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Prenuptial moulting occurs in red-collared widowbirds where the males replace their nonbreeding plumage with breeding plumage. It is thought that large birds can advance the moult of severely damaged feathers. [7] Determining the process birds go through during moult can be useful in understanding breeding, migration and foraging strategies. [8]
Moulting starts from late January and the dark upper surfaces fade to mid-brown quickly. [2] The colour of birds close to moulting (February to April) is pale rusty brown and they appear ragged at this stage. [3] Their voice is unusual and disjointed: ka-hek-ka-hek-ka-hek and usually made in flight.
The eye of a bird is larger compared to the size of the animal than for any other group of animals, although much of it is concealed in its skull. The ostrich has the largest eye of any land vertebrate, with an axial length of 50 mm (2.0 in), twice that of the human eye. [1] Bird eye size is broadly related to body mass.
It has pale legs and a stripe of yellow over each eye. It is around 4 – 4.9 inches long (11 – 12.5 cm) and weighs .25 – .53 ounces. ... unlike most birds that molt once a year. They molt ...
In Europe and Asia, juveniles have pale-yellow eyes while adults typically develop orange-colored eyes, though some may have only brighter yellow or occasionally ochre or brownish eye color. [3] [12] Moulting starts between late March and late May, the male tends to moult later and faster than the female. Moulting results in the female being ...
It has a thin dark pointed bill and a small rounded black tail. After the post-breeding moult, the face is white with a dark spur behind the eye, and there are often dark streaks on the flanks. [14] Birds of the subspecies U. a. albionis are dark brown rather than black, most obviously so in colonies in southern Britain. The legs and the bill ...
Bird ringing is the term used in the UK and in some other parts of Europe, while the term bird banding is more often used in the U.S. and Australia. [49] bird strike The impact of a bird or birds with an airplane in flight. [50] body down The layer of small, fluffy down feathers that lie underneath the outer contour feathers on a bird's body. [51]
Diagram showing the position of the pecten oculi within a bird eye. The pecten or pecten oculi is a comb-like structure of blood vessels belonging to the choroid in the eye of a bird. It is a non-sensory, pigmented structure that projects into the vitreous humor from the point where the optic nerve enters the eyeball. [1]