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Owls have very large eyes for their size, 2.2 times greater than the average for birds of the same weight, [14] and positioned at the front of the head. The eyes have a field overlap of 50–70%, giving better binocular vision than for diurnal birds of prey (overlap 30–50%). [ 77 ]
Traditionally diners cover their heads with their napkin or a towel while eating the delicacy. The bird is so widely used that its French populations dropped dangerously low, leading to laws restricting its use in 1999. In September 2007, the French government announced its intent to enforce long-ignored laws protecting the bird. [4] [5]
Common goldeneyes are diving birds that forage under water. Year-round, about 32% of their prey is crustaceans, 28% is aquatic insects and 10% is molluscs. [15] 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.
The common grackle (Quiscalus quiscula) is a species of large icterid bird found in large numbers through much of North America. First described in 1758 by Carl Linnaeus, the common grackle has three subspecies. Adult common grackles have a long and dark bill, pale yellow eyes, and a long tail.
The feathers making up this disc can be adjusted to sharply focus sounds from varying distances onto the owls' asymmetrically placed ear cavities. Most birds of prey have eyes on the sides of their heads, but the stereoscopic nature of the owl's forward-facing eyes permits the greater sense of depth perception necessary for low-light hunting.
Eyes of most birds are large, not very round and capable of only limited movement in the orbits, [78] typically 10–20°. [123] Birds with eyes on the sides of their heads have a wide visual field, while birds with eyes on the front of their heads, such as owls, have binocular vision and can estimate the depth of field.
The head is white with a dark mask across the eyes, reaching to the sides of the neck. [29] The irises of the eyes are golden to brown, and the transparent nictitating membrane is pale blue. The bill is black, with a blue cere , and the feet are white with black talons. [ 26 ]
Barrow's goldeneye (Bucephala islandica) is a medium-sized sea duck of the genus Bucephala, the goldeneyes.This bird was named after Sir John Barrow.The genus name is derived from Ancient Greek boukephalos, "bullheaded", from bous, "bull" and kephale, "head", a reference to the bulbous head shape of the bufflehead.