Growing up is never easy, but for newly hatched Antarctic fulmarine petrel chicks, the pressure's really on. With little more than three months before the temperatures plummet and winter returns, the chicks must develop and take to their wings before the weather closes in. But these remarkable chicks rise to the challenge, growing at twice the rate of petrel chicks from temperate zones, even though it `takes far more energy to make 1 g of chick at subzero temperatures' explains Wes Weathers. How the birds sustain these rapid growth rates wasn't clear, and Weathers and Peter Hodum wondered if the youngsters'parents had to put in more effort than their temperate cousins to sustain their chicks' spectacular growth rates. Hodum headed south to the Rauer Islands in East Antarctica to measure both chick and adult metabolic rates in four Antarctic fulmarine petrel species, and was amazed to find that although all of the youngsters fledged within two months of hatching, their parents worked no harder than if they were feeding chicks that developed at half the rate (p. 2125)!

Hodum explains that he has always been fascinated by petrels, because of their beauty and the `mystery of their lives'; very little is known about their biology. And Hodum adds that the Rauer Islands are probably the best place in the world to study the birds; four fulmarine petrel species gather there to nest. So he travelled south, during three consecutive field seasons,for the unique opportunity to measure the bird's metabolic rates as the chicks developed.

After injecting both chicks and adults from all four species of fulmarine petrel with naturally occurring isotopes of oxygen and hydrogen, Hodum collected tiny blood samples from the birds, so that he could compare the amounts of each isotope remaining in their bodies to calculate their energy expenditures. He remembers that collecting samples from the chicks was quite straightforward: `they never move from the nest'. But the adults were another matter. Parent fulmarine petrels leave for days on end to forage in the oceans, often returning at night to feed their young, which is a problem during the southern hemisphere's summer; there is no night, so the birds can return at any time of day. Hodum and a team of helpers set up 24-hour watch,ready to intercept the returning adults.

And having chosen to work with the deuterium isotope of hydrogen instead of tritium, Hodum faced another complication. The carefully collected samples had to be sent to a specialised facility in the Netherlands for isotope analysis. After returning to his base in Australia, Hodum faced a frustrating two-year wait before he knew whether his efforts had been in vain.

With the isotope data finally in hand, Hodum was amazed; the adult Antarctic petrels only worked as hard as petrel-parents in more temperate zones, even though the youngsters were growing twice as fast as other species'chicks. Weathers and Hodum were also surprised that the chicks seemed to match their growth rate to the time available. All of the chicks fledged during Antarctica's three-month summer, even though some species' chicks were twice the size of others.

So how do the chicks sustain their accelerated growth rate if the parents aren't over exerting themselves? Hodum and Weathers suspect that the bird's phenomenal growth rate is down to the abundance of top quality food in the Antarctic oceans.

Hodum, P. J. and Weathers, W. W. (
2003
). Energetics of nestling growth and parental effort in Antarctic fulmarine petrels.
J. Exp. Biol.
206
,
2125
-2133.