Ibis (2007), 149, 396–404 © 2007 The Authors Journal compilation © 2007 British Ornithologists’ Union Blackwell Publishing Ltd Resident and transient dynamics, site fidelity and survival in wintering Blackcaps Sylvia atricapilla: evidence from capture–recapture analyses EDUARDO J. BELDA, 1 * EMILIO BARBA 2 & JUAN S. MONRÓS 2 1 Universidad Politécnica de Valencia, Crta. Nazaret-Oliva, s/n, 46730 Gandía, Spain 2 ‘Cavanilles’ Institute of Biodiversity and Evolutionary Biology, University of Valencia, Apartado Oficial 2085, E-46071 Valencia, Spain In their winter quarters, migrant birds may either remain within a small area (resident strategy) or move frequently over a large area looking for locally abundant food (transient strategy). It has been suggested that both strategies could simultaneously occur in the same population. We used time-since-marking capture–recapture models to infer the coexistence of these two behavioural strategies (transient and resident) among wintering Blackcaps Sylvia atricapilla using weekly recapture data over a 7-year period. A related question is whether Blackcaps, if surviving to the next winter, always return to the same wintering area, so we also used this approach to analyse winter site fidelity and to estimate annual survival probabilities. Model selection supported the existence of heterogeneity in survival estimates for both the within-season and the interannual survival probabilities, i.e. there was evidence for the existence of transients. It was estimated that 26% of the Blackcaps were resident during the winter. Mean apparent annual survival probability was 0.46 (se = ±0.11). However, there was some evidence suggesting that not all individuals showed winter site fidelity. The estimated proportion of individuals that, if alive, returned to the wintering area was 28%. This is the first study to show the existence of these two behavioural strategies (residence and transience) among wintering Blackcaps, and the first confirming this pattern using capture–recapture models. These models considering transient and resident dynamics may become an important tool with which to analyse wintering strategies. Survival is a crucial element of life history, especially in short-lived organisms (e.g. Stearns 1992, Newton 2001). Migration can be viewed as a strategy to survive during harsh or extreme environmental conditions, which is well illustrated in many bird species that undertake long migrations (Alerstam 1991, Berthold 2001, Senar & Borrás 2004). However, in spite of survival being the ultimate objective of migration, there are, to our knowledge, few studies analysing the probabilities of survival in wintering areas (e.g. Senar & Borrás 2004). There are many factors that may affect winter survival (for a recent review see Senar & Borrás 2004). Two factors that have an important influence on sur- vival are the search for and defence of food resources (Senar & Borrás 2004), and the previous knowledge of the wintering area, i.e. winter site fidelity (Newton 1972, Cuadrado et al. 1995). With regard to the first factor, two main strategies of searching for food have been described: the ‘resident’ and the ‘transient’ strategies. In frugivorous birds, wandering in search of fruits may improve winter survival by preventing food shortages that eventually occur in discrete territories (Herrera 1985, Levey & Stiles 1992, Rey 1995). This is known as a transient strategy, in which individuals locate and exploit alternative food supplies over a large area (e.g. Newton 1972, Senar et al . 1992, Pérez-Tris & Tellería 2002a, Newton 2004). Alternatively, when resources are predictable and plentiful, wintering birds should behave as residents, with movements limited to a relatively small area, and possibly showing territorial behaviour (Cuadrado 1995). Senar et al. (1992) (see also Senar & Metcalfe *Corresponding author. Email: ebelda@dca.upv.es