While checking various gull spots in the city of Leiden with fellow birder Jan Z today (something we do during our lunch break on Tuesday on a weekly basis, weather and time permitting), we were surprised to come across a higher than average number of ringed Black-headed Gulls Chroicocephalus ridibundus:
17 in total [edit: now corrected to 18].
This is about 4 to 5 times higher than what we are used to this winter.
We checked 4 different locations and at each location, at least 40 Black-headed Gulls were present. The break-down of observed rings per location was as follows:
- Location 1: 3 rings
- Location 2: 5 rings (1 the same as in group 1)
- Location 3: 6 rings (2 the same as in group 2)
- Location 4: 6 rings
Locally ringed gulls
It is not surprising to have ringed Black-headed Gulls in Leiden because over the last few winters, Black-headed Gulls have been actively ringed here (about 20 in the winter of 2011/2012 and about another 40 in the winter of 2012/2013). Almost all ringed individuals that we observed today were local birds which are known to spend the winter at the location where we saw them.
It was nice to see though that some of them had not been observed for a while, including a few individuals which were seen for the first time this winter (to the best of my knowledge).
Most of these showed themselves well. The following is a selection of the ones I took photos of.
This male adult Black-headed Gull of at least 8 years old was ringed in 2007 in Leiden. My last observation dates from 16 February 2013 so it was very nice to see that he is still around.
White 4FH is an adult female, ringed in April 2013 in Denmark. It was not observed until I first saw it in Leiden on January 14 at which time it displayed a head pattern that is normal for winter (basic) plumage. When I saw it for the second time last Friday January 24 I noticed that it was already actively moulting to summer/breeding (alternate) plumage.
White E0CU was ringed in Leiden on 27 January 2011 (so 3 years ago, almost to the day), mainly because it is one of those Black-headed Gulls who completes the moult to breeding (alternate) plumage very early in the winter season. Today it showed a 99% complete hood. This is somewhat sooner compared to previous years but this may be down to the mild winter that we are experiencing here in The Netherlands.
Female White E0TL was ringed in December 2011 at the location where we saw her today. This is only the 3rd time that I have seen her this winter, the last time dates from 7 December 2013.
Similar to White E0TL, male E0TS was ringed ringed in December 2011 at the same location where we saw both of them today and as with E0TL, this is my 3rd observation of E0TS this winter. Note the strikingly dark-red bill and legs.
This is only my 2nd observation of White EJA5 this winter; I first saw him on 9 October 2013. He was ringed in December 2012 in Leiden.
One of the highlights of today was the reappearance of White EJF6, last seen on 22 January 2013, just over a year ago.
Top sighting of today belonged to White LYD, a 17-year old individual which I have only seen twice before: aways at the same location and always at the end of the winter season.
It was ringed in the city of Groningen, in the North East of The Netherlands where it has been observed regularly. It is very likely that White LYD spends a short time in Leiden on its way from the wintering grounds in southern Europe to the breeding grounds somewhere up North.
Can these high numbers be explained?
My feeling is that the high number of gulls that we saw today and the high number of ringed individuals is a good indication that the migration to the breeding grounds has now started.
The appearance of White LYD especially (and possible that of White EJF6), underlines this assumption: it is one of those individuals that is only observed at the very end of the winter season when it seems to be using Leiden as a stop-over during its migration to the north of Holland.
As mentioned, we are experiencing a very mild winter here at the moment, which could mean that the Black-headed Gulls might start leaving their wintering grounds earlier than previous seasons.
While it is common for Black-headed Gulls to stay here in Leiden up to the 2nd week of March, we will have to see how this turns out this year.