but where does it define birds as specifically chickens

Birds could be metaphorical for winged creatures

and "water teeming with living creatures" could refer to the earliest lifeforms which existed in the water

creatures which would then evolve to become the chicken, so egg could in actual fact still potentially come before the chicken

the begining of genesis seems to just briefly sum up time, puttin their own religious twist on it, and in my opinion actually trivialises the issue of evolution....shit i bet there are a lot of airheads who only have a bible as a source of info on time and space and think its as simple as god saying "let there be light" etc.

but meh