11 January, 2000
The cape Bird hut is run by the Kiwis, with whom I will be working for a while. Our job is to conduct the doubly labeled water experiments. The purpose of this experiment is to determine how much energy a penguin
expends on a foraging (feeding ) trip. To get a handle on this, we will
measure the amount of water that the bird uses in respiration for the production of energy. The water in the bird's circulatory system combines with carbon from their food to produce CO2 and energy. The doubly labeled water we will be using contains isotopes of oxygen (O-18)
and hydrogen (H-2)
This "heavy" water will be converted into CO2 as
the bird does work and uses energy. What we hope to do is measure how much of the double labeled water is used during a foraging trip by comparing the amount that is initially injected into the bird versus the
amount that remains when the bird returns from its feeding trip. The net change in the amount of the DLW is proportional to the amount of energy used.
To know when a bird has returned from a foraging trip, we listen carefully for the bird's transmitter to tell if it
is in the colony. When it does return, we must get a blood sample as soon as possible. To insure that we don't miss a birds return, we check the colony with the telemetry receiver every two hours through the
night. If we get a signal, we all get up, put on our gear, and hike down to the colony (15 min) to get our blood sample. During this time we also check the body mass of the penguin. This is to see if the penguin is actually gaining weight during its foraging trip. So far we have found that the birds are gaining 500 to 750 grams of body mass during a trip. Food samples show that the diet of the birds consists of
krill (Euphasia) and the fish (Pleuragramma antarcticum).
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