I often wonder the same thing but feel I'm guilty of transposing my human feelings onto the birds. I felt such anguish when the Bush stone curlew was abandoned by the parents in the scorching hot car park here earlier in the year. I wondered what it was feeling and if it was hungry and if it was lonely.

Just yesterday in my apartment there was a huge bang and I raced outside thinking a palm frond had fallen on something, but it was 2 little black birds (not sure yet what type - I need to look it up) that had flown into the glass railing that surrounds the patio above. They both fell stunned onto my patio.
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One couldn't move at all. The other kept trying to fly but kept flying into my glass doors and back into the glass surround of the patio.

Once I realized they were in dire trouble and trapped in a small area between glass, I calmly and gently picked the stronger one up and cupped in my hands and after a little while I placed it gently on a railing and off it flew.

I hesitantly picked up the 2nd one that I thought was really damaged. I didn't want to put that one on the railing in case it fell off and down to the unit below, so I put it in the pebbled garden that is just off my balcony beyond the glass panelling. He took a while but finally flew off into the rainforest beyond.

It was an amazing feeling. I could feel their little heart beats and they were looking at me with their beady little bird eyes lol but it was as if they "knew" I was helping and they didn't struggle at all. I kept so calm that I think it helped.

I remember learning on the Cornell site about anthropomorphism. I guess it is more about instinct than "feeling".