Like the plover family (Charadriidae), the sandpipers and relatives are cosmopolitan, most species breeding in the tundra of the Arctic Circle during the brief summer (June-July), when there is continuous daylight, then migrating south soon afterwards to spend the rest of the year in the tropics or Southern Hemisphere. Those visiting Java and other islands of the Greater Sundas mainly breed in eastern Siberia or northern China. By August many of these birds have left their remote nesting grounds and begun the remarkable journey to their non-breeding grounds which include southern Australia, about 14,000 kilometres away. Studies of shorebirds using the East Asian-Australasian (EAA) Flyway have shown that several species fly non-stop from Australia to “staging” sites on Taiwan or around the Yellow Sea, travelling distances of 4,500 to 7,600 kilometres, over three to six days, and one bird flew 11,000 kilometres from Alaska to New Zealand in just nine days. Over a lifespan of 20 years, some individuals may fly over 500,000 kilometres! Within the EAA Flyway, Indonesia is particularly important for migratory shorebirds during their southward passage, less so during the non-breeding period, and least important during the northward passage. Most of the internationally important shorebird sites in Indonesia are on Sumatra, including Banyuasin Delta and the coast from Kualatungul to Tanjung Jabung. Compared to the other large family of shorebirds, the plovers, this family is diverse in form, with species ranging in size from the tiny stints (15 grams) to large curlews (up to 1.3 Kg). Typically they have long legs, shortish tails, and long, pointed wings that are ideal for long distance migration. Their bills are generally long and slender, but they vary in relative size and shape among species, depending on habitat and diet. Unlike the plovers that forage entirely by sight, using their large eyes to scan for prey while pausing briefly between bouts of running, the smaller-eyed sandpipers and relatives often locate prey by “feeling” them, as they walk slowly and methodically, periodically probing the sand or mud. Their bills contain tactile receptors that are capable of detecting small changes in pressure caused by prey embedded in a wet substrate. Curlews use their extraordinarily long, downcurved bills to probe deep into the burrows of crabs, crayfish and worms, but must extract their prey to swallow it, whereas straighter-billed species are able to bend the lower part of the upper mandible to manipulate and ingest deeply-buried prey without opening the entire bill. Knots swallow bivalves whole, the hard shells being crushed by the muscular gizzard, and regurgitated as pellets with other indigestible material.
For most of the year, these birds have drab plumage, a mixture of grey, brown, and white, and many species are so similar that their identification presents a serious challenge, particularly when viewed from a distance. Yet prior to their departure for northern breeding grounds, usually around April, most species begin to develop their distinctive breeding plumages, featuring bright reddish-chestnut or cinnamon and bold black markings. The majority of species frequent coastal mudflats, estuaries and beaches, individuals dispersing widely to forage when tides are low, during both day and night, but congregating into large, often mixed-species flocks, to sleep when tides are at the highest. Other species prefer the edges of freshwater wetlands, and one group, the woodcocks, even inhabits montane forests! Most species are gregarious outside the breeding season, and usually forage, roost and fly in tight, coordinated flocks. Java is visited by no fewer than 29 migratory species, eight of which have been found in Baluran , but it is also home to one resident species (Rufous Woodcock Scolopax saturata).