Brewer's sparrows (Spizella breweri) primarily reside in the western United States and Canada. These birds can be found as far north as British Columbia, where their range includes the interior of Banff and Jasper National Forests, as well as the area around Calgary and the southwest corner of Saskatchewan.
Their range continues south into the United States. These birds inhabit the southeastern portion of the state of Washington; in this area they are primarily limited to waterways. The southern half of Idaho houses a large population of Brewer's sparrows that nest near the American Falls Reservoir and the river that leads out of it. They have a population in Montana that spans across most of the state, including Fort Peck Lake, the Missouri River, and the Yellowstone River. All of Wyoming has a relatively even distribution of these birds, although the northeast corner is less densely populated. Brewer's sparrows live in eastern Oregon, primarily in the national parks and the Great Sandy Desert. They reside throughout Colorado, except in the Rocky Mountains and San Juan National Parks. Otherwise they inhabit the rest of Colorado relatively evenly. These birds dwell in all of Nevada and Utah, except around the Great Salt Lake. These sparrows inhabit eastern California, southern California, and a linear strip following Route 5 from Bakersfield north to Mendocino National Forest. Brewer's sparrows are absent in the Tonto, Gila, and Carson National Forests in Arizona and New Mexico. They inhabit western Texas as far east as Midland.
In Mexico, their range includes all of Baja California, from the border with the United States along the Pacific Coast south to the city of San Ignacio. The rest of the population lives in mid-Mexico, along the United States border from the town of El Cuervo to the Amistad Reservoir, and finally south in a loose triangle to Lake Chapala.
These sparrows arrive in the northern half of their range from April to May. They migrate south towards Mexico between August and October. There appears to be a leap-frog effect with their migration, as the northernmost populations migrate south to U.S. winter ranges that are the same as the U.S. summer range of the southern populations. These southern populations migrate southward to Mexico for the winter. (Headstrom, 1970; Pearson, 1917; Reed, 1965)
Brewer’s sparrows are primarily found in areas where big sagebrush (Artemisia tridentata) typically grow. This sagebrush is low to the ground and provides concealment and protection. These birds tend to nests in elevations from 560 to 1,250 m above sea level. In these areas, dry grass and small roots are abundant; these are the materials that sparrows use to create their nests. These nests are made at heights of just a few centimeters up to 2 meters off the ground. Nests are composed of a variety of materials, such as twigs, bark, wood chips, moss, and occasionally feathers.
Their nesting habits do not change during breeding season, though the materials used to build nests may change due to location and what is most readily available.
There are 2 subspecies that have different habitat needs. The "typical" Brewer's sparrows, Spizella breweri breweri, are described above. The timberline Brewer's sparrow subspecies, Spizella breweri taverneri, occurs at higher elevations, where subalpine habitats transition to alpine habitats. These are generally mountainous, forested areas in Canada and Alaska. (Harrison, 1978; Headstrom, 1970; Ho Yan Yu, 1999)
The plumage on the back of Brewer's sparrows is brown with black, vertical stripes. Their breast feathers have subtle streaks of a darker gray contrasted to their very light gray breast. The tops of their heads appear ruffled, as the feathers tend to stick up more than the rest of their plumage. Their faces have large streaks of brown, moving from their beaks to the back of their heads, across an overall gray face and throat. They also have slim white eyerings present. Sexes look alike.
The "typical" Brewer's sparrows, Spizella breweri breweri, are described above. The timberline Brewer's sparrow subspecies, Spizella breweri taverneri, are less drab - their bill is darker as are the streaks on their heads and backs. Their underparts contrast greatly and are lighter in color than typical Brewer's sparrows.
Hatchlings are born with very few feathers, and those that are present are a drab gray down. They remain a pale gray-brown color and their belly is streaked. Several molts occur before drab juveniles begin to resemble adults.
Adult typically have masses of 8.9 to 11.8 g, lengths of 12.5 to 15 cm, and wingspans of 18 to 20 cm. Males are typically larger than females, although measures are mixed. Sexes are similar in mass, but males have slightly longer tail and wing lengths (differing by 3 to 5 mm between sexes). Females have slightly longer bills and toe lengths (differing by less than 1 mm).
Brewer's sparrows are similar in appearance to clay-colored sparrows (Spizella pallida), although Brewer's sparrows are slightly smaller and are considered less colorful than clay-colored sparrows. (Pearson, 1917; Rotenberry, et al., 2020; Weins and Rotenberry, 1980)
Brewer's sparrows typically breed between May and July, but the range can extend from April to August. Pairs are monogamous and breed up to twice in a year. Males typically provide protection and food for their nests, but females take over if males are not nearby.
The act of fertilization occurs quickly and in a protected environment, such as under the cover of low foliage. Males make mating calls to attract females. If females are receptive, they respond by lowering their wings and shivering them. After copulating, neither sexes perform any particular action, though preening has commonly been observed.
The timing of breeding depends on temperatures in late April. Birds wait for warmer temperatures to breed if temperatures are too cold.
Before these birds begin to reproduce, male Brewer's sparrows arrive at their breeding grounds and establish territories, where they attract mates and begin to build nests around late April. (Rotenberry, et al., 2020)
Brewer's sparrows typically reproduce and lay their first brood of eggs from early May to early August. About 3 to 4 eggs are laid per brood, weighing 1.30 to 1.34 g. If their first brood is successful, eaten by predators, or lost to some other destructive force, the pair will lay one more brood later in the year, likely in July. Eggs require incubation for 10 to 12 days, after which they will hatch. Hatchlings leave the nest after 6 to 9 days. Before and just after fledglings leave the nest, parents feed them. Brewer's sparrows are reported to be sexually mature at around 1 year old for both sexes.
Fledglings take a few extra days to become independent after they can leave the nest. This time scale can range from 6 to 9 days until they are fledging and 6 to 12 days until they are independent. (Blumstein and Moller, 2008; Rotenberry, et al., 2020)
Brewer's sparrow parents primarily take care of their newly-hatched birds for about 8 to 9 days before fledglings leave the nest. Each parent will watch over their young, sometimes individually and sometimes together. They harass any approaching predators with the exception of loggerhead shrikes (Lanius ludovicinaus). This is because shrikes attack adults as well. When adults are not protecting baby birds, they are frequently feeding them, even within the first hour after hatching. Parents continue to feed their young several days after they first leave the nest. Some of the food items that parents provide consist of butterfly and moth larvae (order Lepidoptera), spiders (order Araneae), leafhoppers (order Homoptera), flies (order Diptera), and grasshoppers (order Orthoptera). On top of feeding young birds, parents also clean their nests by removing dead birds, feces, and shells within a few hours of it being present in the nest. (Rotenberry, et al., 2020)
Brewer's sparrows live at least 6.2 years in the wild, as measured by bird banding data from 7 birds (Blumstein and Moller, 2008). Blumstein and Moller (2008) reported adult survivorship of about 25% for these birds. These sparrows are not kept in captivity. (Blumstein and Moller, 2008)
Brewer's sparrows are a diurnal, social species. They will interact with other species of sparrows, but will only pair with a single mate of their species during the breeding season. Birds migrate during the spring months to nest in areas with an arid climate and warm temperatures. They migrate nocturnally. Their migration begins when birds arrive in the Great Basin region of Nevada around the end of March and April, then they move to Alberta late in May. They then head south starting in August, arriving in the Mojave Deserts by September. When birds migrate to summer breeding grounds, they begin to build nests and breed shortly thereafter. There is no social system or hierarchy that these birds have been observed to practice.
Individual birds have been observed to preen throughout the day, but may perform a longer, more thorough preening during the mid-afternoon. They bathe frequently in open bodies of water and rarely exercise dust bathing.
Male birds tend to sing with long and short songs, each to attract mates. Long songs are for attracting mates during the breeding season, while short songs are used outside of breeding season. Female birds have not been observed to sing like the males, but both sexes do make some chirping vocalizations. Females perform a mating ritual in which they lower their wings slightly and shiver them. During this ritual, females make a short, twittering call.
Wiens et al. (1987) observed the daily activity budgets of the birds. Though they are not active the entirety of the day, half of their active time is spent singing to attract mates or looking for food. Though birds typically don't live in areas where flight is obstructed, they do not fly more than 1 m above shrubs. Aggressive behavior has also been recorded if predators approach nests. Such acts include swooping down to predators and vocalizing aggressively. (Rotenberry, et al., 2020; Wiens, et al., 1987)
Brewer's sparrows establish foraging ranges within about 50 m of their nests. Established home ranges for these birds have been reported as 0.55 to 2.36 ha. However, year-round, Brewer's sparrows forage near other sparrows within about 1 m. They are not typically territorial outside of the immediate vicinity of their nests. However, if another species enters the nest, parents will actively deter the invader with aggressive vocalization and swooping flying. (Rotenberry, et al., 2020)
Male Brewer's sparrows have two types of songs, referred to as short and long songs. Short songs are significantly shorter and occur at a higher frequency than long songs. Short songs are primarily used to attracted mates during breeding season and for migration. Shorter songs consist of a high-frequency trill followed by a lower, slower trill. Rotenberry et al. (2020) describe it as "weeeezzz, tubitubitubitubitub" while Dawson (1923) describe it as "bzzzzzzzz, chip-chip-chip-chip-chip."
Long songs are described to be that like a singing canary, filled with buzzes, trills, and wheezes at multiple frequencies. These long songs are used by males to attract mates, but only in breeding grounds and during migration. Long songs last 10 to 15 seconds. Only males are known to sing, although females do make some small chirping or "chip" warning noises occasionally.
These sparrows use vision and tactile responses to find food, mate, build nests, and evade predators. (Rotenberry, et al., 2020; "Species assessment for Brewer's sparrow (Spizella breweri) in Wyoming", 2004)
Brewer's sparrows are primarily insectivores, preying on arthropods and larvae of other insects, but they are also known to eat seeds during the winter or while migrating. Brewer's sparrows forage for insects among the foliage and bark of small trees, shrubs, and other scrubby plants. Rotenberry et al. (2020) summarized foraging studies, which found that these sparrows spend more than 75% of their time foraging in shrubs. The larger the individual shrub, the more time they spend foraging in it. The variety of arthropods consumed likely represented opportunistic foraging conditions, including caterpillars, grasshoppers, beetles, ants, and spiders.
Unlike other species, brewer's sparrows do not get most of their water from natural waterways or other bodies of water, but instead they get water from the food they eat. Thus, they are better suited to survive in arid areas, where they stay during the warmer parts of the year, where rainfall may be sparse. (Rotenberry, et al., 2020; "Species assessment for Brewer's sparrow (Spizella breweri) in Wyoming", 2004; Wiens and Rotenberry, 1979)
Adult Brewer's sparrows do not have any means of protection to avoid predation, but instead rely on camouflage and evasive flying. To protect against nest invaders, adult Brewer's sparrows will scare predators away with aggressive flight and vocalizations, with the exception of loggerhead shrikes (Lanius ludovicianus), which prey on adult Brewer's sparrows as well as eggs. Brewer's sparrows have plumage patterned with tan and brown stripes, which allows them to more easily blend in with their arid surroundings. This prevents these birds from being spotted by predators. If sparrows are spotted, they fly low and quickly through shrubs to avoid the pursuing predators.
Most predation occurs in the nest rather than on adults sparrows. Rates of predation change based on their geography and temperature: low-elevation arid areas have higher rates and high-elevation colder areas have lower rates. Snakes and small rodents are documented to be the most prevalent predators of Brewer's sparrow nests.
Avian predators include loggerhead shrikes (Lanius ludovicianus), common crows (Corvus corax), Eurasian magpies (Pica pica), American kestrels (Falco sparverius), and prairie falcons (Falco mexicanus). (Rotenberry and Wiens, 1989; Rotenberry, et al., 2020)
Brewer's sparrows disperse seeds as a result of the food they eat. They are prey to most small mammals such as weasels, chipmunks, snakes, and predatory birds such as loggerhead shrikes (Lanius ludovicianus).
Biting lice (Ricinus fringillae and Ricinus subdiffusus), blowflies (Protocalliphora braueri), mites (Syringophiloidus sialius), and two genera of protozoans (Trypanosoma and Haemogregarines) use these sparrows as hosts. Brown-headed cowbirds (Molothrus ater) are brood parasites of Brewer's sparrows; female cowbirds lay their eggs in sparrow nests and rely on sparrows to raise their young. (Biermann, et al., 1987; Bochkov, et al., 2011)
Brewer's sparrows are a staple of sagebrush flats in the Great Basin. Their incredible songs draw birdwatchers in from long distances. They are also bioindicators of their habitats. The population of Brewer's sparrows in an area is proportionate to the amount of foliage in that habitat; the more foliage, the more sparrows. (Audubon Field Guide, 2020; Bradford, et al., 1998)
Brewer's sparrows have no negative economic effects on humans.
The IUCN Red List has listed Brewer's sparrows as a species of "Least Concern". According to the US Migratory Bird Act, these birds are "Protected" and are systematically monitored while maintaining the range of their migration as an illegal hunting ground. The US Federal List, CITES, and State of Michigan List state that these birds have no special status. However, according to the US Migratory Bird Conservation Report, Brewer's sparrow populations have decreased by 47% over the past 40 years.
There are only a few concerns regarding the conservation of these sparrows. The main concern is controlled fires burning nesting sites made of big sagebrush (Artemisia tridentata). These fires burn the sagebrush, which is overtaken by other invasive species, especially cheatgrass (Bromus tectorum). This annual grass changes the fire intervals, making fire more frequent. More fires lead to less sagebrush, and therefore reduced breeding grounds for Brewer's sparrows.
As there is some concern for these birds, there have been efforts made to conserve their habitats by making their migratory range a protected zone. Populations of brewer's sparrows are also being monitored. Invasive species (cheatgrass) removal may reduce the fire intervals and therefore preserve sagebrush habitats. (Bird Life International, 2018; Cotton, et al., 2009; "Species assessment for Brewer's sparrow (Spizella breweri) in Wyoming", 2004; Wells, 2007)
Ian Rolston (author), Radford University, Lauren Burroughs (editor), Radford University, Logan Platt (editor), Radford University, Karen Powers (editor), Radford University, Galen Burrell (editor).
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
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.
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.
an animal that mainly eats meat
uses smells or other chemicals to communicate
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.
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.
parental care is carried out by females
union of egg and spermatozoan
an animal that mainly eats seeds
An animal that eats mainly plants or parts of plants.
An animal that eats mainly insects or spiders.
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).
parental care is carried out by males
makes seasonal movements between breeding and wintering grounds
Having one mate at a time.
having the capacity to move from one place to another.
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
the area in which the animal is naturally found, the region in which it is endemic.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
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.
uses touch to communicate
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
uses sight to communicate
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