The status, migrations and seasonality of the Little Stint in Kenya

Abstract

The Little Stint Calidris minuta is the most numerous and widespread Palearctic wader species visiting inland Kenya, where over 50,000 are estimated to winter, mostly on the lakes of the rift valley. A few thousand also occur locally on the coast. Adults arrive mainly between mid August and mid September, and juveniles between mid September and October. Most birds leave the coast in late April, but the main departure from the rift is during mid May. Very few birds oversummer. Data are available from some 15,000 birds mist‐netted in the rift and about 800 on the coast. Rift birds have been recovered in the USSR (Kazakhstan), Zaire and Zimbabwe, and have included controls from Zambia, Sudan and Zimbabwe. A comparison of monthly retrap frequencies at Lake Magadi indicates that most August adults, many September adults and many September‐October juveniles are passage; migrants; birds present in April‐May are still mainly wintering individuals. Approximately 2.3% of birds ringed at Magadi were retrapped in a subsequent season. First year birds caught from November onwards were as likely to be retrapped in a later season as adults. The annual decline in probability of subsequent season retrapping at Magadi was indicative of a turnover in the population of about 40%. The longest interval between ringing and recovery was eight seasons. Wing lengths of freshly moulted adults and juveniles were not significantly different. Mean adult winglength decreased by only 0.5 mm during the May‐August migration and breeding period. There was little overlap in the bill‐length ranges of the two sexes. Weights were almost all within the range 18–26 g from November to March. A few higher weights (up to 38 g) were recorded in the rift in autumn, mainly in adults. In spring, mean weight increased in the rift to above 30 g (highest weights above 40 g). but comparable fattening was not found on the coast. Analysis of carcasses from Magadi showed that most October‐March birds contained only 4–10% lipid (as percentage of total weight). Some August‐September birds were fatter (20–30% lipid) and most late April‐May birds were very fat (30–40% lipid). Pectoral muscle total weight and lean dry weight were significantly greater at times of migration August‐September and late April‐May, than in the wintering period. The status and structure, migrations and flight ranges of the rift valley populations are discussed.