American tree sparrows ( (Alsop, 2001)) breed throughout almost all of Alaska, the Yukon and Northwest territories, the very north of Manitoba and Ontario, all of Labrador, and in northern Quebec. Their winter range includes a very small part of southern Canada and all of the United States except for the western most 250 miles, the southern most 450 miles and all of Florida.
The breeding habitat of American tree sparrows is typically near the tree line in open scrubby areas with willows, birches, alder thickets or stunted spruce. They may also breed in open tundra with scattered shrubs, often near lakes or bogs. They winter in open forests, gardens, fields, and marshes. (Naugler, 1993)
- Aquatic Biomes
- lakes and ponds
American tree sparrows are small, grayish-brown birds with a rufous crown and eyeline, a dark spot on the breast, a long notched tail, a dark upper mandible and a yellow lower mandible. They have a grey head, chin, throat, breast and underparts and a rufous patch on the sides of their breast. Males and females are similar in appearance. Juveniles are similar to adults, but have streaking on their sides and breast.
Adult American tree sparrows weigh 18 to 26 g, and are 14 to 16.5 cm in length. Their wingspans range from 21.6 to 24.8 cm.
There are two recognized subspecies of Spizella americana. The western subspecies, Spizella americana ochraceae is paler and slightly larger than the eastern subspecies, Spizella americana arborea. (Alsop, 2001)
- Sexual Dimorphism
- sexes alike
- Range mass
- 18 to 26 g
- 0.63 to 0.92 oz
- Range length
- 14 to 16.5 cm
- 5.51 to 6.50 in
- Range wingspan
- 21.6 to 24.8 cm
- 8.50 to 9.76 in
Baumgartner (1938) followed birds for the first 22 days of development. Order of hatching was not dependent on the order of laying. Earlier hatched birds took the lead in development. During the nine and one-half days in the nest, the four feather tracts of the birds (dorsal, ventral, alar, caudal) go from completely bare to the back covered, lower belly slightly bare, wings 2/3 grown, and tail still a stub, and the birds grow from 1.62 gm to 16.7 gm, while their length goes from 33 mm to 75 mm during the same period. They lose 1.5 gm the first day out of the egg but have gained 3 gm by day 21 (Baumgartner, 1968). On the second day after hatching the young were able to stretch for food. On the fourth day their eyes were half open, after the fifth day, wide open. The first sounds were made on the fifth day but were very soft. Fear was acquired between 7.5 and 8 days as demonstrated by their raucous calls when touched by humans.
During the first 12 days of the fledgling period (which lasts until about a month after leaving the nest in) the birds showed a steady increase in both tail length (14-47mm) and wing length (46-68mm). At the end of the first 21 days the wings were still slightly shorter and the tails about 2/3 the length of mature birds. A tree sparrow was observed to fly 30 or 40 ft fifteen days after hatching, and a little before one month after hatching, the birds could fly all around their territory (Baumgartner, 1938).
American tree sparrows are monogamous. Breeding pairs form after arrival on the breeding grounds, around mid-June. Singing is used by both sexes to show their interest in one another. The female becomes excited when a male comes to sing nearby and she utters a "wehy" sound. This serves to attract the male to her. The male may also spread his wings and flutter, dart to the ground in front of the female, then fly back to his perch, and repeat this process several times. Sometimes breeding occurs without any display during feeding or at the nest. Breeding has been observed during nest building and on the day before an egg is laid. The duration of pair bonds is unknown. (Baumgartner, 1937c)
- Mating System
American tree sparrows breed between May and September and raise only one brood per season. The females builds the nest alone. Nests are built on the ground, and are constructed of moss, grasses, bark and twigs and lined with fine grass and feathers. Nest construction takes about 7 days. The female then lays 4 to 6 (average 5) eggs at a rate of one per day. She incubates the eggs for 10 to 14 days and broods the altricial chicks after hatching. Both parents feed the young until they fledge from the nest and for 2 to 3 weeks afterward. The young fledge from the nest 8 to 10 (average 9) days after hatching. In late summer, families join larger flocks. The age at which American tree sparrows begin breeding is unknown. (Baumgartner, 1937c; Cornell Lab of Ornithology, 2003; CWBO, 1997; Naugler, 1993)
- Key Reproductive Features
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- Breeding interval
- American tree sparrows breed once per year.
- Breeding season
- American tree sparrows breed between May and August.
- Range eggs per season
- 4 to 6
- Average eggs per season
- Range time to hatching
- 10 to 14 days
- Range fledging age
- 8 to 10 days
- Range time to independence
- 2 to 3 weeks
Females incubate the eggs and brood the altricial chicks when they first hatch. After a few days, the females spend more time feeding the young and less time brooding. Males also help feed the young. One male sparrow was observed leading a chick out of the nest by offering it food. Feeding by the parents ends when the chicks are about 22 days old. (Baumgartner, 1937b; Baumgartner, 1938)
- Parental Investment
- no parental involvement
The oldest known American tree sparrow lived at least 10 years and 9 months. The average life expectancy for American tree sparrows is 2.3 to 3.4 years. (Baumgartner, 1937a; Baumgartner, 1968; CWBO, 1997; Naugler, 1993)
- Range lifespan
- 10.75 (high) years
- Range lifespan
- Typical lifespan
- 2.3 to 3.4 years
- Typical lifespan
American tree sparrows are migratory. Though they are diurnal during the rest of the year, this species migrates at night.
American tree sparrows are territorial during the breeding season. Males sing to claim territories and are responsible for territory defense, though females also occasionally chase intruders. The inner part of a territory is used the most and mainly early in the day, with activity spreading to the outside of the territory later in the day. American tree sparrows do not actively defend winter territories. During the winter they form foraging flocks in which dominance hierarchies develop.
American tree sparrows move by hopping on the ground and on branches, and by flying. They do not swim or dive, but do bath frequently. They roost solitarily in conifers, thick bushes, haystacks, cornfields, and marshes. In winter, they may shelter communally under the snow. (McNicholl, 1987; Naugler, 1993)
- Key Behaviors
- dominance hierarchies
- Range territory size
- 0.005 to 0.0038 km^2
We do not have information on home range for this species at this time.
Communication and Perception
American tree sparrows communicate using sounds and physical displays (see Mating Systems section for examples). Only male American tree sparrows sing, though both sexes use calls. The songs of American tree sparrows are composed of high, thin whistles and last 1 to 2 seconds. They are used primarily in territorial defense and to attract mates. Each male sings only one song. Both males and females use calls, which appear to be associated with particular behaviors such as feeding or alarm. Chicks use calls to express hunger, discomfort, and fear beginning at 5, 6, and 8 days old, respectively. (Baumgartner, 1938; Cornell Lab of Ornithology, 2003)
American tree sparrows are omnivorous; they eat a wide variety of seeds, berries and insects. During the winter, American tree sparrows mainly eat grass and weed seeds. During the summer, they primarily eat insects and spiders.
American tree sparrows forage among vegetation on the ground and along the branches and twigs of shrubs and trees. In Massachusetts, they are frequently seen in flocks that seem to roam from bird feeder to bird feeder. American tree sparrows drink about 30% of their body weight in water each day. During the winter, they obtain water by eating snow. (Baumgartner, 1937b; Cornell Lab of Ornithology, 2003; Hamilton, 2000; Knappen, 1934)
- Primary Diet
- Animal Foods
- terrestrial non-insect arthropods
- Plant Foods
- seeds, grains, and nuts
Known predators of American tree sparrows include northern goshawks (Accipiter gentilis), sharp-shinned hawks (Accipiter striatus), screech owls (genus Otus), pygmy owls (genus Glaucidium), Cooper's hawks (Accipiter cooperii), American kestrels (Falco sparverius), weasels (family Mustelidae), foxes (family Canidae) and red squirrels (Tamiasciurus hudsonicus).
When approached by humans, American tree sparrows give a rapid series of "tset" calls. It is unknown how American tree sparrows respond to other potential predators. (Naugler, 1993)
American tree sparrows play an important role in their local communities. They eat many seeds, insects and spiders and are an important food source for their predators. (CWBO, 1997)
- Ecosystem Impact
- disperses seeds
Economic Importance for Humans: Positive
American tree sparrows may benefit farmers by removing weed seeds from their fields. The U.S. Department of Agriculture estimated in 1937 that sparrows, American tree sparrows included, saved farmers $90,000,000 per year by removing weed seeds. (Baumgartner, 1937b; Baumgartner, 1968)
Economic Importance for Humans: Negative
There are no known adverse effects of American tree sparrows on humans.
American tree sparrows are abundant and widespread. There are approximately 26,000,000 American tree sparrows throughout their range. American tree sparrows are protected by the US Migratory Bird Treaty Act, but have no special status under the U.S. Endangered Species ACT or CITES. (Kaufmann, 1996; Naugler, 1993)
Two geographic races are recognized based breeding location. Spizella arborea arborea breeds from the Atlantic coast all the way to the east of the Yukon. Spizella arborea ochracea breeds around and in the Yukon and Alaska.
Spizella arborea ochracea was first recognized as a subspecies in 1881 by William Brewster. He describes them as:
"The ground color of the back is decidedly paler than the eastern examples, bringing out the dark streaks in sharper contrast, which is heightened by the absence of their usual chestnut edging; ash of throat and sides of head is much fainter, in many places replaced by brownish fulvous; the underparts, especially the sides and abdomen, are more strongly ochraceous; and the broad ashy crown patch gives the head a very different appearance."
Males of both races generally winter farther north than females.
Alaine Camfield (editor), Animal Diversity Web.
Kari Kirschbaum (author, editor), Animal Diversity Web.
Ernest Travis (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
uses sound to communicate
living in landscapes dominated by human agriculture.
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
Referring to an animal that lives in trees; tree-climbing.
- bilateral symmetry
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.
uses smells or other chemicals to communicate
- active during the day, 2. lasting for one day.
- dominance hierarchies
ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
marshes are wetland areas often dominated by grasses and reeds.
makes seasonal movements between breeding and wintering grounds
Having one mate at a time.
having the capacity to move from one place to another.
- native range
the area in which the animal is naturally found, the region in which it is endemic.
an animal that mainly eats all kinds of things, including plants and animals
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.
"many forms." A species is polymorphic if its individuals can be divided into two or more easily recognized groups, based on structure, color, or other similar characteristics. The term only applies when the distinct groups can be found in the same area; graded or clinal variation throughout the range of a species (e.g. a north-to-south decrease in size) is not polymorphism. Polymorphic characteristics may be inherited because the differences have a genetic basis, or they may be the result of environmental influences. We do not consider sexual differences (i.e. sexual dimorphism), seasonal changes (e.g. change in fur color), or age-related changes to be polymorphic. Polymorphism in a local population can be an adaptation to prevent density-dependent predation, where predators preferentially prey on the most common morph.
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
- scrub forest
scrub forests develop in areas that experience dry seasons.
- seasonal breeding
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
living in residential areas on the outskirts of large cities or towns.
uses touch to communicate
Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present.
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.
uses sight to communicate
Alsop, F. 2001. Birds of North America, eastern region. New York, NY: DK Publishing, Inc.
Baumgartner, A. 1968. Tree Sparrow. U.S. National Museum Bulletin, 237: 1137-1165.
Baumgartner, M. 1938. A study of development of young tree sparrows at Churchill, Manitoba. Bird-Banding, 9(2): 69-79.
Baumgartner, M. 1937a. Enemies and survival ratio of the tree sparrow. Bird Banding, 8(2): 45-52.
Baumgartner, M. 1937b. Food and feeding habits of the tree sparrow. The Wilson Bulletin, 49(2): 65-80.
Baumgartner, M. 1937c. Nesting habits of the tree sparrow at Churchill, Manitoba. Bird Banding, 8(3): 99-108.
CWBO, 1997. "Chipper Woods Bird Observatory: American Tree Sparrow" (On-line). Accessed 03/03/04 at http://www.wbu.com/chipperwoods/photos/treesparrow.htm.
Cornell Lab of Ornithology, 2003. "American Tree Sparrow" (On-line). Cornell Lab of Ornithology, All About Birds. Accessed March 04, 2004 at http://birds.cornell.edu/programs/AllAboutBirds/BirdGuide/American_Tree_Sparrow.html.
Forbush, E., J. May. 1939. A natural history of American birds of eastern and central North America. USA: Houghton Mifflin Company.
Hamilton, T. 2000. Winter Population Trends of Six Species of Sparrows. Bird Observer, 28(3): 154-163.
Kaufmann, K. 1996. Lives of North American Birds. USA: Houghton Mifflin.
Knappen, P. 1934. Insects in the winter food of the tree sparrow. Auk, 51: 93.
Lima, S. 1995. Back to the basics of anti-predatory vigilance: the group-size effect. Animal Behaviour, 49: 11-20.
McNicholl, M. 1987. Communal sheltering under snow by American Tree Sparrows. Ontario Birds, 5(3): 111-113.
Naugler, C. 1993. American Tree Sparrow (Spizella arborea). Pp. 1-12 in A Poole, F Gill, eds. The Birds of North America, Vol. 37. The Academy of Natural Sciences, Philadelphia, and The American Ornithologist's Union, Washington, D.C.