Lessons from a failed translocation program with a seabird species: Determinants of success and conservation value Daniel Oro a,⇑ , Alejandro Martínez-Abraín a , Elena Villuendas b , Blanca Sarzo b , Eduardo Mínguez c , Josep Carda b , Meritxell Genovart a a Population Ecology Group, IMEDEA (CSIC-UIB), Miquel Marquès 21, 07190 Esporles, Spain b Conselleria de Territori i Habitatge, Generalitat Valenciana, Servei de Conservació de la Biodiversitat, Francisco Cubells 7, 46011 València, Spain c Dpto. Biología Aplicada, Universidad Miguel Hernández, Avda. Universidad s/n., 03202 Elche, Spain article info Article history: Received 20 September 2010 Received in revised form 25 November 2010 Accepted 28 November 2010 Available online 21 December 2010 Keywords: Conservation Chick translocation Dispersal Ecological trap Metapopulation Release site Survival abstract Conservation diagnosis of ex situ techniques (e.g. releasing chicks by hacking) cannot be evaluated without quantitative assessment of the fate of individuals, mainly their survival and recruitment. Here we use a long-term monitoring at a large spatial scale of a hacking programme (i.e. chick translocations) for Audouin’s gulls in an uninhabited site so as to establish a new breeding patch and reinforce the meta- population. The success of the programme relied on the assumption that birds tend to recruit to the site where they fledge (i.e. they were philopatric). Multi-state capture-recapture models applied to a large dataset (more than 43,500 resights at 30 colonies during 1999–2010) were used to evaluate the survival of released chicks and the probability of being philopatric. Adult survival was high, but juvenile survival was lower than that of wild gulls, suggesting that there was a cost associated with hacking only during their first year of life. As expected, most released birds returned to the hacking site, but very few (includ- ing immigrants from abroad) attempted to breed here. Dispersal was inversely correlated with distance from the hacking site and positively associated with the population size of the patch (i.e. conspecific attraction). Even though most hacking procedures met the ecological conditions to succeed, results clearly showed that the program failed to establish a new breeding site. The ability of prospecting and the attraction made by conspecifics at established sites may be a constraint for the success of hacking programs, particularly for social and nomadic species. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Most seabird species are necessarily structured in metapopula- tions, owing to the patchy nature of their breeding sites, typically oceanic or coastal islands, and their social aggregation in colonies, connected by dispersal processes and subjected to extinction–col- onization turnover (e.g. Oro, 2003). Hence, the availability of a large web of occupied patches, with several local populations con- nected by dispersal, is a desirable conservation goal (Gilpin, 1980; Smith and Peacock, 1990). Conversely, an undesirable situation from a conservation perspective occurs when only one or a few of the metapopulation patches host the bulk of the individuals of a given species. Some extreme examples include some seabirds, such as Amsterdam albatross Diomedea amsterdamensis and Short-tailed Albatross Diomedea albatrus, with a single colony, and Heermann’s gull Larus heermanni, whose largest colony holds 95% of the species world population; in these cases a local pertur- bation could threaten the whole species. Thus, at the scale of spe- cies range, a potential conservation aim, when recovering an endangered organism, is to increase occupation rates of empty metapopulation patches and thus reduce the chances of extinction (e.g. Doak and Mills, 1994; Hanski, 1999; Vuilleumier et al., 2007). Consequently, reintroductions, defined as the release of animals to reinforce or to re-establish extinct local populations, and introduc- tions, in which release targets the establishment of new local pop- ulations of endangered flora and fauna, are proper conservation tools often used for management purposes (Sutherland, 2000; van Wieren, 2006). To aid in the establishment of new metapopulation patches, several management techniques can be applied, such as social attraction or the translocation of nestlings from source sites fol- lowed by captive-rearing and release at fledging time (hereafter hacking). This latter technique is based on the principle that birds experience two types of behavioural imprinting during their lives: a species imprinting after hatching, and a site-specific imprinting when fledging. These features are life-history traits shaped by evolution, and evolutionary theory can be applied for conservation 0006-3207/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.biocon.2010.11.018 ⇑ Corresponding author. Address: Institut Mediterrani d’Estudis Avançats IMEDEA (CSIC-UIB), Miquel Marquès 21, 07190 Esporles, Mallorca, Spain. Fax: +34 971611761. E-mail address: d.oro@uib.es (D. Oro). Biological Conservation 144 (2011) 851–858 Contents lists available at ScienceDirect Biological Conservation journal homepage: www.elsevier.com/locate/biocon