Breeding on Trust reserves 2008-09
Thursday 28th May, 2009The 2008-09 breeding season on Trust reserves was very average, characterised by lighter weight chicks, and an unexpected series of egg and chick deaths and abnormalities at one Otago Peninsula reserve.
This reflected a general pattern on the Otago/Southland coast. As DOC Coastal Otago, Biodiversity Programme Manager David Agnew commented, "The breeding season got off to a promising start with high nest numbers, but took a dramatic turn in early November when young chicks started dying in the nest from Green Island to North Otago. At some sites over half the chicks were lost. Then later in the summer, many of the surviving chicks seemed to be very light, indicating some sort of food shortage for the adults."
Nest searching took place as usual in late October/early November, although Trust staff had to endure some unique nest searching conditions in the Catlins. On the 4th November, falling snow made searching conditions fairly miserable at Cosgrove Creek, with searchers sheltering behind flax clumps as the southerly squalls roared through. One penguin nest in particular was more sheltered than others, located two metres down a narrow tunnel, opening out into a cave that would have been quite dingy at the best of times, but made virtually pitch black by the searcher's body jammed in the opening. The small LED torch on the searcher's cell phone was very useful in illuminating the interior and counting the eggs!
At Otapahi reserve, nest numbers were up (32 compared with 22 in 2007/08), as was the number of chicks fledging (29 compared with 22), although fledging weights were significantly lighter than in 2007/08. The average weight was only 4.7 kg, well down from the 5.21 kg the previous year. Fledging weight is an important indicator of subsequent survival, so the lighter weights may very well have an impact later.
Several underweight chicks were brought back from the Catlins and reserves on Otago Peninsula, for feeding at Penguin Place and with Sue Downton and Colin Wolverson at Bushy Beach (Oamaru), to improve their weights before releasing.
The breeding season at Okia Reserve on Otago Peninsula began promisingly, with 18 nests recorded, up one from 2007/08. However there was an unexpected and so far unexplained cluster of six chicks with craniofacial defects, including mandible deformities, and this, along with egg deaths and dead chicks in nests, dramatically reduced the number of chicks fledging from 20 in 2007/08 to just three in 2008/09. Long time penguin researcher, and retired YEPT trustee John Darby, monitored yeps at Okia in the 1980s and could not recall a similar occurrence.
The Trust has been supporting an investigation into the chick deformities led by Maurice Alley at the New Zealand Wildlife Health Centre at Massey University and the Department of Conservation. Many possible causes are being considered, including inbreeding, trauma, hyperthermia during incubation, heavy metal or synthetic chemical intoxication and nutritional deficiency. Hopefully in the next edition of this newsletter there will some conclusions from Massey.