upper mandible, especially on culmen.
Length 113-117 mm (4.4-4.6 inches)
Wing chord 52-54 mm (2.0-2.1 inches)
Tail 48-49 mm (1.9 inches)
Mass 11-15 g