Thursday, 13 June 2013

Visiting a Caspian Gull colony

Two weeks ago I was privileged to visit a 'Caspian Gull colony' in southern Poland with the master of all those green and yellow rings, Jacek Betleja, that all gull fans love to read. I first made contact with him having seen one of his green-ringed birds, 355P, in January last year and he kindly coincided his first visit of the season with my visit to Poland. Late May is an excellent time to visit the colony, with some chicks already hatched, and adults actively feeding them. This colony is located on a grassy island, in the middle of a gravel pit, so there's only one way to get there - Jacek's blow up boat.

The gulls here at Jankowice, near Zator, nest in long grass so you can appreciate that when any ringing takes place all the adults fly off, so you're left with lone chicks. Although I was slightly comforted by the large proportion of adult birds that fitted well within the parameters of Caspian Gull, there were some birds that showed mixed characters (mainly with Yellow-legged Gull). Therefore, with the adults gone, the official line from the Polish Ringing Scheme for ringing these chicks is to call them 'Larus cachinnans colony': -
- chicks ringed in mixed colonies where Larus cachinnans is the dominant species (it is most likely that these chicks are cachinnans, but other species and hybrids are not excluded); this is the most common code, because most colour-ringed birds are from southern Poland, where this species is the dominant one.
Caspian Gull egg


typical Caspian Gull nest scrape in long grass/nettles
Each nest typically contained two chicks, sometimes three

With this breeding colony at a lower latitude than many of the Herrings Gulls that either breed in or visit Britain, this Caspian Gull colony's breeding cycle was more advanced - an explanation for typically more advanced moult of Caspian Gull. The chicks were typically the size of those shown above, though some were rather larger: -
As well as freshwater fish, these gulls are still suckers for human rubbish even within the breeding season. Chicken wings and sausages were just some examples of the detritus that the doting parents bring back for their offspring, with all sorts of rubbish scattered around the nest scrape.

Anyway, Polish Caspian Gulls ringed by Jacek have of course been seen on many occasions in the UK, and have reached as far west as A Coruna in northwest Spain. The older ringing scheme uses green rings with white writing (three numbers and then a P) and the newer rings - easier to read in the field - start with a P and then are followed by three letters. I managed to read 18 different ring combinations, with histories of birds mainly centred in Poland as you'd expect, but also some visiting the Czech Republic, Hungary and Germany.
492P was born at this colony in 2009, and returned again in 2011, as well as having been seen in the local area on a couple of occasions too.
Born in 2009 at this colony, this is the first time PADK has been seen back at its place of birth, now presumably as a breeder. It has been seen several times in southwest Poland, as well as in Budapest, Hungary on 9th March 2011.
This area of Poland also supports most of the country's Night Herons, and it was good to see adults at close range coming into the colony on the same island as the Caspian Gulls.

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