How Cockatoos Evolved

Abstract

By Linda S. Rubin INTRODUCTION

In the discussion of cockatoo evolution, it appears a long debate has been answered that would shed light on the cockatoo's family structure, including the order and relationship of various genera to one another and just how closely they are related. Pivotal to this exploration and an adjunct to the question of

cockatoo ancestry is whether the Australian Cockatiel is an actual member of the cockatoo family.

This is an important question not limited to cockatiel enthusiasts. Should it be found that the cockatiel is indeed a cockatoo- Red-ta and the genera to which it is related is identified-perhaps some parallels might be drawn that could prove beneficial to cockatoo culture at large, or to some species of the cockatoo family.

It is generally understood that cockatiels are quite prolific and a greater number can be reared in captivity compared to many species of cockatoos. Because cockatiels can be raised in greater numbers within a shorter span of time, lessons may be more quickly learned concerning husbandry and other aspects of aviculture. In some instances, this knowledge could be considered where appropriate, perhaps concerning some aspects of health, genetic predisposition to disease, husbandry, nutrition and possibly further evolutionary questions involving environmental adaptation.

For example, many cockatiel breeders feed low-fat diets (e.g., it does seem that cockatiels can simply "glance" at a seed and appear to gain 5 grams!). Feeding cockatiels a diet low in fat can assist in preventing a shortened lifespan, and can help with some difficulties in reproduction and various health issues (for example, weight gain can prompt a propensity for growing tumors and other health issues, especially when space is restricted in captivity). We already know these issues similarly appear to affect the Galah. A significant pool of knowledge in cockatiel culture has already accumulated over the decades and could prove useful in providing a wider view or a reference when examining this family of birds.

Strides in nutrition and avian medicine have added greatly to keeping and raising avian species in captivity, and cockatiels have benefitted from many formal studies and observations providing noteworthy information. Additionally, cockatiel breeders throughout the world have established various gene pools of cockatiels and their mutations, which might prove informative as a reference.

Fortunately for aviculturists, a unique study was undertaken some years ago to address the evolution of cockatoos, which revealed some fascinating results.

RESEARCH STUDY

Researchers at the University of California at Davis; David M. Brown, a Ph.D. student at UCLA; and Dr. Catherine A. Toft, professor at the Center for Populations Biology at UC Davis, conducted the study, "A Cockatoo's Who's Who: Determining Evolutionary Relationships Among the Cockatoos." The study was published in volume 11, No. 2 of the Exotic Bird Report in the Psittacine Research Project of the Department of Avian Sciences at the University of California at Davis, and highlighted intriguing new findings.

To start, Brown and Toft acknowledged a lengthy history of the exhaustive work by other researchers identifying 350 species of parrots, beginning with Linnaeus in 1758, and which revealed the following facts before Brown and Toft began their own investigation.

First, it was found that cockatoos form a unique group in themselves among the parrots. Some of the more notable morphological characteristics include an erectile crest that can be lowered and raised at will (aiding many observers to be able to explain and interpret cockatoo body language), plus alack of dyck texture in feathers that other parrots use to produce the blue and green colors that appear in their plumage.

Second, it was noted that cockatoos have traditionally been divided into two major groups, the predominantly black Calyptorhynchi, Calyptorhynchus, and the predominantly white Cacatuini, including Cacatua.