Is most lumber at places like Home Depot pressure treated or not? Do
they always mark it if it's pressure treated? How about the wood at
Rocklers or Michael's craft store?

I got some hard maple from someone who did a home remodeling, and I
think it was used indoors. Is this likely to be pressure treated or
not?

I need to make some perches and toys for a pet bird and I wouldn't want
it to die from eating pressure treated wood.