Lionfish roundup

[DandyDon]

Some invasive species work out.

I was surprised to learn when reading an article in the Smithsonian about the anniversary of the settling of Jamestown that earthworms are not native to North America, and that when the first European settlers arrived the floors of the forests were piled with dead leaves.

You can read anything...

A total of approximately 182 earthworm taxa in 12 families are reported from America north of Mexico, i.e., USA & Canada, of which 60 (ca. 33%) are exotic/introduced. Only two genera of Lumbricid earthworms are indigenous to North America while introduced genera have spread to areas where earthworms did not formerly exist, especially in the north where forest development relies on a large amount of undecayed leaf matter. When worms decompose that leaf layer, the ecology may shift making the habitat unsurvivable for certain species of trees, ferns and wildflowers.

 

[tarponchik]

Crows and squirrels are natural predators and competitors of our native song birds so I would say the native birds are able to withstand that pressure in most areas. If you have the actual research that shows otherwise I'd love to read it.

It all depends what the landscape is. There was a paper on this subject in Science some 10 years ago. Their conclusion was that songbird offspring in US generally does not survive on forest edges and in small, isolated patches of forest because there they are attacked by the crows. Since crows avoid going deep into the forest, songbirds need forest patches larger than 50-100 m (I forgot the exact number they gave but smth like that) in diameter for safe nesting. I forgot if they mentioned squirrels, but I watch how squirrels destroy nests of American robins and catbirds in my backyard every summer. So your point that local songbirds can naturally withstand the pressure from crows is only true for the original American landscapes. Humans have changed the landscape dramatically, and large patches of forest are hard to find. Edges of highways and powerlines, narrow stripes of cycamores along the creeks in the farmland, and isolated trees in the 'burbs are not a friendly habitat for songbirds.

Generally speaking, the idea that invading species always make the worst pests is wrong, and local species can be just as bad, if humans change the environment to their selective advantage. For example, since most of the species of sharks in the Atlantic were depleted to just 1-10% of their numbers in the 70s, the cownose rays and other rays and small sharks who are the prey of larger sharks enomously grew in numbers. It is estimated that several million of cownose ray visit Chesapeake Bay in summer now, where they eat most of the shellfish.