The impact of upland farming – Part 3 of 4: Ecology of the uplands in transition.

In his book Feral [1], George Monbiot outlines his ideas for the environmental transformation of the British uplands – from open sheep grazed pastures to wooded hillsides. He argues that this will considerably enhance biodiversity. Furthermore, that the release of large predators such as Lynx, Wolves and Wild Boar, will amount to a restoration of keystone species that will bring about an enormous ecological improvement and which will bring everything back into a natural balance. He proposes that afforestation of the uplands should be carried out by the removal of sheep and cattle from grazing the uplands. This will allow the fragments of woods that currently remain on the periphery to regenerate. He also suggests replanting with local tree stock to enhance this process. The large predators would be re-introduced to ensure that a balance is achieved between trees and deer.

It is clear from his book that Monbiot hates sheep and all their works; that he prefers a heavily wooded landscape and dislikes the open vistas of apparently bare mountainsides. He claims that not only do the sheep ‘scour’ the upland landscape and leave it devoid of any birds or insects, but that they also graze within the woods and prevent any sort of natural regeneration. Most of his adverse comments seem to apply to upland Wales, which he describes as ‘the Cambrian desert’.

This post will examine Monbiot’s ideas, mostly from the point of view of birds, as they are the group that I know most about. However, it should be noted that Monbiot’s  radical proposals would also affect everything else in the uplands; from the trees, shrubs, grasses, mosses and invertebrates.

Parts 1 and 2 of this series have examined the upland farmer from the point of view of economics and culture. This post will examine the farmer as a player in the ecological dynamics of the uplands and how the birds will be affected by the change from a farmed landscape to an un-farmed landscape.

screen-shot-2017-02-13-at-13-59-02Golden Plover – a distinctive species of open upland moorland. Photo by Sindri Skulason via Google Images.

A central justification to Monbiot’s ideas, and the principles of the ‘rewilding’ movement which has which flowed from them, is the term keystone species. This means: ‘a species that has a disproportionately strong influence within a particular ecosystem such that its removal results in a severe destabilisation of the ecosystem and can lead to further species losses’ [2]. Monbiot cites the example of wolves in Yellowstone Park, which were initially eradicated from the park in 1926. At that point, Elk Cervus canadensis, began to multiply rapidly and overgraze the park. This resulted in degradation of some ecosystems within the park, and so wolves were re-introduced in 1995. Monbiot’s point is that the wolves were responsible for restoring the balance between grazers and predators to the benefit of the vegetation and the rest of the ecosystem, and that this makes them a keystone species.

All of this is perfectly reasonable in the context of Yellowstone Park, which has had relatively little human interference since it was first designated a National Park in 1872. This is because the Native American tribes that had lived in the area for millennia were systematically removed (or ethnically cleansed)[3]. In other words, the wolves had been absent for a mere 70 years. Their re-introduction from such a short absence managed to restore things to a balance closely resembling the situation before they were eradicated. However, in the UK, wolves were eradicated in England and Wales by the 14th Century and in Scotland by the 18th Century. Since then, upland ecosystems have had time to adjust and in any case have been controlled principally by the farmer or moorland manager.

The most far-reaching of Monbiot’s ideas is the proposal to reafforest the uplands as he seems to envisage. The consequence of so doing would result in a highly dynamic situation of encroaching forest which moves steadily uphill. In order to assess some of the changes another ecological term needs to be introduced – that of edge effect:

‘The change in the number of species occurring in the zone where two habitats are in contact. Since this zone may contain biotic elements from both habitats and some unique to itself it may be rich in species, but because those species are ill-adapted to the immediately adjacent habitat, the rate of local extinction is usually high at edges. Predation in particular, is greatest at the habitat edge. The effect occurs because the overlap region supports some species from both adjacent ecosystems and some peculiar to itself. Ecologists now regard the edge effect as a sign of ecological deterioration. The fragmentation of habitats causes an increase in edge areas, but a decrease in in the internal areas of ecosystems, leading eventually to a loss of species from all affected ecosystems and an increase in edge species, which are usually commonplace.’ [2] [My emphases] 

An illustration of this is given below, which is an idealised upland moor (green circle) with a sessile oakwood (red ellipse) in a valley leading up onto the moor. As the oakwood enlarges with the forces of natural regeneration, it encroaches upon the moor and the two edge effects combine, with the moorland becoming diminished. For a schematic illustration, see Figures 1 and 2 below:

screen-shot-2017-02-14-at-06-17-52

Figure 1Schematic diagram of open moorland (top circle, mostly green) currently grazed with sheep and/or cattle. This is the breeding ground for specialist birds such as Red Grouse, Curlew, Golden Plover, Merlin and so on. The deep green is where those species are most numerous and the lighter coloured areas where those species are compromised by the edge effect, including the slight impinging of predators from the oakwood. The red ellipse is a small sessile oak pasture which is partly open canopied and is grazed by sheep and cattle. The red fuzzy area beyond the boundary of the wood is the area which is affected by predators living in the wood.  

In Figure 1 above, the open moor is characterised by a mixture of heather Calluna, Purple moor grass Molinia caearulea and open stretches of shorter grasses which are readily grazed by the sheep. There are few trees in this area, which is gently undulating and receives high rainfall and wind. The bird species which are characteristic of this kind of habitat are concentrated in the dark green area, with fewer or none in the light coloured areas. A stream drains the moor and this feeds into a valley which is occupied by a small sessile oakwood which is also grazed. This means that the wood has open areas which are covered in grass instead of thick undergrowth. The oak trees are all very old, often covered in mosses and lichens and are occasionally isolated, so the tree canopy is discontinuous.

Figure 2 below shows what happens when the sheep and cattle are withdrawn. The moorland grasses and heather become rank. Molinia encroaches into the areas previously grazed and gradually dominates the heather which becomes weak and leggy. The characteristic bird species which demand open areas, decline in numbers – here represented by the green changing from dark (Figure 1) to light (Figure 2). The sessile oakwood is now overtaken by thick undergrowth and young trees. As these mature, the older trees die off. Furthermore, because of the lack of grazing, the wood extends and creeps up the hill and begins to enter the area previously occupied by the moorland species. As more predators occupy the wood, the range of predation beyond the wood is also extended.

The edge effect is shown by the fuzzy coloured areas. As the woodland edge effect is extended, so the moorland characteristic species retreat and go into decline until they are eliminated.

screen-shot-2017-02-14-at-06-18-13

Figure 2The same areas after grazing has been stopped and the wood and moor allowed to regress. The woodland extends at the expense of the moorland; and the influence of the woodland is now felt well beyond its boundaries, shown by the fuzzy red areas. The remaining moorland habitat is degraded because of the removal of sheep and cattle and this is shown by the lighter green. 

Whilst Figures 1 and 2 illustrate the general principles, they provide little information as to which species will be affected by the transformation of open upland moorland into continuous or even patchy woodland. To do this properly requires an environmental impact assessment which takes into account the habitat requirements for all species of plants and animals; and an intimate knowledge of the nature of succession and how it affects all of those species. A long succession of moorland into woodland spread over many decades is almost impossible to predict exactly, but some indicators of the potential changes can estimated using the habitat requirements of birds, which are well known and recorded. Figures 3 and 4 below show the shift in species as the open moorland is overtaken by woodland. The estimations of the effect of each phase of transition from open moorland to forest can be estimated from the habitat and feeding requirements of the distinctive species of both upland sessile oak pastures and open moorland, which are summarised in Appendices I to VI below the References section. These lists are not intended to be exhaustive, but are simply representative of the characteristic species  of birds within these two ecosystems.

screen-shot-2017-02-14-at-06-18-41

Figure 3Transition of upland sessile oak pasture into dense woodland with closed canopy and thick undergrowth caused by the withdrawal of grazing by sheep and cattle. The existing open canopy and open floor is represented by the blue sector, which shifts into the yellow block and then finally matures into the green block. As young trees overtake the original parent trees, the older trees die off, thus progressively removing specific habitats for, say, the lesser spotted woodpecker. The first changes will be in the woodland floor which becomes overgrown and is no longer suitable habitat for birds which rely upon the open, grazed woodland floor as feeding habitat. 

This suggests that changes occur progressively and in different ways, affecting some species of birds sooner than others. In the above example, the loss of a grazed woodland floor may result in the loss of Pied Flycatcher, Wood Warbler and Tree Pipit fairly quickly, as the woodland floor becomes overgrown. By contrast, Black Grouse will benefit with the new advancing vegetation and young trees, as they are a species of transitional habitats between trees and moorland, as they rely upon both for feeding at different times of year. As the new trees mature and close canopy, species such as Goshawk move in, which are adept at hunting prey in heavily wooded areas. However, towards the end of this dynamic process, it can be seen that the species which are particularly associated with woodland pastures are extinguished. The list above is not exhaustive and does not show the increases  experienced by generalist woodland species such as Tawny Owls, Blackbirds, Robins and many others. These would all increase in numbers and variety, but only at the expense of the specialist species for which upland sessile oak pastures are renowned.

Figure 4 below shows what would most likely happen when open moorland is progressively encroached upon by advancing woodland:

screen-shot-2017-02-14-at-06-19-00

Figure 4Transition of open moorland to predominantly closed canopy woodland with some open patches. The blue block is the starting point of existing open moorland dominated by heather Calluna, purple moor grass Molinia caearulea and other grasses which are grazed by sheep and cattle. As grazing is ceased, the transitional yellow block becomes more prevalent, until it too is overtaken by mature woodland. The loss of open moorland and shorter grasses result in a local but wholesale extinction of the moorland species.

There is considerable difficulty in predicting the progress of ‘rewilding’ to the uplands of the UK. The preceding paragraphs have discussed the possibilities for birds, with Welsh uplands in mind. This model is a very simple one – and which would become much more complex and dynamic if deer were introduced, wild boar arrived to dig up and bury acorns, and both were predated by lynx and wolves. There would be almost complete unpredictability about the rate of afforestation and the precise nature of the undergrowth thus created.

But the effect upon open moorland of withdrawal of grazing would be almost immediate, and certain, as it is overtaken by rank growth and creeping afforestation. The result would be certain loss of bird species which are considered to be distinctive of the Welsh uplands. Wales is a stronghold of many of the species mentioned above and whose habitats are summarised in the appendices below. Nevertheless, it is clear that the withdrawal of grazing and subsequent encroachment by woodland would result in wholesale extinction of many species in the affected moorland.

It is fair to say that the woodland which replaced the moorland would possibly harbour more species eventually, but these would tend to be species which we are already familiar with in our urban gardens. In other words, the likely outcome would be that distinctive species are replaced by commonplace ones – exactly as predicted by the definition for ‘edge effect’ as given above.

Despite Monbiot’s enthusiasm for dense woodland and his revulsion for open landscapes, most people would consider his ideas for rewilding the Welsh uplands as a tragedy, rather than an ecological gain.

References

[1]  Monbiot G, (2013) Feral, Penguin Books, London.

[2]  Allaby M, (2010) A Dictionary of Ecology, Oxford University Press, Oxford.

[3] Cramp S and Simmons KEL (eds) (1979), The Birds of the Western Palearctic, Vol.II, Oxford University Press, Oxford.

[4] Cramp S and Simmons KEL (eds) 1982) The Birds of the Western Palearctic, Vol.III, Oxford University Press, Oxford.

[5] Cramp S (ed) (1985) The Birds of the Western Palearctic, Vol.IV, Oxford University Press, Oxford.

[6] Cramp S (ed) (1988) The Birds of the Western Palearctic, Vol.V, Oxford University Press, Oxford.

[7] Cramp S and Perrins CM (eds) (1993) The Birds of the Western Palearctic, Vol.VII, Oxford University Press, Oxford.

[8] Cramp S and Perrins CM (eds) (1994) The Birds of the Western Palearctic, Vol.VIII, Oxford University Press, Oxford.

Appendices

Each appendix is a table of the species with its habitat requirements and feeding behaviour. These are abbreviated summaries taken directly from The Birds of the Western Palearctic, Vols II to VIII, from the sections on ‘Habitat’ and ‘Food’ within the each species description.

Appendix I – Red Grouse to Common Buzzard

Species Breeding Habitat Feeding behaviour
Red Grouse Lagopus lagopus scoticus [3] ‘Treeless tundra, moors, heaths, bogs…wherever Calluna…dwarf shrubs…flourish. Ssp scoticus confined to heather moors above or well clear of trees.’ Avoids trees in winter when moving down to lower altitudes. Mostly herbivorous, but some invertebrates esp. for chicks.
Black Grouse Tetrao tetrix [3] ‘…Glacial relict…transitional between forest…and open heath, marginal cultivation, bog and fen, or steppe. Presence of trees essential, but not in dense stands or closed canopy.’ Mostly plant material – tree seeds, buds. Feeds on ground in spring, summer and autumn. In trees in winter.
Red Kite Milvus milvus [3] ‘In Wales, small relict population based on small discontinuous open relict oakwoods Quercus petraea …in undisturbed upland valleys up to c400m…providing breeding, resting and roosting places…hunting over adjoining farmland, rough grassland mostly at 200-300 m, but also on higher deforested moorland and rough grassland …and heather carrying substantial flocks of sheep…Preference for extensive open areas with low vegetation where prey species active diurnally…Attachment to trees does not extend to closed forest.’ ‘Predator and scavenger. Wide range of food items…. Hunts by soaring and circling over open ground.’ Hunts up to 7 Km away from breeding site.
Hen Harrier Circus cyaneus [3] ‘Usually avoids steep mountainous terrain, unbroken forests…groups of mature trees…tall dense stands of grassland or vegetation. Otherwise [occupies] wide range open terrain…includes grassland, upland moors, heaths…etc.’ ‘…young and adult songbirds, young nidifugous birds and small rodents. Flies low quartering over ground and seizing prey with sudden pounce, often using hedges and shrubs to surprise prey. In breeding season, hunts predominantly along transect, following habitat edges’
Common Buzzard Buteo buteo [3] ‘Preference for hunting over open tracts with low vegetation…[linked] with varied landscapes including forest clearings with groves or tall isolated trees and hilly slopes, ridges or uplands with some or much tree cover…preference for broad leaved trees and, in Britain, woods of sessile oak Quercus petraea.’ ‘Wide diversity of prey…small mammals, birds, reptiles, amphibians, larger insects and earthworms. Feeding techniques governed …by habitat restrictions. (1) perching then planning onto prey… by surprise attack. (2) soaring or hovering over open terrain before dropping onto prey. (3) walking or standing on ground looking for locusts or earthworms.’

Appendix II – Goshawk to Golden Plover

Goshawk Accipiter gentilis [3] ‘…exclusively in forested and wooded areas, esp of coniferous trees (spruce) and broad-leaved trees Quercus and Fagus. Adept at flying through close forest but prefers to nest in tree-tops, where clear level access is afforded by stream course, ride, fire break or natural glade. Hunting range up to 6 Km, but open country exploited only when it lies near more or less extensive woodland, and when hedgerows or wind-breaks provide good cover.’ ‘Mainly birds up to size of Capercailie Tetrao urugallus and Hare Lepus europeaus. Hunting…swift, aggressive, and adroit pursuit flights…Takes advantage of any cover to approach prey …to take it by surprise. Will stoop from great height like Peregrine Falco peregrinus …to catch prey in air.’
Peregrine Falcon Falco peregrinus [3] ‘For hunting, requires extensive open terrain often including wetland or coastal habitats. For breeding mainly cliffs, crags and other precipitous undisturbed locations such as tall inaccessible structures.’ [now in tall buildings in cities]. ‘Mostly birds…majority taken on the wing; usually over open country and over water, rarely on edge of woods.’
Merlin Falco columbarius [3] ‘Avoids forests and bare precipitous mountain ranges, preferring open tracts of low, rough vegetation on uplands, foothills or plains…Favours undulating or folded landforms providing wide outlooks from ground perches or nest sites, especially heads of upland stream valleys… Reliance on small birds as prey and preference for habitats of low bird density necessitates hunting over fairly wide extent of homogeneous terrain.’ ‘Chiefly small birds caught in open country. [Usually] hunts in low…horizontal flight from perch with final glide less than 1 m above ground. Prey usually caught after short-distance surprise attack. Other techniques included prolonged persistent chasing and vertical stooping…On Yorkshire moors…fed almost exclusively on Anthus pratensis [Meadow Pipit] 90%… Northumberland …almost entirely birds…40 species, [but] 48% [were] Anthus pratensis.’
Golden Plover

Pluvialis apricaria [4]

‘…unenclosed upland moors and peatlands…often windy climate beyond normal tolerance for tree growth….stops short of mountainous terrain, inhabiting sub-montane and montane zones …between 240 m and 600 m in Britain….Sometimes overlaps with Dunlin Calidris alpina on moist cottongrass Eriophorum moors, but differs in tolerating drier terrain…Prefers flattish or gently sloping ground with some raised places suitable as lookouts…some blending of open patches with very sparse low vegetation and other areas providing partial cover, but still not tall enough to block the distant view. ‘Wide spectrum of Invertebrates, principally beetles and earthworms. Some plant material incl. berries, seeds and grasses.  Most food taken from surface or by probing 1 – 2 cm…prey mainly located visually, although some evidence of acoustic location.’

Appendix III – Lapwing to Lesser Spotted Woodpecker

Lapwing Vanellus vanellus [4] ‘Requires ready access to soil carrying appreciable biomass of surface or subsurface organisms, not arid and preferably moist or even near saturation. Habitat may be flat, gently undulating…and must not impede easy walking. Invariably chooses unenclosed terrain affording unbroken all round views. Avoids fields enclosed by hedgerows or walls smaller than c. 5 ha, or parkland with many large trees.’ ‘Predominantly ground-living invertebrates…Prey located by sight and sound… All prey taken on ground.’
Dunlin Calidris alpina [4] ‘Avoids dry stony or rocky sites and those overgrown with dense herbage or tall shrubby plants, preferring moist boggy ground, often interspersed with pools or other standing or flowing water.’ ‘Chiefly invertebrates. Prey located by sight and by touch. Feeding method depends upon substrate (e.g. hard or soft mud) and behaviour of prey (mobile or immobile).’
Common Sandpiper Actitis hypoleucos [4] ‘Prefers fresh water of clear lakes, rivers or streams, especially favouring fairly fast flowing upper courses of streams and rivers…Thus differs from most waders in preferring stony, shingly or rocky edges…’ ‘Chiefly immobile or free-flying invertebrates, particularly insects. Prey located visually; picked mainly from ground (especially between stones and within cracks), from low vegetation, and from faeces of mammals (e.g. sheep).’
Curlew Numenius arquata [4] ‘Chooses damp or wet terrain with dry patches, or sometimes the converse, especially near water. Characteristically an upland bird in Britain… Prefers open landscapes with wide visibility, unbroken by forest or woodland, or by ravines and other features permitting surprise approach. Favours moist, poorly drained upland moors, either of heather Calluna mixed with rough grass… or open recently burnt stretches…’ ‘Omnivorous, though taking principally invertebrates.’
Lesser Spotted Woodpecker Dendrocopos minor [5] ‘…tolerance of high and low temperatures, wind and rainfall…Availability of easily worked decayed wood may be more essential than tree height or species. Prefers open broad-leaved woodland, edges, spinneys, parkland, riparian or other tree lines or avenues, and most moist woods of oak Quercus, hornbeam, Carpinus, willow Salix, alder Alnus, or poplar Populus. …Avoids conifers and any dense, mature stands.’ Almost exclusively insects. Rarely feeds on ground. In summer, chiefly searches for insects on surface of tree trunks, branches and leaves; in winter, pecks at rotten wood to find beetle larvae and adults beneath bark…’

Appendix IV – Meadow Pipit to Wheatear

Meadow Pipit Anthus pratensis [6] ‘Chooses, as a ground dweller, open areas of rather low, fairly complete vegetation cover. Avoids extensive bare rock, stones, sand, soil and close-cropped grass or herbage…and on the other hand, tall dense vegetation, including woods, forests and reedbeds. Flourishes, however, in plots of young planted trees, and perches freely on fence-posts, telegraph wires, stone walls and other points of vantage, but once scattered trees appear, competitive advantage seems to pass to Tree Pipit.’ ‘Mainly invertebrates, with some plant seeds in autumn and winter. Feeds almost exclusively on ground, walking at a steady rate picking invertebrates from leaves and plant stems.’
Tree Pipit Anthus trivialis [6] ‘…basically a ground feeder and ground nester, but unique [amongst congeners] in West Palearctic in attachment to trees and bushes as look-outs and song-posts, no less essential in breeding territory than suitable foraging terrain and nest-sites. Accordingly shuns both open and shrubless habitats and those where habitats and those where density of woody vegetation leaves insufficient open low herbage accessible.’ ‘Chiefly insects with some plant material taken in autumn and winter. Food mostly taken from ground, low herbage and leaf litter, more rarely from twigs, branches tree trunks and stumps.’
Redstart Phoenicurus phoenicurus [6] ‘Requires sheltered but fairly open wooded or parkland areas with access to dry secure nest-holes in trees, rocks, walls, banks or other places without too dense or tall unbroken undergrowth or herbage…prefers broad-leaved or mixed trees …and is adapted to woodland edges, streamside and roadside trees, orchards and gardens in human settlements.’ ‘…largely insects…and spiders… (1) Picks items from ground; apparently does not probe for worms and rarely searches in leaf litter. (2) Feeds in trees and other vegetation…, picking items from trunks, branches and leave, including hovering near foliage. (3) Flies from perch on to prey on ground, normally returning to perch to eat it. (4) Takes aerial prey in brief flight from perch.’
Wheatear Oenanthe oenanthe [6] ‘…requiring ready-made rock or burrow nest-site immediately neighbouring seasonally insect-rich bare patches or short swards for for easy foraging…European habitat also open… flat, sandy, sparsely vegetated arctic tundra…cliff tops, heaths and downland closely grazed by rabbits or sheep…’ ‘Chiefly insects; also spiders, molluscs and other small invertebrates, supplemented by berries. Normally locates prey visually, chiefly on ground or in low vegetation… (1) Running: in flat areas of short turf, runs…short distance, stops to pick up item or to scan ground ahead, and then runs on. (2) Perching: in areas of scattered perches (e.g. stones or low bushes) uses these to scan the ground nearby, drops down for item and then returns to perch or moves to new one…. ‘

Appendix V – Whinchat to Wood Warbler

Whinchat Saxicola rubetra [6] ‘… more continental bias than S. torquata, although favouring moister and less rough habitats. General separation of range suggests avoidance of interspecific competition with S. torquata and greater use of seasonal growth of green vegetation such as bracken Pteridium and tall grasses or herbage in preference to permanent woody shrubs. Accepts sparser and less robust perches than S. torquata, often using posts, fences or tall weeds… more attracted to grassy areas, incl some farmland types… fringes of wetlands and grassy uplands.’ Invertebrates and some seeds. Hunts from perch, flying to and taking prey mainly from ground or in vegetation, sometimes in flight like flycatcher.’
Stonechat Saxicola torquata [6] ‘…inhabits wide variety of dry plains and hillsides, often sub-marginal for agriculture, characterised by scattered bushes, shrubs, stones, walls, or fences … used as look-outs or song-posts commanding lower heathland, grassland or bare patches. In Britain, prefers rough coastal areas where gorse Ulex, heather Calluna or Erica, and bracken Pteridium are interspersed with close-cropped grass; Where grass grows tall and dense, S. rubetra usually takes over.’ ‘Small and medium sized insects and other invertebrates. Locates terrestrial prey from elevated perch then flies, glides or hops to ground, picking prey up on landing or while standing on ground; may return to same perch or a new one.’
Wood Warbler Phylloscopus sibilatrix [6] ‘…requires moist and shady woods with closed canopy and no or sparse undergrowth… Recent intensive study in Westfalen (West Germany) shows deciduous trees, especially beech and oak, to be indispensable for territory…In Britain characteristic of woods of sessile oak Q. petraea…usually preferring mature canopy… little secondary growth and sparse ground cover, but which has convenient low branches for perching…. Thus requires dual-level habitat: tree canopy for foraging and singing; and more or less open ground beneath for breeding.’ ‘Insects and other invertebrates, with some fruit and seeds in autumn. Picks items off leaves (often from underside) and other parts of trees and bushes while moving through foliage.’

Appendix VI – Ring Ouzel to Raven

Ring Ouzel Turdus torquatus [6] ‘…typically open moorland or fell with rarely more than sparse and stunted trees, occasionally at sea-level but normally at 250 m or higher, in Scotland up to 1200 m. Most nesting territories in Britain include small crags, gullies, screes, boulders or broken ground, as well as sloping or flat areas, often of heather, with a few trees or bushes…’ ‘In spring and early summer, adult and larval insects and earthworms; at other times, mainly fruit. Feeds on ground and in trees and bushes.’
Pied Flycatcher Ficedula hypoleuca [7] ‘Range broadly coincides with occurrence of more than 1000 mm of annual rainfall, and with hilly terrain, and with area in which sessile oak Q. petraea is dominant tree, with little undergrowth…. spacing of trees and plenty of low undergrowth appear to be essential.’ ‘Arthropods, flying and non-flying… during breeding season, larval lepidoptera important for nestlings; fruit and seeds taken taken regularly in late summer and on migration… Obtains food directly from trees or ground or by sallying out from perch after flying prey, usually for a short distance.’
Magpie Pica pica [8] ‘Occurs up to considerable altitudes… where ecological conditions are suitable, but is predominantly a lowland bird of open or lightly wooded country offering good opportunities for foraging on ground and for nesting, roosting and taking cover in trees or shrubs. Inhabits woods of many different types, both broad-leaved and coniferous, wherever glades, clearings, or more open stands occur, and especially near margins of natural or cultivated grasslands and croplands.’ ‘Invertebrates, especially beetles Coleoptera, fruits and seeds; occasionally small invertebrates [eggs and nestlings of other birds] and all kinds of carrion, refuse and domestic scraps. Very opportunistic feeder, diet varying considerably according to habitat and local food sources: broadly, consumption of invertebrates highest in spring and summer, and vertebrates and plant material in autumn and winter.’
Carrion Crow Corvus corone [8] ‘…forest country, esp forest edges, groves and river valleys… In Britain marked attraction towards foraging on tidal estuaries… recently, strong build-up has occurred even within the largest towns…Many studies indicate that given its wide-ranging foraging, omnivorous appetite, and skill in exploiting the most diverse opportunities, habitat constraints are not normally limiting…’ Principally invertebrates and cereal grain; also small vertebrates, birds’ eggs, carrion and scraps… varying greatly according to local availability. In general, a ground feeder and scavenger in agricultural landscapes, typically in pasture or rough grassland in spring and summer, and arable fields in autumn and winter. Favourite sites include dung-rich pasture, hayfields, fields of cereal after harvest, areas by water (esp seashore) and rubbish tips.’
Raven Corvus corax [8] ‘So wide ranging that concept of habitat is hardly applicable…Overriding requirements are for nest-site of difficult access, normally on a rock-face or tall tree, and wide, largely undisturbed foraging area with tracts of open surface of any kind on which long-range food-gathering, often involving high flights, can be practised. Thus avoids interior of large or dense forests, scrub woodland, thickets, shrubby terrain, wetlands with tall aquatic vegetation, orchards, plantations, field crops and intensively farmed or grazed lands.’ ‘Plant and animal material, taken opportunistically; animal food may be killed with powerful bill, or scavenged as carrion. Also robs nests and takes invertebrates (esp molluscs on shore); plant material mainly cereals and fruits. Where carrion plentiful, usually takes food by scavenging.’

 

 

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4 Responses to The impact of upland farming – Part 3 of 4: Ecology of the uplands in transition.

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