Can you imagine a four foot long goose? That's what happens when a Canada Goose decides to take a tropical vacation and chooses to stick around.
I've been developing another blog over the last few months as an outlet for my new hobby, bird photography (Geotripper's California Birds). I'm not an expert (yet), nor a hard-case birder (yet), but my friends and coworkers have come to recognize that if I'm walking around somewhere, I am inevitably carrying a camera. The blog is mostly about my bird observations in California and the west, but I started getting interested in birds during my travels in Hawaii beginning in 2002. I consider these two separate projects, but sometimes the subject matter overlaps. Evolution is one of those subjects, as is hot spot volcanism (i.e. Hawaii). What follows is today's post from the California Birds blog:
During the millennia that followed, different flocks of geese took up
residence in different ecological niches, such as lava flows, grassy
slopes, and woodlands. Isolated groups began to diverge, and before long
at least three species developed on the islands. One of them, the Giant
Hawaiian Goose (species name not yet established), was big, almost four feet long. A lack of predators on the island made flight an
energy-intensive but unneeded luxury, so the wings became smaller as the
bird evolved to larger size. The goose was flightless. This worked fine
for a long time, but humans ultimately arrived on the islands, and
probably exterminated them, either by hunting, or by introduction of
egg-eating rats, or by habitat destruction.
The second species was the nene-nui (Branta hylobadistes).
It was also a big bird, but had larger wings so that it was still
capable of weak flight. Like the Giant Hawaiian Goose, it became extinct
soon after the arrival of humans on the islands. It has been
characterized as a bird in evolutionary transition, in the midst of
losing the ability to fly, but it went extinct first. Possibly because it couldn't fly well.
The flying goose, the one that survived was the nene (Branta sandvicensis). The nene's wings were smaller than its Canadian ancestors, because it didn't need to migrate thousands of miles during the change of seasons. But it retained enough flying ability to escape from the island's human invaders. It differed from the Canada Goose in several other respects, including longer legs, reduced webbing between its toes, and a more erect posture. It is adapted to living on lava flows and grasslands, and was less dependent on wetlands than other geese.
It survived, but no longer thrived. Rats ate their eggs and chicks, and later on cats and mongooses were brought to the islands. The species was devastated, dropping from an estimated 25,000 when first European contact was made in 1778 to thirty individuals in 1952. A captive breeding program began, and populations were established on their ancient habitats on Maui and Kauai (where mongooses were never introduced). The wild population is now around 800, with another thousand or so in captivity. They are still highly endangered, but their prospects are slowly improving. They have been named the state bird of Hawaii.
Are you interested in learning a bit more about these fascinating creatures? Here is a link for a National Geographic article on the evolution of the Hawaiian geese and their Canadian cousins, and the scholarly article of the research into the vanished species: