Monday, July 30, 2007

A creationism vs. evolution discussion,. Part 8D

“"They embrace each day with curiosity, mischief, and the desire to eat."

Keas and Answers in Genesis

I will admit, off the bat, to a bias here. I have an inordinate fondness for keas, the clever New Zealand parrots who are both natural comics and inveterate experimenters. I happen to own a copy of the book that AiG references in their article on keas- Kea-Bird of Paradox by Judy Diamond and Alan Bond. On their webpage, though, AiG conveniently left out the subtitle of this fine book:
The Evolution and Behavior of a New Zealand Parrot

So what does AiG say about these mischievous birds? They do get several points right- keas are indeed very intelligent, playful, destructive parrots who have an odd predilection for mutton that once led to their destruction as sheep-killers. However, when it comes to the account of how and why the kea became such an omnivorous, manipulative, clever animal, the explanations of the kea researchers who spent three years in the field observing and documenting kea behavior and uncounted more hours recording behaviors of captive keas and studying kea remains in museums definitely part ways with those of the AiG article author Paula Weston, a journalist with no biological training listed in her bio.

The AiG article claims that the feeding behavior of keas is not related to their evolutionary history.
The diet changed simply because of the kea’s general adaptability, intelligence, curiosity and mischievousness.
The latter is the most likely theory, and has nothing to do with ‘evolution’.
AiG misses the boat entirely. Kea feeding behavior- as well as their intelligence, playfulness and exploratory nature- has everything to do with evolution.

The kea and its close New Zealand relative, the kaka, form a parrot group which diverged from the other groups of parrots long ago. They are not closely related to any existing parrots and diverged from the ancestral parrot stock 15-20 million years ago, shortly after the first parrots evolved 20-23 million years ago.
Page references in the following are from my copy of Kea- Bird of Paradox. Unlike most other parrots, both the kea and the kaka are omnivorous. The kea evolved in a world very different from the one it inhabits today. New Zealand, as an isolated island, had a unique fauna, with many species unrelated to any others anywhere in the world. Among its now-extinct fauna was the moa, a gigantic flightless bird, and the Haast’s eagle, the largest eagle that ever existed, which fed on the moas. Moa carrion provided a source of food for keas.(12) Although AiG claims “Naturalists believe keas were originally herbivores, like other parrots, and that we can look at their current feeding patterns to help understand the past.” Diamond and Best state “At the time of the moas, keas probably fed much as they do today.” (14) Keas did not depend on any one particular foodstuff- although New Zealand beeches were a main food source. Keas are opportunistic feeders, who compete with many other native species for most of their food, and their lives depend on being able to find and take advantage of anything edible that becomes available. . If moa carrion wasn’t available, sheep carrion would do, and if sheep carrion was not available, live sheep would do- keas simply pecked holes in their backs and scraped out the fat underneath the skin. (32) As Diamond and Best wrote, “In a world of dietary specialists, the kea survived as the ultimate generalist.” The kea is what the authors called an “open-program species, (148)” a pattern that has evolved several times, a notable American example being the coyote. Open- program species evolve in environments where there is fierce competition for available resources, where an animal never knows where its next meal is coming from. A more common response to such situations is to specialize- if you are the best adapted to exploiting one particular resource, you will survive as long as that resource is available. This is the path taken by koalas and pandas. The open program species, on the other hand, survive by being intelligent and curious enough to find and recognize any available food source in their environment and take advantage of it.

The authors are quite clear that the open-program behavior is a result of evolution. “Open-program animals evolve in response to a particular constellation of features.(149)” They also discuss how the kea has evolved another behavior- social play.

Unlike mammals, most birds do not exhibit social play. Keas are members of one of only three of the 27 orders of birds that have species that have been observed in social play.
In these orders, only a few species of birds actually show social play- “thirteen species of parrots, seven species of corvids, and several hornbills and Eurasian babblers.” Keas and some corvids (members of the crow family) are by far the avian masters at social play.

What does research show that the birds who engage in social play have in common? They live in groups, adults take care of the young for long periods of time and continue to associate with their young even after they become independent, and they breed later than other birds. Thus, the birds that do exhibit social play are not just random species; they share characteristics that allowed social play to evolve independently in each family of birds. In addition, these characteristics are the same ones that are apparent in mammals that show the most complex social play, such as wolves and primates. “Because birds and mammals share only a very remote evolutionary history, it seems likely that social play has evolved convergently in these groups, with possibly several independent origins.”

So it is not creation that shaped the kea, but evolution. As Diamond and Best conclude:

One can create a sort of evolutionary “recipe” to describe the factors that promote flexibility in animals. For the kea, the first ingredient is a lineage predisposed to sociality. Next comes the relatively low food abundance, so the animal has to be prepared to accept an enormous range of foods. Add to this the short-term limitations on food availability, so the animal must constantly shift food sources. And finally, include delayed maturation and lenience by adults toward the young, so the young have time to play. Against the dramatic backdrop of the formation of the New Zealand islands, this recipe transformed a rater ordinary forest parrot into one of the world’s most unusual birds; a species so flexible that it managed to survive even the extermination of much of its original ecosystem.

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