New gull taxon from the Baltic

A new gull taxon in the Baltic

According to Malling Olsen et al. 15.000 to 20.000 Great Black-backed Gulls Larus marinus pairs breed along the coast of Sweden and another 5000 pairs in Estonia. Along the coast of Finland  the number of breeding pairs vary between 1800 and 2700 (Valkama c.s.). According to Bonlokke et al. the first breeding record for Danmark dates from 1930 and the present population is estimated to be between 1500 to 1600 pairs. Judging from the recoveries of Danish ringed birds compared to f.i. the Finnish recoveries I think the origin of the Danish birds is Atlantic rather than Baltic. The overwhelming majority of Finnish ringed birds are recovered within the Baltic region.

Finnish Great Black-backed Gulls have allways been persecuted and even though they are at present protected during the breeding season still permits are given to kill them during the breeding season. The motivation for the culling seems non-scientific. Although the availability of gull corpses has been and still is enormous as each year tens of thousands of gulls (of all species) are being trapped on rubbish-tips in Finland and then killed for no sane reason at all no one seems to pay attention as to what the gulls killed look like.

Danish ornithologist Kjeld T.Pedersen noted that Great Black-backed Gulls of Baltic origin ( f.i.when fitted with Finnish rings) were different from typical Atlantic birds. They were smaller than and in particular in immature plumages slightly differently patterned than Atlantic L.marinus (see pictures below of Baltic gulls which are only a little larger than male Herring or Caspian Gull). The differences found justify to consider the Baltic gull as a different taxon. I propose to name this taxon Pedersen’s Gull Larus (marinusbalthica. 

The Finnish ringing results show that a small number of Baltic L.marinus did enter the North Sea from where they were reported in The Netherlands. From September 2018 till March 2019 a small influx occurred along the Dutch coast of Pedersen’s Gulls which were for the first time recognized as to belong to this taxon. They arrived with other species via the Baltic such as Caspian Gulls. This raises the question as to what  the sudden influx caused.

Malling Olsen, Klaus & Hans Larsson. 2002. Gulls of Europe, Asia and North America. Helm.

Valkama,J., Saurola, P., Lehikoinen, A., Lehikoinen, E., Piha, M., Sola,P. & Velmala, W. 2014. The Finnish Bird Ringing Atlas Vol.II. Finnish Museum of Natural History and Ministry of Environment, Helsinki.
Bonlokke, Jesper, Jesper Madsen, KasperThorup, Kjeld T.Pedersen, Morton Bjerrum & Carsten Rahbek. 2006. The Danish Bird Migration Atlas. Forlaget Rhodos & Zoologisk Museum Kobenhavns Universitet.

For Atlantic Great Black-backed Gulls see here:

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