Observers check whether summer heat affected migrating birds

A long-running autumn survey in the Solothurn Jura is checking whether this summer’s heat affected migrating birds, SRF reports. Ornithologists and volunteers have monitored migration in Welschenrohr for nearly 60 years.

About 10 volunteers are taking part in the current campaign at the Subigerberg bird observation and ringing station. From sunrise to sunset, they watch the sky and record bird numbers. They also catch birds in nets to identify, measure and ring them.

The nature reserve gives birds a chance to feed before their journey south, station head Barbara Schlup said. Food remains plentiful after the hot summer, including insects and berries. But heat can still cause problems: young swifts may overheat and die in nest boxes, Schlup said. When the ground is dry, worms can retreat into deeper, damp soil where birds cannot reach them.

The birds caught at the station do not all come from Switzerland, and the team does not know what weather they experienced in northern or eastern Europe. Most appeared healthy, Schlup said, and had plenty of fat reserves.

Among the species stopping at the Subigerberg are chaffinches, blackcaps and marsh tits. Staff record each bird’s weight, wingspan, age and health. The team tries to minimise the stress of capture by checking nets quickly, keeping birds for as little time as possible and releasing them promptly. One treecreeper, weighing nine grams, was identified up close by its strong claws and the tail it uses to brace itself against tree trunks.

A robin caught during the campaign already had a ring, showing it had been caught at the station two weeks earlier. Recaptures are also included in the statistics. Catching birds with nets is generally prohibited, but ringing stations require authorisation.

Tags: migrating birds, summer heat, bird ringing