Maui Parrotbill - Hawaiian Evolution Fills a Niche

High in the remote mountains of East Maui, an unbroken expanse of koa and ‘öhi‘a forest supports perhaps the highest diversity of Hawaiian forest birds remaining in the archipelago. Sitting in that lush, dripping terrain, thousands of feet above sea level, the ears strain to pick out the tell-tale descending "cheer-cheer-cheer" call of the Maui parrotbill from among the chorus of more common birds, such as ‘apapane, ‘amakihi, alauahio, and ‘i‘iwi. The mix of calls reflects the behavior of the parrotbill; it will often fly among mixed flocks of the more common green birds, and any group of yellow-green birds draws the binoculars toward them to check for the rare standout.

And what a reward it is to see the parrotbill: a rich olive green body with yellow chest frames the distinctive head, with a bright yellow band just above the eye, which is masked in dark olive. All of this is peripheral to the most distinctive feature of the bird: its strong, hooked parrot-like bill, used for vigorous prying of chunks of koa bark, or snapping straight through strong twigs of understory shrubs in search of its major food – the grubs of native beetles boring through the wood. The force of the jaws working that bill is enormous relative to the "songbird" size of the bird, and sometimes you can hear the crunching and snapping of the twigs and branches as the bird works its way through the understory.

It is a classic example of a specialized endpoint in honeycreeper evolution. Rather than the curved, nectar-seeking bills borne by many of the group, or the massive seed-crushing bills of others, the parrotbill developed in convergent evolution, a prying bill that serves as slicer and wrench at the same time.

The formidable bill also makes for a potentially dangerous encounter with a native Hawaiian species. When researchers set up fine mist-nets in parrotbill habitat, they must be careful not to fall prey to that powerful bill. Typically, thick leather gloves are used to handle these birds! Many years ago, a colleague was carefully handling a Maui parrotbill late in the afternoon, and had one in hand when it was time to conduct a radio check. Since these radio checks require punctuality (lest a researcher be considered lost or hurt, and a rescue effort mounted for them), she was trying to work the radio, while finishing her measurements on a parrotbill still entangled in the net. She couldn't press the radio buttons correctly, so she removed one glove, and while she was working to release the netting from the bird and call in at the same time, the bird reached over and bit her finger to the bone! This was just as she was transmitting on the air, and I never heard such language from an ornithologist before or since! Luckily, the bill had not snapped though her finger bone, and today she bears a unique v-shaped scar that she shows proudly, reciting: "See this? Maui parrotbill, 5000 feet elevation, Kipahulu Valley, 1981!" She may be the only one in the world who can make such a claim!

Today, while the parrotbill is restricted to the wet forests of East Maui, it seems to be holding its own, benefiting from the healthy regrowth of understory shrubs following a decade of feral pig control in Waikamoi and adjacent lands. It is a testimony to the benefits of protective management of habitat for rare birds, and I find it satisfying that one of the most specialized of the Hawaiian honeycreepers seems to have a secure home in the East Maui Mountains Watershed. -Dr. Sam Gon, Director of Science