These are shallow lakes that are mostly dry, and then fill for weeks or months, before drying again. During dry periods, many animals or plants survive as eggs, seeds or other dormant forms, while other species disperse. Floods, bring water from surrounding catchments and floodplains with organic matter, nutrients and fine sediments, and trigger movement of birds and mammals. Floods activate simple foodwebs, comprising abundant algae, zooplankton, waterbugs and crustaceans, which have rapid life-cycles able to exploit windows of productivity. This produces food for frogs and visiting waterbirds.