vrijdag 7 december 2012

Caspian Gulls: the beauties and the trickies (1)

There are the beauties and the trickies of Caspian Gulls (Larus c. cachinnans). The beauties are that which are easily found by there typical bills and white heads. The trickies may have some influence from the Polish hybridzone from where we see a lot of birds in the Netherlands. Mostly unringed birds. Some pictures of first calendar-year CG's in autumn.


First calendar-year (aug-dec)


5/9/2009 - Westkapelle - The first impression is: that one looks good for CG! Pale, thiny legs, pointy bill, white head with a small eye. But when we have a closer look, the stage of moult seems not advanced enough. None of the scapulars are molt yet. Furthermore, the coverts look too patterned for a pure bird, as far as we know. They look better for Herring Gull. Conclusion: a tricky one, whether hybrid or not.
22/9/2011 - Westkapelle - How clear will you get it? The overall typical warm brown colour looks good. And not only the white head with a small eye and nice bill. Also the new scapulars look as plain and greyish as the can be in CG. Moreover, the worn median and greater coverts form a kind of a wingbar. Note the tertials with only small white edges. The beauty.
5/10/2011 - Werkendam - Mmm, the tricky one. The subterminal small black markings on the upper tail looks good while the inner primaries show the typical venetian blinds. But what about the heavily patterned wingcoverts? And what about the markings on the belly and the underwing?
13/11/2012 - Dordrecht - the beauty. Compare the pattern of the greater coverts with the bird above. This is how clear we want to get it.
27/11/2012 - Barneveld - the tricky. Again, the first impression is: 'wow'! What a nice CG....but again we have to look at the greater coverts. May this pattern be possible in a pure CG? Or do we call this a beauty, pure or not?

7/12/2012 - Dordrecht - the beauty. Some CG's can look very similar to 1cy Common Gull Larus canus in this time of year. The contrast between the scapulars and coverts is comparable with that of 1cy Common Gulls .This bird show its long and thin bill at the very distance. Combined with the plain coverts and greyish mantle, this is a beauty with no doubt. 

24/12/2010 - Barneveld - the tricky. Its rather bulky building looks good for Herring Gull. But the pattern of the scapulars, the thiny bill and the fine streaking in the neck points towards CG. Again the coverts are giving the reason to doubt. Not ringed, but it rings bells for a 'western' or Polish CG! 
13/12/2012 - Utrecht - To finish with a very beauty: this one looks great in every way.

Want some more footage? Read the articles of Chris Gibbins on this topic. 

Typical Caspian - British Birds 
About hybrids - British Birds


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