 The South Exmoor SSSI is smaller , covering 3 @,@ 132 @.@ 7 hectares ( 7 @,@ 741 acres ) and including the River Barle and its tributaries with submerged plants such as alternate water @-@ milfoil ( Myriophyllum alterniflorum ) . There are small areas of semi @-@ natural woodland within the site , including some which are ancient . The most abundant tree species is sessile oak ( Quercus petraea ) , the shrub layer is very sparse and the ground flora includes bracken , bilberry and a variety of mosses . The heaths have strong breeding populations of birds , including whinchat ( Saxicola rubetra ) and European stonechat ( Saxicola rubicola ) . Wheatear ( Oenanthe oenanthe ) are common near stone boundary walls and other stony places . Grass warbler ( Locustella naevia ) breed in scrub and tall heath . Trees on the moorland edges provide nesting sites for redpoll ( Acanthis flammea ) , common buzzard ( Buteo buteo ) and raven ( Corvus corax ) . 
