Birds don't care if they are welcome 

They really don't care about our safety 

Not to mention we have never seen them pay for anything.

Why is there a bird at the store?

well that is a good question, birds are mostly looking for food or shelter when inside a facility, most the time the misconception is that birds accidently enter facilities and this is true for a small fraction of  the birds entering facilities around the USA.  

Birds are perfectly fine to make themselves feel welcome in most facilities.

as you can see this bird has no problem roaming the aisles just like your everyday shopper.