Waterbirds are birds which ecologically depend on wetlands. In indonesia, based on their locomotions, they are categorized into resident and migratory birds. Resident birds spend all parts or their life cycle in Indonesian territory, while migratory birds regularly move between their breeding sites to one or more non-breeding locations. Most of the migratory waterbirds visiting Indonesian territory are shorebirds from the families Charadriidae and Scolopacidae which stop by to look for food, so that the chances of finding eggs or chicks are nil.
Some of the residents breed solitary, such as the Asian Woollyneck (Ciconia episcopus) and some duck species from Anatidae family, while others nest in colonies—sometimes with other bird species on a single tree, such as the egrets (Egretta spp.). Unlike the branch-nesting egrets, the Pacific Reef-egret (Egretta sacra) and the Bronze-winged Jacana (Metopidius indicus) lay their eggs on the ground, while some ducks from the Anatidae family prefer tree holes to place their nests in.
Birds from the Northern Hemisphere usually breed in the summer from May to July, then begin their southward migration journey—to where temperatures are higher and food is abundant—in August to September, before winter sets in. During their migration period from November to March, they forage for as much food as possible before starting their return journey to breed in March to May. As one of the 228 Important Areas for Birds and Biodiversity in Indonesia, the 45 hectares Pulau Rambut Wildlife Reserve in the Kabupaten Kepulauan Seribu in Jakarta is an important habitat for waterbirds and a Ramsar Site. Pulau Rambut Wildlife Reserve is also a stopover site for the Christmas Island Frigatebird (Fregata andrewsi), a Critical statused bird on the IUCN Red List, which migrates all the way from Christmas Island in Australia.