Dabbling ducks generally use distinct day roost and nocturnal habitats, the set of which constitute their 'functional unit'. The rate at which these birds may switch between day roosts has never been quantified. Using resightings of nasalsaddled birds and capture-recapture modelling in the Camargue, southern France, we estimated the weekly probability that a teal Anas crecca switches from one day roost to another one nearby (transition probabilities). We also estimated the probability that a teal survives and remains in our study area, consisting of four neighbouring roosts (apparent survival). Birds were highly faithful to one specific water body if they remained in our study area (i.e. weekly rate of switching between roosts was only about 2-6%), but the probability that an individual remained within one of the four roosts from one week to the next (local weekly apparent survival rate) was only 60-70%. Intensive search efforts led to a 60% detection probability. Low local apparent survival coupled with very high site fidelity within the system suggests that two distinct strategies may coexist, i.e. frequent movement between distant winter quarters vs very high fidelity to the very same local wetland. Such strategies may be used successively by the same individuals, or may alternatively represent distinct bird categories (i.e. transients vs residents). In any case, these different strategies suggest that habitat management procedures need to be considered at both local and flyway scales simultaneously. The former may ensure that sites repeatedly used by the same individuals can provide adequate conditions to birds when they remain in a given winter quarter, while the latter will ensure transient birds find appropriate sites within the network of distant wetlands they may use as successive wintering quarters during a season.

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