Female Brown-headed Cowbirds (Male vs Female Identification)

Brown-headed bullbird (catfish) is probably North America’s best-known brood parasite, with females laying as many as 40 eggs in a single season in the nests of other unsuspecting breeding birds. Males and females are different in appearance and cannot be easily confused. But are there other traits and behaviors that male and female brown-headed bullthrushes share? Let’s take a closer look.

Unlike the male brown-headed bullbird, which, as the name suggests, has a brown head, the females of this species are brownish-gray all over. Their cheeky egg dumping habit sets them apart from many other birds in the United States.

As brood parasites, brown-headed bullbirds do not exhibit the traditional “nesting,” hatching or maternal brooding behavior seen in most other birds. Females have no relationship with their own offspring and do not take part in the care or upbringing of any offspring.

For a more in-depth look at the fascinating and unusual behavior and habits of these elusive nest invaders, read on.

Close-up of a perched brown-headed bullbird female

How do you know if a brown-headed bullbird is a male or a female?

Male brown-headed bullbirds are black with a brown head and conical gray beak. Females do have the same thick gray beak, but instead of the same iridescent black plumage as males, they are grayish-brown all over, with striped markings on the throat and belly.

Male and female brown-headed bullbirds look nothing alike and behave differently.

female brown cowbird

male brown cowbird

What does a female brown-headed bullthrush look like?

The female brown-headed bullthrush is about the same size as the red-winged blackbird. Their plumage is grey-brown with a slightly darker upper part and lighter striped markings on the belly and breast.

They are stocky birds with short tails and wings, gray conical bills, dark brown eyes and black legs and feet.

Closeup shot of a female brown-headed bullbird perched on a mossy log

size difference

Female brown-headed bullthrushes are slightly smaller than males, and there is a significant difference in the average body weight recorded between the sexes. Females are at the lower end of the size range, 16 cm to 22 cm (6.3 in to 8.7 in) across the species.

Female brown-headed bullbirds weigh an average of 38.8 grams (1.37 ounces) compared to 49 grams (1.7 ounces) for males.

behavioral difference

During the winter, both male and female brown-headed bullbirds can often be seen foraging in farmland and parks with other species, but in the spring their behavior can change considerably.

Males become more vocal as they try to attract a mate, while females are harder to spot because they are invisible in the vegetation, looking for potential host nests where they can successfully lay eggs.

Male on the left, female on the right, brown-headed bullbird

call and sing

Only male brown-headed bullbirds sing, although females do respond to the male’s song with a series of calls known as chatter.

This call is often heard during courtship, with male brown-headed bullbirds attracted by the flowing notes. Females also make short clicks when feeding.

nesting and feeding

Unlike most birds, brown-headed bullbirds do not build nests or raise their own young. Instead, they lay their eggs in nests built by other breeding birds, and their offspring are then raised by unsuspecting host birds.

During the breeding season, the female brown-headed bullbird spends a long time looking for a viable nest where she can lay her eggs. They will seek out actively laying birds and take the opportunity to approach their nests briefly unattended.

Cowbirds then usually break, damage or remove one or more eggs, then lay one or more of their own eggs in their location, and leave the location without the resident birds knowing that the eggs they are hatching are no longer theirs of their own.

Female brown-headed bullbirds repeat this process up to 40 times in a season, acting alone rather than in the company of males in their deceitful behavior.

Female brown-headed bullbird foraging on the ground

As hatching progresses, females may return to the nest where they laid their eggs. While some birds may continue to hatch one or more cowbird eggs without knowing it is not their own, others may instinctively realize that their nest has been infiltrated by opportunistic cowbirds and will not belong to them eggs pop out of the nest.

In such cases, “mafia behavior” may be observed, where the female brown-headed bullbird retaliates and destroys the entire nest from which her own eggs were ejected.

Both male and female brown-headed cowbirds feed on grains, seeds, and insects, including beetles, grasshoppers, and flying insects.

During the breeding season, females have been observed to increase their insect intake and also eat more snail shells and egg shells from their host’s nests in order to generate enough calcium to meet their own intense spawning needs.

Birds similar to the female brown-headed bullthrush

The female brown-headed oxrobin is very similar in size and appearance to the female shiny oxrobin, but on closer inspection the bill is longer and wider. Bronze-headed bullbird females are also easily confused with female brown-headed bullbirds, but the former’s eyes are reddish-brown and the mouth is wider and slightly darker gray-brown than the female brown-headed bullbird.

A close-up shot of a pair of brown-headed bullbirds perched together on a branch

Can a female brown-headed bullbird raise her young alone?

Female brown-headed bullbirds are parasites and do not play any active role in raising their own or other birds’ young. When they lay their eggs in the host bird’s nest, their relationship with their offspring ends. There are no extant records of brown-headed bullbirds building nests or raising young.

Are female brown cowcocks territorial?

Because cowbirds do not build nests or establish their own territories, they are not classified as territorial birds in the traditional sense, and are often seen foraging in mixed-grazing flocks with other species.

Males will defend their mates from other males, using song to assert their status over competing males, while females may display mild aggression when they hear the chatter of nearby females.

Close-up of a female brown-headed bullbird perched on a tree

common problem

What color is the female brown-headed bullbird?

The female brown-headed bullthrush is brown-gray all over, with a dark brown upper body and gray-brown stripes on the chest, abdomen, and lower body.

Can a female brown-headed bullbird sing?

Female brown-headed bullthrushes can be heard emitting rapid chatter in response to the male’s song. Male brown-headed bullbirds rarely hear chatter. Females can also be heard making short clucking noises as they feed.

Can a female brown-headed bullbird sing?

Only male brown-headed bullbirds sing; females vocalize, but their vocalizations are classified as calls rather than songs.