Presumed Heuglin's Gull L heuglini
1-4: © Visa Rauste, 06-05-06. Tampere, Finland.
All the birds in this section were photographed at Tampere dump in Finland. They are all presumed but not proven heuglini, though for convenience the word 'presumed' is dropped and all are referred to subsequently as heuglini.
2cy Heuglin's Gull often is said to resemble Caspian Gull L cachinnans and this first bird is a very strong example of this. In fact, these images show no definite character that excludes either species. The scapulars show a mix of adult-like feathers with only a shaft streak and rather boldly marked feathers. The plain feathers are rather dark for cachinnans but birds from the east are known to be darker than the Caspian Gulls appearing in W Europe. Here is an example of a ringed Ukrainian bird demonstrating that boldly marked feathers also occur in cachinnans. This Heuglin's Gull above shows some old second generation wing coverts plus a few much fresher inner greater and more central median coverts that must have grown in more recently. This probably is unusual for heuglini, as most birds seem to replace scapulars and wing coverts in one round of replacement. There are two separating characters that are useful of which only one is definite. If the inner primaries are more or less all dark, this is strongly indicative for heuglini (e.g. this bird), but note that the conspicuous pale inner webs of cachinnans ("Venetian blind") also regularly occur in heuglini (in e.g. this bird). The second and best way to separate these species is to wait until the bird utters the long call, even if a few observations in Finland and Estonia suggest that adult heuglini-type gulls can exceptionally give very cachinans-like long calls.