The heat starts with the arrival of the Sun. [excerpt]Does it actually say that the Sun gives heat in Genesis 1?
So, sticking to the schedule set forth in Genesis, one little sticky wicket at a time, the birds are already flying around BEFORE there are land animals. There's no where for them to land and lay eggs.
The mind can run rampant around that one of course.
BTW, one of the reasons to stick to the wickets in the most exacting manner is that this involves the FIRST SEVEN DAYS, and if you can't get them correct how you gonna' get the next 6000 years right? Fur Shur you don't want to be adding nonsense to the text about new fangled notions of scientific research, right?!