It began with some strange behaviour of white storks in Uzbekistan.
For five months, a team of ornithologists at the Max Planck Institute (MPI) in Germany of have been tagging white storks to reveal startling GPS maps of their large winter migrations. However, among a colourful map of cascading journeys from north to south, a strange red blob above Uzbekistan appears to barely have moved. Why are the storks staying still?
‘They are eating from the fish farms instead of migrating,’ says Ivan Pokrovskiy, co-author of the study and researcher at the MPI. He observed the white storks living permanently in Uzbekistan instead of taking their usual southerly route towards Afghanistan and Pakistan. ‘Usually, the water is poured out from fish farm ponds during the winter,’ he tells Geographical, ‘however, in this area in Uzbekistan many natural ponds are used for fish farming, so it is not possible to pour out the water. The storks can settle here and use these ponds for feeding.’ The team hypothesise that human-induced feeding has suppressed the Uzbek stork migratory behaviour.
This is not the only case of the white storks changing course due to human excess. The study, which followed eight migratory populations of young storks, found that many of them favoured landfill sites to their traditional routes. In fact, storks from southwest Germany overwintered in the garbage dumps in northern Morocco instead of their usual spot in the Sahel.
‘Feeding on anthropogenic food sources such as landfills seems to be beneficial,’ the authors assert in the paper, ‘because birds can shorten their migration distance and decrease their daily energy expenditure.’ However, they also point out that these short-term benefits could damage southern ecosystems eventually. Fewer birds travelling south to feast on insects such as locusts could also have wider implications for agriculture.
‘Understanding how human actions alter migratory patterns may be key not only to protecting migratory species but also to maintaining diverse and stable ecosystems,’ the study concludes.