Emigration rates and population turnover of teal Anas crecca in two major wetlands of western Europe

Abstract

During the winter of 2003/04, we studied emigration rates of teal Anas crecca in two major wetlands: the Camargue (southern France) and the Loire estuary (western France). We derived local survival probabilities as a step in ultimately estimating emigration rates from individual mark-resighting (visual recaptures) history of birds fitted with nasal saddles. In goodness-of-fit tests of time-dependent models for local survival, we only detected the presence of transients among young females in the Loire estuary, which indicated that this category of individuals includes an 'unstable compartment' continuing its migratory journey further to the south. We observed low monthly local survival and high emigration rates (range: 0.01-0.81) in both areas, which suggests high turnover rates. In the Loire estuary, temporal changes in emigration rates matched the post-and pre-nuptial migration peaks (i.e. October-November and February-March). By combining local survival probabilities and count data, we derived an estimate of the ratio between the winter peak count of teals in our study areas and the minimum number of birds that actually frequented the areas over the entire wintering period (October-March). In both cases, we estimated the number of teal visiting the two wintering sites be about twice as large as the maximum number of birds counted instantaneously.

Blood and cloacal swab sampling for avian influenza monitoring has no effect on survival rates of free‐ranging ducks

“…Mortality and movement rates are known to differ between sex and among age classes in ducks (Caizergues et al . ). Re‐encounter and recovery rates may also change over years due to environmental variation.…”

“…The dataset also comprised all incidental mark resightings sent to us by observers throughout Europe; ring recoveries were similarly sent to us by hunters from France and other countries. Mortality and movement rates are known to differ between sex and among age classes in ducks (Caizergues et al 2011). Re-encounter and recovery rates may also change over years due to environmental variation.…”

Movement Patterns in a Partial Migrant: A Multi-Event Capture-Recapture Approach

“…Huge efforts have been devoted worldwide to monitor migratory birds using the ringing of tens of millions of individuals. These ringing schemes have greatly helped avian ecologists to understand timing and patterns of movements [9] – [11] , assess population turnover rates [12] – [14] , and estimate demographic parameters like survival and site fidelity [15] . Unfortunately, due to spatial heterogeneity in recovery probability ringing data are not well suited to quantify movement patterns.…”

Spring migratory routes and stopover duration of satellite‐tracked Eurasian Teals Anas crecca wintering in Italy

“…, Caizergues et al . ). Birds from Veneto tended to be the first to leave their wintering location; this was probably related to the hunting management of the site, where abundant food is provided until the end of the hunting season on 31 January.…”