As an aside, we have a peanut feeder opposite a window of a side room, with no direct access to the feeder. Access is through the back door. When the feeder is virtually empty a blue tit taps on the window with a sort of "Ere, we need some nuts" attitude. How do they know that those on the other side of the glass are the same ones that provide the nuts? Facial recognition?

Also fascinating, Joe, and a great question! I can’t think how one could even begin to try to determine the answer.

As an aside, we have a peanut feeder opposite a window of a side room, with no direct access to the feeder. Access is through the back door. When the feeder is virtually empty a blue tit taps on the window with a sort of "Ere, we need some nuts" attitude. How do they know that those on the other side of the glass are the same ones that provide the nuts? Facial recognition?

I do not have an instagram account

I don’t have one either, Geoff, and I don’t want one! On the panel that pops up when you first visit the page it says “Sign up for Instagram to stay in the loop.” Those who, like you and me, don’t want to “stay in the loop” can simply click or tap on the X to close the panel. You can then watch the video without further ado.

https://www.instagram.com/reel/DPXL_HWkY_J