Te Papa’s curator of terrestrial vertebrates Dr Colin Miskelly tells the 11th instalment of the story of the emperor penguin that went where none had gone before. Previous blogs on the penguin were posted between 23 June and 12 September 2011.
One of the unknowns regarding the emperor penguin that came ashore at Peka Peka last June was how old it was. The bird did not have the jet-black chin and brightly-coloured auricular patches of a breeding adult, indicating that it was less than 4 years old. But its chin was darker than those in published images of fledgling and one-year-old emperor penguins, suggesting that it had completed at least one moult after fledging.
Most wild emperor penguins hatch in July and go to sea in December when about 5 months old. This first set of juvenile feathers last until the birds moult the following December-January, when about 17 months old. Because the Peka Peka bird came ashore in June, it would have been 11 months, 23 months or 35 months old. But which age class was it?
New light on this question has been shed by Lauren DuBois, assistant curator of birds at SeaWorld San Diego. Lauren has provided images of a captive bred bird that hatched in September 2010. By January 2012 (at 15 months old) this bird had completed its first moult, and looked the same as the adult that it is standing next to.
Ten wild-caught juvenile emperor penguins from the July 2011 hatch were taken into captivity in December 2011. These birds came from the Cape Washington rookery on the western side of the Ross Sea, south of New Zealand. The ten birds were photographed in January 2012 when about 6 months old, and show a range of chin plumage colouration from the usual off-white through to birds as dark as the Peka Peka bird.
Based on these images, there is now little doubt that the emperor penguin that stepped ashore at Peka Peka on 20 June 2011 was about 11 months old.
Confirmation of his age supports the decision to release the bird near Campbell Island. A satellite-tracking study of fledgling emperor penguins in the Australian Antarctic sector in 1996 and 2007 managed to follow a few birds through to May and June, when they would have been 10-11 months old. One of these birds tracked as far north as 54.2 degrees south, and several others were not far behind. The last signal received from the Peka Peka emperor penguin after release was at 52.3 degrees south, within 200 km of the minimum latitude recorded in this small scale tracking study (17 birds), and 1250 km of latitude south of Peka Peka.
Also relevant is the sighting of three emperor penguins at sea east of Argentina by Maurice Rumboll on 15 September 1975. These birds were at 40.5 degrees south, which is slightly further north than Peka Peka.
When released, the Peka Peka emperor penguin was within the latitudinal zone of the Southern Ocean where juvenile emperor penguins live.
Previous blogs on this topic:
For a later blog on this bird: