Hummingbirds exhibit a trait known as sexual dimorphism, meaning males and females of the same species display distinct differences in appearance and behavior. Distinguishing between the sexes is often challenging due to the birds’ tiny size and rapid movements. While identification depends on the specific species, several general rules regarding coloration, size, and conduct apply across the family.
Plumage and Coloration Differences
The most immediate and reliable way to differentiate the sexes is by examining their plumage, especially the throat and tail feathers. Male hummingbirds utilize brilliant, iridescent colors for display, a product of structural coloration where microscopic feather structures split light like a prism. This results in the jewel-toned blues, greens, and purples.
The most prominent feature is the gorget, an iridescent throat patch that males use to attract mates and warn off rivals. The gorget’s color changes dramatically based on the angle of light, sometimes appearing intensely bright and at other times looking dull or black. In contrast, female hummingbirds typically possess duller, cryptic coloration, which helps them blend into their surroundings while incubating eggs.
A female’s throat is usually white or pale, sometimes with faint dusky streaking or spotting, and lacks the male’s vibrant gorget. Females often have white tips on their outer tail feathers, a trait typically absent on the solid-colored, dark tails of adult males. This muted coloration is a survival adaptation, allowing the female to stay camouflaged while she attends to the nest, a task the male does not share.
Size and Physical Structure
Beyond color distinctions, males and females also show subtle variations in physical structure, although these are often difficult to use for field identification. Females in many species tend to be slightly larger and heavier than males. This size difference, which can be 15 to 25 percent greater in mass in some species like the Ruby-throated Hummingbird, is likely an adaptation to accommodate the physiological demands of producing and incubating eggs.
Another morphological difference is bill length. In several species, the female has a slightly longer bill than the male. This longer bill allows females to access nectar from deeper or differently structured flowers, potentially reducing feeding competition with males.
Behavioral Indicators
The roles each sex plays in reproduction lead to distinct behavioral patterns that help observers determine a bird’s sex without close visual inspection. Male hummingbirds are known for their intense territoriality, aggressively defending prime food sources like feeders or flower patches from all intruders. This defense often involves loud buzzes and calls, as well as dramatic aerial dive displays performed to attract mates or intimidate rivals.
Conversely, female behavior focuses entirely on the reproductive process after mating, as the male provides no parental care. Observing a hummingbird building a nest, incubating eggs, or feeding nestlings is a definitive indication of a female. She is typically only aggressive when defending the immediate vicinity of her nest, rather than a broad feeding territory.