PRELIMINARY INVESTIGATION OF NOCTURNAL HABITAT USE BY MIGRATORY WADERS (ORDER CHARADRIFORMES) IN NORTHERN NEW-SOUTH-WALES

Nocturnal and diurnal habitat use by migrant waders was studied at thr ee sites in the Richmond estuary, northern New South Wales. Numerous s pecies of migrant wader showed significant differences in habitat use between night and day. Sanderling (Calidris alba), red-necked stint (C alidris ruficollis) and, possibly, double-banded plover (Charadrius bi cinctus) foraged on mudflats during the day but moved to ocean beaches to forage during night low tides. Pacific golden plover (Pluvialis fu lva), greater sandplover (Charadrius leschenaultii), eastern curlew (N umenius madagascariensis) and bar-tailed godwit (Limosa lapponica) dis played less significant differences in habitat use, although densities increased at night on moist sandy mudflats. The numbers of terek sand piper (Xenus cinereus) and curlew sandpiper (Calidris ferruginea) decr eased on sandy mudflats at night although where these birds went is un known. Nocturnal foraging by X. cinereus may be restricted to moonlit nights. Greenshank (Tringa nebularia) also displayed differences in ha bitat use by foraging more on moist sandy mud at night and less in sea grass. No significant differences were found for whimbrel (Numenius p haeopus). Habitat use by both N. madagascariensis and N. phaeopus appe ars related to lunar phase. Six hypotheses are postulated to explain t he observed differences: (1) exploitation of changes in prey behaviour and availability; (2) predator avoidance; (3) human avoidance; (4) in creased light on mudflats from urban areas; (5) avoidance of roosting flocks of gulls and terns; and (6) relationship with prevailing enviro nmental conditions. The data presented provide a basis from which furt her work will be undertaken.