Blue jays are a common backyard bird found throughout much of North America. They are known for their bright blue feathers and loud, rasping calls. But while both male and female blue jays sport the same vibrant blue plumage on their backs and heads, they can be distinguished by subtle differences in their color patterns.
Plumage Differences Between Male and Female Blue Jays
The most noticeable difference between male and female blue jays is in their chest plumage. Adult male blue jays have bright white chests and throats, while females have lighter gray-white underparts. This can be seen clearly when comparing the two side-by-side.
Additionally, male blue jays tend to have brighter, more azure blue feathers on their backs and tails. Female back and tail feathers are often a slightly duller or grayer shade of blue. The blue coloration on a female blue jay may contain more black barring or streaking as well.
When perched, the white or gray-white underside of a blue jay can help identify its sex. But when seen flying overhead, the subtle variations in back and tail plumage color are harder for casual observers to discern.
Beak Color Differences
Another subtle way to distinguish male from female blue jays is by examining their beak color. Adult males tend to have uniformly black beaks. Females, on the other hand, usually have beaks that are part black and part gray-brown.
The black portion of the female’s beak is on the top mandible, while the lower mandible fades to a light horn color. There can be subtle variations, but most female blue jays will show this two-toned bill coloration.
Plumage Variations by Age
Both sexes of blue jays start life with greenish-brown plumage without any blue coloration. The green-brown juvenal (first-year) plumage helps camouflage young, vulnerable blue jays in the trees and bushes.
As they mature, young blue jays gradually molt into their adult blue and white feathers. This process can take one to two years, so intermediate plumages may exist.
The order in which blue jays acquire their mature plumage is:
- Back feathers molt to blue first.
- Then the wings, tail, and head.
- The neck ring appears.
- Finally, the throat and chest transform to white or gray-white.
The white or gray chest and throat coloring is usually the last to fully emerge. So even if a blue jay shows some blue on its back or head, it may still be a subadult if its underside retains green-brown hues.
In addition to physical plumage, there can be subtle behavioral distinctions between male and female blue jays.
Males tend to be slightly more bold, aggressive, and territorial than females toward potential predators or rivals. For example, a male blue jay may vigorously swoop at a cat, hawk or other intruder in its territory.
Females are a bit shyer and tend to rely more on secrecy and hiding nests during breeding season. They also perform all incubation and much of the chick rearing.
However, both sexes of blue jays exhibit a wide range of vocalizations and sometimes band together to mob potential predators. Their behaviors largely overlap across the sexes.
While male and female blue jays may appear identical at first glance, a closer look reveals some subtle physical and behavioral differences between the sexes. Males tend to have cleaner white underparts, brighter blue upperparts, and all-black beaks. Females have more muted gray-blue plumage and two-toned beaks.
Juvenile blue jays lack any blue coloration, gradually acquiring their mature feathers over one to two years. Adult males also tend to be a bit bolder and more aggressive than females.
So with some careful observation, one can distinguish male from female blue jays. But you may need to see them up close or even have them in hand to be completely certain!
|Duller blue with black barring
|Partially black, partially brown
|Very bold and aggressive
|Shy, relies on secrecy
This table summarizes some of the key differences in physical appearance and behavior between male and female blue jays.