Current Biology has argued that British backyard bird feeders have caused a split in central European blackcap warblers into 2 distinct populations that may become separate species. The finding is incredible as evolution usually takes eons, while this has occurred in less than 30 generations.
The bird feeders are serving a crucial role - for 1 species to diverge into 2, a physical separation is needed so the 2 populations can breed independently and evolve differently. Warblers migrate in the winter and routes are genetically determined. The population studied has historically wintered in Spain. Those flying north died from lack of food in barren winter landscapes.
Bird feeders basically changed the ecosystem, giving warblers an incentive to stay in England during the winter. Also, the birds flight back home in central Europe is several hundred miles shorter than a trip back from Spain, so British migrators immediately begin breeding on their return.
A genetic split has occurred, results already visible in the birds’ anatomy - difference in wing and beak structure and even dietary preferences
How BIG an impact have these bird feeders had? Well, bird feeders are now doing the job mountains, oceans, etc. normally do.
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