European white storks (Ciconia ciconia) have exchanged their usual annual migration to warmer climates for a winter of rummaging through tips and dumpsters, according to new research from University of East Anglia's (UEA) School of Environmental Sciences.
These rubbish tips present a steady supply of food for these birds - waste scraps mostly made up of junk food - which in turn proves more favourable to their chances of breeding, says the study published this week in Movement Ecology.
Research has revealed that some birds are making round trips of up to 95 kilometres - just to feed at these garbage tips.
White storks usually migrate to Africa before the European winter sets in, but since the 1980s an increasing number of storks no longer leave Europe at all, most of them spending the winter in Portugal and Spain.
By skipping winter migration, these birds can instead conserve energy they would otherwise expend on long travels, secure good nesting grounds locally, breed more and earlier in the year, and have greater survival rates for their chicks.
The only reason storks do migrate is to find food, which is hard to do in winter in the colder regions, as their natural diet largely consists of prey such as rodents, amphibians, lizards, and snakes.
Now with the steady source of garbage food provided by these dumps, many white storks have no need to leave in the winter. Portugal and Spain now have about 14,000 wintering white storks, says the study.
The influx of storks causes similar problems to what coastal Sydneysiders face with ibises, which are also frequently seen as a public nuisance as they rummage through bins in search of sustenance.
However, advocating for closed bin tips, as many are pushing for the European Union to do, may have detrimental effects on these large birds who have come to rely on the constant food source.
The research team followed the courses of 48 white storks, documenting their GPS-tracked location five times a day. The data they collected confirmed a majority of these birds were using their nests all year, even outside of breeding season, which is highly unusual for this species.
The study also showed many storks travelled up to 48.2 kilometres outside of breeding season and up to 28.1 kilometres during breeding season to visit landfills to forage for food. These figures are much larger than what was previously estimated.