South American Bird Species Study at the frigid tip of South America’s Cape Horn sits a tiny bird that is confounding biologists. On Diego Ramirez Island, about 100 kilometers from the continent’s mainland, scientists have identified a new species of “rayadito” (a type of seedeater). These tiny birds—a little larger than a hummingbird—are already a focus for research on the islands’ biodiversity, and a new genetic study suggests they may be more unique than previously thought.

The researchers compared the entire genomes of six rayaditos to see how they differed. They found only three narrow regions of the genome that differed, and two of these genes are related to the birds’ plumage colors. The results suggest that a mix-and-match process of mutations and adaptation to different landscapes drives the diversity among seedeaters.

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A similar process is probably responsible for the diversity of plant species in a wide range of other habitats, including tropical forests and grasslands. The findings could also help us predict how the tropics might respond to climate change.

Scientists are concerned about the impact of forest loss on migratory birds. But a new analysis suggests that, in spite of widespread destruction, the rate of extinctions is much lower than expected. In fact, the tropics appear to be a refuge for migratory species, at least for now.

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