Not the spotted owl of Oregon but Spix's macaw of Brazil is the mostendangered species of bird on Earth. Only 32 of these big, beautifulparrots remain alive, of which 31 are females _ most of them in aBrazilian zoo, a few scattered in other collections around the world.

No. 32 has been moping around a single tree in the open woodlandwest of Brasilia ever since 1987, when the last wild female wascaptured.

Is this sole surviving wild loner male or female?

In the bird world, it takes one to know one. Most avian species aremonomorphic. That is, both sexes look so much alike that onlyhuman sexing specialists can determine their gender, by deftpalpation.

Brazilian wildlife conservationists have been keeping a constant vigilaround No. 32's tree for years, to prevent poachers from making offwith the last unfettered specimen of Spix's macaw. If he/she turnedout to be a he, they have long planned on releasing one she-macaw tohelp found a new wild population, and snatch the species back fromthe brink of extinction.

Snaring No. 32 just long enough to determine its sex was out of thequestion, says molecular zoologist Richard Griffiths of OxfordUniversity. "That bird is the only Spix macaw who knows how tosurvive in the wild," he told BioWorld Today. "How you eat, howyou avoid predators, how you survive; it's the only one that knows allthat stuff." He added, "So it's critical to keep it out in the wild, andalso bolster up the numbers out there, in case that last wild birdhappens to die."

Griffiths, a post-doc in the ecology and behavior group of Oxford'szoology department, recently determined by remote DNA analysis ofmolted feathers that the solo bird is indeed a male, and thus capableof jump-starting the threatened species.

Which Sex? Ye Shall Know Them By Their Genes

"It was the first time ever that sexing has been done by DNAextraction from a feather," he said, and explained that "just as humanfemales have two X chromosomes, and males one X and one Y, sofemale birds have a W and a Z chromosome; males, two Z's."

Griffiths obtained a genomic library for a closely related parrot, thehyacinth macaw, donated by Stratagene Cloning Systems of La Jolla,Calif. "We isolated the W-linked [female] gene from that," he reportsin today's issue of Nature, titled "Sex of the last wild Spix's macaw."

"Getting that hyacinth sequence," he said, "gave us the gene, which ishighly conserved. It allowed us to design PCR primers that we couldamplify directly from knowing that sequence. It was the short cut intofinding that Spix gene."

The hyacinth macaw, though akin to the Spix, is of a different genus(Anodorhynchus hyacinthinus). The Spix, Griffiths pointed out, "isthe only one in its genus (Cyanopsitta spixii), which also makes itvery well worth trying to look after. It's an unusual macaw."

When three dark-blue, cast-off flight feathers reached Oxford fromBrazil early this year, Griffiths took only their last half-inch tips toextract and amplify a 104-base-pair stretch of their DNA.

"The non-sex-linked sequences amplified wonderfully," he recalled,"but there was no trace of a W-linked marker, which proved that No.32 is male."

Following up quickly on this potential paternity candidate, theBrazilian zoologists on March 17th released a female near that male'sfavorite roost in the woodland. In bygone days, before the Spixmacaw population dwindled, Griffiths said, "some of the same birdsused to nest in that same tree for up to 50 years. That's one of thereasons they were easy to catch."

As for the presumptive father-to-be, "he's been alone since 1987, sohe's probably quite an old bird," the Oxford zoologist remarked,adding, "Macaws live for a long time, 50 or 60 years, so there's areasonable chance that he's still got some life left in him yet."

Mating Pair: One On One In The Woodland?

What, if anything, transpired between mid-March and early June?

"That's a key question," said Griffiths. "As far as I know, theyhaven't actually come across each other. People there watching thosebirds are hoping they are going to bump into each other; they arehoping that the contact is inevitable."

Spix's macaws are about 2-feet long, with dark blue plumage andgray tufts atop their head. Bright yellow eyes and black beak,Griffiths said, "make them really quite striking."

That fetching appearance, and their rarity, he said, used to fetch bigprices on the black market. "The last prices of, say, $60,000 havebeen bandied about for one of these birds smuggled to a very wealthycollector, so it's very much the executive type."

Today, he pointed out, "people who possess these birds are liable toprosecution, because the only way they can come out of Brazil now isby smuggling."

The first person to shoot down a Spix's macaw, back in 1819, wasthe Austrian naturalist who gave the big parrot its name. "Jean-Baptiste von Spix wandered around Brazil at that time," Griffithsrelated, "discovered a huge collection of birds, plants and animals,and shipped them all back to Austria."

Griffiths hopes to develop his feather-based, patent-pending, DNAanalysis into "a universal avian sexing test for a lot of other birdspecies. Two-thirds of the world's birds can't be sexed just bylooking at them," he pointed out, "and a lot of these species are introuble, so the only way you can get a captive breeding programworking well is by knowing what sex the adults are."

"It's an incredible technique," ornithologist John Aikin toldBioWorld Today, "that opens up whole new possibilities for us tounderstand the relatedness, and in this case, the sex, of individualanimals _ the precious few that remain." Aikin is curator of birds atthe San Francisco Zoological Society.

"We were the first to show," said conservation geneticist DavidWoodruff, of the University of California at San Diego, "that feathersare a rich source of DNA. You can probably sex birds based on adown feather that birds molt, or off a feather you find at the bottomof the cage," he told BioWorld Today.

Anent Griffith's feat, Woodruff added pointedly, "One of the keythings we have not been able to do up to now is sex birds quickly." n

-- David N. Leff Science Editor

(c) 1997 American Health Consultants. All rights reserved.