As mentioned already, they can be called at any given point in a 24 hour period. During the winter when their food sources are scarce it becomes easier to do so. During non peak times of the year my general rule of thumb is "done by 10am" and "after 7pm". This is not to say that inbetween can't be productive either, just that this a generality that seems to be the norm for me.
I've never heard anyone ever say "My AR made me do it!"
You know better, and now you're on "Ignore".