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Keywords:

  • Allee effect;
  • Anas laysanensis;
  • density dependence;
  • Gompertz model;
  • kernel estimators;
  • Laysan duck;
  • Midway Atoll;
  • translocation

Abstract

Translocation is an important tool for wildlife conservation and biodiversity restoration, but an inefficient one because of the unpredictability of success. Predictors of success such as habitat quality of the release site and number of individuals released have been identified, but the dynamics of successful translocations remain poorly understood. In particular, little is known about the relationship of individual post-release movements to population establishment. In 2004, Laysan teal Anas laysanensis were reintroduced by translocating 20 wild birds from Laysan Island to Midway Atoll. Twenty-two additional wild founders were brought the next year. We monitored the survival, reproductive success and movements of the 42 translocated individuals and their offspring for 4 years. Additionally, we monitored population size from 2004 to 2010. Unlike most translocations, we did not observe elevated post-release mortality despite flight-feather trimming to prevent immediate dispersal off-island: first year survival was > 90% and survival rates until 2009 were 0.65 ± 0.08 for founding adults. Laysan teal flew between the two main islands of Midway Atoll, and offspring had significantly larger maximum movement distances than founders. We monitored 84 nests and observed a significant, negative relationship of home range size to productivity for founding females. Flightless founders did not show fidelity to their release sites, but had strong fidelity to annual home ranges after attaining flight. Although we observed a component Allee effect on mate-finding, this did not translate into a demographic Allee effect, and generally, the high fitness of founders contributed substantially to successful population establishment. Laysan teal abundance increased linearly until 2009, but showed evidence of population regulation afterwards. The population estimate was 473 (95% confidence interval 439–508) in 2010. On the much larger main Hawaiian Islands, we expect greater post-release movement, a stronger component Allee effect, lower survival and lower reproductive rates because of predation to preclude successful reintroductions of this species to sites without predator management.