CONDITION INDEXES FOR WADER CHICKS DERIVED FROM BODY-WEIGHT AND BILL-LENGTH

Growth in nidifugeous wader chicks depends on food availability, and growth rates may be considerably reduced when food is in short supply. Bill-length and body-weight respond differently to reduced growth rates, and to recovery after a period of reduced growth. A condition index (CI) can therefore be derived from the relationship between bill-length and body-weight: CI = observed weight/expected weight for the observed bill-length. Standardized weights for observed bill-lengths are presented for Lapwing Vanellus vanellus, Black-tailed Godwit Limosa limosa, Redshank Tringa totanus, and Oystercatcher Haematopus ostralegus. Annual variations in condition indices were similar across species and in the case of Lapwing were correlated with total rainfall in May. Similar fluctuations in chick survival were also correlated with rainfall in May suggesting a relationship between condition index and fledging success.