IPA: /ˈbɜrdˌfid/
KK: /bɜrdfid/
Food that is specifically made for birds, usually consisting of different types of seeds.
I filled the feeder with birdfeed to attract more birds to my garden.
Birdfeed is formed from "bird" (from Old English "brid", meaning a young bird or chick) and "feed" (from Old English "fēdan", meaning to provide food). The word "birdfeed" refers to food provided specifically for birds.
Think of a young "bird" that needs "food" — that's what birdfeed is, food for birds.
No commonly confused words.