The decline of 2 species of divers

Ducks declining at worrisome rates
Two diving ducks have begun to mysteriously vanish from the vast continental store of breeding, wintering and migrating waterfowl
By Alanna Mitchell
Toronto Globe and Mail

For centuries, likely millennia, the ducks of North America have followed the same ritual, wintering in the warm southern parts of the continent and breeding in the cool north.

Their numbers dip and crest, but every spring and fall, millions upon millions of ducks can be counted on to take to the skies and fly from one end of North America to the other, a phenomenon unmatched on any other continent.

But now there's a glitch in the pattern. Two types of diving ducks, scaups (both greater and lesser varieties) and scoters (the white-winged, surf and black varieties), have begun mysteriously vanishing from the vast continental store of breeding, wintering and migrating waterfowl.

Scaup numbers have dropped by 41 percent - to 3.5 million from 6.3 million - from the long-term averages that have characterized the birds since waterfowl biologists began yearly counts in 1955. The population is dropping by about 150,000 a year.

Scoter numbers are down 58 percent, to about 700,000 from 1.8 million. In each case, this is the lowest number ever recorded. And the numbers of both scaups and scoters continue to fall, an anomaly in the world of waterfowl.

The only other duck to suffer large declines is the prairie's pintails. But it's no mystery. They are starving from years of drought.

The decline of the scaups and scoters has biologists baffled. Scientists held an emergency meeting on the scaup situation in 1999 and came up with a long list of research questions, many of which have sparked intensive studies. It made them realize they don't have a clue why these birds are dying off - or, therefore, how to save them. They even fear extinction.

And what if the scaups and scoters disappear altogether? That, too, is an unknown, said Stuart Slattery, a wildlife ecologist with Ducks Unlimited Canada. If the ducks are critical to whatever ecosystem they are in, the effects could be far-ranging and dire, causing other extinctions.

Scientists have found that the center of the mystery is in Canada's part of the western boreal forest, the scraggly northern lands of British Columbia, Alberta, Saskatchewan and Manitoba, as well as vast tracts of the northern territories.

The wetlands of this relatively pristine landscape are where the majority of scaups and scoters arrive in the spring to breed, lay eggs and nest. Other, smaller populations reproduce in the boreal forest of Alaska. But these are stable.

The early research on scaups, made difficult by the fact that the nests are in remote boreal bogs and are far apart from one another, has found that the females have become thin and feeble and are not breeding properly. This affects the structure of the scaup population as a whole and is probably driving the declines.

The twin declines of scaup and scoter contain deeper mysteries, though. Scoters are sea ducks while scaups are drawn to freshwater. While they breed in the same Canadian western boreal forest, they winter in vastly different parts of the continent.

To Slattery, the answer to the riddle of the disappearing ducks could lie in one of three places: where the ducks winter, where they travel or where they breed. The only certainty is that the effects show up in the boreal forest as the ducks are trying to reproduce.

A likely suspect is toxins, which they could pick up as they winter in the south, or as they migrate back to the northern nesting grounds, or as they encounter them all over North America and deposit them in the boreal forests, where they affect breeding mothers and their young.

Other causes might be renewed oil and gas exploration in the western boreal forest, which could affect the ducks in an unknown way, or global warming in general, or lack of food as they migrate.

Distributed by Scripps Howard News Service