<P> The chalk grassland environment above the cliffs provides an excellent environment for many species of wild flowers, butterflies and birds, and has been designated a Special Area of Conservation and a Site of Special Scientific Interest . Rangers and volunteers work to clear invasive plants that threaten the native flora . A grazing programme involving Exmoor ponies has been established to help to clear faster - growing invasive plants, allowing smaller, less robust native plants to survive . The ponies are managed by the National Trust, Natural England, and County Wildlife Trusts to maintain vegetation on nature reserves . </P> <P> The cliffs are the first landing point for many migratory birds flying inland from across the English Channel . After a 120 - year absence, in 2009 it was reported that ravens had returned to the cliffs . Similar in appearance but smaller, the jackdaw is abundant . The rarest of the birds that live along the cliffs is the peregrine falcon . In recent decline and endangered, the skylark also makes its home on the cliffs . The cliffs are home to fulmars, which resemble gulls, and to colonies of black - legged kittiwake, a species of gull . Bluebird, as mentioned in the classic World War II song "(There'll Be Bluebirds Over) The White Cliffs of Dover" is an old country name for swallows and house martins, which make an annual migration to continental Europe, many of them crossing the English Channel at least twice a year . </P> <P> Among the wildflowers are several varieties of orchids, the rarest of which is the Early Spider Orchid, which has yellow - green to brownish green petals and looks like the body of a large spider . The Oxtongue broomrape is an unusual plant that lives on the roots of a host plant . It has yellow, white, or blue snapdragon - like flowers and about 90 per cent of the UK's population is found on the cliffs . Viper's - bugloss, a showy plant in vivid shades of blue and purple with red stamens, also grows along the cliffs . In his play King Lear, Shakespeare mentions rock samphire, an edible plant that grows on the cliffs . It was collected by gatherers who hung from ropes down the cliff: Half - way down / Hangs one that gathers samphire; dreadful trade! (Act IV, Scene VI). This refers to the dangers involved in collecting rock samphire on sea cliffs . </P> <P> The abundance of wildflowers provides homes for about thirty species of butterfly . The rare Adonis blue can be seen in spring and again in autumn . Males have vibrant blue wings lined with a white margin, whereas the females are a rich chocolate brown . This species' sole larval food plant is the Horseshoe Vetch and it has a symbiotic relationship with red or black ants . The eggs are laid singly on very small foodplants growing in short turf . This provides a warm microclimate, suitable for larval development, which is also favoured by ants . The caterpillar has green and yellow stripes to provide camouflage while it feeds on vetch . The ants milk the sugary secretions from the larval "honey glands" and, in return, protect the larvae from predators and parasitoids, even going so far as to bury them at night . The larvae pupate in the upper soil, and continue to be protected by the ants, often in their nests, until the adults emerge in the spring or autumn . </P>

Where did the clay found in cliffs on the north shore of long island come from