Feeding during the day on a wide range of invertebrates, the goldeneye captures its prey on or near to the sea or river bed after a short dive with the wings closed and tail spread. Diving for over 30 seconds to depths of four metres, it forages amongst submerged vegetation and overturns small rocks and stones (8) (9).
The goldeneye breeds from December through to April, beginning with the male bird defending a territory and displaying in groups to attract a mate. This involves a number of displays, with the most distinctive being a ‘head-throw-kick display’, in which the male throws the head back over the body whilst emitting a growling noise and kicking the water out with its feet (3) (8). The nest is typically built 10 to 15 metres off the ground in a tree hole, and is lined with downy feathers from the female bird’s breast (10), although the female goldeneyen often lays its eggs in the nests of another female or even that of another duck species. A clutch of 8 to 11 eggs is laid and incubated by the female for up to 30 days (8). The chicks can already feed themselves when they leave the nest, so the female may abandon the chicks soon after hatching, with the chicks joining those of another female’s brood (10).
After breeding, adult goldeneyes may travel to coastal areas, large lakes or rivers to undergo a flightless period and moult. Large gatherings of birds are common at such locations, with the male birds arriving first, and this moult period may last as long as four weeks. Many populations then undergo a southward migration, beginning in late August, with most birds arriving at the wintering grounds by early December. The female goldeneyes tend to migrate further than the males, while juveniles migrate even further. The goldeneye returns to its breeding grounds from mid-February, with its arrival timed to coincide with the thawing and reappearance of open water (8).