Dendroica occidentalis

occurs (regularly, as a native taxon) in multiple nations, but breeds in a single nation

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (250-20,000 square km (about 100-8000 square miles)) BREEDING: southwestern Washington south through mountains to southern California and west-central Nevada. Populations fragmented within range (AOU 1983, Pearson 1997). NON-BREEDING: primarily from Durango and southern Nuevo Leon south to Oaxaca, from Chiapas to Guatemala, and southern Honduras to western Nicaragua (Pearson 1997). Rare and/or local in coastal California (from central California south) and in west-central Nicaragua and Costa Rica; accidental to western Panama (AOU 1983, Stiles and Skutch 1989, Pearson 1997). Highest densities in Central Volcanic Belt of Mexico (Howell and Webb 1995). MIGRATION: through Sonora, Chihuahua, San Luis Potosi, and rarely northern Baja California.

Mountains of w US; winters to Nicaragua.

Length: 14 cm

Weight: 10 grams

Comments: BREEDING: Generally in upland coniferous forests with high canopy volume; shrub understories less important (Pearson 1997, AOU 1998). Prefers mature stands of pine and fir, with large trees and dense cover; prefers scattered groups of tall trees emergent from canopy (USDA Forest Service 1994). Douglas-fir (PSEUDOSTUGA MENZIESII) an important tree species throughout breeding habitat. Nests in older second-growth (> 40 yrs) and mature forests (> 120 yrs; Meslow and Wight 1975).

In Washington and Oregon, found in Douglas-fir, western hemlock (TSUGA HETEROPHYLLA), Pacific silver fir (ABIES AMABILIS) and other firs (ABIES spp.). Also occurs in low densities in subalpine forests dominated by subalpine-fir (ABIES LASIOCARPA), which may include lodgepole pine (PINUS CONTORTA) and other conifers (Manuwal et al. 1987). In northwest Washington east of Puget Sound, once bred in oak-fir associations, but habitat is vanishing. In southern Washington Cascades Douglas-fir forests, found most abundant in young (55-80 year; average 7.9 birds per visit); relatively dry old-growth (210-440 year; 6.2 birds per visit); and mature (95-190 year; 5.6 birds per visit) stands; less abundant in wet (300-730 year; 1.6 birds per visit) and mesic (250-700 year; 2.1 birds per visit) old-growth stands (Manuwal 1991).

In Coastal Oregon Douglas-fir forests, was one of most commonly detected species, but was more abundant in young stands (40-72 year; two-year average 69.6 pairs per 40 hectares) than in mature (80-120 year; 41.1 pairs per 40 hectares) or old-growth stands (200-525 year; 48.4 pairs per 40 hectares), where canopy cover decreased with stand age (Carey et al. 1991). Positively associated with percent conifer cover, larger trees and taller trees; negatively associated with deciduous tree and shrub understory (Morrison 1982). In a comparison of streamside to upslope sites in mixed-coniferous forests dominated by Douglas-fir, was never detected in riparian sites (McGarigal and McComb 1992).

In Oregon Cascades, was most frequently detected species in young (30-80 year) and mature (80-200 year) Douglas-fir stands, and was second-most frequently detected species in old-growth stands (200-500 year; Gilbert and Allwine 1991). A synthesis of studies in Oregon Cascades Douglas-fir/western hemlock forests, showed the species most abundant in natural old-growth (200-450 yr), natural mature (80-190 year) and young closed canopy plantation (30-60 year) stands, and absent in clearcut and retention-cut plots (clearcuts with 2-14 trees per hectare or 1-6 trees per acre retained; Hansen et al. 1995).

In coastal California, breeds in Douglas-fir and coast redwood (SEQUOIA SEMPERVIRENS) habitats (Dunn and Garret 1997); in Douglas-fir forests found most abundant in older, cooler, and higher-elevation stands, and counts were highest in stands >300 years (Raphael 1987). In Marin County, occurs in moderately dense Douglas-fir and douglas-fir/coast redwood forests in canyons at mid- to high elevations with east or north exposures (Shuford 1993, cited in Pearson 1997). In California mountains, found in red fir (ABIES MAGNIFICA), white fir (ABIES CONCOLOR), sugar pine (PINUS LAMBERTIANA), ponderosa pine (PINUS PONDEROSA), Jeffrey pine (PINUS JEFFREYI), lodgepole pine, and sequoia (SEQUOIA GIGANTEA) forests (Verner and Larson 1989, Dunn and Garrett 1997). In a mixed conifer-oak forest, showed a preference for foraging in ponderosa and sugar pine (Airola and Barrett 1985).

Usually nests on outer limb of conifer, 6-18 meters above ground (sometimes 0.6-15 meters high).

NONBREEDING: In a variety of habitats during migration including woodland and scrub habitats composed of live oaks (QUERCUS spp.), cottonwood (POPULUS spp.), tamarisk (TAMARIX spp.), chaparral, desert woodlands, cottonwood-willow, large mesquite, and pecan orchards (Rosenberg et al. 1991, Dunn and Garrett 1997). Winters in conifers, especially pines and pine-oak habitats from 1,500 to 3,000 meters (Howell and Webb 1995, Dunn and Garrett 1997, AOU 1998). In Mexico, Hutto (1992) describes this species as a two-zone generalist, using both cloud forest and pine-oak-fir forest. In Costa Rica mostly in hedgerows or at forest edge, forages in conifers, especially Guatemalan cypress (CUPRESSUS LUSITANICA) (Stiles and Skutch 1989).

Systems

• Terrestrial

Depth range based on 1 specimen in 1 taxon.

Environmental ranges
  Depth range (m): 0 - 0
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

On lower Colorado River Valley, Arizona, transient in late-April to late May, and mid-August to mid-October (Rosenberg et al. 1991). Winter in highlands from central Mexico into Central America to northern Nicaragua; accidental in western Panama, often occurs with Townsend's warbler (DENDROICA TOWNSENDI) (Ehrlich et al. 1988; Stiles and Skutch 1989; Howell and Webb 1995).

Comments: Forages actively in branches of conifers for insects (e.g., beetles, caterpillars, flies, etc.) and spiders. Often forages high in trees, 30-60 meters above ground (Terres 1980). In Sierra-Nevada mixed conifer, foraged 5 to 25 meters above ground (Airola and Barrett 1985), and in Giant Sequoia forest foraged above 10 meters (Kilgore 1971).

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

Frequently found in association with yellow-rumped warbler (DENDROICA CORONATA).

Maximum longevity: 9.1 years (wild)

Clutch size is 3-5. Nestlings are altricial and downy.

The following is a representative barcode sequence, the centroid of all available sequences for this species.

There are 6 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

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Barcode of Life Data Systems (BOLDS) Stats
Public Records: 6
Specimens with Barcodes: 6
Species With Barcodes: 1

United States

Rounded National Status Rank: N4B,NNRN : N4B: Apparently Secure - Breeding, NNRN: Unranked - Nonbreeding

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: Relatively widespread and abundant; population apparently stable overall, but may have declined significantly in areas such as northern Sierras; population fragmented.

Year Assessed

Assessor/s

Reviewer/s

Contributor/s

Justification

History

• 2008
  Least Concern
• 2004
  Least Concern

Comments: Threats largely unstudied. Activities that degrade or eliminate coniferous forest canopy and insect prey would be detrimental. Threats include logging and development of forest habitats on breeding and wintering grounds, possible increase in exposure to brood parasitism by brown-headed cowbirds (MOLOTHRUS ATER), and hybridization and possible competition with Townsend's warbler (DENDROICA TOWNSENDI) (Dunn and Garrett 1997, Pearson 1997, Muehter 1998). TIMBER HARVEST: Clearcutting and severe thinning of overstory eliminates habitat, and species may be area-sensitive, avoiding clearcut edges. Throughout much of breeding range, timber harvest has eliminated and severely fragmented extensive areas of habitat. For example, based on an analysis of Landsat imagery in western Oregon, 13 percent of closed-canopy forest on non-wilderness public lands and 45 percent on private lands were lost between 1972 and 1988, dramatically fragmenting the forest landscape and reducing the size of remaining forest patches (Spies et al. 1994). Quality of subtropical and tropical pine forest habitats on wintering grounds may also be declining due to overharvesting, short rotational schedules, and removal of broad-leaved understories, with unknown consequences for this species (Petit et al. 1995). PREDATION: Only one record of predation; by an American kestrel (FALCO SPARVERIUS) (Pearson 1997). Accipiters probably predators of adults. Changes in predation rates given landscape changes to forest habitats and possible changes in abundance of nest predators are unknown. BROOD PARASITISM: Only one record of brood parasitism by brown-headed cowbird (MOLOTHRUS ATER) known (Pearson 1997). Rates of parasitism given fragmentation of forest habitats and westward expansion of cowbirds unknown.

Restoration Potential: Still a common species in appropriate habitat. After logging, should recover with succession as forest canopy develops. Forest management to maintain moderate to dense canopies would benefit species. An international perspective on habitat management is needed given the limited size of the breeding and wintering ranges.

Preserve Selection and Design Considerations: Occurs in young, mature, and old-growth forest stands, and abundance is likely related more to canopy structure than to stand age (this needs to be quantified). Avoids edge of Douglas-fir (PSEUDOTSUGA MENZIESII) forests of northwestern California. Of 15,077 observations less than one percent were on edges of clearcuts; was not significantly associated with any other measure of fragmentation (Rosenberg and Raphael 1986). In much of breeding range, suitable forest habitat on private lands has been cleared and fragmented by logging and development; clearing has been somewhat less on public lands (e.g., Spies et al. 1994).

Management Requirements: Requires coniferous forest with well-developed canopy, most often associated with Douglas-fir.

TIMBER HARVEST: Associated with moderate to dense coniferous tree canopy, although it may be present in open forest stands. Not found in clearcuts or very young successional stands (Hagar 1960, Hansen et al. 1995), but moves in once canopy layer is well-developed (Pearson 1997). No information available on relative reproductive success or survival in different silvicultural treatments or stand sizes. In southern Washington Cascades, prefers Douglas-fir and true fir (ABIES spp.) averaging 90 percent canopy cover, canopy height ranging from 14-68 meters (Pearson 1997). In coastal Oregon Douglas-fir forests, Morrison (1982) found territorial birds (n=9) preferred areas with heavy total conifer cover (range 53-90 percent cover), dense canopy (not defined), and trees more than 31 centimeters dbh and more than 20 meters high; were negatively associated with percent deciduous tree cover and shrub cover. In Sierra-Nevada red-fir (ABIES MAGNIFICA) forests, Hejl and Verner (1988) found the species most abundant in stands of moderate (40-59 percent) and dense (60-100 percent) canopy closures. Beedy (1981) found greater abundance in open canopy red fir (170 trees per acre more than 4 inches dbh, and 509 square feet per acre basal area) and mixed conifer stands (245 trees per acre more than 4 inches dbh, and 370 square feet per acre basal area) than in closed canopy stands (red fir: 265 trees per acre more than 4 inches dbh, and 100 square feet per acre basal area). In giant sequoia stands, removal of brush and sapling understory that had grown up as a result of fire suppression did not significantly affect numbers of breeding pairs (Kilgore 1971).

Management Research Needs: Need information on breeding phenology; philopatry; territory size; disease, nest predation, and other sources of mortality; rates and response of cowbird parasitism; limiting factors. Need further information on hybridization and competition with Townsend's warbler and possible relations to habitat and habitat change. More detailed information needed on habitat preferences, particularly forest stand structure, canopy structure, and measures that can be easily used by forest managers (e.g., canopy closure). Need information on abundance, reproductive success, dispersal and survival in relation to habitat, silvicultural treatment, forest succession, rotation schedules, and forest structure; also landscape relations, area sensitivity. Information needed on threats, extent of habitat alteration and fragmentation on breeding and wintering ranges; effects of pesticides and herbicides used in forest management. Need better information on insect prey base and relation to forest structure; migration routes and stopover sites.

Stewardship Overview: Most abundant warbler in the montane coniferous forests of Oregon and Washington. However, area of breeding and wintering ranges is limited and total population is relatively small. Vulnerable because it is a habitat specialist, has a narrow geographic distribution on breeding and wintering grounds, and there are no large breeding populations (Reed 1992). Classified as a species of concern by the U.S. Fish and Wildlife Service Office of Migratory Bird Management (USFWS 1995). Listed as a conservation priority on the Partners in Flight WatchList for species of concern based on its limited breeding and wintering distributions and threats on breeding range (Muehter 1998). Dependent on coniferous forests with moderate to dense canopies. Total area of suitable breeding habitat has been reduced by timber harvest and land development, but species will re-inhabit a forest stand once canopy becomes well-developed. Hybridizes and may compete with Townsend's warbler (DENDROICA TOWNSENDI) in Washington and Oregon.

Species Impact: An insectivore, may be beneficial in controlling coniferous forest insect pests.