The Common Goldeneye  is a medium sized sea duck. Their closest relative is the similar Barrow's goldeneye.  Adult males ranges from 45-52 cm (18-21 inches) and from 888 to 1400 grams (1.9 to 3.1 lbs), while females range from 40-50 cm (16-20 inches) and from 500 to 1182 grams (1.1 to 2.6 lbs). The species is aptly named for its golden-yellow eye. Adult males have a dark head with a greenish gloss and a circular white patch below the eye, a dark back and a white neck and belly. Adult females have a brown head and a mostly grey body.  Their breeding habitat is the taiga. They are found in the lakes and rivers of boreal forests across Canada and the northern United States, Scandinavia and northern Russia . They are migratory and most winter in protected coastal waters or open inland waters at more temperate latitudes. Naturally, they nest in cavities in large trees. They will readily use nestboxes, and this has enabled a healthy breeding population to establish in Scotland where they are increasing and slowly spreading with the help of nestboxes. They are usually quite common in winter around lakes of Britain and some are being encouraged to nest in nestboxes which are put up to try and have them there all year round.  Often the natural tree cavities are made by broken limbs, unless they are made by pileated woodpeckers or black woodpeckers, the only tree-cavity-making animals who make a cavity large enough to normally accommodate a goldeneye. Average egg size is a breadth of 43.3 mm (1.7 inches), a length of 59.3 mm (2.3 inches) and a weight of 64 grams (2.3 oz). The incubation period ranges from 28 to 32 days. The female does all the incubating and is abandoned by the male about 1 to 2 weeks into incubation. The young remain in the nest for about 24-36 hours. Brood parasitism is quite common both with other common goldenyes as well as other duck species and even tree swallow and European starling eggs have been found mixed with goldeneye eggs! The broods commonly start to mix with other females' broods as they become more independent. Goldeneye young have been known to be competitively killed by other goldeneye mothers, common loonsred-necked grebes. The young are capable of flight at 55-65 days of age.  These diving birds forage underwater. Year-round, about 32% of their prey is crustaceans, 28% is aquatic insects and 10% is molluscs. Insects are the predominant prey while nesting and crustaceans are the predominant prey during migration and winter. Locally, fish eggs and aquatic plants can be important foods. They themselves may fall prey to various hawks, owlseagles, while females and their broods have been preyed upon by bears, various weasels, mink, raccoons and even northern flickers and red squirrels.  Approximately 188,300 common goldeneyes were killed by duck hunters in North America during the 1970s, representing about 4% of the total number of ducks killed in the region during that period. The rate is probably similar today. Both the breeding and winter habitat of these birds has been degraded by clearance and pollution. However, this is the only duck in North America known to derive short-term benefits from lake acidification. They Range all across the northern United States, Europe, and Asia.  Drakes plumage is a distinct black and white pattern.  Loud whistling produced by the wings while flying is characteristic of this species.  Green sheen to head with circular spot near bill identifies it compared to the male Barrow's Goldeneye; females are similar.  Nests in tree holes and duck boxes.
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Bufflehead

The Bufflehead is a small African sea duck.  They range from 32-40 cm long (12.5-16 inches) and 270-550 grams (9.5 oz.-1.2 lbs), with the drakes larger than the females. Averaging 35.5 cm (14 inches) and 370 grams (13 oz), they rival the Green-winged Teal as the smallest American duck.  Adult males have a dark head with a large white cap behind the eye and a mainly white body with a black back. Adult females have a brown head with a smaller white patch behind the eye and a mainly brown body.  The name Bufflehead is a combination of buffalo and head, referring to the oddly bulbous head shape of the species.  They are migratory and most winter in protected coastal waters or open inland waters on the east and west coasts of North America and the southern United States. Bufflehead is an extremely rare vagrant to western Europe.  Their breeding habitat is wooded lakes and ponds in Alaska and Canada, almost entirely included in the boreal forest or taiga habitat. They nest in cavities in trees, often using old Flicker or Pileated Woodpecker nests, occasionally 425 meters (1400 feet) from water. Mountain Bluebird, Tree Swallow, Northern Flicker, and European Starling are nest site competitors and there was recorded instance of a female Barrow's Goldeneye killing a Bufflehead adult female and her brood. Smaller cavities are preferred to less competition with larger goldeneyes. A clutch may range from 5 to 10 eggs. Eggs are typically about 36.3 mm (1.4 inches) in breadth and 50.6 mm (2 inches) in length, weighing about 37.4 grams (1.3 oz) on average. The incubation period ranges from 28 to 33 days, during which the female is quite attentive. Locally, the clutch survival rate may range from 45% to 5% based on factors like cold weather, rain, competitors (i.e. grebes or other ducks) or predators (like Northern Pike). The female abandons the nest after 5 to 6 weeks, and the young fledge at 45 to 55 days of age.  These diving birds forage underwater. On freshwater they eat mostly insects and, on saltwater, they feed on predominantly crustaceans and molluscs. Aquatic plants and fish eggs often become locally important food items as well.  Buffleheads do not tend to collect in large flocks; groups are usually limited to small numbers (less than 10).  About 70,000+ Buffleheads are killed yearly by duck hunters, which is probably overkill, but this only comprises about 1% to 2% of waterfowl-hunting in North America. Besides duck-hunting, habitat clearance is the other major threat to this bird, with extensive logging occurring in the boreal forests. Although Buffleheads do use man-made nest boxes, they still need the forest habitat. They Range across northern North America.  Much smaller than the other two species of Goldeneyes.  Short neck with small bill and a head puffed out to almost twice its normal size (hence the original name of Buffalo- Head).  No whistling wings like the other goldeneyes.  Very active and restless.  Nests in tree holes and duck boxes.