Hedgerows provide vital resources for mammals, birds, and insect species. As well as being an important habitat in their own right, they act as wildlife corridors allowing dispersal between isolated habitats.
Mammals - Hazel dormice Muscardinus avellenarius are one of our rarest small mammals. There are still native populations as far north as the Lake District, Cumbria and Northumberland but they have been lost in other northern and central counties. Their current stronghold is in southern England and Wales. Hedgerows play an important role for dormice. They emerge in spring and in the following months they generally spend all their time above ground in the trees and scrub. In April they feed on blackthorn and hawthorn flowers to replace body fat used in hibernation. In early summer they feed on ash Fraxinus excelsior keys, honeysuckle Lonicera periclymenum flowers and insects such as aphids Aphis sp. Later in the year they rely on blackberries and hazelnuts to provide the food resource to build fat reserves for the coming winter. The diversity of plants as food resources is therefore vital in supporting dormice. They are used as dispersal corridors and are an important link between small copses that are too small to support a viable dormouse population on their own. Crucially they also support breeding populations independent of other habitats. The huge loss of hedges has led to isolated populations and local extinctions. Even small gaps in a hedgerow will provide an obstacle to dormouse dispersal. Research carried out by Royal Holloway, University of London, has shown that hedgerows support as high numbers of dormice as woodlands do, so their removal will have significantly reduced dormouse populations nationally.
Linear landscape features such as hedgerows are important for bats. Hedgerows, woodland edge and ditches can all form commuting routes between roosting sites and feeding areas. These features can aid navigation and provide shelter from wind during flight. Hedgerow trees may also provide roosting opportunities for bats throughout the year. A network of well connected hedgerows and other linear features within a landscape allows many species of bat to extend their foraging and roosting capacity. Hedgerows also provide a habitat for insect courtship, breeding and feeding, hence providing foraging areas for bats. Some species of bats (such as the greater and lesser horseshoe Rhinolophus ferrumequinum, R. hipposideros, brown long-eared Plecotus auritus and Natterer's bat Myotis natt ereri) take insects directly from foliage (known as 'gleaning') and tend to stay close to or within vegetation cover. Hedgerows also comprise an important foraging habitat for barbastelle bats Barbastella barbastellus. Hedgerow removal can lead to the loss of important connections within the landscape for commuting bats and also a reduction in insect diversity and hence foraging opportunities. Management of hedgerows for bats should aim to produce tall (ideally a minimum of 3m), wide and continuous hedges, comprising native species.
Bank voles Clethrionomys glariolus are habitat specialists that prefer woodland and hedgerows with dense shrubby cover. Mature and diverse hedgerows provide food and nesting habitat for harvest mice Mus minutus, with the main nest-supporting shrub species in field margins being bramble Rubus fruticosus and thorns Crataegus monogyna and Prunus spinosa. Hedgehogs Erinaceous europaeus probably rely on hedgerows to nest in especially in areas where arable farming is dominant. Habitat edges including hedgerows and also used for foraging for beetles and other invertebrates
Invertebrates - Species-rich hedgerows can provide an important habitat for invertebrates. They supply food, shelter and breeding sites for pollinators such as bees and for pest predators such as scorpion flies Panorpa communis. Bumble bees Bombus spp. are known to use hedgerows to guide their foraging activity. Stag beetles Lucanus cervus can sometimes be found among decaying stumps at the base of a hedge. All invertebrate species are affected by insecticide, herbicide and fertiliser spraying regimes which will impact on invertebrate predators. Maintaining a diversity of perennial plants in the hedge bottom for host and nectar plants is beneficial to invertebrate diversity.
More than 20 of the butterfly species found in lowland Britain breed in hedgerows, including the brown hairstreak butterfly Thecla betulae, a priority BAP species, which lays its eggs on blackthorn. The Holly blue Celastrina argiolus butterfly caterpillars will only be found in hedges containing holly or ivy whilst the brimstone Gonepteryx rhamni prefers buckthorn Rhamnus cathartica or alder buckthorn Frangula alnus. The Purple Emperor Apatura iris and Pearl-bordered fritillary Boloria euprhrosyne are among species that use hedgerows for nectar, basking or as transport corridors from other 'core' habitats. Hedges are also used by some species such as the Peacock as territorial sites; males establish perching sites on hedges and rise up to inspect other butterflies as they fly past. The Barberry carpet moth Pareulype berberata , also a BAP Priority species, lives in hedgerows.
Birds - Many species of birds are associated with hedgerows. Woodland birds such as blue tit Parus major, great tit Parus caerulus, wren Troglodytes troglodytes, blackbird Turdus merula, robin Erithacus rubecula and chaffinch Fringilla coelebs are more common in taller, wider hedges. A taller hedge provides more habitat and is therefore more likely to provide space for a larger number of breeding territories. Birds that favour scrubby or open woodland, such as dunnock Prunella modularis, yellow hammer Emberiza citrinella and whitethroat Sylvia communis, also use hedgerows. The hedge plants also provide songposts and perches for territorial and breeding birds. The nests, as they age, may then support populations of invertebrates. The hedge base is important for ground-nesting species like the grey partridge Perdix perdix.
Amphibians - Hedgerows which connect with ponds help great crested newts Triturus cristatus move through the countryside (Langton et al 2001).