(Listen to the radio version here.)
If a group of Red Junglefowl had managed to find Hawaiʻi on their own 800 years ago, they would have either died out or found a way to eke out a living in the unfamiliar environment just like every one of the other species that somehow ended up there. They’d have had to find their place within the community of birds already on the islands, competing for food resources with some, exploiting some for nesting material or territories, and being exploited by others. The survivors and their descendants would most certainly have altered the ecosystem, but most likely in fairly small ways. They’d not have caused mass extinctions.
But those junglefowl were brought to Hawaiʻi by humans, and our species being what it is, the humans simply could not leave well enough alone. They brought not just chickens—very close genetically to the original, truly wild Red Junglefowl of Southeast Asia—but also pigs and a dog (the Hawaiian poi dog, which is now extinct). Polynesian rats were also on board, either as stowaways or brought intentionally, possibly for easy protein during a long voyage.
Most meat-eating people cannot or choose not to live on chickens and pigs alone, and the Polynesians were no exception. They started hunting as soon as they arrived in Hawaiʻi. Birds in most places can easily survive humans hunting them for subsistence or sport, but being on small islands with few or no natural predators, most Hawaiian birds produced far fewer young per year than their mainland relatives. And on any mainland there is ever so much more land where population reserves can be waiting in the wings when a population in one area dwindles.
Large flightless birds were the first to disappear, but many songbirds dwindled as well, hunted both for food and for their beautiful feathers. The brilliant feathers of birds such as ʻIʻiwis were highly prized by Hawaiian aliʻi (nobility) for use in decorating ʻahuʻula (feather cloaks) and mahiole (feathered helmets).
As many as 80,000 feathers could be used in a single cloak, leading to the endangerment and extinction of several of the more colorful species. Fortunately, a few brightly colored ones, like my beloved ʻIʻiwi, are still barely hanging in there, but dozens of species disappeared entirely. Extinction is forever.
Hunting by the first Polynesians wasn’t the only issue suddenly facing Hawaiian birds. Once those first humans decided to stick around, they cleared forests and introduced non-native plants for agriculture. Even worse, the pigs they intentionally released on the islands, and the rats that came along for the ride, wreaked even more havoc on habitat. Pigs uprooted young trees, dooming forest regeneration, and devoured flowering shrubs and small plants, critical food sources for many of the Hawaiian honeycreepers. Humans, pigs, and rats all ate many of the same berries and fruits that native birds depended on. Adding insult to injury, the omnivorous humans, pigs, and rats ate the eggs and young of ground-nesting birds. The poor Nēnēs and other waterfowl got it from every direction.
Over hundreds or thousands of generations, in a large enough area with large enough populations to start with, species can adapt to new assaults like this. There wasn’t enough time for most ground-nesting birds in Hawaiʻi, especially the flightless species, but the Nēnē, Koloa Maoli (Hawaiian Duck), and Laysan Duck hung on.
Over time, many birds would have adapted, and birders visiting Hawaiʻi today would have an easy time finding many native species, including those splendid moas—or as we call them, Red Junglefowl or chickens—which would have become part of the natural bird community. But Captain Cook’s arrival sparked a whole array of new assaults on native Hawaiian birds, and even on those Red Junglefowl. Nothing would ever be the same.