OSLO (REUTERS) - Scientists have for the first time discovered a general shift in diets across an entire group of animals while studying birds on the Galapagos islands that once helped inspire Charles Darwin's theory of evolution.
The Spanish-led team observed 19 of the 23 species of Galapagos land birds visiting flowers to eat nectar and pollen, apparently because their preferred foods of seeds or insects are in short supply on the remote Pacific islands off Ecuador.
The taste for flowers among Galapagos birds had gone unnoticed until now. "The whole bird community expanded its niche and included floral rewards into the diet," the scientists wrote in an edition of the journal Nature Communications published on Tuesday.
"This phenomenon ... has been previously reported for single species but never for an entire community," they wrote.
The birds the scientists studied over four years visited more than 100 types of flower and included finches, mockingbirds and flycatchers.
Four bird species were omitted from the study, either because they were extremely rare or lived outside the 12 islands involved.
"The families of land Galapagos birds have members in the South American continent that also visit flowers," lead author Anna Traveset of Spain's Mediterranean Institute for Advanced Studies told Reuters in an e-mail from the Galapagos islands.
British naturalist Darwin visited the Galapagos in 1835 and his observations that related bird species differ from island to island helped inspire his 1859 book about evolution, "On the Origin of Species".
Darwin also noticed a shortage of insects. "I took great pains in collecting the insects, but excepting Tierra del Fuego, I never saw in this respect so poor a country," he wrote.
The new study also suggests a bigger-than expected role for birds in pollination, a job usually dominated by bees. Birds studied had an average 233 pollen grains stuck to them. "Bird pollination is important for many native species,"Traveset said.
Dave Kelly, a biologist at the University of Canterbury in New Zealand who was not involved in the study, said there was emerging evidence that some plants were in decline in parts of the world where bird pollinators were threatened.
He said: "Bird-pollinated plants are typically failing more so than insect-pollinated plants."