Rusty blackbird (Euphagus carolinus) COSEWIC assessment and status report: chapter 6



Few studies have been conducted on the Rusty Blackbird and, as a result, little is known about the biology and ecology of this species in Canada.


The Rusty Blackbird is normally monogamous and nests solitarily, although there are records of loose colonies in the Atlantic provinces and in some parts of Alaska (Kennard 1920; Spindler and Kessel 1980; Orians 1985; Avery 1995). In the south of the breeding range, birds generally arrive on the breeding grounds from early April to late May, with most arriving in mid-April (Avery 1995; Cyr and Larivée 1995; Campbell et al. 1997). In the most northerly regions, the Rusty Blackbird arrives on its breeding grounds towards mid-May (Sinclair et al. 2003).

Females build the nests, which are typically placed in thickets of small conifers, deciduous shrubs or in dead trees, usually over or close to water (Kennard 1920; Gauthier and Aubry 1995; Campbell et al. 1997). Nests are generally constructed of conifer twigs, dead grasses with small roots and other parts of plants, mosses and lichens, and are lined with fine grasses and occasionally feathers, mammal hairs and sphagnum (Campbell et al. 1997).

The Rusty Blackbird generally produces one clutch per year, although replacement nests may be built (Avery 1995). The eggs vary from pale blue-green to pale grey and have dark to light brown markings (Avery 1995). The female alone incubates the eggs, and the male brings food to the incubating female (Avery 1995). Incubation begins after the first egg is laid and lasts 14 days (Bent 1958). The number of eggs/clutch is 3 to 6, with an average of 4.47 ±0.08 (n = 80 nests; Avery 1995). Young generally remain in the nest for 11-13 days (Bent 1958; Gauthier and Aubry 1995; Campbell et al. 1997) and may leave the nest several days before they are able to fly (Campbell et al. 1997). Depending on the latitude, groups of birds gather and begin dispersing in late July and early August (Campbell et al. 1997), with migration beginning in late August and continuing until early October (Sinclair et al. 2003).


Although there are no studies of adult Rusty Blackbird survival, there are some data available on nestling survival. A study carried out in New England at the beginning of the 20th century found that 93% of nests raised at least one chick to fledging (n = 14; Kennard 1920), while a more recent survey in British Columbia found that 25% of nests produced at least one chick to fledging (n = 4; Campbell et al. 1997).

There are a few reported cases of predation on the Rusty Blackbird. For example, Campbell et al. (1997) reported a Gray Jay (Perisoreus canadensis) killing three young in a nest in British Columbia. Also, the aggressive behaviour of adult blackbirds toward American Marten (Martes americana), Northern Harrier (Circus cyaneus) and Sharp-shinned Hawk (Accipiter striatus; Avery 1995; C. Savignac, unpubl. data)suggest these species may be potential predators.


In the northern part of the breeding range, groups of a few dozen to several hundred individuals begin to gather at the end of July (Avery 1995; Manitoba Avian Research Committee 2003). In Alberta and northeastern British Columbia the species has been reported to migrate east in early October (Semenchuk 1992; Campbell et al. 1997). Returns of banded birds in North America suggest that Saskatchewan and Manitoba populations migrate southeastward toward the winter range, which probably corresponds to the Mississippi Valley area; whereas populations breeding in northeastern regions tend to migrate southwest, overwintering mostly east of the Mississippi (Brewer et al. 2000).

Diet and foraging

The Rusty Blackbird feeds mostly on invertebrates, such as aquatic insect larvae, crustaceans and snails that are associated with aquatic environments. It may also include salamanders and small fish in its diet (Avery 1995). The species forages for food primarily on humid soils, along the banks of riparian zones and in shallow, slow-moving water (Avery 1995). In the fall and winter, although still primarily feeding on aquatic invertebrates, the Rusty Blackbird supplements its diet with seeds and small fruits (Avery 1995). During severe winter conditions, the Rusty Blackbird can also attack and feed on passerines and shorebirds (Bent 1958; Avery 1995). The Rusty Blackbird may also make irregular use of feeders in winter (Cyr and Larivée 1995; Campbell et al. 1997).

Interspecific interactions

Few data are available on interspecific interactions during the breeding period (Avery 1995). On its migration routes and wintering areas, the Rusty Blackbird can join mixed flocks composed of other blackbird species, such as the Red-winged Blackbird (Agelaius phoeniceus), European Starling (Sturnus vulgaris) and Common Grackle (Quiscalus quiscula; Avery 1995; Dolbeer et al. 1997). Ellison (1990) suggests that habitat conversion on the breeding grounds could encourage colonization by Red-winged Blackbirds and Common Grackles, the former of which is known to displace Rusty Blackbirds during the breeding season (Avery 1995).


No data currently exist on Rusty Blackbird home range sizes. However, intensive efforts to locate Rusty Blackbird nests in New England at the beginning of the 20th century never found adjacent nests closer than 400 m (Kennard 1920).


During the breeding season, the Rusty Blackbird prefers riparian areas in forested wetlands. However, the species will use wetlands remaining in regeneration cutovers (Campbell et al. 1997), riparian areas in cutovers (Darveau et al. 1995; Whitaker and Montevecchi 1999), stream buffers untouched by fire in recent burns (Consortium Gauthier et Guillemet – G.R.E.B.E. 1991), treatment ponds in forested areas (R. Popko pers. comm.) and the banks of hydroelectric reservoirs (J. Gauthier pers. comm.). Productivity in these habitats is unknown.

Page details

Date modified: