Ibis (2007), 149, 826– 835 © 2007 The Authors Journal compilation © 2007 British Ornithologists’ Union Blackwell Publishing Ltd Inter-annual variation in provisioning behaviour of Southern Rockhopper Penguins Eudyptes chrysocome chrysocome at Staten Island, Argentina ANDREA RAYA REY, 1 * PHIL TRATHAN 2 & ADRIAN SCHIAVINI 1 1 Consejo Nacional de Investigaciones Científicas y Técnicas, Centro Austral de Investigaciones Científicas, Bernardo Houssay 200 (V9410BFD) Ushuaia, Tierra del Fuego, Argentina 2 British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK Understanding the relationship between reproductive performance and food availability requires knowledge about many different variables, including such factors as the length of incubation shifts, provisioning rates and patterns, as well as how variability in these factors affects reproductive output. To examine some of the most important aspects of parental investment, we studied the provisioning behaviour and patterns of adult Southern Rockhopper Penguins Eudyptes chrysocome chrysocome breeding at Staten Island, Argentina. We investigated foraging trip duration, provisioning rates and chick survival using adult foraging patterns. Our results show that Rockhopper Penguins had clear sex-specific differences in their pro- visioning behaviour. Females provision chicks throughout chick rearing. By contrast, males provision chicks only during the crèche stage and at a slightly lower rate than females during this period. Foraging trips increased in length as the breeding season progressed. Rockhopper Penguins from Staten Island performed longer trips throughout the breeding season than do other species of Eudyptes at several other locations. Our results also show differences in parental investment between years that were related to differences in chick survival. We suggest that this was most likely to be related to female rather than male foraging behaviour as only females showed inter-annual differences in their provisioning rates. Parental care in birds involves investment of both time and energy in activities such as nest building, egg-laying, incubation, chick feeding and nest defence (Clutton-Brock 1991). Provisioning is a large part of parental care and bi-parental care is the most common pattern among birds (Clutton-Brock 1991). However, for birds in general and for seabirds in particular, reproductive performance is also believed to vary in relation to prey availability (Croxall et al. 1988, 1999, Montevecchi 1993, Monaghan 1996). Understanding the relationship between food availability and reproductive performance requires knowledge of many different variables and also how these relate to reproductive output. This includes variables such as the length of incubation shifts, provisioning rates and patterns, and how variability in these factors affects breeding output. With knowledge of such variables, it should be feasible to use breeding success as an indicator of marine variability. This should be feasible, particularly if there are no extraordinary weather events, disease events or abnormal predation events that affect chick survival. Species of Eudyptes (including Rockhopper Penguins) breed mostly in the sub-Antarctic zone. Their breeding chronology is usually highly synchro- nous both between individuals and across years (Warham 1972, William & Croxall 1991, Hull et al. 2004). In Eudyptes, only females feed the chick(s) during the guard stage of the breeding season while both males and females provision the chick(s) during the later stages or crèche period (Warham 1975, Williams 1995). Provisioning rates have been studied in a number of species of Eudyptes. Foraging trips are daily or near-daily in the Macaroni Penguin Eudyptes chryso- lophus and Northern Rockhopper Penguin Eudyptes chrysocome moseleyi over the entire breeding cycle, but with some overnight trips (including one or more nights at sea) at some stages (Barlow & Croxall *Corresponding author. Email: arayarey@speedy.com.ar