Identification of the Female Eastern Bluebird

While the striking deep blue and brick-red plumage of a male eastern bluebird is unmistakable, the female’s plumage is likely to be confused with other gray or brown birds. Some observers say that the female eastern bluebird is a dull or a  bluish-gray version of the male. 

What does the Eastern bluebird female look like? From a distance, the female bluebird looks gray above and brownish below. A closer look reveals a gray with a bluish tinge on the back and blue feathers in the wings and tail. The throat, sides of the neck, and breast are rich-brown. The center and lower belly are whitish.

More details are below:

Female bluebird facing away

  • The top of the head and back are bluish-gray.
  • Most of the folded wing looks bluish-gray except for the blue primary wing feathers and the shoulders and primary wing coverts.
  • The tail is blue. Photo: Rick from Alabama.

Female bluebird from the side

  • The sides of the neck, throat, breast, and flanks are warm brown.
  • The center of the belly is white.
  • The side position clearly shows the blue primary wing feathers and blue wing coverts. Photo: Frank.

How can you identify a female bluebird from a male? 

Identifying a female eastern bluebird is relatively easy when she is next to a male. A female by herself requires paying attention to key details.

The main difference between a female and male eastern bluebird is the color intensity. Males have a bright deep blue top of the head, back, wings, and tail. The throat, sides of the neck, breast, and upper belly are brick-red. The center of the belly is white.

Male (right) and female (left) eastern bluebird. Photo: Patricia Pierce.

Female bluebirds exhibit a similar color pattern, but colors are subdued. The top of the head and back are gray to bluish-gray, rather than the deep blue of the male. The throat, sides of the neck, breast, upper belly, and flanks are warm brown. The shoulders, primary wing feathers (noticeable in folded wings), and tail are blue.

Eastern bluebirds of both sexes are about the same size, with females being slightly heavier. This difference may not be noticeable in the field in most birds. 

Eastern Bluebird weightMaleFemale
Range 28-31 g29-32 g
Average 29.5 g30.5 g
Average 1.04  oz1.07 oz

How to identify a nestling female bluebird from a male?

Benedict Pinkowsky (1974c) monitored and studied 184 nestling eastern bluebirds over the course of several years.

It was known that nestling male and female bluebirds have different plumages. Pinkowsly found that though feather colors can be distinguished by day 10, by day 13, females can safely be told from males based on plumage.

Two 13-day old eastern bluebird nestling. The male (left) shows blue tail feathers while the female (right) shows a gray tail with whitish margins on the outer tail feathers. While not visible in this photo, males also have blue on their wings.

The main differences in plumage between nestling females and males are as follows:

  • Nestling females’ primary wing feathers and wing coverts are gray, while the males’ are blue.
  • Pinkowsky suggest that the back of a nestling female is lighter gray with whitish spots larger than those on a male. However, this photo appears not to support Pinkowsky’s findings as the nestling female here is almost spotless in the back.
  • The tail of a young bluebird female in the nest is perhaps the most telling sign of her sex. Young females have gray tail feathers with a distinct whitish margin, more noticeable on outer feathers. Males have blue tail feathers.

Do female (and male) eastern bluebirds change color in the winter? 

Unlike many other birds that have winter and summer plumages, adult eastern bluebirds, and bluebirds in general, wear the same plumage throughout the year. 

Female and male eastern bluebirds molt their plumage during the end of the summer and the Fall seasons. The fresh plumage in adult birds is brighter than the old one, but the colors and plumage pattern are the same.

Fledglings of the year also acquire their adult plumage during the same periods as the adults. From the gray with whitish dots and streaks, fledgling bluebirds molt into a plumage similar to an adult plumage by the end of the Fall. 

First-year bluebirds with adult plumages reach sexual maturity as early as 8 to 11 months after fledging and are capable of breeding by the following spring and summer after leaving the nest. 

Is there an age-related color variation in bluebirds?

The rather distinctive gray plumage of juvenile eastern bluebirds born in the spring and summer is replaced with the adult plumage by the end of the Fall.

Overall, among adult bluebirds, younger individuals look very similar to older ones.  However, first-year birds, those that have just acquire their adult plumage, are generally duller and more grayish than older individuals. 

After the second year, there is no age-related plumage variation. Bluebirds can be bluer than others due to environmental reasons when they acquire their fresh plumage every year.

female_eastern-bluebird in Mexico
Female eastern bluebird in Mexico. Photo: Nigel Voaden.

Female eastern bluebirds may show color variation in parts of their range

Female eastern bluebirds have warmer colors in the southern part of the species range, namely Mexico and Central America. In contrast to bluish-gray back and top of the head in females in North America, females in Mexico and Central America have reddish-brown breast, back, sides of the neck, and head. 

Despite the general increase of reddish-brown as one goes south, females in some populations in Mexico and Central America can have grayish-blue backs that resemble those in eastern North America.

Eastern bluebirds in Mexico and Central America are primarily resident and may only perform short seasonal movements.

The female and male eastern bluebird plumage has contributed to the their popularity

Eastern Bluebirds are popular due in part to the difference in plumage between females and males. 

Bluebirds are unique in the way they easily distinguish between sexes compared to many other small birds. Even a casual observer can distinguish sexes and tell when a pair is together and what the male and female do. 

Having sexual dimorphism, a term used by ornithologists to indicate that each sex has a different plumage, has also sparked the interest of scientists in bluebirds. 

Studies focusing on behavior, mating systems, breeding, migration, and general ecology become easier when sexes have different plumages. Information gathered in the field can be associated with each sex.  

Bluebirds are noted even in passing by many people, unlike many other birds. If the light conditions are right, bluebirds can display a splash of color. Blue, which is not a common color in nature, is sure to call the attention of many.

People recognize bluebirds by their distinctive looks, but they are even more distinctive among themselves. According to scientists studying bird colors, unlike humans, bluebirds can see ultra-violet light. Studies have shown that bluebird males reflect more strongly in ultraviolet light than females.

References:

  • Pinkowski, Benedict. 1997. Breeding Adaptations in the Eastern Bluebird. C., The Condor, Vol. 79, No. 3, pp. 289-302 (14 pages) Published By: Oxford University Press.

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