cachinnans x michahellis?

[lou bertalan]

hello

good news from southern romanian plains, a small cachinnans colony has been discovered by joszef szabo and ciprian fantana at one of the olt-river reservoirs. this is now the westernmost known breeding site of caspian gull in the country. it's on a small well vegetated island on a large reservoir lake near arcesti (on such lakes further north in transilvania michahellis is breeding in a few pairs!).
some of you might know that one of the aims of my extensive collecting of large gulls data and images from romania is to seak for possible hybrids mich x cach, by studying variation in both species and of course by looking for mixed pairs. the documentary photos made by joszef unfortunately are not good enough to clinch one of these birds as a mich i'm afraid. it could be either a 4cy cach (not so probable in my eyes), or a pure mich or a hybrid itself. primary pattern looks better for michahellis. what do you think???
strangely, in some of the previous photos the same potential nest is occupied by a pair of cachinnans, later pics showing this other bird with michahellis characters long-calling.
have a look and tell me your opinions about this bird please! note texts under the photos.



lou

breeding place (nest) occupied by a pair of cachinnans, later same place with one cachi and the possible hybrid. apparently no pulli at this nest yet.

6 2010.06.10 arcesti jj DSC09890 - Kopie.JPG (278.32KiB)Viewed 4383 times

same pair, apparently both partners = cachinnans

6 2010.06.10 arcesti jj DSC09886 - Kopie.JPG (177.35KiB)Viewed 4382 times

3 pulli with a landing adult (different nest)

6 2010.06.10 arcesti jj DSC09894.JPG (211.7KiB)Viewed 4383 times

the problematic bird, displaying.
primary pattern more like michahellis with very small p9 mirror, not so large p10 mirror, strong subterminal band on p10 and an underwing p10 tongue within variation of michahellis. albatross pose and palish yellow legs however point towards cachinnans.

6 2010.06.10 arcesti jj DSC09908.JPG (208.53KiB)Viewed 4383 times

same bird long calling, now with raised head. wings held way up like in cachinnans. i have wondered if it is a 3rd summer cach - but no immaturity signs are visible in these pics. i have not yet seen an adult caspian with such small mirrors!

6 2010.06.10 arcesti jj DSC09909.JPG (192.77KiB)Viewed 4383 times

[Ronald Klein]

It is sure cachinnans, because their "albatrossing" is a diacnostic feature. For my experience the importance of wingtip-pattern often will be overestimated. May be it is a bird in 4th or 5th year.

[lou bertalan]

thanks ronald,

the "albatrossing" pose was my main concern too. still, even though there is some variation in the shape of p10 tongue (ventral) and its demarcation line to the black part, in the vast majority of cases this demarcation line is more or less straight and forms a rectangle to the outer part of black, like here, a 4cy type from the end of april: http://lou.bertalan.de/gulls/m_phi.php? ... nuary-june - this has a very similar pattern (no p9 mirror) and p10 tongue is similar in length but as mentioned, there is this rectangle at the inner end of the tongue. michahellis on the other hand usually show a rounded tongue - hope that makes sense and explains my thoughts.