occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Breeding

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Breeding range extends from western and north-central Alaska to southern Keewatin and Labrador, south to central British Columbia, central Saskatchewan, northern shores of Lake Superior and Lake Huron, southeastern Ontario, Vermont, New Hampshire, Maine, northeastern New York, Massachusetts, and Nova Scotia (Avery 1995). During the nonbreeding season, this species ranges from southcoastal Alaska, southern Canada, and northern United States south to Texas, Gulf Coast, and northern Florida (but primarily in the southeastern United States) (Avery 1995).

Length: 23 cm

Weight: 64 grams

• Terrestrial
• Freshwater

Comments: Breeding habitat includes moist woodland (primarily coniferous), bushy bogs and fens, and wooded edges of water courses and beaver ponds. Nests are in trees or shrubs, usually in or near water, frequently in a conifer to about 6 meters above ground. During migration and winter, habitat is primarily wooded wetlands and riparian areas but also includes various open woodlands, scrub, pastures, and cultivated lands (AOU 1983).

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

Locally Migrant: No. No 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.

Arrives in northern U.S. February-April (Terres 1980).

Comments: Eats insects and various other invertebrates, some small amphibians and fishes, seeds, grains, small fruits; forages on ground and in shallow water (Terres 1980).

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

Estimated Number of Occurrences: 81 to >300

Comments: This species is represented by a large number of nesting occurrences (subpopulations).

>1,000,000 individuals

Comments: Post-breeding global abundance estimated at 4,900,000 individuals by Blancher (2003) based on analysis of North American Breeding Bird Survey (BBS) and Canadian Breeding Bird Census (BBC) data. For the same time period, Rich et al. (2004) estimated a global population of about 2,000,000 birds based on BBS survey data. The disparity between population estimates demonstrates the current lack of abundance data and the potential inadequacies of using the BBS to survey for this species due, in part, to the relative inaccessibility of most of the species breeding range (Hannah 2004).

Results from the North American BBS indicate a survey-wide average of 0.27 birds/survey route for 1966-2004 (Sauer et al. 2005). Breeding densities are generally very low, even at the center of the breeding range (Flood 1987, Hannah 2004). Densities are generally higher in northwestern Canada than in Atlantic Canada. In northern Saskatchewan, densities ranged from 2 to 31 individuals/km2 (Hobson et al 2000); in the Hudson Bay lowlands of northern Manitoba densities were 20 individuals/km2 (Gillespie and Kendeigh 1982); in the Old Crow region, Yukon Territory, densities range from 18 to 90 individuals/km2; and in British Columbia, densities of 5 individuals/km2 were reported (Erskine 1977). In Alaska, densities are relatively high, ranging from 10 to 30 territories/km2 (Hannah 2004).

Clutch size is 4-5. Incubation, by female, lasts 14 days. Young are tended by both parents, leave nest at about 13 days.

• 2007
  Vulnerable
• 2004
  Least Concern

Canada

Rounded National Status Rank: N4B - Apparently Secure

United States

Rounded National Status Rank: N4B,N4N : N4B: Apparently Secure - Breeding, N4N: Apparently Secure - Nonbreeding

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: Still common, but overall abundance appears to have declined precipitously over the past few decades.

Global Long Term Trend: Decline of 30-50%

Comments: A significant, range-wide decline of approximately 90% over the past 4-5 decades is indicated by data from the Breeding Bird Survey, Christmas Bird Counts, and Quebec Checklist Program (Greenberg and Droege 1999, Niven et al. 2004, Savignac 2004, Sauer et al. 2005). Analyses of abundance classifications in bird distribution books and annotated checklists reveal a long-term decline dating back to at least the early part of the 1900s (Greenberg and Droege 1999).

Comments: On wintering grounds, potential threats and/or causes for observed population decline include destruction of wooded wetlands and blackbird control programs; on breeding grounds, acid precipitation and conversion of boreal forest wetlands have been implied (Greenberg and Droege 1999).

Habitat degradation: Land-use practices that degrade or reduce wooded wetlands are detrimental to this species' habitat needs (Avery 1995). Greatest loss of wooded wetlands is on the wintering grounds. Between the mid-1950s and mid-1980s, about 25% of remaining wooded wetlands in the southeastern U.S, an area that encompasses most of the species' winter range, were drained and converted (Hefner and Brown 1984, Greenberg and Droege 1999). However, modern rates of wooded wetland conversion may not be sufficient to explain the severity of recent declines; changes on the breeding grounds may also be limiting this species (Greenberg and Droege 1999). Several other species that utilize high-latitude wetland habitats for breeding, such as the Horned Grebe (Podiceps auritius) and Lesser Yellowlegs (Tringa flavipes), are also experiencing survey-wide (BBS) declines (Sauer et al. 2005).

Clearcut logging on breeding grounds removes habitat and may also encourage establishment of competitors Common Grackles and Red-winged Blackbirds (Agelaius phoeniceus) (Ellison 1990), or encourage invasion by Brown-headed Cowbirds (Molothrus ater), a common and potentially problematic nest parasite (Avery 1995). Conversely, recently logged habitat, when saturated with water, may provide breeding habitat for this species; Ellison (1990) found several Rusty Blackbird nests and fledglings in recent clearcuts in Vermont. Although recent clearcuts may satisfy habitat requirements for this species, no data exists on the relative quality of these sites (Hannah 2000, 2004).

Blackbird control programs: Rusty Blackbirds may form mixed-species flocks in winter with other blackbirds and starlings, regularly exceeding 1 million birds. As a result, species has been subjected to lethal control to reduce nuisance, health, and crop damage problems (Avery 1995). Winter roost control programs in the eastern U.S. coincided with declines in Common Grackle populations (Avery 1995, Greenberg and Droege 1999). The overall effect on Rusty Blackbird populations is unknown but suspected localized and nominal, as this species typically constitutes <1% of winter roosts (Avery 1995).

Wetland acidification: Acidification of boreal wetlands due to industrial emissions is also of concern, particularly in eastern North America, but overall effects are unknown (Greenberg and Droege 1999). Since Rusty Blackbirds inhabit areas with naturally high soil acidity, it is difficult to determine the real impact of acidification (Darveau et al. 1989, Savignac 2004). Declines in snail abundance in acidified soils in the Netherlands have been linked to declines in passerine production (Graveland et al. 1994); given the high proportion of snails and mollusks in Rusty Blackbird diets, the impacts of acidification on food resources could be of concern (Greenberg and Droege 1999).

Biological Research Needs: Research using stable isotopes to link wintering and breeding populations, and to connect demographic changes with specific regions of North America, is underway in the United States and Canada (CWS 2005). Additional research is needed to understand the cause(s) of the population decline. Natural history and breeding biology, including productivity and courtship behavior, require further study. Also needed is information on foraging behavior and diet, flocking habits, and habitat and resource use during the nonbreeding season (Greenberg and Droege 1999).

Comments: Two subspecies are recognized in North America: Euphagus carolinus carolinus, which occupies most of the species' range, and the darker E. c. nigrans, which breeds in Newfoundland, Nova Scotia, Magdalen Island, and possibly eastern New Brunswick (AOU 1957, Avery 1995).

Few comprehensive molecular or morphological studies have been conducted on relationships between rusty blackbirds and other members of the sizeable family Icteridae. Brewer's blackbird (Euphagus cyanocephalus) is likely the closest relative. Species in the genus Euphagus are probably more closely allied with the grackles (Quiscalus) than to Agelaius blackbirds (Avery 1995).