"We here see in two distant countries a similar relation between plants and insects of the same families, though the species of both are different. When man is the agent in introducing into a country a new species this relation is often broken ." Charles Darwin, Voyage of the Beagle
This is an incredibly insightful passage on introduced species and why some are so successful. The literature is replete with examples of organisms released by humans into areas where they are non-native and those species become quickly established because they have no predators or pathogens. Likewise, I know of failures of reintroductions because a species important to the target species was missing. The case I'm thinking of is the planting of trees and their subsequent failure because the soil lacked symbiotic fungi that gave the trees water and nutrients.
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| A female House Sparrow, native to Europe and now found throughout the world. This one is interesting: note the crossed bill. Why has this species been so successful? |
I believe that the short answer to your question is that the House Sparrow is amongst a number of species which adapts well to the ecological disruption caused by a certain two-legged pest with a worldwide distribution.
ReplyDeleteWhere North America birds are concerned, here is a piece on a (perhaps overly) successful introduction:
http://blog.nature.org/science/2013/11/26/wild-turkey-restoration-the-greatest-conservation-success-story/
I can testify that the published range maps sell Maine and the maritime provinces of Canada short. . .
Oh yea, no doubt part of the success of House Sparrows is their association with humans but not all ecologically similar species have been as successful. The Eurasian Tree Sparrow is a good example. I also suspect Rooks were released in NYC about the same time. Would make for an interesting book to go through that period of American history and see what animals made and those that didn't.
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