BBC: The UK's nature reserves act as 'ecological welcome mats' to new species, according to scientists.
Since the 1960s, there has been a natural influx of wetland bird species from continental Europe.
Species such as whooper swans, Cetti's warblers and little egrets have used the nature reserves to colonise new areas of the UK, found the scientists.
The findings are published in the Proceedings of the Royal Society B: Biological Sciences.
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