New Zealand Journal of Ecology (2015) 39(2): 231- 244

Assessing the impact of nest searches on breeding birds — a case study on Fiordland crested penguins (Eudyptes pachyrhynchus)

Research Article
Ursula Ellenberg 1,2,7*
Eric Edwards 3
Thomas Mattern 1,2
Johanna A. Hiscock 4
Rebecca Wilson 5
Hannah Edmonds 6
  1. Eudyptes EcoConsulting Ltd, Dunedin, New Zealand
  2. Department of Zoology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
  3. Department of Conservation, Wellington, New Zealand
  4. Department of Conservation, Southern Islands Area Office, Invercargill, New Zealand
  5. Department of Conservation, South Westland, Weheka Area Office, Haast, New Zealand
  6. Department of Conservation, Te Anau Area Office, Te Anau, New Zealand
  7. Present address: Department of Ecology, Environment and Evolution, School of Life Sciences, La Trobe University, Melbourne campus, Bundoora, VIC 3086, Australia
*  Corresponding author

Long-term population monitoring has become an important tool for conservation management and indicator of environmental change. In many species nest counts are used as an index of population numbers. A pilot study using double-counts in Fiordland crested penguins (Eudyptes pachyrhynchus) found that up to 12% of nests had failed following the first count, raising concerns about search-related disturbance effects and the reliability of long-term monitoring data. Here, we assess the impact of nest counts, and provide recommendations on how to reduce human disturbance effects during nest searches. In 2011, miniature temperature loggers (iButtons) were deployed into 120 nests to quantify temporary and permanent nest abandonment. Observations at nest sites allowed subsequent analysis of a range of factors potentially affecting penguin disturbance responses. In almost a third of all nests both first and second searches caused temporary nest abandonment that lasted up to 4.5 h, creating considerable predation opportunities. To reduce the likelihood of nest abandonment, counts are best conducted during the second half of the incubation period when nests are attended by single, well-established adults. Steep nesting areas proved suboptimal for long-term monitoring. Actual nest failure rates were low in 2011 (about 2% per search) and not all failures were immediately related to search disturbance. Hence, double-counts may be used in Fiordland crested penguins to improve nest count reliability as long as predation pressure is low and field protocols are adapted to minimise disturbance impact of nest searches. We show that well-designed research projects can inform and improve management decisions. For gathering reliable long-term population data, we encourage the reassessment of best-practice protocols to minimise monitoring-related disturbance effects.