Chickens!

Czech Republic
Protection of Nature - Rare Animals
April 23, 1998
Two se-tenant pairs, one pair shows Grey Partridge (Perdix perdix) and Black Grouse (Lyrurus tetrix).

Jersey
Jersey Wildlife Preservation Trust
March 12, 1971
One of the four stamps shows White-eared Pheasant (Crossoptilon crossoptilon).

United States
Ring-Necked Pheasant
July 31, 1998
The Ring-necked pheasant (Phasianus colchicus) was introduced into North America from Asia and is established over much of the continent, especially in agricultural lands. The male (shown in the stamp) has a red eye patch, brilliant green head, and (usually) white neck ring and body patterned in soft brown and iridescent russet. The female is a mottled, sandy brown with a shorter tail.

Bulgaria
Fauna
November 25, 1993
Set of six, one stamp depicts Common Pheasant (Phasianus colchicus).

Poland
Game Birds
February 28, 1970
Common Pheasant (Phasianus colchicus)
Black Grouse (Tetrao tetrix)
Gray Partridge (Perdix perdix)
Western Capercaillie (Tetrao urogallus)

Norway
Wildlife in Norway
January 2, 2009
Grouse (Tetraoninae)

Estonia
Bird of the Year
April 3, 2008
Black Grouse (Tetrao tetrix)
The black grouse is a large game bird in the grouse family. It is closely related to the Caucasian grouse.

Canada
Birds of Canada
July 12, 2016
Set of five, one stamp shows a sharp-tailed grouse (Tympanuchus phasianellus).

Sweden
Domestic Animals
January 2, 1995
Set of three, one stamp depicts Swedish Bantam (Gallus gallus domesticus).
(Engraver: Lars Sjööblom)

Cover from 1962 from "Hy-Line Chicks"

United States
Definitive Issue
April 29, 1988
The ring-necked pheasant is the official state bird of South Dakota.
(designer: Chuck Ripper)

The new Lunar Year is a year of the rooster - what better roosters than those of France to start off with. Since this is a thread for real birds, I chose the collection of 2015.

Serbia
Children's Stamps - Fables
November 17, 2014
Set of four, one stamp shows The Cock and the Jewel, a fable attributed to ancient Greek story teller Aesop (620 - 564 B.C.).

Indonesia
Provincial Fauna and Flora
November 6, 2009
East Java Province: Red Junglefowl (Gallus gallus) and Tuberose (Polyanthes tuberosa)

Japan 2016 Welcoming the Year of the Rooster.