The Short Childhood of Ancient Murrelets

Sentimental parents may complain that children grow up too quickly, but no human child leaves home as swiftly as the offspring of a little northern seabird. Two days after hatching, chicks of the ancient murrelet flee their nests, never to return.

Members of the auk family--the Northern Hemisphere's answer to the penguin clan--ancient murrelets are found all along North Pacific shores, from China and Korea through the Aleutians, southcentral and southeastern Alaska, and British Columbia. Small creatures themselves, with adults weighing about half a pound, they feed far from land on the much smaller animals comprising the zooplankton.

We share the planet with perhaps a million ancient murrelets; nearly half of them breed in British Columbia's Queen Charlotte Islands. That is where Canadian zoologist Tony Gaston spent four years studying them, as he reports in the magazine Natural History.

Reef Island, where Gaston worked with student Ian Jones, seems a strange place to study seabirds. It's covered with a dense forest of Sitka spruce and other rain-forest conifers, not typical habitat for nesting seabirds. But these are not typical seabirds.

One oddity is that the ten thousand murrelets living on the island are virtually invisible by day; the place seems uninhabited. Only well after dark do any birds appear, with members of breeding pairs exchanging egg-sitting duties in the burrows they dig for nesting. Later arrivals include younger birds prospecting for nest burrow sites or possible mates.

Oddest of all, young males looking for unattached females advertise by perching high in the treetops and singing for hours. The researchers found themselves in a bemusing situation--being serenaded by seabirds singing from trees in the middle of the night.

Successful serenades lead eventually to two comparatively enormous eggs: each weighs approximately one-quarter of the female's weight. [Think of that as like a 120-pound woman giving birth to two 30-pound babies, and you can see that it's a stunning feat.) The eggs produce one-ounce chicks. They don't gain weight while residing in the family burrow, because the parents bring no food back to the nest. Instead, generally on the second night after hatching, the adult birds lead the downy youngsters out of the burrow. Like feathered pied pipers, they use a characteristic call to lure the little birds along. The chicks answer with loud peeps.

This family parade proceeds only a short distance before the parent birds fly off to sea. The chicks immediately stop peeping and begin to run as fast as they can toward the nearest beach.

That can be as much as 500 yards away, and not one of those yards is likely to be easy for the chicks. The tiny fluffballs may have to scramble over fallen logs, wriggle through ferns and dense shrubbery, tumble down cliffs--and avoid owls and other predators.

Yet, guided by the brighter light over the ocean, the downslope of the land toward the water, and--eventually--the familiar calls of their parents, a surprisingly high proportion of the chicks make it to shore. Reaching the water's edge, they plunge immediately into the sea. Bobbing like downy corks, they still have to survive being tumbled by surf, hunted by hungry fish, and even harassed by unrelated adult murrelets.

Despite the hazards, the great majority of the fast-paddling chicks successfully rendezvous with their families. Gaston reports that first daylight finds many groups of two adults and two chicks, all heading away from shore. Generally they meet up less than 200 yards from shore, but dawn finds them more than three miles from the breeding colony.

The chicks can keep up with adults because their feet are disproportionately large. They can deal with the cool seawater because their down is nearly waterproof, they have a thick layer of fat right under their skin, and their circulatory system is designed so they lose little heat through their big webbed feet. (As Gaston put it, "A chick in the hand feels like a warm cupcake with two icicles attached.")

Ancient murrelets have evolved a system of taking their young to the food, rather than making frequent trips from food to nest as other seabirds do. This and their nocturnal habits enable them to establish large colonies in areas inhabited by many predators, where seabirds following the standard pattern would be wiped out. It seems an improbable solution, hard on the egg-laying mothers and the challenged chicks, but it certainly works. We have a million murrelets to show that it does.