There were two sets of the Gamebird Series Prints with stamps.  These are still open editions. 

The current value of each print is around $50.00. 

A Likely Refuge	1981
Coming Together	1985
Nary A Care	1986
Lifting To The North	1987

Outfoxed	1988
Leaving Home	1989
Family Affair	1990
Come Rain Or Shine	1991