The breeding biology of the European Storm-petrel Hydrobates pelagicus in Brittany, France
Atlantic seabirds , Volume 3 - Issue 4 p. 149- 164
In recent years (1996-1999), data have been collected on European Storm-petrel Hydrobates pelagicus colonies on the coast of Brittany, France, in order to investigate various breeding parameters, especially laying period, hatching success and breeding success. Data were obtained by regular examination of breeding sites and by estimating chick age at the time of ringing. Adults first returned to colonies in March or April. The laying period extended from the end of April to the beginning of August and showed high annual variability, with the date by which 50% of eggs had been laid ranging from mid May to early July. Annual variability in the timing of laying was probably due to variations in oceanographic conditions and food resources just before laying and had important implications for accurate censuses of breeding colonies. Data obtained from single visits at the same time in different years should be interpreted carefully, especially when using tape-playback methods only, as the proportion of attended nest sites may vary according to the interannual variation in the timing of laying. Estimates of hatching and breeding success were about 65% to 95% (over three years) and 0.53 (one year) respectively. The first chicks fledged in mid August, whereas the latest fledged in late October, or even sometimes November.
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