First record of hybridisation between Northern Eudyptes moseleyi and Southern Rockhopper Penguins E.c.chrysocome

Sarah Crofts1* & Brad J. Robson2

1 Falklands Conservation, 41 Jubilee Villas, Stanley, Falkland Islands, South Atlantic, FIQQ 1ZZ;

2 RSPB, 79 Drumadown Road, Randalshough, Monea, Enniskillen, Co. Fermanagh, Northern Ireland BT93 7BQ, UK.

Full paper

Abstract

A Northern Rockhopper Penguin Eudyptes moseleyi, typically a vagrant species to the Falkland Islands, spent six consecutive breeding seasons (2009-14) at a Southern Rockhopper Penguin E. c. chrysocome colony on East Falkland. During November 2014 it paired with a Southern Rockhopper Penguin and produced a hybrid chick. Although the chick did not survive, an increase in sightings of Northern Rockhopper Penguins at the Falklands suggests that further hybridisation between the two species is likely.

Introduction

Rockhopper penguins have a wide breeding distribution in the South Atlantic, Indian and Pacific Oceans (Williams 1995). Formerly considered one species, the Rockhopper Penguin Eudyptes chrysocome was split on phenotypic and genetic differences into the Northern Rockhopper Penguin E. moseleyi (Tristan-Gough and Amsterdam-St Paul) and Southern Rockhopper, Eudyptes c. chrysocome (extreme southern South America and the Falklands) and E. c. filholi (sub-Antarctic islands in the Indian Ocean and off New Zealand (Banks et al. 2006; Jouventin et al. 2006; de Dinechin et al. 2007; Birdlife International 2015).

Hybridisation in birds typically occurs as a result of restricted mate choice where two closely related species overlap in distribution and one taxon is rarer than the other (Randler 2002; Simeone et al. 2009). The Falkland Islands, in the Southwest Atlantic, support breeding species of Eudyptes penguins: some 320,000 pairs of Southern Rockhopper Penguins (Baylis et al. 2013) and < 50 Macaroni Penguins E. chrysolophus (Huin 2007). The two species occasionally form pairs and produce hybrid offspring (White & Clausen 2002). Four other Eudyptes penguins have been recorded as vagrants to the Falkland Islands: Royal E. schlegeli, Snares E. robustus, Erect-crested E. sclateri and Northern Rockhopper Penguins (Napier 1968; Woods & Woods 2006; Matias et al. 2009; Dehnhard et al. 2012). However, there are no reports of hybridisation with these species.

The largest and nearest population of Northern Rockhopper Penguins to the Falkland Islands is at Tristan da Cunha and Gough Island which hold > 80% (268,000 pairs) of the estimated breeding population (Cuthbert et al. 2009; Robson et al. 2011). The first record of a Northern Rockhopper Penguin at the Falklands was an adult in a Southern Rockhopper Penguin colony at McBride Head (Figure 1) on 24 November 1995. Since then, there have been nine further sightings of 6-7 individuals (Table 1). All records were of Northern Rockhopper Penguins in colonies of Southern Rockhopper Penguins during the austral summer. We describe the hybridisation between a Southern Rockhopper Penguin and a vagrant Northern Rockhopper Penguin.

Acknowledgements

We thank Jan Cheek for access to the colony at Diamond Cove. Alan Henry, Mark Cutts, Klemens Pütz, Joanne Rapley and Jacki Bennett kindly provided sightings and photographs; Nathan McNally, Megan Tierney, Micky Reeves and Norman Ratcliffe provided help in the field. John Croxall commented on an earlier draft and we also thank the two referees, Peter Ryan and one anonymous.

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