Found on lakes across Canada and the northern U.S., common loons are skilled divers and are not adapted for walking on land, so you’ll probably only ever catch sight of one from the shore, or perhaps from out on the water on a boat or canoe.
Males and females look alike, but certain aspects such as size and behavior will help you to make a confident and positive identification. Read on for tips on how to tell if the common loon you spotted is male or female.
Female common loons look identical to males, but can be more than 25 percent smaller. They share the same red eyes and speckled, glossy black and white plumage. Nest-building and incubation duties are split between the pair, and both are fiercely territorial over their nest, eggs and young.
When spotting a lone common loon, it’s virtually impossible to tell accurately whether that individual is a male or female, with no visual clues or giveaway behavioral traits. When pairs are together, the chance of a positive ID increases, due to the size difference between the larger, heavier male and the smaller, lighter female.
However, some small subtle differences in behavior and habits may be observed that will help guide you to correctly tell whether the expert underwater hunter you’re looking at is a male or a female common loon.
So if you’re interested in learning more, then please enjoy our guide to female loons.
It's virtually impossible to differentiate between male and female loons, with size being the best way, when theres a pair together
The only visual difference between male and female common loons is their size, with males typically around 25 percent heavier and larger than females. They are otherwise identical in coloring and plumage markings.
Both males and females build the nest together, and both sexes incubate eggs and feed young, with no discernible difference between the shares of these tasks taken by males and by females.
Female (left) and male (right) Common Loons with their chick
Loons change appearance during the year, undergoing a full molt at the end of the breeding season. When breeding, female loons have white breasts, black heads, and a mixture of distinctive mottled, speckled and striped black-and-white markings on their necks, backs and wings. The glossy black heads have an iridescent sheen, which looks purplish-blue in some lights. They have black-charcoal bills and bright red eyes.
After breeding has finished, female loons (like males) undergo a full molt, with these bold markings temporarily replaced with a far more drab and nondescript brown-gray plumage.
Their breasts remain white, but a duller, less vibrant shade, and their backs change from their deep glossy black to a washed out shade of dark gray.
In eclipse plumage, the common loon’s bill lightens to a paler shade of gray, and their eyes fade from the piercing red to a more uniform shade of paler brown.
Male and female common loons share the same plumage
Female loons are typically smaller and lighter than males, with around a 25 percent difference in size. No sex-specific data exists for body length or wingspan: adult common loons measure in the range of 66 to 91 cm (26 to 36 in) in length with a wingspan range of 127 cm to 147 cm (4 ft 2 in to 4 ft 10 in), and females will naturally fall at the lower end of this range.
In terms of mass, males also weigh up to 27 percent more than females. From data recorded in 2014, female weights are in the range of 2.7 kg to 6.2 kg (6.0 lb to 13.7 lb) compared to 4.1 kg to 7.6 kg (9.0 lb to 16.8 lb) for males.
Breeding pair of Loons in flight together
Although male and female common loons form long-term pairs, and commonly breed together for several consecutive breeding seasons, they do not remain paired over the winter months, going their separate ways during migration but reuniting on their nesting grounds in spring.
Females arrive at spring breeding grounds several days later than males, so if you’re keeping an eye out for loons early in the season, the first birds you’ll see will probably be males rather than females.
Female and male loons are both highly territorial during the breeding season, attacking any intruders that approach their eggs or young, and both will see off mammals, including beavers, otters, mink and racoons that may venture too close.
A pair of Common Loons engaging in a courtship dance, flapping their wings and splashing water around them
Loons are relatively vocal birds. Only males can make what is known as the ‘yodel’ call, made as a warning when their territory is threatened, and emitted by extending their neck and throat across the water’s surface.
A contact call, known as the ‘tremelo’ and sometimes referred to as the ‘crazy laugh’ is thought to signal agitation or distress, and is made by both males and females. It is also heard in flight, when mixing with other loons, and may serve as a form of communication between pairs to warn of nearby predators.
Soft mewing calls are made between pairs, ahead of copulation or during courtship. A louder fourth call, known as a ‘wail’ is also made as a contact call between a female and a male, or between either parent and young loons.
Pair of common loon in summer, Quebec, Canada
Male common loons arrive on breeding grounds ahead of females, and take this headstart to check out potential nest sites. Final site selection ultimately falls to the male, but nest construction is shared evenly between the pair.
Once eggs have been laid, incubation is divided fairly evenly between the female and the male. Some research indicates that females take a larger share of overnight incubation, and also spend more time incubating than males as hatching approaches.
Parental care after hatching is also divided fairly evenly. Young loons are well-developed when they hatch and take to the water within hours. You may catch sight of young birds hitching a ride on the back of a parent. Some observations show that it’s slightly more common for the ride-giver to be the male loon.
Some minor differences in diet between the sexes have been recorded, with female loons eating a larger proportion of crayfish and other crustaceans than males. According to a 1973 report, of the common loons examined for the study, males were reported to have a diet containing more perch, trout and sucker, while females’ stomachs contained more crayfish and minnows.
Common Loon sat on the nest
Male and female common loons share nesting, incubating, and chick-raising duties reasonably evenly, with males taking the dominant role in site selection, and playing a pivotal role in caring for young while they become more independent.
Threat to nest sites is a significant concern for breeding loons, and the high rate of survival of young is directly related to the joint effort in the entire breeding process.
This means cases where a female loon is left alone to incubate and raise young are not guaranteed to have a successful outcome.
During the breeding season, female common loons are black and white. Their black heads have a glossy purple-green sheen. After the breeding season, common loons undergo a molt, losing their glossy markings.
They become a dull shade of brownish-gray on their backs, heads and wings, with a whitish breast and underparts. Their bills become a lighter gray, and their eyes change from bright red to a less vibrant brown.
Female loons are vocal birds, and their vocalizations include a mewing call, a wail and an alarm call known as a tremelo. A fourth call, known as a ‘yodel’, is only made by male common loons.
Get the latest Birdfacts delivered straight to your inbox
© 2023 - Birdfact. All rights reserved. No part of this site may be reproduced without our written permission.