American Tree Sparrow

About

The American Tree Sparrow is a small, migratory songbird known for its distinctive rusty cap and bicolored bill. It breeds in the Arctic and subarctic regions of North America and winters across much of the United States and southern Canada, often found in open, shrubby habitats.

Size & lifespan

Length

12.5-16 cm (4.9-6.3 in)

Wingspan

20-25 cm (7.9-9.8 in)

Weight

13-28 g (0.46-0.99 oz)

Lifespan

Typically 2-3 years in the wild, with a maximum recorded age of over 10 years.

Diet

Omnivore, primarily granivorous in winter, insectivorous in summer.

Physical characteristics

Plumage

Adults have a rusty-red cap and a rusty eye-line. The back is streaked brown and black, with two prominent white wing bars. The underparts are grayish-white, with a distinctive dark central breast spot (often described as a 'stickpin' or 'inkblot'). The flanks are washed with buffy-brown streaking. The rump is grayish-brown.

Beak shape

Conical, finch-like bill. Bicolored: the upper mandible is dark (blackish), and the lower mandible is bright yellow or yellowish-orange.

Eye color

Dark brown.

Leg color

Dark gray to blackish.

Distinguishing features

Rusty cap, rusty eye-line, bicolored bill (dark upper, yellow lower), and a single dark central breast spot.

Juvenile appearance

Juveniles are similar to adults but have a streaked crown (lacking the solid rusty cap) and more extensive streaking on the breast and flanks, often obscuring the central breast spot. Their bill may be less distinctly bicolored.

Seasonal changes

No significant seasonal plumage changes; plumage remains consistent year-round, though fresh plumage in fall may appear slightly brighter.

Sexual dimorphism

Males and females are outwardly identical in plumage.

How to identify

1. 1

   Rusty Cap

   Look for the distinct rusty-red cap on the head. This is a key field mark for adults.

2. 2

   Bicolored Bill

   Observe the bill color: dark (blackish) on the upper mandible and bright yellow or yellowish-orange on the lower mandible. This is unique among North American sparrows with rusty caps.

3. 3

   Central Breast Spot

   Scan the grayish-white breast for a single, small, dark spot in the center. This 'stickpin' mark is often subtle but diagnostic.

4. 4

   Rusty Eye-line

   Note the rusty stripe extending from the eye towards the back of the head, contrasting with a grayish face.

5. 5

   White Wing Bars

   Two clear white wing bars are visible on the dark wings.

6. 6

   Behavior

   Watch for its ground-foraging behavior, often scratching with both feet simultaneously, and its tendency to form flocks in winter.

7. 7

   Song/Call

   Listen for its sweet, tinkling song (breeding season) or its sharp, metallic 'tseet' call (year-round).

Habitat & range

Biomes

Tundra, taiga, boreal forest edges, open woodlands, shrublands, agricultural fields, grasslands, and suburban areas.

Geographic range

Breeds in Arctic and subarctic North America, including Alaska, northern Canada, and Greenland. Winters across southern Canada and most of the contiguous United States, south to northern Mexico.

Elevation range

Typically found from sea level up to approximately 1,500 meters (5,000 feet), though can occur higher in some areas.

Preferred environments

During breeding, prefers open tundra with dwarf shrubs, willow thickets, and stunted conifers. In winter, favors open fields with scattered shrubs, weedy edges, hedgerows, forest clearings, and suburban gardens, often near water sources.

Behavior

Activity time

Diurnal.

Feeding habits

Primarily forages on the ground, scratching with its feet to uncover seeds and insects. Also gleans seeds from low vegetation and occasionally catches insects in flight. In winter, seeds of grasses, sedges, and weeds (e.g., ragweed, pigweed) are crucial. In summer, insects (beetles, caterpillars, flies) and spiders form a significant part of the diet, especially for nestlings.

Social behavior

Highly social during winter, forming large, often mixed-species flocks with other sparrows and juncos. During the breeding season, they are territorial and typically found in pairs.

Flight pattern

Undulating flight pattern, typical of many sparrows, with rapid wing beats followed by a brief glide.

Migration pattern

Long-distance migrant. Breeds in the far north and migrates south for the winter, covering thousands of kilometers. Migration occurs in flocks, primarily at night.

Territoriality

Territorial during the breeding season, with males defending nesting territories through song and displays. Less territorial on wintering grounds, where they forage in flocks.

Breeding & reproduction

Breeding season

Late May to August.

Nesting habits

Nests are typically built on or near the ground, often well-concealed at the base of a small shrub, tussock of grass, or under a low branch of a conifer. The nest is a cup-shaped structure made of grasses, moss, and twigs, lined with fine grasses, hair, and feathers.

Clutch size

3-6 eggs, typically 4-5.

Egg description

3-6 eggs, pale bluish-white or greenish-white, heavily speckled and spotted with reddish-brown, purplish-brown, or black, often concentrated at the larger end. Approximately 18 x 13 mm.

Incubation period

11-13 days, primarily by the female.

Fledging period

8-10 days after hatching, young leave the nest.

Parental care

Both parents feed the nestlings and fledglings. The female primarily incubates, but the male may bring food to her on the nest.

Where to find

Field tips

1. Look for ground foragers. American Tree Sparrows spend a lot of time on the ground, scratching for seeds. Watch for movement in low vegetation.
2. Check feeders. In winter, they are frequent visitors to bird feeders, especially those offering millet or black oil sunflower seeds.
3. Listen for calls. Their distinctive 'tseet' call is often the first indication of their presence, especially when they are in flocks.
4. Observe flock behavior. They often associate with Dark-eyed Juncos and other sparrows in winter. Look for their unique field marks within these mixed flocks.
5. Patience in shrubby areas. They can be quite secretive in dense shrubs, so patience and careful observation are key.

Similar species

Quick facts

Primary Habitat (Winter):

Open fields, shrublands, weedy edges

Primary Habitat (Breeding):

Arctic/subarctic tundra, boreal forest edges

Key ID Mark:

Rusty cap, bicolored bill, central breast spot

Diet:

Seeds (winter), insects (summer)

Sociality (Winter):

Highly social, forms flocks

Migration:

Long-distance migrant

Fun facts

• The 'tree' in their name is a bit misleading; they rarely nest in trees and often forage on the ground. The name likely comes from early European settlers who confused them with the Eurasian Tree Sparrow, which does nest in trees.
• American Tree Sparrows are incredibly hardy, capable of surviving harsh northern winters by consuming large quantities of seeds and fluffing their feathers for insulation.
• They have a specialized digestive system that allows them to efficiently process the tough outer husks of seeds, extracting maximum nutrition.
• During winter, a single American Tree Sparrow can consume up to 30% of its body weight in seeds each day to maintain its energy reserves.

Scientific classification

Kingdom

Animalia

Phylum

Chordata

Class

Aves

Order

Passeriformes

Family

Passerellidae

Genus

Spizella

Species

Spizella arborea

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