Who are you calling "invasive"?
The Hawaiian Islands are a crucible of natural selection, and a laboratory for studying evolution. The islands spawned dozens and dozens of new species from the few original species that found their way to the isolated volcanic landscape over several million years (a successful new arrival on average every 20,000 years; these things don't happen fast), and in the present day, we are observing intense competition between native species and introduced species that piggy-backed with humans, in the first Polynesian wave more than a thousand years ago, and in the current wave of the last two hundred years. Unfortunately, it is the native species that tend to lose out.
The natives have been battered by introduced diseases, especially mosquito-borne bird malaria, predation by mongooses, cats, dogs, and rats, and by severe loss of habitat due to grazing, agriculture and urbanization. Most of the native species survive in high-altitude forests above 4,000 feet (too cold for mosquitos), and they can be difficult to see. I know, because I try to photograph them on every trip and for the most part I am stunningly unsuccessful. Especially this last week.
Still, the invaders are a beautiful and diverse lot, and it's not their fault for being here; I do enjoy getting close-ups of them when I can. I "collected" some new species this week, in the digital sense. The first two photos are of some Red-Vented Bulbuls (Pycnonotus cafer), an Asian species that arrived on the islands in the 1950's, probably as escaped pets. They were cute and friendly with us in Waimea Canyon on Oahu, but they love orchid buds and fresh fruits, and as such are an agricultural pest.
We heard beautiful songbirds in Waimea, and the singers were probably White-Rumped Shamas (Copsychus malabricus), a species of thrush from Malaysia who arrived on Oahu in 1940. They aren't described as pests, but they have penetrated deep into the native forests and probably compete with the native species for food and territory. I had a hard time getting a sharp shot of the adult Shama, but the juvenile came right out in the open for me (below).
There are three species of cardinals on the islands, including the familiar American version that people see on St. Louis baseball caps. They are one of the most colorful birds that are commonly seen. I knew of the Northern Cardinal (the American one), and the Red-Crested Cardinal from Brazil, but I hadn't seen the one below on my previous trips. It doesn't have the crest like the others.
It's called the Yellow-Billed Cardinal (Paroaria capitata), and it is a fairly recent arrival from South America, having first been observed in 1973. It's spreading out from the Kona area on the Big Island. Um...do my pits smell??
Another colorful pest in urban areas in the Java Sparrow (Padda oryzivora), which arrived from India in 1867. We saw a lot of them in Kona on the Big Island. The one below hung out on our lanai looking for handouts (not this time...).
And finally, we have the Saffron Finch (Sicalis flaveola
). The one I captured is probably a juvenile, as the adults have a orange blush about the head. They arrived in the 1960's from South America.
When you ever make it to the islands, don't hang out in Waikiki! There is so much more to see. A valuable resource for bird-hunting is the book Hawaii's Birds
, published by the Hawaii Audubon Society. It is my best source about the birds, both native and invasive. And since I really am a geologist and not an ornithologist, I am open to corrections on my bird identifications!