Physical Description
16-20" (41-51 cm). The Common Goldeneye is one of our smaller sea ducks, only slightly larger than the Hooded Merganser. It is a sexually dimorphic species, in which males and females have distinctly different field marks. Both sexes have rather short necks and round bodies, which creates a “chunky” appearance. Their head is decidedly triangularly shaped, sloping down the front and rear. The neck and body are all white and the back and tail are mostly black. The males are distinguished by their glossy green heads, with a prominent round white spot at the base of the bill. Females have chocolate brown heads, and during the breeding season may have a small yellow spot on their bill. In flight, the large white wing patches are highly visible, but more often the Common Goldeneye is identified in flight by the high whistling sounds made by its wings. The species name clangula (CLANG-u-la) is a reference to this phenomenon, which also gave rise to its colloquial name, the “whistler”.
Male juveniles can be mistaken for the Barrow’s Goldeneye, but the ranges of these two ducks don’t usually overlap. The Barrow’s Goldeneye has a steep forehead that resembles a square more than a triangle and males have a crescent shaped rather than round white spot at the base of their bill.
Distribution and Breeding Habitat
Depending on the time of year, the Common Goldeneye can be found around lakes, wetlands, costal bays and streams throughout Canada and the US, except in the extreme south, where their populations are declining. Goldeneye’s are some of the earliest spring migrants, and move into northern New England, Canada and even Eurasia as soon as open waters appear.
Common Goldeneye’s require cavity nest sites on the edge of water, so their breeding habitat is limited to aquatic areas with dead trees, but they are not particular about forest types and can be found in boreal, deciduous, aspen and montane woods. Like mergansers, they favor calm, clear lakes without much vegetation or fish, but differ in that they will inhabit large lakes, especially those with lots of shoreline.
Diet
Unlike other sea ducks, Goldeneyes are both accomplished divers and fliers. They can achieve speeds of 50 miles an hour in the air and dive down to a depth of 20 feet, where they can remain submerged for approximately half a minute. While underwater, Goldeneyes overturn loose stones in their search for crustaceans (crabs, crayfish and amphipods) which constitutes about ¾ of their diet. The remainder of their diet includes small fish, and aquatic plant foods, like pondweed seeds and tubers. Ducklings feed mainly on dragonfly and damselfly larva. Interestingly, Goldeneye’s are one of the few birds that have benefited from lake acidification, which tends to reduce the amounts of emergent or submersed vegetation and zooplankton in lakes.
The zebra mussel is an invasive crustacean that is currently overtaking many northern lakes and threatens dozens of native clam and fish species. Fortunately, Goldeneyes are known to feed heavily on mussels, and although conclusive studies are still lacking, there are indications that this sea duck may help with efforts to control the expansion of destructive zebra mussel populations.
Pair Formation and Territoriality
Elaborate courtship behaviors usually begin in December and paired birds often arrive together at the beginning of the breeding season. The males display a number of amazing snapping head-throw movements with complex nodding and ducking, while females may lie prone, stretched out and floating in the water for up to 15 minutes. Like mergansers, the hens (females) exhibit strong homing instincts or philopatry, returning to the same nest areas and sometimes even the same nest cavity each year. Occasionally, the common Goldeneye pairs may reunite for more than a single breeding season, but this is uncommon and usually hens mate with a different drake (male bird) each year. First breeding occurs after ducks have reached two years of age or more.
It has now been established that drakes defend a fixed breeding territory that can vary dramatically in size depending on the proximity to other breeding pairs of Goldeneyes and closely related birds, such as buffleheads. The home territory includes the nest site and adjacent water areas where the pair feeds and preens. Nesting begins during March or April, depending on the latitude, elevation and dates of ice breakup.
Nesting Behavior
Nest Building: The common Goldeneye favors large, mature trees containing cavities; this seems to be the only requirement, as females will use live or dead trees of almost any tree species. Although cavities close to the water are preferred, they may be located up to ¾ of mile away. All types of cavities are used, including old Pileated Woodpecker holes, hollow tops of standing trees (chimneys) as well as those formed by broken tree limbs. Nests have been found up to 30 feet from the ground, but can be built at any height in between. Nesting sites (including boxes) that have been used before are highly preferred. Boxes lined with wood shavings and located at least 20 feet off the ground are ideal. Nests are usually lined with material from the cavity and down feathers from the female’s chest.
Competition for optimal habitats can be high, especially in areas where older, rotting trees have been cut down. The availability of cavities is often the chief limiting factor for Goldeneye breeding abundance. Although the ranges of wood ducks, buffleheads and mergansers don’t always overlap with Goldeneyes, these ducks all require nesting cavities and can become an issue. In areas with wood ducks, Goldeneyes are even known to invade occupied wood duck nests. Unlike wood ducks, which are known for their perching abilities, Goldeneyes rarely perch on tree limbs and instead, sit at the entrance of their nest cavity.
Egg Laying: Females lay 1 egg every other day, usually in the morning or late afternoon. The egg laying period last for about 14 days, and during this time, the female will visit the nest 2-3 times without laying. The smooth eggs are bluish green or olive and slightly glossy. Hens that have had previous breeding experience often lay slightly larger and heavier eggs. Miraculously, even eggs that are cracked from freezing can still hatch, which is fortunate for a duck that begins to nest when snow and ice may still be present. Common threats include northern flickers, European starlings, raccoons, red squirrels, minks and black bears that prey upon the nest; losses of up to a quarter of the brood are common.
Dump nesting, or the practice of laying one’s eggs in another nest is prevalent among Goldeneyes, and may occur more frequently in nesting areas that offer fewer tree cavities. Average clutch size is 7, and the female will accommodate the addition of eggs to her nest, in turn reducing the size of her own clutch. However, the hen may abandon the nest if a total of more than 7 eggs are added, and these eggs will never have an opportunity to hatch. This practice is believed to increase the overall genetic fitness of a species, by increasing the flow of genes through the population.
Incubation: Females spend 50-75 % of the day on the nest during laying, increasing the amount of time as the clutch nears completion. Only females are involved with incubation, which lasts from 28-32 days. After 1-2 weeks of incubation, the males abandon the nesting females and disperse to lakes on molt migrations. Because drakes need to replace their feathers at this time of year, they travel to protected areas where they can safely molt (molting leaves ducks flightless for up to 5 weeks).
Nest defense increases through incubation, with females performing Broken-wing distraction displays when flushed during the last 6 days of incubation. Females may desert the clutch if disturbed early on, but this may vary depending on conditioning. Second clutches are rare. Females are also known to defecate on eggs if flushed.
Nestling Care: The most vulnerable period for many ducks is the period between hatching and entering the water for the first time. To aid in the transition, eggs hatch synchronously, with all eggs hatching within a 12 hour period. The young are born precocial, or highly developed; they are born with their eyes open and covered with black and white down. Nestlings remain in the nest for less than 36 hours, after which the hen cajoles them to make the jump down from the nest. Even though the fall may be rapid and from high elevations, deaths are rare as birds are still mostly composed of soft cartilage. Once on the ground, nestlings follow the female to the brood territory (lake, river, pond).
The hen cares for the young until they can fly, usually 56-65 days. She may be seen swimming through the water with young on her back, and may even lead young to water sources with larger populations of invertebrates, the primary food of ducklings. Mortality of young is fairly high, especially in areas with heavy hunting pressure.
Winter Movement and Dispersal
Goldeneyes are often seen as a harbinger of winter, as they’re the last birds to leave in the fall, staying until ice precludes them from the water. Even then, birds will often only move as far as they need to in order to find open water. High concentrations are found in coastal bays and can be seen along shore lines from Alaska to Baja California. Birds in mild climates in which the waters do not freeze may not migrate at all.
The ecology of Common Goldeneyes during the period from fledging to first breeding is virtually unknown. We do know that juveniles tend to fly farthest south, while drakes tend to winter farthest north. Hens seem to favor areas in between, but there is certainly a fair amount of overlap.