Cowbirds in North America – All you Need to Know

Brown-headed cowbird

Cowbirds are parasite birds that lay their eggs in the nests of others, often causing the death of the hosts young, and they somewhat lack charm. Sneaking in when the nest is unattended, they will lay their eggs and then check if the eggs are removed they go back and destroy all the eggs of the host bird.

It is not known how cowbird chicks learn to behave like cowbirds instead of the host species. One study has shown it may be because the mother cowbird keeps an eye on their young as they grow.

Cowbirds are from the New World blackbird family, and there are six species that range across North and South America. Of these, three cowbirds are found in North America, but only one is widely seen, the Brown-headed Cowbird.

This guide will help you identify the species of cowbirds spotted in North America according to avibase. The birds in this list are ordered by how frequently they are spotted in the state, from most frequent to least frequent, according to bird watchers’ checklists for the state submitted to ebird.

3 Species of Cowbirds in North America:

  1. Brown-headed Cowbird 10.3%
  2. Bronzed Cowbird 0.2%
  3. Shiny Cowbird

1. Brown-headed Cowbird

brown headed cowbird

Male Brown-headed Cowbirds are black-bodied with brown heads and with short tails. Females are smaller and are gray-brown all over with slight streaking.

  • Length: 76.3-8.7 in (19-22 cm)
  • Weight: 1.3-1.8 oz (42-50 g)
  • Wingspan: 14.2 in (36 cm)

Brown-headed Cowbirds remain all year in eastern states, southern states, and along the Pacific Coast but those that breed in northern and western US states and Canada migrate south for winter.

You can find Brown-headed Cowbirds in grasslands and fields but rarely in wooded areas. They forage on the ground, especially near grazing animals, waiting for them to kick up some food.

Grass and weed seeds make up most of their diet, but they also eat insects. They will also come to backyard feeders, and females cowbirds eat eggs and shells for the calcium.

Brown-headed Cowbird Sounds: Their song has an almost water-like quality of a series of rapid, high-pitched whistles and gurgling sounds that only last a few seconds. They also make short calls.

Bobby Wilcox, XC645459. Accessible at www.xeno-canto.org/645459.

Brown-headed Cowbirds do not build nests. They are often considered a nuisance as they destroy the eggs of smaller songbirds to lay their eggs in the nest and have the bird foster their chicks. They may also harass the host or destroy the nest if they remove their egg.

Fun fact: Are they brave or foolish? Brown-headed Cowbirds have also been known to lay their eggs in the nests of raptors!

2. Bronzed Cowbird

Bronzed Cowbirds are bigger and more stocky than other cowbirds, and the males have red eyes that stand out against their black color. Their wings are dark glossy blue.

Females are brown in the west of their range but darker in the east. They also have red eyes, but juveniles have black eyes.

  • Length: 7.9 in (20 cm)
  • Weight: 2.3-2.6 oz (64.9-73.9 g)
  • Wingspan: 13.0 in (33 cm)

Bronzed Cowbirds are only found in southern US states from California to Florida, mainly during summer for the breeding season. In winter, they are in Mexico and Central America.

Look for Bronzed Cowbirds walking on the ground in open fields and pastures in the east and also in more wooded areas in the west of their range. They will also come to backyard feeders and will eat seeds, grains, and insects.

Bronzed Cowbirds sounds: Harsh jeeps form their song, and they also scream and make chattering calls.

Peter Boesman, XC232762. Accessible at www.xeno-canto.org/232762.

Nests are not built by Bronzed Cowbirds instead, they lay their eggs in the nests of other species.

Fun Fact: Bronzed Cowbirds males ruff up their nape feathers and hold open their wings in a dramatic mating display. They lay their eggs in the nest of other species and so do not build nests or look after their young.

3. Shiny Cowbird

Shiny cowbird

Shiny Cowbirds males are glossy dark velvety purple all over, but from a distance, they can look black. Females are brown and look similar to female Brown-headed cowbirds.

  • Length: 7.1 in (18 cm)
  • Weight: 1.1-1.4 oz (31-40 g)

Shiny Cowbirds are mainly found in South America, southern Central America, and the Caribbean, but they also live in Florida and along the southern coast of the US.

They feed on insects, seeds, and grains from the ground in open areas. They will also hunt for insects in trees and will visit backyard feeders.

Shiny Cowbirds sounds: Low guteral croaks and high-pitched squeaks.

Ricardo José Mitidieri, XC601365. Accessible at www.xeno-canto.org/601365.

Shiny Cowbirds, like most cowbirds, do not build nests and instead lay their eggs in the nests of other species.

Fun fact: Shiny Cowbirds will lay their eggs before the host lays so that their chicks are born first and grow stronger before the host chick and become the only survivor.

Cowbird Migration and Frequency in Summer and Winter

Checklists for the state are a great resource to find out which birds are commonly spotted. These lists show which cowbirds are most commonly recorded on checklists for on ebird in summer and winter.

Cowbirds migrate and are more common in summer

Cowbirds in Summer:

Brown-headed Cowbird 21.5%
Bronzed Cowbird 0.4%
Shiny Cowbird <1%

Hummingbirds in Dakota in Winter:

Brown-headed Cowbird 2.6%
Bronzed Cowbird 0.1%