One of Scotland's rarest birds will be the subject of a national survey to see how the population is faring after years of decline. In Scotland, choughs are only found in a small area of the south-west, with a remarkable 90% of the birds making their home on the island of Islay. A member of the crow, or corvid, family, choughs primarily feed on insects and larvae and in particular those that are found in the dung of cattle. A team of surveyors has now begun work to chart the fortunes of the charismatic birds, known for their striking red…