Charles Darwin finches | Charles Darwin's Theory of Evolution by natural selection

Charles Darwin finches

In Galápagos, An Insidious Threat to Darwin's Finches

Ground pangolinNature as critically endangered, and several others, including the warbler finch and the woodpecker finch, seem to be suffering serious declines.

The reasons for this are complex and probably involve a dark synergy between habitat destruction, disease, and predation by introduced species. One of the main culprits has recently been identified as a parasitic fly – also an introduced species – called Philornis downsi. Researchers who work in the Galápagos warn that unless a method is found to control the fly, one or more of the iconic finch species could be lost.

“There are studies that show mortality due to Philornis in the nest, and it’s quite high, ” said Charlotte Causton, a researcher for the Charles Darwin Foundation who is coordinating the effort to find a response to the fly. “You’ve got these species of birds that are critically endangered and a large number of their fledglings are dying.”

The fly, which is known only by its Latin name (Philornis means “loves birds”), belongs to same family as the housefly. Its native range includes Trinidad and Brazil and probably other countries in South America, though no one is quite sure.Philornis downsi female llections –

As adults, Philornis downsi are harmless, but their larvae lead short, ghoulish lives. but it was not until the late 1990s that it began to attract attention from ornithologists.

“We’ve been struggling ever since, ” Causton said.

As adults, Philornis downsi are harmless, but their larvae lead short, ghoulish lives. Females lay their eggs in birds’ nests just as chicks are emerging. A day or two later, the eggs hatch and the larvae – about the size of a grain of rice – make their way inside the nostril cavities of the baby birds. The larvae eat away at the chicks’ nasal cavities for about three days; then, in subsequent larval stages, they migrate to the bottom of the nest, where they remain hidden during the day. At night, they emerge to feed on the chicks’ blood. In many nests, the parasite load is so high – in one nest, 184 Philornis downsi larvae were counted – the chicks can’t survive. Those that do live often end up deformed and have difficulty feeding.

“Usually their beak is all messed up, ” said George Heimpel, an entomologist at the University of Minnesota who has done research on the fly. “And for Darwin’s finches we know that the beak is an important part of their livelihood.” It is the shape of the various finches’ beaks, which enables them to make use of different food sources, that has fascinated students of evolution ever since Darwin.




February, Nat Geo Mag: "What Darwin Didn't Know"

by Snakebyte_XX


Darwin's First Clues
He was inspired by fossils of armadillos and sloths.
By David Quammen
Photograph by Luciano Candisani, MInden Pictures
The journey of young Charles Darwin aboard His Majesty's Ship Beagle, during the years 1831-36, is one of the best known and most neatly mythologized episodes in the history of science. As the legend goes, Darwin sailed as ship's naturalist on the Beagle, visited the Galápagos archipelago in the eastern Pacific Ocean, and there beheld giant tortoises and finches

Finches on Galapagos Islands evolving

by ShaGua

WASHINGTON - Finches on the
Galapagos Islands that inspired Charles Darwin to develop the concept of evolution are now helping confirm it — by evolving.
A medium sized species of Darwin's finch has evolved a smaller beak to take advantage of different seeds just two decades after the arrival of a larger rival for its original food source.
The altered beak size shows that species competing for food can undergo evolutionary change, said Peter Grant of Princeton University, lead author of the report appearing in Friday's issue of the journal Science.

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