MORTALITY AND FERTILITY OF EUROPEAN CHARADRII

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SUMMARY

A review of published data on the mortality and fertility of 23 species of wading birds (Charadrii) breeding in or visiting western Europe.

Recoveries of ringed birds are the main source of estimates of mortality. In some cases recaptures of marked birds can also be employed. Apparent mortality in the first year after fledging is usually higher than in later years, though most estimates are probably biased by the preponderance of recoveries due to shooting. Adult mortality-rates in stable populations vary from about 15·7% (Oystercatcher) to 51·9% (Common Snipe) with most in the range 30–45%. Closely related species tend to have similar mortality-rates. There is a strong inverse correlation between death-rate and body-size, using wing-length and weight as indices of size.

Studies of fertility are scarce and meagre, though. clutch-sizes are adequately known. Few waders are double-brooded, though many re-nest if their first nest is destroyed. In most thriving breeding colonies, 66–96% of the eggs laid hatch. Survival of chicks from hatching to fledging, which is hard to measure, typically averages 40–80%, though success often varies widely from year to year.

Intensive long-term studies of breeding groups make the most effective contribution to knowledge of population dynamics. For the many species for which breeding studies are likely to remain impracticable, studies of population composition in winter or on passage may provide useful substitutes, but only if techniques of sampling and of age- and sex-classification can be improved.

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