Adult: old, mature bird in definitive plumage. It is not possible to know its exact year of birth.
Alula: a group of feathers, usually three, attached at the digital bone, near the wing-bend on upper forewind.
Autumn: in wide sense, period that goes from the end of the moult until December 31.
Breeding plumage: colorful plumage gained by many birds for breeding period, primarily males, through abrasion or in a prebreeding moult.
Carpal: wing feather placed between greater coverts and alula
Cere: bare skin on the base of upper mandible and around nostrils; it’s usually coloured in adult birds and in breeding time.
Complete moult: all feathers of the body, wings and tail are changed.
Crown: upper part of the head.
Eclipse plumage: cryptic, female-like plumage attained by male ducks in summer.
Emargination: a step or abrupt narrowing of the web of a feahter, occuring towards the tip of the outer web of the feather
Eye-ring : a ring of bare, unfeathered skin, around the eye, usually coloured.
First year (1st year): age category referring to the first year of the life of the bird, from hatch until December 31.
First year autumn (1st year autumn): age category referring to the first autumn of the life of the bird, from its postjuvenile moult until December 31.
Flight feathers: the long quills on the wing, primaries, secondaries and tertials.
Grater coverts: wing feathers covering the bases of secondaries
Juvenile: fledged bird wearing the first set of true feathers, but which has not yet moulted any of these feathers.
Lesser coverts: small feathers placed upper wing, near the median coverts
Median coverts: small feathers placed in the middle of the wing, between greater coverts and lesser coverts
Moult: a natural process of renewal of the plumage, whereby the old feathers are shed and new ones grown; moult pattern is very different between species or between different ages in the same species.
Moustachial stripe, moustache: usually narrow stripe, often dark, running from near the base of the lower mandible and along the lower edge of the cheek.
Non-breeding plumage: usually equivalent to adult winter plumage, a more cryptic plumage appearing among species with seasonal plumage changes.
Partial moult: no all feathers of the body, wings or tail are changed; some are retained.
Prebreeding moult: moult taking place late winter, before the breeding period; some species acquire their breeding plumage.
Primaries: the quills growing on the outer wing, the part of the wing outside the wing bend.
Postbreeding moult: moult taking place after breeding period; most of the small birds acquire the adult plumage in their first postbreeding moult.
Postjuvenile moult: first moult where all or part of the juvenile plumage is lost.
Primary coverts: wing feathers covering the bases of primaries
Rectrices: the main tail feathers.
Retained feathers: unmoulted feathers which remain on wings or tail after a moult.
Rump: feathers placed on lower back, nearets the tail
Scapulars: feathers covering the shoulder of birds.
Second year (2nd year): age category referring to the second year of the life of the bird, from January 1 until December 31.
Second year autumn (2nd year autumn): age category referring to the autumn on the second year of the life of the bird, from its second moult until December 31.
Second year spring (2nd year spring): age category referring to the spring on the second year of the life of the bird, from January 1 until its second moult.
Secondaries: the quills growing on the inner wing.
Shaft: the main axis of a feaher where webs grow.
Speculum: distinctive, glossy patch on upper secondaries, often on ducks.
Spring: in wide sense, period that goes from the January 1 until the end of the moult.
Suspended moult: a temporary interruption which is subsequently resumed at the point of interruption; usually due to migration.
Third year (3rd year): age category referring to the third year of the life of the bird, from January 1 until December 31.
Third year autumn (3rd year autumn): age category referring to the autumn on the third year of the life of the bird, from its third moult until December 31.
Third year spring (3rd year spring): age category referring to the spring on the third year of the life of the bird, from January 1 until its third moult.
Tertials: the innermost wing feathers, usually with somewhat different shape and pattern; they are three in small birds.
Undertail coverts: small feathers covering the base of on tail reverse.
Underwing coverts: small feathers covering the base of long feathers on wing reverse
Uppertail coverts: small feathers covering the base of rectrices on tail.
Young: a young bird before acquire the first set of true feathers.
Web: the barbs on each side of the shaft of a bird’s feather
Wing coverts: small feathers covering the wings.