Science Matters – why catch a flycatcher?

The spotted flycatcher. Photo: Liz Cutting.

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We had a visit recently from Mark Wilson, a bird scientist at the British Trust for Ornithology (BTO), his car laden with nets and poles.

He was hoping to enrol the spotted flycatchers nesting in a nest box on our garage in a BTO study that aims to find out where these and other summer visitors to Scotland spend the winter.

Spotted flycatchers are summer visitors to the UK, breeding here then flying off to overwinter somewhere in sub-Saharan Africa.

They naturally nest in scrubby woodland, and, as their name suggests, eat flying insects.

Recently, overall numbers of these little birds have declined dramatically in the UK, but appear to be holding up better in Scotland than in England.

It may be that this difference in fortunes is due to factors such as habitat loss, climate change and/or pesticide use having less of an impact in Scotland than in the south.

Alternatively, the migratory routes and destinations of these birds could differ between northern and southern breeding populations.

This study, which will include up to 20 adult spotted flycatchers, and similar numbers of other migrant species – garden, willow and wood warblers as well as whinchats and tree pipits – is designed to check whether this is the case.

Mark set about trying to catch our birds with perch nets as they went back and forth to the nest box feeding their young.

On catching the female, he fitted her with a tiny ‘geolocator’ backpack weighing just 0.3 to 0.4g and a red leg ring, and then released her unharmed.

Geolocators record light levels at regular intervals, allowing the time of sunrise and sunset, and thus the latitude and longitude of the bird’s location each day, to be worked out.

First, however, the geolocators must be recovered. So, in spring 2022 we are not only expecting the flycatchers to return, but also Mark, who will come to retrieve the tag.