/ 27 January 2004

Novel means of tracing swallow migration

A group of South African and Hungarian scientists have discovered a novel way to unravel the mysteries of the annual European swallow migration between the northern and southern hemispheres.

By chemically analysing feathers of the little nomads collected during their African sojourn, the researchers are determining from which European breeding area the birds originate.

This piece of the migration puzzle had been largely eluding ornithologists up till now, Hungarian ornithologist Tibor Szep said this week on a research visit to Bloemfontein.

Until recently, ringed birds that were re-caught provided the only clues. Unfortunately only an estimated one% of the total migrating population ringed in Europe are caught in southern Africa.

This gives only a very vague indication of the global swallow population’s European origins.

One of Szep’s South African collaborators, Steven Piper from the University of Kwazulu-Natal, explained the new method developed by the Hungarians: ”The baby swallows in Europe are fed insects caught around the nest.

”The insects get all their nutrients from the vegetation growing in the nesting area, which in turn receives its nutrition from the surrounding soils.

”Therefore each breeding site has a unique ‘fingerprint’ of trace elements which is mirrored in the chemical composition of the young birds’ feathers.”

Judit Vallner, a chemist and Szep’s colleague at the eastern Hungarian College of Ntiregyhaza, devised an extremely accurate and specific technique to analyse the composition of the delicate feathers.

Not only must the occurrence of a specific trace element be determined, but also its concentration, in order to compose the particular chemical map. The concentration could be as little as one millionth of a part.

Vallner also developed a special technique to first clean the feathers of contaminants such as dust and parasites.

Bloemfontein is one of the key South African research sites of the project, financed under the South African-Hungarian Scientific and Technical Co-operation Treaty.

The Free State capital lies in an area where swallows from both the western and eastern migration flyways converge in the summer months. The city also boasts the best long-term swallow ringing program in the whole of southern Africa.

It is one of ten places in South Africa where the team has so far collected feathers from large swallow populations for their ”fingerprint” database. This will help establish the pattern of the swallows’ African connection.

European swallows usually leave their northern breeding areas from August to October. They arrive in southern Africa around November and December, following a journey of thousands of kilometres across mountains, oceans and deserts.

Apart from linking the birds’ northern and southern destinations, the new method provided for tracking pollution and its effect on humans, Szep added.

The occurrence of an area’s pollutants, especially heavy metals, tended to be very pronounced in the young feathers of the birds, he explained.

The swallow, one of the most abundant breeding bird species in Europe, could therefore serve as a very suitable ”indicator species” of rising pollution rates.

Szep’s ultimate goal with the research is to trace the effect of global warming on the world’s swallow population. ”It is very important to establish what the birds do if something goes wrong on their breeding grounds.”

The new technique has immensely accelerated the pace of working towards this goal.

However, he still expected it to take many years before getting the final picture, Szep said. — Sapa