One bird in each valley? Not quite (5)
I believe the answer is:
eagle
'one bird' is the definition.
(eagle is a type of bird)
'each valley? not quite' is the wordplay.
'each' becomes 'ea' (abbreviation).
'valley?' becomes 'glen' (glen is a kind of valley).
'not quite' means to remove the last letter (most but not all of the word).
'glen' with its final letter taken away is 'gle'.
'ea'+'gle'='EAGLE'
'in' is the link.
(Other definitions for eagle that I've seen before include "Bird with hooked bill and long broad wings" , "Score of two strokes under par for a golf hole" , "may be soaring" , "Flyer" , "Bird of prey; former children's comic" .)