The Great Scottish Crow Mystery - 1

I don't know much about crows. I do know that the local hoodies aren't popular because they have some nasty habits - like pecking out the eyes of defenceless new-born lambs - and that some people therefore spend a fair bit of time trying to trap them; and I also know that they're one of the most intelligent of birds, making them quite difficult to catch. So I'm very grateful to Tom Bryson, who lives in Ormsaigbeg, for describing to me what he rightly calls The Great Scottish Crow Mystery.

Hoodies, some people will be pleased to hear, are on the retreat. Back in the 1920s they could be found anywhere north of a line from Dumfries to Dundee, while their all-black carrion crow cousins were found south of it. The two birds are distinct species but they interbreed along this 'hybrid line'. This is unsurprising: the two species come from an ancestor population which was forced south during the last ice age, some taking refuge in Spain, the others in southeast Europe, where they developed separately.

Today, the hybrid line runs much further to the northwest, from the Clyde to the Orkneys - and Tom recently saw a carrion crow in Glencoe. The hoodies' retreat isn't only happening in Scotland. For example, in Denmark the hybrid line used to run along the German border, but now it's also much further to the northwest.

Why are the hoodies in such rapid retreat? Tom has his theories - they'll be in Part 2 of The Great Scottish Crow Mystery.