I came across these 2nd-calendar year and third-calendar year Herring Gulls displaying what I can only describe as pair-bonding behaviour.
The (brief) display consisted of mew-calling (the first time I’ve seen a second-calendar year gull doing this), walking in parallel and choking. It is very odd to see this in gulls so young.
I doubt that they were actually pairing-up and were just going through the motions (early hormones?) but it was fascinating to see the second-calendar year already knowing how to respond to such signals.
Leiden, the Netherlands, 17 February 2017.