The nouns are:
No the word perched is not a noun. It is a past tense verb and also an adjective.
perch noun a thing on which a bird alights or roosts, typically a branch or a horizontal rod or bar in a birdcage.
Yes, bird is a noun, a singular, common, concrete noun.
Yes, the word 'bird' is a noun, a word for a thing.
No, perch is a verb. The chickens perched on the fence. The chickens perched carefully on the fence. - carefully is an adverb.
That bird's eggs. The possessive noun is in bold.
The noun "branch" is a regular plural noun, a noun that forms its plural by adding "s" or "es". The plural form of branch is "branches".The plural possessive form is branches', a regular plural possessive.
The noun 'birds' is the plural form for the singular 'bird', a common, concrete noun; a word for a thing.
The word 'branch' is a count noun; one tree branch, two tree branches; one bank branch, four bank branches; a river branch, several river branches.
Eagle is a kind of bird not a name of bird therefore it's a common noun.
No, it is a noun. If it is used with another noun (e.g. bird cage), it is technically a noun adjunct, not an adjective. (the word bird is also rarely a verb, meaning to go birding.)
A word that is the name of a person, place, or thing is a noun. The thing that flies through the air is a bird. Therefore it is a noun. If you could say, "Let's bird that picture," you would use bird as a verb. Birdie can be a verb eg He birdied the last hole.