Thursday, June 14, 2012

A quieter couple of days were brightened up by an extremely confiding Pomarine Skua which spent most of this morning touring the Island. The wholly dark underwing suggests that this bird is a full adult and the lack of a breast band is considered to be a feature of some male birds.

Genetic studies have shown Pomarine Skuas to be most similar to Great Skuas, in fact the two species have one of the smallest mitochondrial DNA differences of any two vertebrate species that have ever been analysed. But observations on morphology and behaviour show Pomarines to be most similar to Arctic Skua. So, how can a skua be so closely related to one species (genetically speaking), yet display many of the characteristics of another? Well, it is thought that Poms have evolved from an extensive hybrid population of Great x Arctic Skua. The last two photos show the Shelduck's displeasure for today's avian highlight. This particular pair of Shelduck have also forcibly removed the parents of two broods of Solfach Shelduck. Happily they have adopted the two broods, taking the number of chicks in their own mega-brood to 18. (c) Richard Brown

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