Kaua’i’s native rainforest is a last refuge for a number of endemic Hawaiian bird species. Before I start introducing some of them individually, it’s important to understand the broader conservation issues facing Hawaiian birds. And believe me, they are legion.
The Hawaiian islands, to our knowledge, were colonized by humans in the last two thousand years, but the islands – and most of their other species – are much older than that. So many of them have not co-evolved with humans. Nor do they have a history with the species we brought with us – first pigs and fowl brought by native Hawaiians, then myriad other species (black rats, mosquitoes, eucalyptus trees…) brought later by Europeans. The number of non-native species introduced to Hawaii is unbelievable: of the plants and animals you’d see on an average day anywhere in coastal Kaua’i, virtually none is native. Introduced species have displaced, consumed, and out-competed native ones. There are introduced birds replacing native birds; introduced cats, rats, and mongoose eating birds and their eggs; introduced plants replacing the native trees on which birds depend for food and nesting material; and introduced mosquitoes spreading introduced avian diseases.
Mosquitoes in Hawai’i are just a nuisance to us but are deadly to birds. The combination of introduced mosquitoes and introduced birds brought an epidemic of avian pox and avian malaria, to which native birds have no immunity. At higher, cooler elevations, transmission of these diseases is less likely, so more native birds are found in the mountains. If they go too far downhill, they may get malaria – then will either succumb to the disease, or be caught by rats when they’re weakened by it. Of course, as the climate warms, the elevation above which malaria and pox aren’t transmitted moves up, and the birds can only go so far up the mountain.
Large-scale agriculture in Hawai’i, from cattle ranching to sugarcane plantations, has removed much native forest from the lowlands. The more inaccessible highlands, as a result, are where most of the remaining forest is found. This is lucky in terms of malaria transmission, but still means that there’s a very limited area in which native birds can live. And again because of malaria, reforestation at lower elevations will not be very useful.
Because native bird populations are quite small, they’re also at risk of being drastically damaged by hurricanes. Not only could hurricanes kill birds, but there’s evidence that the birds may drop down to lower elevations to avoid the worst of the high winds – and then, guess what, they’d get malaria.
And somehow my job of staring at bird nests is going to help make things better.