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Grasshopper
Sparrow*
Ammodramus savannarum
Contributed by Robert Leo Smith
[Published in 1968:
Smithsonian Institution United States National Museum Bulletin 237
(Part 2): 725-745]
*The following subspecies are discussed in this
section: Ammodramus savannarum pratensis (Vieillot), A.
s. floridanus (Mearns), A. s. perpallidus (Coues), A.
s. ammolegus Oberholser. Most of this account is based on the
author's study of the eastern race of the grasshopper sparrow (Wilson
Bulletin, 1959, 1963). Alexander Sprunt contributed a brief
account of the Florida grasshopper sparrow, but kindly consented
to withhold it so that all subspecies could be incorporated into
the one account.
Although the grasshopper sparrow, Ammodramus savannarum,
ranges from the Atlantic Coast to California and from southern
Canada to southern Florida, Arizona, and Mexico, it is one of our
more obscure birds. It is seldom noticed, even by those who are
familiar with other birds. It usually keeps well hidden in the
depths of the grass, and when pursued it flies only when nearly
tramped upon. Its courtship, nest building, and rearing of young
are carried on in a grass world of its own, well hidden from human
eyes. Its song so closely resembles the stridulations of the
grasshopper that many persons do not recognize it as a bird song.
The eastern race, A. s. pratensis (Vieillot), is found
from the northeastern Atlantic seaboard through the tall grass
prairie country to eastern Oklahoma and northeastern Texas, and
from extreme southern Ontario and Quebec to central North and
South Carolina, central Alabama, and Georgia. Thomas Burleigh
(1958) writes that the birds nest locally in northern Georgia
where grassland farming makes more habitat available. In recent
years they have been found breeding south of the fall line in
Macon County.
The western race, A. s. perpallidus (Coues), ranges from
western Ontario, Minnesota, western Oklahoma, and central Colorado
west to the Pacific Coast, and from the extreme southern prairie
provinces of Canada south through eastern Washington and Oregon to
central Nevada and southwestern California. So much of its
habitable range is broken by mountains and deserts, its
distribution is very spotty. The bird, however, may be more common
than supposed, its absence in many regions reflecting the absence
of observers rather than birds. D. W. Johnston (1949), who
collected the first grasshopper sparrow in Idaho in 1947 in Latah
County, writes (in litt.) that "here, too, it seemed to me
that the birds were not unduly rare, although there had been much
ornithological field work in the area previously."
The Florida grasshopper sparrow, A. s. floridanus (Mearns),
inhabits the Kissimmee Prairie region. It was described in 1902 by
Edgar A. Mearns, who based his description on a pair of birds
collected on the Kissimmee Prairie near Alligator Bluff, Osceola
County. Not until a quarter century later were additional
specimens collected. According to W. H. Nicholson (1936) its range
begins at a point 20 miles southwest of St. Cloud and extends to
Okeechobee City. D. J. Nicholson writes that the center of
abundance of the Florida grasshopper sparrow is "from 7 to 10
miles west of Kenansville, Osceola County, Florida, on the
Kissimimee Prairie to within 10 miles of Bassenfer, Okeechobee
County, Florida." The species does not breed over all the
area, but forms scattered colonies, sometimes 30 miles apart.
An interesting situation occurs in the wide territorial gap
between the ranges of pratensis and floridanus.
David W. Johnston writes that the species' absence from the
coastal plain is difficult to account for, as "much of this
physiographic province has been converted to grassland. My only
explanation is historical, namely the possibility that this
species simply has not yet had time to invade or perhaps to
develop a physiological toleration of the climatic conditions
there." Also isolated on its breeding area is the Arizona
grasshopper sparrow, A. s. ammolegus Oberholser. This race,
described by H. C. Oberholser (1942) from a series of breeding
specimens collected by Alex Walker in 1932, breeds in central
southern Arizona, chiefly in the Huachuca Mountain region.
The grasshopper sparrow is a grassland bird, most plentiful in
managed grasslands and absent from fields with 35 percent of the
area in shrubs. They inhabit small grain fields to a limited
extent, but their densities in such areas are a fraction of those
found in grassland. Johnston and Odum (1956) observe that the
grasshopper sparrow and the meadowlark (Sturnella magna)
are the only true grassland species of the Athens, Ga. area, and
in fact of most of the southeastern United States. Alden Miller
(1951) writes that it is confined exclusively to grassland
formation in California.
The eastern race appears to be most abundant on cultivated
grasslands, particularly those containing orchard grass (Dactylis
glomerata), alfalfa (Medieago sativa), red
clover (Trifolium pratense), lespedeza (Lespedeza
spp.), all of which form the clumps the species seemingly
requires. Old fields of poverty grass (Danthonia spicata),
dewberry (Rubus spp.) and broomsedge (Andropogon spp.)
also are inhabited by the grasshopper sparrow, but the birds leave
as the shrubs fill in the fields. On the islands off the New
England coast this bird is found in old fields with red cedar (Juniperus
virginiana) and bayberry (Morella pensylvanica).
Prime habitat for the western subspecies perpallidus and
ammolegus is the prairie. Kendeigh (1941) notes that
grasshopper sparrows are more plentiful in prairie grasses than in
bluegrass.
In the forested regions of the east grasshopper sparrows
originally were restricted to extensive natural clearings and
sparsely wooded areas. They are found in such situations today in
Minnesota (Roberts, 1936) and Michigan (Walkinshaw, 1940).
Walkinshaw writes: "In Crawford County in natural clearings,
grown sparsely to grass, the species was found on open areas only
a few acres in extent where no stock was pastured and no haying
was done. Here the birds were found in the natural wild state
before man had taken over the land for his use.
Clearing the land for agriculture permitted the species to
spread. Todd (1940) writes: "Undoubtedly the species has
greatly increased in number during the past century and it is
interesting to find that in extending its range it has invaded
territory far beyond its usual altitudinal and faunal
limits." Forbush (1929) notes that the grasshopper sparrow is
a bird "of the coastal plains, river valleys and lower
uplands. It is rarely found at elevations much above 1,000
feet." But in Pennsylvania on the western flank of the
Alleghenies, the species is found at elevations over 2,000 feet
when local conditions are suitable, and Maurice Brooks (1944)
found it in West Virginia "on the Allegheny Backbone, in
Pocahontas County, at an elevation of 4,300 feet."
The Florida grasshopper sparrow occupies an aberrant type of
habitat for the species. Howell (1932) writes that this race
"lives among the stunted growth of saw palmetto and dwarf
oaks (Quercus mimina) a foot or two high, seemingly
preferring this habitat to the grassy areas." D. J. Nicholson
writes it inhabits the more open parts of the Kissimmee Prairie
"where the saw palmettos are small--10 to 15 inches high--and
the grass is sparse with patches of bare ground showing here and
there. . . . they avoid heavy growth of palmettos or dense grass.
. . . Frequently the cattlemen burn the prairie, and the birds
seem to prefer these burned-over areas where the cover is very
light and rather open."
Spring.--The grasshopper sparrow
returns to its nesting grounds, often unnoticed, usually from
mid-April to early May, although it may appear as early as the
last of March. My earliest arrival date for north central
Pennsylvania is Mar. 31, 1945, when a resident male returned to
his old territory on the study area. A second male arrived two
days later, but a short cold spell delayed the arrival of the rest
of the population until April 12.
Cruikshank (1942) states that the species arrives in a marked
wave about New York City during the first week of May, and
stragglers pass through as late as the first week of June. I have
never observed any marked wave in central or western Pennsylvania;
there a few birds appear first, then the population builds up over
a period of 1 to 2 weeks. My observations indicate that the first
arrivals are males. They generally do not appear on the nesting
areas until the grass is tall enough to conceal them.
Territory.--Upon arrival at
their nesting grounds, male grasshopper sparrows undertake
territorial establishment. The first arrivals have the area to
themselves and generally confine their singing to the morning
hours. As more birds return, territorial activity increases in
intensity, reaching a climax about 2 to 3 weeks after the first
birds arrive. Then song is heard throughout the day.
The male proclaims territory by singing the
"grasshopper" or territorial song (see Voice).
When engaged in a song duel, the male alternates song with
display. Crouching with head lowered between the shoulders, he
raises and flutters one or both wings. Then after hearing the song
of his neighbor, he stands erect and sings back. The song
completed, he again crouches and flutters his wings while his
rival sings. The wing fluttering, conspicuous only during
territorial establishment, is never accompanied by a song or
a call, and is confined to the intervals between songs.
I regard the wing fluttering of the grasshopper sparrow as a
hostile display. During the period of territorial establishment
the song of a rival is a sufficient stimulus to release it. Often
the birds are hidden by the vegetation or the topography of the
field so they cannot see one another. They sense the presence of a
rival by the sound of his song and manifest this by a hostile
display, as if the rival were nearby in the grass.
I have never observed a territorial dispute that elicited an
intimidation display of high intensity, although some could have
taken place in the grass, out of sight. The only physical
encounters I observed during hundreds of hours spent with the
species occurred after a bird saw another invade its aerial
territory. In each instance the bird chased the intruder, then
retired to a singing perch, fluttered his wings, and sang the
grasshopper song. I have witnessed a number of such clashes at
disputed boundaries. Since the deep grass conceals territorial
infringements on the ground, this mode of defense could be most
important. Perhaps the grasshopper sparrow recognizes the limits
of its territory only from a grasstop point of view.
The territorial "grasshopper" songs usually are
delivered from the highest perches in the territory. These may
include a clump of grass, an alfalfa stalk, a tall weed, a small
bush, fence post, utility wire, tree, or farm equipment left in
the field, hay cocks, or grain shocks. The birds appear restricted
to low perches only by their habitat, and use low ones simply
because no higher ones are available. This was demonstrated
experimentally. When a wooden stake tall enough to stand two feet
above the grasstops was placed in a bird's territory, the bird
claimed it within minutes. When a still higher perch was
introduced the next day, the bird abandoned the first for the new,
higher perch.
Song perches are clustered about certain singing areas, usually
near the periphery of the territory, apart from the nesting areas.
Among the birds I have studied, singing perches were from 165 to
412 feet from the nest. Their position may be influenced by row
crops in the territory when grasshopper sparrows then confine
their singing perches to the vicinity of grass plots.
The size of 22 territories plotted on my study area ranged from
1.2 to 3.3 acres; 11 were between 1 and 2 acres, 9 between 2 and 3
acres, and 2 were over 3 acres. Their average size was 2.03 acres.
Kendeigh (1941) reports the average size of 6 territories was 3.4
acres.
Territorial boundaries are maintained rigidly during the
periods of territorial establishment, nest building, and
incubation. After the young hatch, territorial defense declines
and considerable movement of birds into other territories occurs.
The movement is often initiated by young birds just able to fly,
that flutter into adjoining territories where the parents follow
in answer to the feeding call.
Prior to second nesting, territorial defense increases sharply
for 2 to 3 days. The males sing the "grasshopper" song
and flutter their wings. Territorial boundaries may be shifted in
response to disturbances made by harvesting of hay and small
grains. In one instance a male grasshopper sparrow shifted his
territory for the second nesting to include the eastern half of
his neighbor's territory. The hay on this portion had been mowed
early, and new growth afforded cover lacking in the original
territory. The neighboring male in turn took over the western half
of the first male's old territory. In the end both birds had new
growth and newly mowed hayfields in their respective territories.
Interestingly, these two birds occupied approximately the same
territories the following year. Another male, whose territory was
bisected by a strip of field corn, took over a corner of his
neighbor's territory when the increasing height of the corn walled
off the lower half of his own territory and made it useless.
After the second broods leave the nest, grasshopper sparrows no
longer defend territorial boundaries, although adults and young
remain in the general vicinity until they disappear in the fall.
Courtship.--Within 10 to 14 days
after their arrival, the males introduce the sustained song (see Voice),
which for a short time almost replaces the grasshopper song and
signifies that courtship is at its height. Most courtship activity
is hidden in the grass, but occasionally a male rises above it on
quivering wings, delivers this song in a low fluttering flight,
and then drops out of sight again. The female may answer this song
with a trill of her own (see Voice), which she often sings
alone. The male responds by singing the sustained song or by
flying to her. At times the male pursues the female and sings the
sustained song as he gives chase.
W. H. Nicholson writes that the male Florida grasshopper
sparrow "has a fluttering mating flight similar to that of
the seaside sparrow except that it is low, 3 to 5 feet above the
ground for 50 to 100 feet; upon alighting on a twig or saw
palmetto it bursts into song."
Nesting.--Nests of the grasshopper
sparrow are extremely hard to find. During the course of my study
I was able to locate only four. All were hidden at the base of
clumps of grass, alfalfa, clover, dead vegetation, or other cover,
and often had one or two paths leading to the entrance. The nest
itself is built of stems and blades of grass and lined with fine
grass and rootlets, occasionally with horsehair (Burleigh,1923;
Simmons, 1925; Trautman, 1940). Sunk in a slight depression, the
rim is level with or slightly above the surface of the ground. The
top is usually arched or domed at the back, giving it an ovenlike
appearance. Nest measurements range as follows: outside, 4.50 to
5.50 inches; height, 2 to 2.25 inches; inside, 2.50 or 3 by 3.25
inches; inside depth, 1.25 to 1.30 inches (Simmons, 1925; Dixon,
1916).
W. H. Nicholson (1936) describes the nest of the Florida
grasshopper sparrow as follows: "Many of the nests were a
single dead palmetto leaf without any other vegetation to conceal
them; others were under dead drooping palmetto leaves with small
dwarf oaks and wire grass growing on all sides, while several
others were in thin tussocks of dead wire grass which looked too
small to hide the bird, much less the nest." Nests were
"lined with fine wire grass and arched over with grass
blades."
Nest-building of the eastern and western grasshopper sparrows
reaches its height in late May. This is followed by a second
nest-building period in very late June and early July. D. J.
Nicholson writes that the nesting of the Florida grasshopper
sparrow begins "about the middle of April to the first week
in May; second nestings are begun about the first of June; and
again in July they breed a third time."
Eggs.--The grasshopper sparrow
commonly lays 4 or 5 eggs; although frequently sets of 3 are found
and occasionally as many as 6. They are generally ovate and have a
slight gloss. The ground color is creamy white, speckled and
spotted with shades of reddish browns such as "Rood's
brown," "russet," "Mars brown," or
"chestnut brown," and undermarkings of "pale
purplish gray," or "pale neutral gray." The spots
are usually sharp and well defined; they may be scattered over the
entire egg or concentrated toward the large end where they often
form a loose wreath or become confluent over the cap. Many eggs
show as many gray undermarkings as spottings of the red browns.
The pattern of markings of this species might be considered
somewhat delicate, especially as compared with the eggs of the
Savannah or song sparrow. The measurements of 92 eggs average 18.7
by 14.4 millimeters; the eggs showing the four extremes measure 20.8
by 14.7, 18.3 by 15.8, 16.3 by 13.7, and 17.9 by 13.6
millimeters.
A. s. pratensis. The measurements of 50 eggs average
18.6 by 14.4 millimeters; the eggs showing the four extremes
measure 20.8 by 14.7, 18.3 by 15.8, 16.3 by
13.7, and 17.8 by 13.7 millimeters.
A. s. perpallidus. The measurements of 32 eggs average
18.7 by 14.3 millimeters; the eggs showing the four extremes
measure 20.3 by 15.0, 19.6 by 15.2,17.8 by
14.2, and 17.9 by 13.6 millimeters.
Incubation.--The exact
incubation period of the grasshopper sparrow is unknown, as it is
only with considerable luck that a nest with a partial or a
recently completed clutch can be found. King (1940) reports
finding a nest on May 29, 1940, containing five eggs. On June 10,
the same nest contained four young and one egg. Assuming that the
young were shortly out of the egg and the fifth had yet to hatch,
the incubation period would have been 12 days. D. J. Nicholson
writes that the incubation period of the Florida grasshopper
sparrow is "11 to 12 days--not more." Simmons (1925)
writes that the incubation period of perpallidus
"lasts for about 12 days."
The female alone incubates the eggs and broods the young. She
sits very closely on the nest. When leaving, she slips off, runs a
distance through the grass and then flies. On her return she never
flies directly to the nest, but drops down into the grass some
distance away and goes to it on foot, by one of the several paths.
If flushed from the nest the female may dart off, run a short
distance, arise in a short fluttering flight, then drop to the
ground again where she spreads her tail and trails her wings as if
injured. At other times the female may flutter directly off the
nest as if crippled or may fly from the nest to a point 25 to 30
feet away and hide in the grass.
W. H. Nicholson writes that some female Florida grasshopper
sparrows "will run off the nests before they are found;
others will sit tightly until almost stepped upon before they
flutter off uttering weak squeaking notes not unlike a
mouse." He (1936) writes further: "When they did leave
they did not fly, but ran off dragging tail and fluttering the
wings as if crippled. If followed they would lead the intruder off
about twenty feet from the nest and then fly to some nearby
palmetto and begin scolding. Several times the bird would run
along the ground within eight feet of me scolding with a weak tik-tik-tik."
During the incubation period the male spends his time singing
and defending the territory, but shows little concern over human
intruders. When they appear he simply stops singing and hides in
the grass. The actions of both sexes are such that they attract no
attention to the nest location.
The behavior of both male and female changes after the young
hatch. One male I observed sang both songs throughout the day his
young hatched. The female flushed from the nest but did not feign
injury. She flew a short distance, hid in a swath of hay and
chipped softly. The male chipped several times, broke into the
grasshopper song, fluttered both wings, and then continued to chip
vigorously. As I left the area the male sang the sustained song,
interrupted it with a grasshopper song, followed by the trill (see
Voice).
Young.--Grasshopper sparrows at
hatching are blind and covered with grayish-brown down. Walkinshaw
(1940) gives the weight of young at hatching as between 1.7 and
2.3 grams. This is approximately the same weight as the egg. At 4
days wing feathers break through the sheath; breast and side
feathers still are in the sheath; back, belly, and rump are bare.
At 6 to 7 days body feathers emerge from the sheath and appear
dark brown to blackish with yellowish buff edge. A distinct buffy
crown patch is present; the commissure is bright yellow. By day 9
to 10 the young are well feathered, though the tail feathers are
still short. Walkinshaw gives the weight increases as of the
second day, 2.9 grams; sixth day, 8.7 to 9.1 grams; and seventh to
eighth day, 9.7 to 10.5 grams. Wetherbee (1934) reports the weight
of 14 immature birds as ranging between 14.0 and 18.3 grams,
averaging 16.09.
Upon my approach to the nest the young invariably gaped for
food, but expressed no sign of fear. On June 7, 1944, my dog
discovered the nest of one pair and threw two of the four out of
the nest. As I replaced these, the two in the nest gaped for food.
Later in the day, immediately after the female fed the young, one
bird gaped and three did not respond. This same pattern was
followed at other nests. Recently fed young did not respond in any
way; if hungry they gaped when I moved near the nest.
Young birds on my Pennsylvania study area remained in the nest
9 days. Michigan birds observed by Walkinshaw (1940) remained in
the nest the same length of time. When out of the nest, the young
run mouselike through the grass and rarely appear above the
grasstops.
Both male and female are very solicitous about the young.
During incubation the birds exhibit little concern about human and
animal intrusions in their territories except those of cats. After
the young hatch, the birds react to human intrusion with vigorous
alarm. They may fly in wide circles above the trespasser, raising
their crest feathers and flicking their wings and tail. On the
ground they bob up and down on their legs like a spotted sandpiper
(Actitis macularia) and utter a sharp chi-ip. When
highly alarmed they give this double note so rapidly it almost
runs into a trill. Often the male will interrupt his chipping to
break into a grasshopper song. If the birds are carrying food to
the young at the time, they invariably eat the insect and continue
their alarm behavior. When a dog enters the territory, the birds
drop into the grass, crouch low, and remain silent until the
animal passes.
Plumages.--The juvenal plumage
and post-juvenal molt of the grasshopper sparrow have been studied
in detail by George M. Sutton (1935, 1936). He found a number of
discrepancies in the descriptions by Dwight (1900), which were
apparently based on a poorly aged specimen.
According to Sutton, the natal down is replaced by the juvenal
plumage in a complete postnatal molt. It is worn for a short time
as a complete plumage and is probably complete at 10 to12 days of
age. At this time the rectrices are stubby; the feathers of the
back and scapulars are plain dark olive-brown or blackish brown,
edged with buff, and totally lack any sort of russet spots on the
tips. Richard R. Graber (1955) describes the juvenal plumage in
detail as follows:
"No sexual dimorphism. Forehead and crown streaked, brown
and black, with median and superciliary stripes of light buff or
buffy white. Nape mottled, buffy white and black. Back, feathers
black, edged with buff or buffy brown. Upper tail coverts black,
edged with buff. Rectrices black, narrowly edged with buff, except
median pair (broadly edged). Remiges slate gray or black, edged
with buff or buffy brown. Tertials black, edged with white.
Superciliary buffy white, streaked with black. Auriculars buffy
brown. Post-auriculars concolor with nape. Under parts white or
buffy white more strongly tinged with buff on chest, sides,
flanks, and crissum. Upper chest rather sparsely streaked with
blackish or dark brown. Other under parts unmarked. Stub-tailed
birds much darker throughout than older birds."
The post-juvenal molt, according to Sutton (1936), takes place
in late June or early July with the young of the first brood.
Second and third brood young may be wearing part of the juvenal
plumage as late or even later than mid-September. The body
feathers of the juvenal plumage are lost first, while the flight
feathers and tertials may be held for a longer period. At 20 days
russet-tipped feathers appear on the back; the superciliary line
still is sharply streaked; the rectrices are sheathed at the base.
At 4 weeks the juvenal feathers are lost on the crown and the
superciliary line, together with all remaining body feathers
lacking russet tips. At 36 days the buff-margined juvenal feathers
are practically gone, replaced by buffy feathers on the chest,
sides, flanks, and lower throat. The back is thickly set with
incoming fully-sheathed feathers, and new lesser wing coverts with
a strongly yellowish cast appear. At about 6 weeks the juvenal
rectrices are lost almost simultaneously. The molt of the juvenal
primaries starts from the innermost outward.
A dull yellow superciliary is present in some juvenal males,
but apparently is absent in juvenal females. The yellow
superciliary spot is acquired by both male and female birds with
the post-juvenal molt in the latter part of summer and fall, and
not in April with a partial prenuptial molt as described by Dwight
(1900).
The first winter plumage contains no streaked feathers on the
chest. The back feathers are black with apical chestnut spots
edged with pearl gray. The median crown stripe, edging of
tertiaries and wing coverts, sides of the head, superciliary line,
and under parts are rich buff. New feathers above and in front of
the eye are deep yellow. The neck feathers are red-brown medially.
Middle of the abdomen is pure white.
There is no evidence of a prenuptial molt except for
replacement of feathers lost accidentally. Sutton (1936) states
that "the large majority of spring birds are exactly like
fall adults except that the plumage is a little more worn. Fall
birds are beautifully fresh, breeding birds are noticeably worn,
late summer birds are very decidedly worn, and spring birds are in
an exactly intermediate position between fall and summer."
The second winter plumage is acquired by a complete postnuptial
molt. According to Dwight (1900) it differs little "from the
first winter dress, the buff less obvious and the colors
deeper."
The adult western grasshopper sparrow, A. s. perpallidus,
is paler and grayer than the eastern race, with more chestnut and
rusty brown and less black above.
Oberholser (1942) describes the Arizona race as similar to A.
s. perpallidus. The upper parts are decidedly paler, with more
chestnut and rufous and also with much less, sometimes almost no,
black on the back. The lower parts are lighter and not so dull.
The Florida race, A. s. floridanus, is much darker above
than A. s. pratensis, paler and less buffy below. Feathers
of the upper parts are mainly black, edged with grayish, with
little or no brown. The under parts are less heavily washed with
pinkish buff than A. s. pratensis.
Food.--Insects form the staple food
of the grasshopper sparrow; and the most prominent among these is
the grasshopper. Judd (1901) found that grasshoppers (genera Xiphidium,
Scudderia, Hippiscus, and Melanopus) formed
23 percent of the bird's food during eight months of the year, 60
percent of its food in June and 37 percent of its diet from May to
August. Thus the name of the bird is appropriate from the
standpoint of its diet as well as its song.
Judd examined 170 stomachs of this sparrow collected between
February and October from both the east and west. Food consisted
of 63 percent animal matter and 37 percent vegetable matter.
Insects comprised 57 percent of its total food, spiders, myriapods,
snails, and earthworms, 6 percent; harmful beetles made up 8
percent and caterpillars 14 percent. Beetles were of three
families: click beetles (Elateridae), weevils (Sitones
and related genera), and smaller leaf beetles (Systens spp).
Judd writes: "Caterpillars are eaten more freely in May than
at any other time, and constitute 33 percent of the food of that
month. More than half of the caterpillars destroyed are cutworms.
In one stomach from Bourbon County, Ky., were six cutworms (Nephelodes
violans), each an inch long. The army worm seems to be also a
favorite article of diet. Eleven percent of the total food
consists of ants, dung beetles (Atoeniys and Apodius),
and 1 percent bugs, including leaf hoppers (Jassidae), leaf
bugs (Capsidae), assassin bugs (Reduviidae), and
smaller soldier bugs (Hymenarcys and Trichopepla).
Vegetable food consists of grain, chiefly waste, 2 percent;
wood sorrel (Oxalis) 2 percent; ragweed (Ambrosia) 5
percent; pigeon grass (Setaria), panic grass (Panicum),
and others 17 percent; smartweed (Polygonum), purslane (Portulata),
ribgrass (Plantago), and sedges (Cyperacease) 11
percent.
Howell (1932) writes of the Florida race: "Examination of
the stomachs of 10 specimens taken on the Kissimmee Prairie showed
the bird's food to consist of animal matter (insects and spiders),
69 percent, and vegetable matter, 31 percent. The insects taken in
greatest quantity were grasshoppers and crickets, beetles,
weevils, and moths and their larvae, with a few flies and bugs.
Seeds of sedges composed most of the vegetable matter, with some
grass seed and seeds of star grass (Hypoxis)."
Behavior.--The grasshopper
sparrow is a secretive bird, difficult to observe. It seldom
flies, but runs ahead of the searcher through the grass and
flushes only when hard pressed. As William Brewster (journal)
describes it: "when flushed the sparrows rise swiftly and
vigorously, twisting a little. . . the flight then becomes steady
and direct and is performed in long, regular undulations, the
wings being vibrated rapidly." He adds: "On the ground
they both run and hop." Witmer Stone (1937) notes that in
flight the bird "turns to one side or the other like a
snipe." Simmons (1925) writes that when flushed the western
grasshopper sparrow rises "in a zig-zag flight for a few
yards" and then "dives back into the weeds. . . . In
open fields, flight is extended and rapid."
The bird perches in a peculiar crouched position, as if ready
to dart off in an instant.
D. J. Nicholson comments on the colonial nature of floridanus:
"They breed in small colonies--three or four to a dozen
pairs. These colonies are very local and are not found everywhere
over this vast prairie, many apparently suitable spots being
unoccupied."
These same words might well apply to the eastern and western
grasshopper sparrows as well, for they show the same colonial
nature and fluctuate considerably in abundance from year to year.
One cause of population changes might be attributed to
grassland management practices. On my study area, for example, the
fields during the early part of the study were run down and
supported a poor growth of timothy, alfalfa, and red clover. From
1944 on, the fertility of the fields increased considerably and
the grass mixture was changed to a thick, vigorous growth of
alfalfa, ladino clover, and brome grass (Bromus inermis).
The grasshopper sparrows in the area settled in hay and abandoned
fields where the vegetation was not so heavy.
Oscar Root (1957, 1958, letter), who kept a long-time record of
local population fluctuations on a level, artificially drained
airport of 100 acres at North Andover, Mass., found the
grasshopper sparrow populations there built up to highs, followed
by severe reductions in numbers the following year. He believed
mowing the grass on the area prior to his counts reduced the
population. However, when mowing was postponed to allow completion
of nesting by the sparrows, the population still remained low. He
states that certain areas always productive in the past were
without grasshopper sparrows, though in prime shape and
undisturbed.
The birds about Concord, Mass., have shown a similarly
fluctuating pattern of abundance through the years (Griscom,
1949).
An unusual concentration of grasshopper sparrows is described
by Brewster in his Nantucket journal. Here on June 27, 1874, he
and Maynard found grasshopper sparrows extremely plentiful. He
writes that "they were equally distributed for an extent of
three to four miles. Often there were three or four pairs breeding
in an area a hundred yards square." This species was fairly
common on the Islands in the 1920's, but in recent years it has
become local and uncommon and appears to have been replaced by the
Savannah sparrow (Passerculus sandwichensis) (Griscom and
Folger, 1948). Mrs. A. B. Davenport writes that the same situation
is true on Conanicut Island, off Rhode Island. The bird was
formerly abundant on Martha's Vineyard and north to Essex County,
Mass.; today it is rare and local, replaced by the Savannah
sparrow (Griscom and Snyder, 1955).
Thus it appears that populations of grasshopper sparrows
fluctuate sharply at times in spite of the availability of
suitable habitat. No reason can be given, but in some areas it
appears to be giving way to the Savannah sparrow, a bird that
occupies the same fields and is able to maintain its numbers when
shrubs invade the area.
Voice.--The male grasshopper sparrow
possesses three primary forms of vocalization, the grasshopper
song, the sustained song, and the trill; the female has only one,
the trill.
Of these the most familiar is the grasshopper song from which
the bird derives its name. The song consists of one to three
introductory notes followed by a long, very high-pitched trill.
The length of this song varies from 1 to 2 1/5 seconds, and
averages about 1 2/3 seconds. The pitch, according to Saunders,
varies from F#7 to D8;
and the pitch interval varies from 1 to 3 1/2 tones. The
introductory notes are usually of lower pitch than the
trill." The trill is simple and nearly always on the same
pitch throughout.
Brand (1938) determined the pitch of this song to range from
9,500 to 7,675 vibrations per second, with a mean of 8,600. By
contrast the frequency of a piccolo is 4,608 cycles per second.
The songs of the other races resemble closely those of pratensis.
Zimmer (1913) describes the song of the western grasshopper
sparrow as a pit-tuck zee-ee-ee. Simmons (1925) describes
it as a "thin, wiry monotonous grasshopper like pit-tuck
zee-ee-e-e-e-e-e-e-e-e-e or kalsick ha tsee-e-e-e-
e-e-e-e-e-e-e-e."
W. H. Nicholson (1936) describes the song of the Florida
grasshopper sparrow "as sounding like twittle-e-dee
repeated several times in rapid succession with a tik-tik-tok-buzzzzzz
at the finish. Many times I have heard them sing the latter part
of this song without the former, but never the former part alone.
The latter part has a distinct insect-like sound."
The sustained song is more elaborate and more musical than the
grasshopper song and is subject to considerable individual
variation. It ranges up to 5 seconds in length. The sustained song
in its entirety consists of a grasshopper introduction followed by
a sustained series of melodious notes. The song may be written as tip-tup-a-zee-e-e-e-e-e-e-e-e
zeedle zee-e-e-e zeedle zeedle zee-e-e-e-e-e-e. The
grasshopper introduction often is omitted, especially after
territories are well established.
Jouy (1881) mistakenly attributed this song to Henslow's
sparrow (Passerherbulus henslowii). He writes:
"Besides their characteristic note of te-wick, they
have quite a song which may be fairly represented by the syllables
sis-r-r-rit-srit-srit, with the accent on the first and
last parts. The song is often uttered while the bird takes a short
flight upward; it then drops down again into the tangled weeds and
grasses where it is almost impossible to follow it."
This is an adequate description of the sustained song of the
grasshopper sparrow which is often given in flight. During 5 years
of concurrent observations of both species in the same fields, I
never heard a Henslow's sparrow sing a song that even remotely
resembled the sustained song of the grasshopper sparrow.
The primary function of the sustained song is to attract and
hold a mate. The grasshopper introduction, however, is hostile in
character and serves as a warning early in the season. Later, when
the grasshopper introduction is dropped, the males respond to the
sustained song with a grasshopper song. Then both birds launch
into a duel of grasshopper songs.
The least common vocalization of the male grasshopper sparrow
is the trill. Unless one is frequently in the field among these
birds, the observer is apt to miss it entirely. Walkinshaw (1940)
calls it a nesting song, and Saunders (1951) describes it
graphically. It can be written ti-tu-ti-tu-ti-i-i-i-i. The
song consists of a series of moderately loud, short, alternate
notes, given rapidly and ending in a downward trill. It is
delivered on the ground or from a perch. The trill generally is
not given until the pair is formed, and is then uttered only in
the vicinity of the nest. It may follow one of the other two
songs, or it may be given alone, often in answer to the female.
This song apparently serves as a bond to hold the pair together,
and as a signal to the female and young that the male is
approaching the nest.
The female grasshopper sparrow has a song quite similar to the
trill of the male, but softer, lacking the downward trill, and
more suggestive of the song of the chipping sparrow (Spizella
passerina). It may be written ti-ti-i-i-i-i-i-i-i. Its
primary function is apparently to declare her presence on the
territory to the male. She also gives the trill when she is
approaching or is near the nest. When so used it serves to
announce her location, to maintain the pair bond, and to signal
both the male and the young that she is approaching the nest.
Song falls into seasonal and daily patterns. The male sings the
grasshopper song from arrival until mid-August. The sustained song
is introduced approximately at the time of the females' arrival.
After pairing, the volume of song drops for a few days, but
singing does not cease entirely. The sustained song is confined
mostly to evening twilight; the grasshopper song is the common
daytime song. During the periods of egg laying and incubation the
male sings both songs frequently, especially in early morning and
late evening, continuing until darkness. Song wanes during June
when the birds are busy feeding young. Prior to re-nesting the
sustained song is heard frequently for several days before it
wanes again. The trills of both male and female are given from the
period of pair formation to the completion of nesting.
The grasshopper sparrow does not have an extended morning
awakening song. When it wakes the bird may start to feed in
silence, or it may utter a few call notes, or snatches of the
grasshopper or sustained songs. Once the bird starts singing, it
interrupts the song sequence frequently with feeding. By mid-July
the morning singing has almost ceased, and daytime song is rarely
heard, but in the cool of evening, as feeding activity stops,
twilight singing may still be heard until darkness falls. At this
period the sustained song with its greater carrying power seems to
be the most conspicuous, and for this reason has been erroneously
described as a postseason elaboration of the regular song of the
species. Night singing, particularly when the moon is full, is a
common habit with all races of the species.
The call note of all races of the grasshopper sparrow most
commonly heard is a two-syllabled chi-lip or til-lic.
Given by both sexes, the call functions primarily as an alarm
note; as such it varies in intensity. When rapidly given in high
intensity alarm, the notes suggest the slow clicking of a fishing
reel. Less frequently, especially under situations of low
intensity alarm, the call note is only a sharp tik.
While feeding the grasshopper sparrow utters a single note tik
or chip. It is similar to the alarm note, but is higher
pitched and less sharp and vigorous. The food call of the young is
a double note chi-ip similar to that of the adult but with
a more liquid quality.
Field marks.--Adult grasshopper
sparrows are short-tailed, flat-headed, and the only sparrows of
the grasslands that lack streaks or markings on the breast. Young
birds of the year have streaked breasts and are often confused
with adult Henslow's sparrows, which are more sharply streaked
with black on the breast, sides, and flanks. The young Henslow's
sparrow with relatively unstreaked breast may be confused with the
adult grasshopper sparrow, but the distinctly chestnut wings of
Henslow's sparrow separates this species at all ages from the
grasshopper sparrow.
The only other bird with which the grasshopper sparrow might be
confused is Leconte's sparrow (Passerherbulus caudacutus).
This sparrow, however, inhabits prairie marshes, an environment
too wet for the grasshopper sparrow. Both adult and young
Leconte's sparrows are streaked, but the under parts are light
yellowish brown instead of cinnamon buff, and they lack the yellow
before the eye and on the bend of the wing.
Enemies.--It is ironical that the
grasshopper sparrow's greatest benefactor is also his greatest
enemy. This sparrow depends upon its man for maintenance of
habitat through grassland management but these fields are cut for
hay. Haying usually begins in mid-June, the height of this bird's
nesting season. The nest usually escapes destruction from mower
blades, but some nests may be crushed by implement wheels. If the
nest escapes destruction by haying operations, it is exposed to
weather and predators. Grass used for silage is cut early, around
the first of June. This is the height of nest building by the
grasshopper sparrow. I have found that in fields regularly cut for
grass silage, resulting in early loss of cover, the population of
grasshopper sparrows is very low. The loss of cover later in the
nesting season does not result in abandonment of the field or the
nest, if the nest has not been destroyed. I have never noted
grasshopper sparrows leaving a field after haying, despite the
loss of cover. This is in sharp contrast to Henslow's sparrow,
which leaves a field when the grass is cut.
Among the predators of the grasshopper sparrow are the skunk (Mephitis
mephitis), weasels, spermophiles (Citellus spp.),
foxes, and cats. Cats take their toll of grasshopper sparrows,
especially after the hay is cut, although they probably catch
fewer of these birds than of other sparrows. Dogs at times
discover grasshopper sparrow nests accidentally.
W. H. Nicholson writes that hogs, snakes, spotted skunks (Spilogale
ambarvalis), and striped skunks seem to be the major enemies
of the Florida grasshopper sparrows. He states; "I have found
25 to 30 nests under construction; upon returning later I found
practically all of them destroyed by the above."
As the nests are well concealed and the birds stay close to the
grass, hawks probably are insignificant as predators, except after
the hay is cut. Marsh hawks (Circus cyaneus), though common
in grasshopper sparrow habitat, appear to have little influence on
the species. The grasshopper sparrow apparently pays no attention
to them, for I have observed males singing while marsh hawks were
hunting nearby. When, however, a sharp-shinned hawk (Accipiter
striatus) approaches, the grasshopper sparrows stop singing at
once, give a few alarm notes, and drop into the grass. After the
hawk has disappeared, they come out of hiding and resume their
singing.
The cowbird (Molothrus ater) parasitizes a few nests of
the grasshopper sparrow, but the incidence is extremely low.
Friedmann (1938) lists three known occurrences of parasitism of
the eastern grasshopper sparrow and three for the western race.
Hicks (1934b) found one grasshopper sparrow nest containing a
cowbird egg in Ohio. This low incidence reflects the difficulty
cowbirds must have in locating nests of this species.
Walkinshaw (1940) observed small red ants attacking young birds
in the nest and entering two pipped eggs. The female ate all the
ants in and around the nest.
Terres (1939) reports that an immature grasshopper sparrow was
caught in the vertical web of a golden garden spider (Miranda
aurantia). The bird was released, apparently unharmed.
Fall and Winter.--By
late August the nesting season is over, the young grasshopper
sparrows are independent, and the adults are silent and more
retiring than ever. The birds stay close to the grass and refuse
to fly unless very closely pressed and when flushed quickly seek
cover again. Unlike many other sparrows, they do not flock. During
migration they may join other migrant fringillids, like the field
and song sparrow, and appear in rather unlikely places. I have
observed migrating birds along brushy fence rows, and I caught one
immature individual in a trapping station in an elderberry
thicket. By late September most grasshopper sparrows have left the
breeding grounds, although a few may linger on until late October
and early November.
Simmons (1925) writes that the eastern grasshopper sparrow
during migration in the Austin region of Texas is found in
"closely cropped pastures dotted with mesquite, floored with
some stubble and buffalo grass, and edged with weed patches, brush
thickets, weedy fence rows, and plowed ground."
Skinner (1928) writes that in the sand hills of North Carolina
wintering grasshopper sparrows inhabit sandy grassy fields,
especially those with broomsedge. Lowery (1955) states that this
species is a "rather uncommon or at least seldom observed
winter resident" in Louisiana, where it inhabits "broomsedge
fields with a few small trees or brush piles." Tyler (1913)
writes that in California wintering grasshopper sparrows inhabit
"old weedy fields, weed-grown vineyards and berry
patches."
There are few winter records north of the above range. Trautman
(1940) reports a male bird found on Dec. 29, 1928, in the Buckeye
Lake, Ohio, region with a "pathological condition present in
the bill and feet, for both were considerably swollen and a toe
was gone." Griscom and Snyder (1955) cite a winter record for
Dec. 6, 1892, at Arlington, Mass. A grasshopper sparrow banded by
Oscar Root at North Andover, Mass., on Nov. 30, 1940, was
collected nearby on Jan. 19, 1941. Another bird was collected at
Rose Blanche, Newfoundland, Nov. 27, 1950 (Peters and Burleigh,
1951a). Easterla (1962) records two, of which one was collected,
wintering near Sedalia, Mo., Jan. 14, 1961.
The Arizona race, ammolegus, winters from northwestern
Mexico to Guatemala. The Florida grasshopper sparrow is resident
and remains on the breeding grounds all through the year.
Grasshopper Sparrow*
Ammodramus savannarum
Contributed by Robert Leo
Smith
*Original Source: Bent,
Arthur Cleveland and collaborators (compiled and edited by Oliver
L. Austin, Jr.). 1968. Smithsonian Institution United States
National Museum Bulletin 237 (Part 2): 725-745. United States
Government Printing Office
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