Genetic and foraging differences exist between two island populations of Hawaiian Petrels

Six species of procellariiform seabirds are included on Appendices of the Bonn Convention on Migratory Species (CMS) that are not as yet listed within the Albatross and Petrel Agreement.  Two of these species, the Pink-footed Shearwater Puffinus creatopus and the Galapagos Petrel Pterodroma phaeopygia, were proposed in 2011 by Parties to ACAP for listing.  The remaining four species are the Endangered Bermuda Petrel or Cahow P. cahow, the  Endangered Henderson Petrel P. atrata, the Vulnerable Hawaiian Petrel P. sandwichensis and the Endangered Peruvian Diving Petrel Pelecanoides garnotii (click here).

It is intended to expand the coverage of ACAP Latest News to include all six of these petrel species, noting that several threats they face are similar to those facing many of the currently listed ACAP albatrosses and petrels, notably alien predators at breeding sites and climate change at sea.  This first news item features recent research conducted on the Hawaiian Petrel, endemic to the USA's Hawaiian Islands, and published in the journal Oecologia by Anne Wiley (Department of Zoology, Michigan State University, East Lansing, USA) and colleagues.

The paper's abstract follows:

"Foraging segregation may play an important role in the maintenance of animal diversity, and is a proposed mechanism for promoting genetic divergence within seabird species.  However, little information exists regarding its presence among seabird populations.  We investigated genetic and foraging divergence between two colonies of endangered Hawaiian petrels (Pterodroma sandwichensis) nesting on the islands of Hawaii and Kauai using the mitochondrial Cytochrome b gene and carbon, nitrogen and hydrogen isotope values (δ¹³C, δ¹⁵N and δD, respectively) of feathers.  Genetic analyses revealed strong differentiation between colonies on Hawaii and Kauai, with Φ_ST = 0.50 (p < 0.0001).  Coalescent-based analyses gave estimates of <1 migration event per 1,000 generations.  Hatch-year birds from Kauai had significantly lower δ¹³C and δ¹⁵N values than those from Hawaii.  This is consistent with Kauai birds provisioning chicks with prey derived from near or north of the Hawaiian Islands, and Hawaii birds provisioning young with prey from regions of the equatorial Pacific characterized by elevated δ¹⁵N values at the food web base. δ¹⁵N values of Kauai and Hawaii adults differed significantly, indicating additional foraging segregation during molt.  Feather δD varied from -69 to 53‰.  This variation cannot be related solely to an isotopically homogeneous ocean water source or evaporative water loss.  Instead, we propose the involvement of salt gland excretion.  Our data demonstrate the presence of foraging segregation between proximately nesting seabird populations, despite high species mobility.  This ecological diversity may facilitate population coexistence, and its preservation should be a focus of conservation strategies."

Reference:

Wiley, A.E.,  Welch, A.J., Ostrom, P.H., James, H.F., Stricker, C.A., Fleischer, R.C., Gandhi, H., Adams, J., Ainley, D.G., Duvall, F., Holmes, N., Hu, D., Judge, S., Penniman, J. & Swindle, K.A. 2012.  Foraging segregation and genetic divergence between geographically proximate colonies of a highly mobile seabird.  Oecologia 168: 119-130.

John Cooper, ACAP Information Officer, 17 January 2013