The story I am looking for involves a little girl who thinks she is hideously ugly. Her foster mother tells her that she is as well. The girl gazes out a window at the gardener who is a perfect specimen of beauty. The twist at the end, is that the girl is human and the others are actually monsters. Another story involved a cruel man who kills his pet bird, then slowly turns into a bird himself. I think this story was called Quid Pro Quo. Any ideas are appreciated.
I believe you're looking for The 5th Fontana Book of Great Horror Stories (1970). The last short story in the anthology is Quid Pro Quo by Mary Danby. The paperback version has a cover that appears to be a half-man, half-bird type of creature:
The other story you describe as part of the anthology may be The Monster by Ronald Chetwynd-Hayes (based on the title), although The Blue Lenses by Daphne du Maurier seems to match some of what you describe.
I believe the first story you mention is one I'm also looking to identify. Does it end with her (step)father admonishing her for admiring the gardener and quoting the "bible" that humans were made in God's image and are covered in hair with a long tail etc.?
I have a feeling that it might be "The Monster" by R. Chetwynd-Hayes. If so it is in an anthology called 65 Great Tales of Horror edited by Mary Danby I shall be checking this out