The size, shape and colour of bird eggs vary widely among species. The wood pigeon is the most frequently seen bird in the United Kingdom, according to a study by the British Trust for Ornithology, followed by the chaffinch, blackbird, wren and robin.
The wood pigeon is mostly grey with a pink-tinged breast. It has a white, green and purple patch on its neck. It builds its nests from twigs in trees or on buildings. The task of incubating the eggs is shared by adults. The wood pigeon's eggs are glossy white and smooth to the touch. They are elliptical in shape and measure 1 1/5 inches by 1 3/5 inches.
The patterned plumage of the chaffinch makes it hard to spot on the ground. It may be recognised in flight by the white outer tail feathers and a flash of white on the wings. A chaffinch nest is cup-shaped and constructed from grass, wool, spiders’ webs, moss and feathers. It is usually found in trees or shrubs. Chaffinch eggs are light blue with purple and brown patches. They are smooth and glossy and measure about 3/5 inch by 4/5 inch.
Blackbirds are easily recognisable due to their black colour and contrasting yellow eye ring and bill. The nest is cup-shaped and messily constructed from twigs, grass and mud. Nests may be found in bushes, hedgerows and sometimes outbuildings. Blackbird eggs are light greenish-blue with reddish-brown spots. They measure around 9/10 inch by 1 1/10 inch and are smooth and glossy.
Wrens are small and flighty with deep brown plumage and a short tail. They construct several ball-shaped nests from grass, leaves and moss. These can be found in banks, trees or walls. The eggs are white with red spots. They are smooth and glossy and measure approximately 1/2 inch by 3/5 inch.
The Robin has a bright orange-red breast. It has olive-brown upper parts and a white belly. Its nest is constructed with moss, hair, wool, grass and leaves and may be found in walls, dead trees or banks. The eggs are matt white or pale blue with reddish-brown spots. They measure approximately 3/5 inch by 4/5 inch and are heavier at one end.