The Western tanager (Piranga ludoviciana) is a medium-sized songbird found in western North America. This brightly colored bird breeds in open coniferous forests across much of the western United States and southwest Canada. It winters primarily in central Mexico. The Western tanager is a somewhat common species across parts of its breeding range, though its numbers have declined in recent decades.
Breeding Range and Habitat
The Western tanager breeds from southeast Alaska across western Canada to the southwest corners of the Northwest Territories and Manitoba. Its breeding range extends south throughout the western half of the United States, including all of Washington, Oregon, California, Idaho, Montana, Wyoming, Colorado, Utah, Nevada, New Mexico, and Arizona. The species reaches its southeastern limits in western Nebraska, western Oklahoma, western Texas, and the Guadalupe Mountains of southeast New Mexico.
This tanager inhabits a variety of open coniferous forest types within its breeding range, including Douglas fir, ponderosa pine, lodgepole pine, and spruce-fir forests. It tends to prefer mature forest stands with semi-open canopies. Western tanagers also breed in mixed forests with scattered conifers. They are often found along forest edges or in openings with standing dead trees.
Wintering Range and Habitat
Western tanagers winter primarily in central Mexico. Their winter range centers on the Trans-Mexican Volcanic Belt, a region of high mountains and valleys in south-central Mexico. This range extends from southern Sinaloa south through western Durango and Nayarit to Michoacán, México State, Puebla, Oaxaca, and Chiapas. Western tanagers are also regular in winter in the Sierra Madre Occidental and Sierra Madre Oriental in eastern Mexico.
In winter, these birds inhabit semi-open areas including tropical deciduous forest, open woodland, forest edge, and second growth. Western tanagers often mix with other songbirds in flocks while on their wintering grounds.
Population and Conservation Status
The global population of the Western tanager is estimated at 5.9 million breeding birds. Population trends have been measured through the North American Breeding Bird Survey, an annual census of breeding birds across North America. Data from 1966-2015 suggest the species has declined by an estimated 39% over that period. It is unclear what factors are causing the decline. Habitat loss on the wintering grounds in Mexico may play a role.
Despite population declines, the Western tanager remains a fairly common species over much of its breeding range. The IUCN Red List categorizes it as a species of Least Concern. Partners in Flight estimates a global breeding population of 5.9 million, with 98% spending some part of the year in the U.S. They estimate a species population of 4.5 million in the U.S., with 78% in the Intermountain West region.
Breeding Density and Abundance
Breeding Bird Survey (BBS) data provides additional detail on the abundance and population trends of Western tanagers in different parts of their breeding range:
- States with the highest relative abundance on BBS routes include Idaho, Oregon, Washington, Montana, and Colorado.
- In Idaho, Western tanagers were detected on 95% of BBS routes from 2005-2015. Average number detected per route was 14.4.
- In Oregon, the species was found on 77% of BBS routes over the same period. Average per route was 5.5.
- In California, Western tanagers were tallied on 64% of routes. Average was 2.8 per route.
- BBS data from 1966-2015 shows significant declines in British Columbia (-2.5% per year) and Nevada (-3.3% per year). Trends were stable to slightly declining in most other parts of the range.
Within favored breeding habitat, Western tanagers generally occur at moderate densities. However, abundance can vary locally with the availability of appropriate habitat. For example:
- A study in Oregon mixed conifer forest found average densities of 50 birds per 100 acres.
- Surveys in Arizona ponderosa pine forest recorded densities between 2 to 5 pairs per 100 acres.
- At higher elevations in Colorado, densities ranged from 16 to 30 pairs per 247 acres in spruce-fir forest.
Seasonal Patterns and Migration
Western tanagers are strongly migratory between their breeding and wintering grounds. They begin arriving on their breeding grounds in mid to late April. Migration peaks in May and early June. At more northerly latitudes, they may not arrive until early June.
Fall migration begins in late August, as the birds start moving south through the western states and Mexico. Migration peaks in September and October. Most individuals are absent from the U.S. by late October. The latest records are in early November.
Western tanagers migrate alone or in loose flocks. Migration routes generally follow mountain chains like the Rocky Mountains and Sierra Madre ranges. The birds make extensive overwater crossings across the Gulf of California and between southeast Alaska and British Columbia.
Migration Timing and Routes
Here are some details on Western tanager migration patterns:
- In California, the first migrants arrive in late March. Fall migration lasts from late August through October.
- They pass through lowlands in Arizona primarily in May and September.
- At higher elevations in Arizona and New Mexico, the species is absent from April to mid-May and from mid-September to late April.
- In Colorado, most migration occurs from late April through May and mid-August through September.
- Farther north, they pass through Montana in May and September. Through Wyoming in late May and early September.
Banding recoveries and sightings of color-marked individuals reveal some north-south migration routes for Western tanagers, including:
- Birds from southeast Alaska winter along the Pacific coast of Mexico.
- Tanagers breeding inland in British Columbia take an inland route south via the Rocky Mountains into Mexico.
- The species moves south down the Pacific Coast through California and Baja California, Mexico.
- There is east-west movement across Arizona with birds migrating between California and Mexican wintering areas.
Breeding Biology
Western tanagers breed in the western mountains from April through early August. They are primarily monogamous and thought to mate for life, returning to the same breeding site each year. Males arrive before females to establish and defend nesting territories.
Nest building begins shortly after pairs form. The female chooses the nest site, typically on a horizontal branch high in a conifer tree. She builds the nest out of twigs, bark, lichens, and other materials. It takes 6 to 9 days to construct the nest.
The female lays 3 to 5 pale blue eggs. She incubates them alone for about two weeks. Both parents feed the nestlings a diet of insects. The young birds fledge from the nest 13 to 14 days after hatching. Pairs usually raise a single brood per season.
Breeding Timeline
Here are some details on the breeding phenology and stages for Western tanagers:
- Courtship and pairing early April to early June
- Nest building from late April through June
- Egg laying mainly May and June
- Incubation period 13 days
- Nestling period 13 to 14 days
- Fledging from late May through late July
The table below summarizes the timing of key breeding events for Western tanagers in different parts of the range:
Location | Breeding Season | Peak Egg Laying | Peak Fledging |
---|---|---|---|
California | Mid-April to Mid-July | May | June |
Oregon | Late April to Late July | Late May | Late June |
Montana | Late May to Mid-August | Early to Mid-June | Early to Mid-July |
Colorado | Early May to Early August | Late May to Early June | Late June to Early July |
Arizona | Early May to Mid-July | May | June |
Habits and Behavior
Western tanagers are active and conspicuous in their open forest breeding habitats. The males’ bright yellow and red plumage makes them stand out. Their common call note is a musical “pit-er-ick” whistle.
They regularly forage relatively high in the canopy, outwardly gleaning insects from leaves and branches. They also fly out to catch insects in mid-air. Western tanagers occasionally feed closer to the ground on seeds and fruits. They are frequent visitors to bird feeders during migration and in winter.
During migration, they travel alone or in small groups. They often join mixed-species flocks while wintering in Mexico. Nesting pairs are territorial but may gather in loose flocks after breeding. They roost in dense vegetation at night.
Diet and Feeding
The diet of Western tanagers consists primarily of insects and other invertebrates. Beetles, bees, wasps, butterflies, and spiders are common prey. The also eat ants, caterpillars, grasshoppers, and flies. Less frequent food items include seeds, berries, and nectar from flowers.
Western tanagers forage mainly in trees and shrubs, though will feed on the ground as well. Their feeding behaviors include:
- Gleaning insects from leaves and branches while perched
- Hovering to pick insects from foliage
- Hawk-like aerial flycatching to capture insects on the wing
- Probing into crevices in bark for hiding insects
- Occasionally feeding on fruits or seeds on the ground
Adults feed insects to their young during the breeding season. Nestlings are fed a variety of insects including caterpillars, beetles, ants, bees, and flies.
Threats and Conservation
The Western tanager remains a widespread and locally common species, but has undergone long-term population declines across many parts of its range. The causes of the declines are not well understood. A variety of factors may be contributing.
Habitat loss, both on the breeding grounds and in wintering areas, is likely one issue. Timber harvesting can degrade and fragment mature montane forests used for breeding. Urbanization also results in lost habitat. In Mexico, tropical deciduous forests favored in winter have declined due to land use changes.
Climate change may impact tanagers by increasing drought stress and wildfire activity in western forests. Insect populations may be declining in some areas due to pesticide use. Collisions with buildings and towers during migration are another source of mortality.
Wide-ranging conservation initiatives focused on protecting mature and old-growth western forests could benefit Western Tanagers. Managing timber harvests to maintain adequate canopy cover and large trees may help provide quality breeding habitat. Efforts to conserve wintering habitat in Mexico are also important.
Some land trusts and conservation groups have targeted acquisition and protection of montane forest utilized by Western tanagers. Continued monitoring through programs like the Breeding Bird Survey can identify population trends and guide future conservation efforts.
Summary and Conclusion
In summary, the Western tanager remains a fairly common breeding bird across much of its range in western North America. However, Breeding Bird Survey data indicate the species has undergone long-term population declines since the 1960s. Causes of the declines are unclear but likely involve habitat loss both on the breeding and wintering grounds, as well as other factors.
Western tanagers breed at moderate densities in open coniferous forests across the western United States and southwest Canada. They are migratory, wintering primarily in western and central Mexico. The species can be observed on migration routes and wintering areas from August through May.
Conservation efforts focused on protecting breeding and wintering habitat can help reverse population declines. Ongoing monitoring and research are needed to better understand the ecology and habitat needs of the Western tanager.