Counting emperor penguins during a winter huddle near Australia's Mawson station (Photograph by Graham Robertson, Australian Antarctic Division)

The best time to count emperor penguins is in the middle of winter when the males are enduring their long incubation fast. At this time of year the females are at sea feeding, and since there are only a few non-breeding birds hanging about, each bird represents one breeding pair....Unfortunately for the counters, winter presents its own special problems - the birds cram tightly in hectare-size huddles to keep warm making it difficult to count them, day-length is only three hours of twilight and wind-chill temperatures occasionally reach minus 50 degrees C.

Fifteen people from the stations assisted with the counts, and we tried every method we could think of. We made snap estimates (gut feeling of numbers with no attempt to actually count). We counted them from a three-metre high step ladder, then from 11 metres up on a scaffold tower mounted on a sledge that we towed behind a vehicle along the flanks of the birds. We counted them by eye at the colony and later on from photographs taken from our lofty vantage points. We measured with a rangefinder the area of huddles and multiplied this by the density of bird in huddles (estimated by measuring the circumference of incubating males - we achieved this by passing a cloth tape measure around birds while duck-waddling behind them as they shuffled along, egg-on feet, on the sea-ice) to derive the total number of huddling birds.

We used reference groups of 100 or so birds and estimated the number of these groups in the whole mob. And we gently herded small groups of birds between two people and counted them sheep-like as they passed by (after one brief attempt we declared this method too disruptive). Finally we floated a remotely controlled camera from a helium-filled balloon about 50 metres above the colony to get aerial pictures from which we could count the birds?

Activities

• Have the students list the various ways of estimating the numbers of birds.
  - Can they think of any methods besides those in the Graham Robertson text above?
  - Which method would be the most reliable?
• Give the students a similar situation (such as the numbers of spectators at a football match) and have them come up with various counting methods.
• Have students examine the aerial photograph below, and ask them to come up with ways of estimating total numbers. (They could estimate, then sub-sample, and then verify their result by actually counting the number of birds).
  Click here to obtain the picture as a black-and-white PDF file for printing out.

PHOTO: King penguin colony at South Spit, Heard Island (aerial photograph courtesy of Dr Eric Woehler, Australian Antarctic Division)