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Hawaii’s Honeycreepers Have Evolved Astounding Colors and Bill Shapes

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My little escape to Hawaii is over and sadly, it’s time to get back to reality. But first, like every other dopey tourist just back from an exotic vacation, I’m going to force you to listen to every excruciating detail of my trip - it’s the traveler’s prerogative.

Ok, so maybe not every detail, but I do want to talk about Hawaii’s birds. It’s not as off-topic as you might think - by my estimation, most Cape Codders have visited or will visit Hawaii at some point. In fact, I knew of at least six other Cape Codders who were either visiting or living on the Big Island just while I was there.

If you do visit Hawaii, I hope you’ll pay attention to the bird community, because it’s the weirdest one I’ve encountered anywhere in the world. While some of the native habitats resemble Central or South American tropical rainforest, where you might expect to see hundreds of bird species, the reality of Hawaii is very different. In ten days I only saw 53 species, which is a total you could exceed in a few hours of Cape Cod birding on a frozen January day. And of those 53 species, only 19 were native, meaning they arrived and evolved there on their own. So what’s the deal?

Lying almost 2000 miles from the nearest continent, it is very difficult for new species to find and colonize Hawaii on their own. In fact, most of the native songbirds of Hawaii, known as the honeycreepers, evolved from a single House finch-like ancestor from Asia. The resulting speciation over 5-7 million years produced a suite of species sporting an astounding variety of colors and especially bill shapes to fill all of the available ecological niches, a process known as “adaptive radiation”. In this respect, Hawaii’s honeycreepers rival Darwin’s famous Galapagos finches.

I was lucky to see one of the rarest of Hawaii’s honeycreepers, known as the Aki for short, which is good because I can’t pronounce the many-voweled real name. This small, yellowish finch filled the woodpecker niche by evolving a remarkable “Swiss Army Knife” bill with a sharp lower mandible and a long, elegantly curved upper mandible. It actually has to open its bill to get the curved part out of the way so it can use the lower bill to hammer away on branches.

Unfortunately, because they had the islands to themselves, the Honeycreepers did not evolve defenses against mammalian predators or mosquitoes carrying avian malaria, both of which have devastated Hawaii’s native birds since the arrival of the Polynesians and later the Europeans. Of the original 56 species of honeycreeper, only 18 remain, with more likely to go extinct soon.

The end effect is of course a bit depressing if you are a birder, because the songbirds you see in the touristy lowlands are an ungodly mix of exotic species from Asia, Africa, and North and South America, all introduced by humans. It was very odd to see our Northern Cardinals feeding side by side with game birds from India, finches from Africa, and tanagers from Brazil in the same coastal scrub forests. The remaining native species are making their last stand in cooler, protected, high-elevation forests where malaria-toting mosquitoes cannot survive, and where biologists are working hard to keep pigs, cats, mongooses, and other introduced species out.

Definitely visit Hawaii – the weather is perfect, the snorkeling is amazing, the people are wonderful, and the landscape is breathtaking. Go for the 13,000 foot volcanoes, the tide pools full of sea turtles, and the active lava flows. And do your best to see Hawaii’s dwindling native bird species while you are there. Just don’t expect a species list comparable with continental rainforests – it’s been a tough last fifteen hundred years for Hawaii’s evolutionary wonders, the honeycreepers.

Mark Faherty writes the Weekly Bird Report.