Heuglin's Gull (L. heuglini / antelius)

(last update: 26-2-2014)

Dark markings on the greater primary coverts.

Gibbins (2004) mentioned adult heuglini to have dark markings on primary coverts more frequently than graellsii, although he does not quantify this. When you check the pages on adult heuglini, you'll soon understand what is meant, although many birds also show perfectly plain grey greater primarey coverts. So far, there is no research on adult heuglini that really quantifies this feature.

Above: heuglini adult, February 02-09 2009, United Arab Emirates. Picture: Chris Gibbins. Bird at the fish-market. Note black on primary coverts. P10 just to grown an inch or so.

In the Netherlands, we have checked breeding birds on this characteristic. The majority (76%) of breeding Lesser Black-backed Gulls in the Netherlands (Moerdijk colony) showed black on the primary coverts (n = 962) and we found no marked difference between the sexes (males 78% (n = 434); females 74% (n = 496); Pearson χ2 = 2,622; P = 0,105; df = 1). Our data of known-age Lesser Black-backed Gull (n = 76) suggest that both the number of primaries showing black (b=-0.071, r2=0.072, P=0.020) and the presence of black on the primary coverts (b=-0.189, r2=0.046, P=0.068) are age-related.

We scored 54 adult birds of known age in 6cy-14cy. 41 birds (75%), in all nine age-classes, were found showing neatly demarcated black pigmentation. 62 breeding LBBG in our sample are considered to be ‘sub-adult birds’ showing primary coverts with extensive black markings, pale brown tips and diffuse borders. 666 birds show limited black markings which are neatly demarcated; we consider such birds to be ‘mature adults’ (see image below).

Above: two example primary covert patterns to illustrate the division between ‘sub-adult’ and ‘adult’ Lesser Black-backed Gulls in our analysis. Top: the greater primary coverts in sub-adult LBBG oHZ show extensive dark centres and diffuse borders. Also note the dark centres on the secondaries and brown-black P9 and P10. Below: LBBG yET with neatly demarcated black markings, which are considered to be still possible in ‘adult’ birds. In fact, LBBG yET was ringed as pullus in June 1995, and now in its 12th calendar year. We created a photo gallery of black markings on primary coverts in all known-age breeding Dutch graellsii.

Table above: Black pigmentation on primary coverts in known-age Lesser Black-backed Gulls (retrapped birds excluded). Values are % for their own age-class. Age in calendar years (CY).