RED-WINGED BLACKBIRD (Agelaius phoeniceus) RWBL Sample size: 1264 |
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Although this migratory bird project censused upland, primarily deciduous forest, we did record various icterid blackbirds, especially redwings, as they moved upriver in spring. Red-winged Blackbirds breed in wetlands and non-forested adjacent uplands from Alaska to James Bay, Ontario to Newfoundland; south through all US states to Costa Rica and western Cuba [Yasukawa and Searcy 1995 (BNA)]. In New England, nests are typically in salt or fresh marsh vegetation, shrubs in wooded swamps, sedge meadows or cropland [Veit and Petersen 1995, (BNA)]. Nesting begins in late April in Connecticut [Robertson 1972]; in all populations studied, more than half of the females mated with polygynous males i.e. two or more females per male in prime habitat [Searcy and Yasukawa 1995]. During the breeding season, food is primarily invertebrate with some vegetation, during migration and winter they feed mostly on wild seeds and crop grains such as ragweed, corn, wheat and sunflower seeds, or birdseed at feeders [Yasukawa and Searcy 1995 (BNA)]. During fall, New England birds migrate south an average of 800 km to the southern US [Dolbeer 1982]. Redwings commonly migrate and roost in large flocks, often in Phragmites reeds, and often in mixed flocks with Common Grackles, European Starlings and Brown-headed Cowbirds [Dolbeer et al. 1978].
Spring migration is during the day, with males arriving back well before females [Yasukawa and Searcy 1995 (BNA)]. Spring migrants are seen in Massachusetts from the second week of March [Veit and Petersen 1995], and the same dates in Vermont [Laughlin and Kibbe 1985]. Many thousands of birds congregate into large fall flocks in September and October, mostly leaving by November, although small flocks and individuals may winter in southern New England [Veit and Petersen 1995].
Conversion of preferred marsh and upland breeding habitats to agriculture reduces the numbers of breeding birds [Besser et al. 1984]. Farmers are legally permitted to kill redwings, grackles and starlings to reduce crop damage; usually in areas of winter roosts [Yasukawa and Searcy 1995 (BNA)]. However, Red-winged Blackbird numbers in North America showed little overall change through 1981 [Dolbeer and Stehn 1983]; although Breeding Bird Survey data from New England (1966-2000) indicate a long-term decrease [Sauer et al. 2001]. Nevertheless, Nero [1984] considered the redwing “perhaps the most abundant bird in North America” and Meanley and Royall [1976] estimated the US population at about 190,000,000 in 1974/75.
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Observations
Red-winged Blackbirds are among the earliest migrants to move through the Connecticut Valley, the first males arriving as early as the second week of March. This study focused on upland deciduous forest habitat, while redwings breed in wetlands and adjacent non-forested habitats. Sample sizes were thus low, except for presumed daytime migrant flocks overwhelmingly concentrated at A sites along the Connecticut R. Very few Red-winged Blackbirds were recorded on the forest transects in MA, NH or VT, nor in B or C sites in CT.
Because most redwings probably migrated before we started our censuses, we recorded significant numbers of birds only in periods 1 and 2 (late April – first week of May). The following flock sizes were estimated at A sites in CT: 150, 50, 35, 25, 15, 14, 10, 7 etc. In each year of the study, CT observers noted that these flocks were moving upriver.
The timing of the arrival of spring migrants in all states commenced in period 3, peaking in period 4 and dropping a little in period 5. |
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RWBL Map
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