Although quantitatively outnumbered by mammals, birds are the most diverse class of prey in the golden eagle's diet, as more than 200 species have been identified at eagle nests. Little analysis has gone into how regularly golden eagles will attack the nestling and fledglings of other birds, although it has been interpreted that this behavior is not uncommon. Nestling-aged rock pigeons (Columba livia) have been observed as prey in golden eagle nests. The first record of a golden eagle eating eggs was recorded when a golden eagle was observed consuming Canada goose (Branta canadensis) eggs in eastern Idaho. After galliforms, the next most significant group of prey among birds is the corvid family, making up 4.1% of the diet from around the range. Most prevalent among these are magpies and the large-bodied Corvus (crow and raven) genus. On Santa Rosa and Santa Cruz Islands in California, common raven became the most common prey species after feral pigs were eradicated from the latter, making up 24% of a 454 sample size from 14 nests. The raven was also the most prevalent bird prey in central Arizona, in a sampling of 1154 from 119 nests. The black-billed magpie (Pica hudsonia) was an important prey item in Washington state, making up 9.7% of the remains there, and was the most significant avian prey in Montana. In 10 studies in Europe, corvids made up more than 5% of the prey remains, usually represented by carrion crows/hooded crows (Corvus corone/cornix), rooks (Corvus frugilegus), Alpine chough (Pyrrhocorax graculus), ravens or Eurasian magpies (Pica pica). Smaller species such as jays and nutcrackers only occasionally turn up as prey, mainly in North America, though the Eurasian jay (Garrulus glandarius) has also been known as prey. The next best represented family of birds are the waterfowl, making up approximately 1.4% of the golden eagle's breeding season diet. Waterfowl of all sizes from green-winged teal (Anas crecca) to trumpeter swans (Cygnus buccinator), tundra swans (Cygnus columbianus) and mute swans (Cygnus olor) have been successfully hunted by golden eagles. Full-grown swans can weigh well over and are probably the largest birds habitually hunted by golden eagles. Moderately sized species, including larger Anas ducks such as mallards (Anas platyrhynchos) and geese such as bean goose (Anser fabalis) are perhaps most often recorded. Waterfowl are mostly recorded during the nesting season in Northern Europe, comprising 15.4% of prey in Gotland and 14.4% of prey in Belarus. In some years at Malheur-Harney Lakes Basin in Oregon, Anas ducks can make up to 20% of the prey consumed by the locally nesting eagles. Mostly in the United States, wintering golden eagles may become habitually predators of wintering and migrating groups of waterfowl, with species such as Canada geese, cackling geese (Branta hutchinsii), snow geese (Chen caerulescens), and Ross's geese (Chen rossii). Since geese are found in large concentration when seasonal conditions require it, these species can be hunted with relative ease. Waterfowl are typically hunted using the contour flight with short glide attack technique, in order to surprise the prey before it can take flight or dive. In one case, a golden eagle was able to capture a mallard as it took off in flight. Other water birds are generally less frequent prey but may become regular in the diet in marsh-like northern regions and coastal areas. Scotland, being surrounded by coasts and possessing quite a wet climate, often hosts water birds which become prey such as colonies of petrels (largely northern fulmar (Fulmarus glacialis)), making up to 17% of the recorded prey in 26 nests with a 119 sample size in the Outer Hebrides, migrating throngs of sandpipers and plovers (up to 5.9% and 2.8% in 25 nest in the northern Inner Hebrides) and gulls (making up a whopping 23% of prey recorded in 25 nests in the West-Central Highlands). Among shorebirds, usually only larger types such as godwits, curlews, Tringa sp., stone-curlews and oystercatchers turn up as prey as smaller species are probably too flighty and agile to catch. Eurasian cranes (Grus grus) are regularly predated in Northern Europe, turning up at 6.8% of nests in Estonia and 5.8% of nests in southern Finland. Hooded cranes (Grus monacha) are reportedly prey for golden eagles in China. Demoiselle cranes (Anthropoides virgo) have been caught in mid-air as they migrate over the Himalayas and both sandhill (Grus canadensis) and whooping cranes (Grus americana) may be hunted in North America. The last known breeding pair of golden eagles in Maine (which did not return after 1999) were reported to hunt an unusually large number of herons, specifically great blue herons (Ardea herodias) and American bitterns (Botaurus lentiginosus). Elsewhere, herons are basically negligible in the diet. Other water birds recorded as prey include cormorants (up to 8.6% of the recorded prey in Santa Rosa and Santa Cruz Islands), auks, grebes and loons.