Illustration Friday: Bottled
From about the 1950's it was quite common for people to find that blue tits had pecked a hole in the aluminium top of their milk bottles, and eaten some of the cream. Birds are lactose intolerant, and they don't drink milk....but cream does not contain lactose, and is rich in much needed calories.
Today far less milk is delivered to people's doorsteps, and most of that milk is semi-skimmed rather than full cream, so this habit has almost stopped completely.
For more discussion about this behaviour, see this article.
Texture layer from les brumes
With many thanks to the above.