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Zonotrichia leucophryswhite-crowned sparrow

By Gayle Soskolne

Geographic Range

Zonotrichia leucophrys is most known for its widespread distribution, which extends mostly from the upper parts of Alaska, down to the middle of Mexico along the west coast of North America. The white-crowned sparrow, however, also breeds all along the upper parts of Canada and winters along the width of the southern United States (Chilton et al. 1995). Their wide distribution may have to do with the various subspecies of Zonotrichia leucophrys. Some of the subspecies are year-round residents, such as Z. l. nuttalli, while others migrate short distances, and still others migrate thousands of kilometers south every year.

Habitat

Zonotrichia leucophrys has proven to be very flexible in its choice of habitats. Varying from the edge of parking lots, to the meadows in the Rocky Mountains, or to boreal forests. The only features necessary for them are tall coniferous trees on the edge of a territory, grass, and bare ground for the birds to forage on, and coverage dense enough to hide a nest or roosting area (Chilton et al. 1995). Because of these fairly easy requirements, the white-crowned sparrow has been shown to breed in many different areas - at altitudes as low as 800 meters, or as high as within the Rocky Mountains. In the spring and fall, this bird lives in groups with other sparrow species. In the winter, the subspecies of Zonotrichia leucophrys that do migrate remain in a steady group with which they forage and roost.

Physical Description

This particular species of bird is very easy to recognize because of its fairly limited variation of plumage. Both males and females have two distinctive black stripes that extend along the crown of the head and behind the eyes, which boldly outlines the solid white feathers on its head. The white-crowned sparrow has a solid light gray breast and dark brown flight feathers. The coverts are each tipped with a white band. Though juveniles have very similar plumage, they tend to be more brown (instead of gray) and the head has brown, not black, stripes that surround a slightly darker "white" patch. There is no seasonal variation in Zoneotrichia leucophrys' plumage, but there has been geographical variation noted (Chilton et al. 1995).

The body mass of males tends to be slightly higher than females throughout the year. During the summer, the average weight of males is 28.27g for males, while it is about 25.47g for females (Chilton et al. 1995). Both sexes' mass, however, decreases at the beginning of the breeding season (more so in females), and increase by that same amount at the start of winter (Chilton et al. 1995).

  • Average mass
    25.82 g
    0.91 oz
    AnAge
  • Average basal metabolic rate
    0.336 W
    AnAge

Reproduction

Though the various subspecies of Zonotrichia leucophrys differ in breeding sites and the dates of their arrival to breeding grounds, the basic system of breeding is very similar. The males are usually the first to arrive on the breeding grounds, and after the females have arrived it is only about one to three weeks before they make their first nests. Most pairs only produce one brood. This is done after an average of about 2 days from the time the cup-shaped nest was built (Morton 1997). The females incubate the eggs, and develop a brood patch during the nest construction to make this process more efficient. Incubation lasts about 12 days, throughout which the female is responsible for turning the eggs, as well as leaving during the day to forage for herself.

The male white-crowned sparrow finally begins to contribute to this effort once the eggs have hatched. He brings food, contributing more and more to feeding the young as they mature. But about halfway through their development (~day 5), his contribution steadily begins to decrease.

When first born, the young birds are naked except for a few down feathers along some tracks on their transparent pink body. Most of them fledge by the tenth day, and reach their adult weight by day 30-35.

Though not very common, brown-headed cowbirds have been known to be a brood parasite of the white-crowned sparrow. When this occurs, the cowbirds only lay about one egg per nest, and their young tend to be just as successful as those of the sparrow.
  • Average eggs per season
    4
    AnAge
  • Average time to hatching
    13 days
    AnAge

Lifespan/Longevity

Behavior

The white-crowned sparrow is a fairly solitary species (Valone et al. 1998). Although it travels with a small group of about eight during migration, males are extremely territorial. Every year, most return to guard the same non-overlapping established territories as the year before (Morton 1997). In response to an intruder or predator, the male puffs up his chest, holds up its crown feathers, and sings very loudly. Fighting is also fairly common when the male is first settling into its territory, during the breeding season. Through this type of behavior, as well as the specific territories that a male can guard - a definite hierarchy is established within this species.

Zonotrichia leucophrys actively forages for seeds and other food elements by hopping around on the bare ground. This differs remarkably from the state of shallow nocturnal hypothermia that engulfs it at night (Chilton et al. 1995).

These birds are almost always monogamous. The male white-crowned sparrow does not perform courtship feeding, but rather wait until the female initiates courtship. She begins by bowing with her head arched, and parts her tail feathers to expose the cloacae. The male responds by raising his crown feathers, lowering his spread tail feathers, and standing on her back for about 3 seconds before flying off (Chilton et al. 1995).

To avoid uncovering the location of their nest to potential predators, such as Belding's ground squirrel (Spermophilus beldingi) or the Western terrestrial garter snake (Thamnophis elegans), the white-crowned sparrows fly towards their nest, but stop short by a few meters. They travel the rest of the way on foot (Chilton et al. 1995). If the nest is ever approached, the female does a distraction display by wagging her tail feathers, and running away from the nest (Norment 1993).

Communication and Perception

Food Habits

About ninety-two percent of what the white-crowned sparrow consumes is plant matter (Chilton et al. 1995). The small tough bill of this species makes seeds, buds, grass, and fruit ideal constituents of its diet. During spring, however, Zoneotrichia leucophrys adjusts its diet and begins eating mainly insects and seeds. By mainly ground feeding, this bird relies on dense shrubbery to provide adequate coverage from potential predators. It has been shown that feeding activity actually decreases with lack of proper coverage (Chilton et al. 1995). The white-crowned sparrow also does not store food, nor does it have a functional crop - possibly explaining why it focuses its most intense feeding times early in the morning, and again late at night.

Conservation Status

So far, Zonotrichia leucophrys has not required any management. While practices as logging seem to disturb many species of birds, this practice actually has provided the white-crowned sparrow with new habitats (bare ground and grasslands for easy foraging) (Chilton et al. 1995). Cattle grazing has proven to be the only deterrent of this species' habitat requirements (Knopf et al. 1988).

Contributors

Gayle Soskolne (author), University of Michigan-Ann Arbor, Terry Root (editor), University of Michigan-Ann Arbor.

Glossary

Nearctic

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.

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acoustic

uses sound to communicate

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.

chemical

uses smells or other chemicals to communicate

endothermic

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

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

iteroparous

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).

motile

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.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

visual

uses sight to communicate

References

Chilton, G., M. Baker, C. Barrentine, M. Cunningham. 1995. White-Crowned Sparrow. The Birds of North America, 183.

Morton, M. 1997. Natal and breeding dispersal in the mount white-crowned sparrow Zonotrichia Leucophrys oriantha. Ardea, 85(1): 145-154.

Norment, C. 1993. Nest-site characteristics and nest predation in Harris' sparrows and white-crowned sparrows in the northwest territories, Canada. Auk, 110(4): 769-777.

Ramstack, J., M. Murphy, M. Palmer. 1998. Comparative reproductive biology of three species of swallows in a common environment. Wilson Bulletin, 110(2): 233-243.

Valone, T., A. Wheelbarger. 1998. The effect of heterospecifics on the group-size effect in white-crowned sparrows (Zonotrichia leucophrys). Bird Behaviour, 12(3-4): 85-90.

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