At approximately 200 hectares, Westminster Ponds /Pond Mills Environmentally Significant Area (ESA) is the largest publicly-owned ESA in London. The ponds and the mixture of habitats make this site an excellent place to view wildlife. More than 200 species of birds have been recorded in the area. It is an important stopover for migrants, with almost all the warblers, flycatchers, thrushes and finches in the London area being reported, as well as ducks, grebes, herons and other water-birds. Summer residents include forest birds such as Great Crested Flycatcher and Wood Thrush, and open-country species such as Field Sparrow and Eastern Meadowlark. Great Horned Owl and Red-tailed Hawk also nest in the ESA.