APRIL heralds the springtime return of many migratory birds that make their summer home in Argyll and Bute.

Among them are the familiar swallows and house martins whose appearance after a long flight from Africa is a welcome sign that spring is finally here.

A range of other visiting songbirds will also arrive soon to swell the dawn chorus.

The extensive natural woodland around Loch Lomond is famous for hosting a wide range of species, including “star” birds such as flycatchers and redstarts.

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But it can be an anxious time for ornithologists who study bird populations.

This is because each species faces multiple risks, during their wintering period in Africa and on their long migration, and numbers arriving back could fall year-on-year as a result.

Surveys during recent years show that some species are doing better in Scotland than in England.

The British Trust for Ornithology revealed that in England the spotted flycatcher population had fallen by 18 per cent, but north of the Border the number of these smart little birds were up by 66 per cent.

Reasons behind the overall decline, which amounts to 39 per cent across the UK since 1994, are unclear.

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Declines in large flying insects that are food for flycatchers, or conditions along migration routes, or in wintering areas of West Africa, have been suggested.

Other summer-visiting species that are doing well in Scotland are the chiffchaff - a small warbler - and that true harbinger of spring, the cuckoo.

However, on the down side, greenfinches which used to be a common garden bird showed a drop of 50 per cent and the curlew, a large wading bird that occurs along the Clyde, was down 16 per cent.

The RSPB said it needs to understand more about the threat these birds face and what lies behind the welcome increases in Scotland but continuing losses in England.

The BTO said it was really pleased when it saw the spotted flycatcher was up in Scotland, and it thanked the many bird enthusiasts who survey breeding sites throughout the summer.