Adélie foraging

Measuring parental foraging effort

Adélie crossing weighbridge
Adélie crossing weighbridge

To do this, a group of about 50 breeding pairs is fenced off from the rest of the colony. The only way in or out of this area is over a weighbridge.  Breeding penguins inside the fenced area each have a small PIT tag injected under the loose skin around the neck. These tiny devices, measuring 16 mm long and 2.5 mm wide, weigh only 0.2 g. PIT tags, which function like individual barcodes, are used in conjunction with electronic weighbridges so that as a bird crosses the weighbridge, sensors read the tag, weigh the bird and record the direction of travel (i.e. entering or leaving the colony). We are using this information to measure:

Remote data-collection

We are using instruments like time depth recorders, satellite tags, and transmitters to find out what birds are doing while they are at sea.  The streamlined, battery-powered,  transmitting devices can be temporarily attached to the feathers on a penguin's lower back with sticky tape. This minimises any adverse effect the tag may have (like drag when swimming), and also reduces the likelihood of the tag being dislodged.  Studies have shown that tags have no significant effect on the duration of a foraging trip or on nesting success.

Radio transmitter tags (txs) and satellite tags

Adélie with a TDR and TX taped to its lower back
Adélie with a TDR and tx taped to its lower back

Txs give out a brief electronic pulse about 55 times every minute. These pulses can be picked up by a person holding an antenna and a receiver. The loudness of the beeps from the receiver indicates the direction towards and closeness of the transmitter -- and of course the penguin to which it is attached! This can be a very useful way of finding a particular penguin in a colony of thousands. Signals from txs can also be used to determine:

Satellite tags automatically transmit data on a bird's location to orbiting satellites. The information recorded can then be downloaded from the satellite.

Time depth recorders (TDR)

Time-depth recorder
Time depth recorder

These weigh 25.4 g and when taped to a penguin's lower back add about 1% to the bird's total cross-sectional area.  TDRs are normally attached for one or two foraging trips. TDRs sample both light intensity and temperature every second, and can store more than 2 million sensor readings.  The light sensor allows the duration and depth of a dive to be found – the deeper the dive, the darker the water! 

 

Stomach flushing

Adélie baffing into a bucket
Adélie baffing into a bucket

To find out what birds are eating during the breeding season we collect diet samples.  To do this we use a tube to gently add about half a litre of warm water into a penguin's stomach. Tipping the bird upside down causes the water and some of the stomach contents to pour into a collecting bucket.

At the colonies we assess:


Adélie Penguins