The Common Grackle (Quiscalus quiscula) is an abundant and gregarious blackbird found in partly open situations with scattered trees, open coniferous and deciduous woodlands, forest edges, and suburbs. It breeds across approximately the eastern two thirds of Canada (from Alberta to southern Quebec) and the United States (from Montana, Colorado and easten New Mexico to the Atlantic and Gulf Coasts), with the winter range contracting to the southeast of the much broader breeding range. The range has been expanding westward in recent decades. Two forms (both appearing all black at a distance) were at one time recognized as distinct species: The "Bronzed Grackle", which occurs in most of New England and west of the Appalachians, has a bronze back, blue head, and purple tail; the smaller "Purple Grackle", found east of the Appalachians, has a narrow bill, purple head, bottle green back, and purple tail. Birds from the mid-Atlantic states show variable head color and a purplish back with iridescent bands of variable color. The familiar song of the Common Grackle resembles the sound of a creaking gate; the call note is a loud, deep chuck.

Common Grackles are omnivorous . They forage mainly by walking on the ground or wading in very shallow water. Outside the breeding season, they usually forage in flocks.

Common Grackles often nest in small colonies of 10 to 30 pairs (sometimes as many as 100 or more) and several males may perch in adjacent treetops to sing their creaking, grating songs. In courtship, the male fluffs out his body feathers, partly spreads his wings and tail, and delivers a short scraping song; he also postures with his bill pointing straight up. The nest is typically built in dense vegetation less than 6 m above the ground. The nest, which is built by the female, is a bulky open cup of weeds, grass, and twigs, usually with some mud added, and the inside is lined with fine grass. The 4 to 5 (sometimes as few as two or as many as 6) pale blue eggs are blotched with brown. Incubation is by the female only for 12 to 14 days. Both parents feed the young, bringing them mostly insects. The young leave the nest around 16 to 20 days after hatching.

Common Grackles are present year-round across much of their range. Migration usually involves large flocks. In the north, migration takes place quite early in spring and rather late in the fall.

(Kaufman 1996; AOU 1998; Dunn and Alderfer 2011)

Global Range: BREEDS: northeastern British Columbia and southern Mackenzie to Newfoundland, south to southern Texas, Gulf Coast, and southern Florida, west to Wyoming, Colorado, and New Mexico. WINTERS: Kansas, southern Great Lakes region, New England and Nova Scotia south to southeastern New Mexico, south Texas, Gulf Coast, Florida.

Common grackles range over almost all of eastern North America east of the Rockies, extending far into Canada in the summer breeding season.

Biogeographic Regions: nearctic (Native )

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

Common grackles are medium-sized blackbirds. Their plumage is black, and has a sheen that is glossy and iridescent. Generally, their heads, necks and breasts are glossy purplish-blue or bluish-green. However, common grackles in different parts of North America have somewhat different colored plumage. In New England and in the West, the subspecies has a brassy bronze body coloration. East of the Allegheny Mountains, the body is purple, and in the southeast the feathers have a greenish hue. Common grackles have long, sharp, black bills and yellow eyes. Their tails are long and keel-shaped.

Adult common grackles are 28 to 34 cm long. Females are smaller and duller than males and have a shorter tail. Males usually weigh about 122 g while females weigh around 94 g. Young common grackles look similar to adults, but have brown plumage and brown eyes.

Range mass: 92 to 131 g.

Range length: 28 to 34 mm.

Other Physical Features: endothermic ; bilateral symmetry ; polymorphic

Sexual Dimorphism: male larger; sexes colored or patterned differently; male more colorful

Length: 32 cm

Weight: 127 grams

Systems

• Terrestrial
• Freshwater

Common grackles are found in open areas with scattered trees (preferably coniferous), including around human habitation. They can also be found in farmlands, orchards and swamps. Common grackles have adapted so well to human structures that they are quite common in open areas such as suburban developments, city parks and cemeteries. In fact, human alteration of forested habitats for agriculture has resulted in an expansion of the range of common grackles and an increase in their numbers.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: savanna or grassland ; forest

Other Habitat Features: urban ; suburban ; agricultural

Comments: BREEDING: Partly open situations with scattered trees, open woodland, forest edge, marsh edges, islands, swamp thickets, coniferous groves, cities, suburbs, farms.

Nests in deciduous or coniferous trees up to 18 m above ground, also shrubs, roadside plantings, swamp vegetation, natural cavities, marshes. NON-BREEDING: In migration and winter also in open situations, cultivated lands, fields.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

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.

Northern interior breeding populations make the longest migrations. Arrives in northern U.S., western states, and Canada mid-March to early April (Terres 1980).

During breeding, common grackles' diets consist mainly of insects and other invertebrates. The diet may also include goldfish, minnows, crayfish, small frogs, salamanders, mice, and small bats, which are caught from the air. During migration and winter, common grackles eat mostly grains from farm fields and seeds, particularly corn and acorns. They also eat some fruits.

Common grackles are generally very opportunistic foragers, they follow plows in search of grubs, and even consume human garbage. Adults have been observed snatching earthworms from feeding robins. Grackles forage primarily on the ground, though they also utilize trees, shrubs, and other vegetation. These gregarious birds feed in large flocks, especially outside of the breeding season. They primarily use their bills instead of their feet to uncover food on the ground.

Animal Foods: birds; mammals; amphibians; fish; insects; terrestrial non-insect arthropods; terrestrial worms; aquatic crustaceans

Plant Foods: seeds, grains, and nuts; fruit

Primary Diet: carnivore (Insectivore , Eats non-insect arthropods)

Comments: Eats various invertebrates, grain, seeds, fruits, sometimes small vertebrates and bird eggs; forages on ground, in shrubs and trees, and in shallow water (Terres 1980). In North Dakota, insects dominate the diet in spring; grains increased in the diet in summer and dominated the diet in late summer and early fall (1994, Am. Midl. Nat. 131:381-385).

Common grackles provide food for several birds and small animals as well as helping to control populations of insects and other prey. They also disperse seeds through their droppings during the parts of the year when seeds make up most of their diet.

Common grackle nests are occasionally parasitized by brown-headed cowbirds, although cowbird eggs in these nests are largely unsuccessful.

Ecosystem Impact: disperses seeds

Humans kill large numbers of common grackles to control populations in areas where they destroy crops. Fox squirrels, eastern chipmunks, rat snakes, domestic cats, gray squirrels, bullsnakes, and racoons eat the eggs and nestlings of common grackles. Red-tailed hawks, northern harriers, Cooper's hawks, short-eared owls, and great horned owls are predators of adult common grackles.

Known Predators:

• humans (Homo sapiens)
• fox squirrels (Sciurus niger)
• eastern chipmunks (Tamias striatus)
• rat snakes (Pantherophis obsoletus)
• domestic cats (Felis silvestris)
• gray squirrels (Sciurus carolinensis)
• bullsnakes (Pituophis melanoleucus)
• raccoons (Procyon lotor)
• red-tailed hawks (Buteo jamaicensis)
• northern harriers (Circus cyaneus)
• Cooper's hawks (Accipiter cooperii)
• short-eared owls (Asio flammeus)
• great horned owls (Bubo virginianus)

Quiscalus quiscula is prey of:
Accipiter striatus
Accipiter cooperii

Based on studies in:
Canada: Manitoba (Forest)

This list may not be complete but is based on published studies.

Quiscalus quiscula preys on:
Araneae
Insecta
Pimephales notatus
Butorides virescens
Actitis macularia
Bombycilla cedrorum

Based on studies in:
Canada: Manitoba (Forest)

This list may not be complete but is based on published studies.

Roosts communally in large flocks (sometimes >100,000 individuals), in summer and fall in northeastern U.S.; often with starlings (Caccamise et al. 1983). Mean dispersal distance 21 kilometers for males, 15 kilometers for females (Moore and Dolbeer 1989).

Common grackles use physical displays and vocalizations to communicate. Common grackles produce one song type, which is individually distinctive and is probably used as identification. The harsh song is said to sound much like a squeaking, rusty gate. The male song is most often heard around the date of the first copulation, and its frequency decreases over the course of incubation. Females sing much less frequently than males, and appear to sing most often when song-answering with their mate.

Communication Channels: visual ; acoustic

The maximum lifespan recorded is just over 22 years, although most do not live that long. About half of all common grackles reach adulthood.

Range lifespan

Status: wild: 22 (high) years.

Average lifespan

Status: wild: 275 months.

Maximum longevity: 22.9 years (wild)

Common grackles are usually monogamous, though polygyny occasionally occurs. Pair formation begins in flocks in early spring. Formation of pairs is indicated by flights and mutual displays between a single female and multiple males. A male and a female show preference for one another by flying together, usually with the female in the lead. As the pair-bond is established, the pair leaves the flock to fly and sing together.

The female of a pair typically chooses the nest site. Though this is usually done after pair formation, females sometimes chosen sites several weeks before pairing with a male. From pair formation through incubation, the male remains in close association with his mate by perching near her, following her, and engaging in mutual displays. This pattern exhibited by the male probably functions to guard against extra-pair copulations. Once incubation has begun, his attentiveness decreases steadily.

Adult common grackles sometimes function as helpers to other birds of the species. In one recorded case, two males frequently showed up at the same nest to feed the young, and there was no antagonistic behavior between them. It is assumed that one of the males was the father of the offspring.

Mating System: monogamous ; cooperative breeder

Common grackle nests are built by the female, usually in coniferous trees, though more unusual sites have been documented. These include woodpecker holes, on rafters, under the eaves of barns, in the crannies of ospreys' large nests, and in clumps of cattails. The nests are large and bulky, constructed of woody stems, leaves and fine grasses. Other materials may be used, including fishing line, feathers, manure and tape. The nest cup is lined with mud, and finally fine grasses and horsehair.

Copulation begins soon after the female has completed the nest. She lays 1 to 7 eggs (usually 5 to 6). The eggs are smooth-textured, and highly variable in color. They are typically light blue to pearl gray, though they range from nearly white to dark brown. Some are scrawled with blackish brown, especially at the larger end, and others are spotless. The female incubates the eggs for 12 to 14 days. At this time, about half of common grackle males desert the female and the nest. Those that remain participate in parental care after hatching.

During incubation, various displays and calls are given by both sexes. Parental care, including brooding and feeding, is performed mainly by the female, although males have been observed feeding young. The food supply is monopolized by more aggressive nestlings. The young leave the nest about 12 to 15 days after hatching, and remain near the nest for another 1 to 2 days. The adults continue to feed the young for several weeks.

Common grackle nests are sometimes parasitized by brown-headed cowbirds, but the cowbird eggs in these nests are largely unsuccessful. Common grackles are usually single-brooded, but can double-brood in some areas. Common grackles breed between March and July.

Breeding interval: Common grackles breed once yearly. Common grackles are usually single-brooded, but can double-brood in some areas.

Breeding season: Common grackles breed between March and July.

Range eggs per season: 1 to 7.

Average eggs per season: 5.

Range time to hatching: 12 to 14 days.

Range fledging age: 12 to 15 days.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate)

Average birth mass: 105 g.

Average eggs per season: 5.

Brooding and feeding of the altricial chicks are performed mainly by females, although there have been reports of males assisting in feeding the young. The food supply is monopolized by more aggressive nestlings. The young leave the nest about 12 to 17 days after hatching, though they remain near the nest for another 1 to 2 days. Adults continue to feed the young for several weeks. About half of all grackle males remain with the female through hatching and help in the parental care of the young.

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Protecting: Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Female); pre-independence (Provisioning: Male, Female)

Clutch size 4-7 (commonly 5-6). Sometimes 2 broods per year. Incubation 12-14 days, by female. Young tended by both sexes, leave nest at 10-17 days, remain in nest vicinity 2-3 days. Nests usually in loose colonies.

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

 
There are 5 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.
 

Download FASTA File

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 5
Species: 7
Species With Barcodes: 1

Common grackles are one of the most successful and wide-spread species in North America, with an estimated total population of 97,000,000 individuals. Eastern forests were cleared for agriculture in 1700s and 1800s, creating additional nesting habitat and increased food sources. The planting of shelterbelts has facilitated the spread of this species in the west. Common grackles are very common, and are killed as an agricultural pest in many parts of their range.

US Migratory Bird Act: protected

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

Canada

Rounded National Status Rank: N5B - Secure

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Management Requirements: See Glahn et al. (1991) for information on the impact of ground-based surfactant roost control treatments on local urban and agricultural blackbird/starling problems.

Common grackles are one of the most significant agricultural pests today, causing millions of dollars in damage to sprouting corn. The roosting sites of common grackles and other blackbirds may harbor the fungus, which causes histoplasmosis, a human respiratory disease that can be fatal. However, only roost sites that have been used for more than 3 years tend to become infected. Nonetheless, this phenomenon is used as one of the primary justifications for killing large numbers of roosting blackbirds and starlings.

Negative Impacts: injures humans (carries human disease); crop pest

Common grackles may help to control populations of crop pests.

Positive Impacts: controls pest population

Comments: Damages sunflower crops in Dakotas and Minnesota (Cummings et al. 1989).

Comments: Composed of two groups, formerly considered as separate species: QUISCULA (Purple Grackle) and VERSICOLOR (Bronzed Grackle) (AOU 1998). In a phylogeny of quiscaline icterids based on morphological characteristics, Bjorklund (1991) treated VERSICOLOR and QUISCULA as separate species. In a study of mtDNA variation, Zink et al. (1991) regarded VERSICOLOR and QUISCULA as conspecific. See Zink et al. (1991) for a discussion of the probable mode of evolution of the purple and bronzed phenotypes of Q. QUISCULA (the seemingly high rate of gene flow may be an artifact of recent isolation of a group of grackles in which the bronzed phenotype evolved rapidly, and rapid and extensive range expansion, including the formation of the "hybrid" zone between the two phenotypes).