See nidicolous.

When a species' breeding population or range has declined by 25 to 50% in the last 25 years, has recovered from a historical decline, is a rare breeder, or is of either European or international importance, it is placed on the amber list of Birds of Conservation Concern. The list was revised in 2002 by a number of conservation organisations.

Parts of the bird have specific names that can help in identifying birds. See diagrams.

The charts show the maximum number of any one species visiting the garden at any one time in a particular week. This method of counting is used in the Garden Birdwatch survey.

Eclipse plumage describes the plumage of drake wild fowl in the autumn when they have shed their wing feathers. The usual spectacularly bright plumage would put them at risk from predators, so they moult to a drabber plumage (similar to the female) which offers better camouflage and more protection.

The time when a chick is getting its first set of proper feathers.

A young bird that has learnt to fly. This is often mistakenly used to mean a nestling, but many birds learn to fly while still dependent on their parents.

A High BTO Alert is issued for birds that have seriously declined in numbers. For example perhaps because of the loss of habitat, or other possibly unknown reasons. See also red list species. The list was compiled in 1999.

This is a bird species of the hirundinidae family and is often used by birders to describe mixed groups of Swallows and martins. Swifts are not hirundines.

An immature bird is a juvenile that has undergone its first moult but does not yet have full adult plumage.