Moerdijk Field Research 2005-2006

(last update: 14 August 2010)

Valery Buzun, in his 2002 article in British Bird about Heuglin's Gull, placed great emphasis on the wing-tip pattern in this taxon. Seasonal timing of our research at Moerdijk doesn't allow firm statements about the exact wing-tip patterns in Dutch Lesser Black-backed Gulls, as many birds show abraded P10 and P9 when breeding. Since the white parts in a wing-tip are more vulnerable to wear and tear as are pigmented parts, we may bias dark birds in our sample when scoring the exact patterns.

Seasonal problem at Moerdijk: wing-tip of LBBG oTL doesn't allow firm statements about exact pattern of P10-P9.

The image above illustrates the problem when scoring wing-tips in May in the Netherlands. Another problem are the differences in scoring classes between Valery's heuglini and our graellsii.
The pies below show the distribution and classification for P10 and P9 we have used at Moerdijk (remember that Dutch LBBG show no significant difference between sexes for either the P10 or P9 patterns).

And the pies below show the distribution and classification for P10 and P9 used by Valery. His research was done for two regions: one poipulation for the Ob and another population in Russian Zavorot. Valery is more specific in the exact pattern of the mirrors on P9 and P10, as he classifies mirrors as "open" (mirror reaches the edge of the feather) and "closed" (black of the medial band runs down along the feather edge, enclosing the mirror. He only found birds with broken sub-terminal black bands on P10 at the Russian Zavorot.

And the distribution for p9 is illustrated below. Obviously, most birds have no mirror on P9.

For heuglini, the common pattern would be P9 without a mirror and P10 with open mirrors. This is a common pattern found throughout the Dutch population. But also closed mirrors can be found at Moerdijk. Unfortunately Valery doesn't enlarge upon the exact definition of "closed". Should it be intense black running along the feather edge, or may it turn grey? And when does grey becomes of-white or white so the mirror will be classified "open"? We can not really quantify the portion of Lesser Black-backed Gull at Moerdijk, showing this pattern (due to extensive wear), but below we add two example birds in whichj the mirrors may be called "closed":

Below: Lesser Black-backed Gull o4H:

Below: Lesser Black-backed Gull o5E:

Continue at: UNDERSIDE P10 for heuglini.