There are several groups of birds that are famous for being tricky to ID — gulls, shorebirds, and fall warblers are usually the first to come to mind. In the late summer, another group can often be added to the list — ducks. While this group in the winter and spring can be an easy group to tackle — males are often very distinctive from other species, they are also usually seen in groups, meaning you aren’t just relying on the females to come to an ID, there’s usually at least one adult male in each group. But after their breeding season, many don’t need their flashy plumage to attract a mate, many will molt into much subtler plumage, similar to a female’s.
Waterfowl are a group that can display extreme color dimorphism between males and females. Female selection has led to many males being brightly colored and patterned. But males only need this flashy plumage to attract a mate, at other times of the year, it serves no true purpose and can bring unwanted attention from predators. These conflicting requirements have led many male waterfowl to have evolved to molt into what is considered eclipse plumage.
Eclipse plumage is a transitional molt that most male dabbling and diving ducks undergo in late summer, temporarily replacing their bright breeding plumage with something far more cryptic and female-like.
Breeding season is over by early summer, and male ducks have very little need to be so good looking anymore. What they do need, is to survive their next molt. During this period, waterfowl replace their flight feathers all at once — not gradually like most birds — which means they’re temporarily flightless and extremely vulnerable to predators. Drab plumage becomes a survival advantage, allowing them to be less obvious to predators when they are most vulnerable.
Eclipse males are tricky, but not impossible to identify with the right images in mind. A few things to look for:
• Bill color is the first clue to look for. Even in full eclipse, a male Mallard keeps his yellow-green bill — the female’s is orange and black. This clue applies to pretty much all of the species that have an eclipse plumage.
•Look for traces. Many males will show ghost remnants of their breeding colors — a slightly warmer breast, a few glossy head feathers
•Eye color: In several species of ducks, males have brightly colored eyes, while females will have brown eyes. Even when these species are in eclipse plumage, males will keep their eye color.
What you’re seeing during eclipse is actually the result of two overlapping molt cycles happening at once. Male ducks undergo what’s called a prebasic molt in late summer — the full replacement of body feathers — followed quickly by a prealternate molt in fall and early winter that restores their breeding plumage in time for courtship.
Female ducks go through a simpler cycle, molting once after breeding season without the dramatic color change.
If you want to see eclipse plumage for yourself, it will soon be time to be checking all your local watering holes. July through September, late Summer to early Fall, is prime time. Head to any wetland, retention pond, or lake where ducks linger year-round. Mallards are the most accessible study subject, but many other duck species display an eclipse plumage, including:
Dabbling Ducks
•Mallard — Males look ratty starting in late June; July and August are peak eclipse season, with birds retaining a yellow bill as a key ID clue.
•Wood Duck — Males shed their bright colors and shiny body feathers for subdued grays and browns; retaining a red bill and red eye as giveaways.
•Gadwall — Eclipse males resemble females but retain the distinctive white wing patch.
•Northern Pintail — Eclipse males resemble females but usually keep longer gray tertials and a well-marked speculum.
•Blue-winged Teal — In eclipse plumage, males look similar to females but retain a darker bill and traces of the white facial crescent.
•Cinnamon Teal — Males molt to dull brown, female-like plumage; the pale blue forewing remains
•Green-winged Teal — In eclipse, males look nearly identical to a female.
•American Wigeon — Males lose their chestnut and white tones, becoming dull brown while retaining some gray and the pale bill.
•Northern Shoveler — Males molt from bold chestnut and green into mottled brown, though the large spatulate bill remains distinctive.
Diving Ducks
•Canvasback — Males lose the rich chestnut head, molting to a duller rusty-brown.
•Redhead — Males become dull brownish.
•Ring-necked Duck — Males adopt duller, browner tones resembling females.
•Lesser Scaup — Males become brownish with less contrast.
•Greater Scaup — Similar to Lesser Scaup in eclipse.
•Bufflehead — Males lose much of the white head patch, becoming drabber with reduced iridescence.
•Harlequin Duck — Males molt to dark sooty-brown with faint remnants of white facial spots.
•Long-tailed Duck — Undergoes one of the most complex molt cycles of any duck, with eclipse plumage involving significant darkening of head and body.
•Ruddy Duck — Males molt into a drab-brown, similar to a female, but with a more defined cap, and a whiter cheek that lacks the lines through it.
Sea Ducks
•Common Eider — Males become brown and mottled, losing the distinctive black-and-white breeding pattern.
•King Eider — Males lose the colorful bill shield and orange head, becoming dark brownish.
Mergansers
•Hooded Merganser — Males lose their hoods; the all-black bill and yellow eye remain useful ID features.
•Common Merganser — Males swap their green heads and stark white bodies for simpler brown and gray plumage.
•Red-breasted Merganser — Males lose the dark green head and spiky crest, becoming brown-headed.
While this group of birds is harder to ID this time of year, it also accentuates the need to be able to ID female birds. If you have them down, and know how to ID female waterfowl, you will have no problem picking out the males who are in their eclipse plumage, and vice versa.
Birding Academy News
New: I will be adding new species mastery mini-courses, each new course will be introduced as a Bird of the Week at the end of each weekly newsletter.
So our first Bird of the Week is:
The American Robin
The American Robin (Turdus migratorius) is a member of the family Turdidae and the largest thrush native to North America, with a range spanning from Alaska and northern Canada south through Mexico and into Guatemala. Adults are sexually dimorphic: males display a deep rufous-orange breast, slate-gray upper side, and a nearly black head, while females are paler and less contrasting overall. The species occupies a remarkably broad ecological niche, utilizing open woodlands, forest edges, suburban landscapes, and alpine meadows across its range. The American Robin is an opportunistic omnivore, shifting seasonally between invertebrate prey — primarily earthworms and beetle larvae obtained through ground foraging — and fruiting plants, with fruit composing the majority of their winter diet. Migration in this species is partial, traveling in flocks short distances in search of food, often with year-round presence of wintering flocks in areas with abundant mast and berry crops. Five subspecies are currently recognized, showing variation in size and plumage saturation across the geographic range.
Check out my birding course membership at:
Www.thebirdingacademy.com