Habitat fragmentation and the ecology of artefacts
I watched a bull moose (Alces alces) browse willow at a forest edge along Cascade Creek in Wyoming a few years ago, the characteristic palmate (lobed) antlers marking it out from the dendritic (branching) and multiple points of the equally large antlers of the bull elk (Cervus canadensis) I had seen a few days before. These two species are the largest in the deer family, but even they do not prepare you for the staggering size of the Irish Elk (Megaloceros giganteus) an extinct giant deer that is now only seen in skeleton form in museums (1). Even without its covering of flesh and skin, the size of the Irish Elk at Leeds City Museum is daunting, conjuring up an animal that is seven feet tall (2.1m) at shoulder height, but it is the palmate set of antlers that are most impressive, if not verging on the absurd, since they have a span of 12 feet (3.7m) the almost spoon-shaped palm of the antler having a series of large finger points radiating outwards (2). Impressive as that antler span may be, it immediately provokes questions about the mobility of a deer that seems to have wings on its head, and the sheer muscle power that would have been needed to have lifted those antlers up and down.
What made the Irish Elk go extinct?
Irish Elk first appeared about 400k years ago, and with a distribution based on fossil bone relicts that eventually spanned from Ireland in the west, through the middle latitudes of Eurasia to as far as a mountainous range to the east of Lake Baikal in Russian Siberia (3). It got its common name because of the large number of giant deer skeletons that were discovered in the nineteenth century under peat bogs in Ireland (1) the one in Leeds having been donated to the Museum in 1847 after its discovery in Lough Gur in Co. Limerick. That the giant deer disappeared over a period of a few thousand years - from Europe about 12.9k years ago, but persisting until at least 7.7k years ago in western Siberia and European Russia (4) - begs the question of why it went extinct? Consider that giant deer survived through a period when they would have faced some very nasty predators in the sabre-toothed felid carnivores, various large bears (including the cave bear) the cave lion, and tiger and leopard in its southerly distribution, and the presence of Neanderthals and any hunting pressure that they may have applied (5). So why then did the giant deer go extinct coming in to the Holocene, when the much smaller deer and moose did not? The speculation that the large antler set offered defensive protection from predation may be relevant when they outlived those nasty predators, but was their extinction ultimately the result of the size of those antlers when there would have been a nutritional burden of replacing them each year that would have got harder during worsening habitat conditions?
The focus on males in an analysis for extinction holds little credibility when, as is seen today, that only one male deer is needed for multiple matings. Perhaps it was overspecialization in its diet, the disappearance over that period of extinction coinciding with changes and loss in vegetation formations that it was adapted to. This would have led to nutritional stress, combined with reduced reproductive rates among females, and opening giant deer up to greater mortality and threat from predation. It has been speculated from its bone structure, the morphological features of the skull and lower jaw, the shape, height and position of teeth, that giant deer were a mixed feeder, both a browser and a grazer (5). However, it may not have been able to constantly inhabit short grass plains or tundra, when its diet probably usually consisted of branches of trees and bushes, young underwood, tall herbs, and lush water’s edge plants, all arising from a landscape with a high primary productivity. Thus the loss of certain food components important for this species could have been crucial for survival.
During the Allerød interstadial, a warm and moist period that occurred during the final stages of the last glacial period between 11,000-12 000 years ago, the plant growing season was approximately 150 days in length, but during the cooling of the Younger Dryas, a period of 1,300 years of cold climatic conditions and drought that brought the Allerød interstadial to an abrupt end, the growing season was 30 days less at approximately 120 days in length, leading to a disturbance in the previously formed floral provinces (3). Forests became lighter and the areas free from forest vegetation were instead occupied by tundra in northern Europe, and steppe in southern Europe, both plant associations having a much lower primary productivity (5). In addition, the digestibility of plants consumed by deer varies with season, being highest in the early spring, decreasing during the remainder of the plant growing season, and being lowest in the non-growing season (3). Thus, plant digestibility probably played an important role in the yearly energy budget of Irish Elk, so that it had difficulty adapting to a longer non growing season, when plant digestibility was at its lowest, and when it would be in competition for habitats and food resources with the deer species that did survive that period.
Seeing our landscapes today as the giant deer may have seen them
The extinction of Irish Elk apparently due to rapid habitat reduction and fragmentation, and the subsequent decline in opportunities for dispersal and range shifts, points to the potential inability of mammals, particularly specialised large mammals like giant deer, to have adjusted to changing climate and habitat conditions. Consider that the rapid upturn in climate conditions after the end of the Younger Dryas led to a return of the lush, forested and riparian vegetation on which they were dependent, and which could have ensured their survival if only they had found some refuge with sufficient primary productivity during that colder period. As much as we may lament the unfortunate circumstances that led to their extinction, and which were beyond our control, it would only be a few millennia more into the Holocene before the habitat changes that our ancestors wrought in the adoption of agriculture would likely once again have put the survival of Irish elk at risk. I have tried to see our landscapes today as the giant deer may have seen them if they had survived. I can only conclude that our propensity as the exceptional species to initiate habitat fragmentation and degradation has reached a similar ability to the global climatic shifts that characterised glacial periods. Thus even in temperate mesic (moist) conditions, we maintain landscapes in a faking of the steppe grasslands of Eastern Europe and Central Asia, where the aridity and temperature extremes between night and day, and between winter and summer, just cannot support woodland growth. We do not have the extent of a diverse lush growth and high primary productivity of a natural landscape that could support the giant deer.
Habitat fragmentation is a major limiting factor for the distribution of species in human-altered landscapes, and is probably the greatest threat to the survival of small populations of many mammal species in individual habitat fragments as they drop below a minimal level of viability, or suffer from unpredictable environmental events (e.g. a succession of poor breeding years). It doesn’t matter that much of the fragmentation took place in the distant past, as thresholds of fragmentation that are critical to the survival of mammal populations are probably still being reached. To an extent, the effects of fragmentation depend on the extent of specialisation of the species, and what variety of landscape niches are utilised. Thus the reduction in population for a species that relies on a continuous natural habitat begins to bite when the distance between fragments prevents dispersal, and connectivity breaks down. Those species which utilise edge habitats could at first benefit from fragmentation as the extent of edge habitat increases, but increasing fragmentation again leads to a breakdown in connectivity and population decline. However species that utilise a number of niches could show an increase in population with fragmentation as the mosaic of niches becomes more mixed. There comes a point though when habitat loss supersedes habitat fragmentation, breaking down connectivity and leading to population decline.
Some years ago, Paul Bright used a set of life history traits for British mammals to predict their response to habitat fragmentation (6). These traits were fundamental descriptors of a species' biology, and included population density, home range, intrinsic rate of increase based on reproduction rates and longevity in the wild, total number of habitats estimated to be able to sustain permanent populations, and a judgement on whether the species could maintain permanent populations in the new habitats created by fragmentation. Through principal component analysis, Bright was able to separate out four distinct groupings of mammals that differed in respect to their susceptibility to the adverse effects of fragmentation. The most susceptible group contained those with relatively low density, slow breeding, often poorly mobile species that utilise mostly natural habitats. As well as a range of bats, this group included mountain hare (our only native lagomorph) hazel dormouse, wildcat, red squirrel and pine marten. It also included otter and water shrew, riparian species vulnerable because of their restriction to a few habitats (waterways, lakes and coasts) and their occurrence at low population density. Of two intermediate groups in their vulnerability to fragmentation, the larger included species that have wider habitat tolerance, and included a range of bats, the two native deer (roe and red) polecat and badger. The smaller intermediate group had field and common vole, and yellow-necked mouse, which may be vulnerable to habitat fragmentation because they have relatively high habitat specificity. Species not likely to be adversely affected by habitat fragmentation were characterised by high rates of growth, successfully exploiting a wide range of habitats group, and included hedgehog, weasel, stoat and fox, as well as small rodents in shrews, mice and bank vole.
It had been my thinking, after reading Bright’s predictions on vulnerability that perhaps we should look more often through the eyes of other species to gauge how extensive is the habitat fragmentation and degradation that we have wrought. For a small mammal that makes it’s living in woodland, such as the common or hazel dormouse (Muscardinus avellanarius) the small home range diameter of 60m (area = 0.28ha) (6) could suggest that it is easily accommodated within many of the ancient woodlands in England, and thus its prospect may be immemorial – the same today as it ever was – but then you have to consider that the total area of ancient woodland is so much lower now. By contrast, roe deer have a home range diameter of 437m (150ha) (6) which spans more than the size of most ancient woodland fragments, and so you will see roe deer transiting between woodland, quickly traversing open fields while they avoid livestock. Of course, the deer aren’t aware of the landscape modification that has fragmented the woodland landscape of their habitat selection, it is but the hostile environment they have to transit to get to the next area of cover and safety.
We don’t manage landscapes for wild deer
Over-hunting led to roe deer becoming scarce in England in Medieval times, becoming extinct in central and southern England and all of Wales by 1700 (7). However, after 1800, several reintroductions from Scotland into Dorset, Sussex and East Anglia, coupled with natural spread into northern England, has reinstated roe deer in most counties. As with all species that are able to thrive in spite of us, we control them through culling – an estimated 350,000 deer are killed each year (8,9) but I can’t tell you how many of those are roe deer as there is no official count. The common dormouse is also a relatively common and widespread species across the middle latitudes of continental Europe (10). However, in England, it is confined to southern counties when its distribution would have covered most of England (11). In retrospect, I wish I had not alighted on the dormouse as an example, since efforts to maintain and increase its range smack very heavily of the over-management paradigm, the dream constellation for the conservation industry of a cute animal because it tucks its tail over its face as it rolls tightly into a ball when it is hibernating for half the year, or when in daily torpor during spring and early summer, and the prescription that it does better in coppiced woods and with artificial nest boxes (12).
The coppicing is a bit of a logical fallacy,
justified on the basis of feeding habits: dormice are specialist feeders
in that they require a wide variety of arboreal foods including flowers
(nectar and pollen), fruits (berries and nuts) and some insects, their
food supply thus depending over the summer months on a succession of
fruiting trees and shrubs (13). This implies a woodland with a high
diversity of tree types and a species-rich understorey that is not
shaded-out by taller trees that would inhibit flowering and fruiting.
Dormice do not normally travel far from their nest, usually less than 70m,
but they avoid activity on the ground, preferring to move among trees
having plenty of near horizontal branches, and being able to climb between
the understorey and canopy without difficulty in what have been called
“three dimensional arboreal routes” and which offer visual protection
from predators (13). You might then wonder how that fits with the twin
obsessions of the conservation industry of grazing and coppicing woodland.
The grazing will just clear out all that understory, whereas the coppicing
destroys vertical and horizontal structure. I have only once seen
recognition that coppicing is devastating to the dispersal ability of the
The biodiversity benefits of a large-scale return to coppice management are always oversold. Species may be associated with coppice woodlands, but it is open space or dense shrubby habitats which they require, not the management system per se. There is a recognition of this issue for dormice, but only in an exhortation to lengthen the cycle of coppicing, as hazel does not usually fruit well before it is seven or more years old. Thus the ideal cycle length of coppicing for dormice is alleged to be probably 15 to 20 years, which is of course longer than desirable for many butterflies (12) another part of the dogma about the benefits of coppicing. Active coppicing prevents the establishment of mature canopy woodland conditions and limits the amount of old dead and dying wood, both key features of a varied woodland ecosystem. This is important to dormice because, given the choice, they prefer to use robust resting places such as hollows or cavities in trees, and which give them protection from predation (15). Dormice are at risk mainly from nocturnal predators, when they themselves are mostly active, principally being taken by owls, such as the barn owl and tawny owl, but also by all the mammalian predators across their European range (eg. pine marten, foxes, wildcat, wolves etc.)(15). The problem is that tree hollows tend to be scarce in British woodlands particularly in coppice, in young plantations and, in the vigorous undergrowth that provides feeding areas for dormice. Hence there is a need for older trees and shrubs with hollows and rotten branches to be available. Hollow tree stumps may also be used as hibernation sites. And yet we have the nonsense of the conservation industry putting up boxes for birds, rodents and bats because of the lack of tree cavities.
What ecology are we studying?
I’m beginning to think that it is hopeless to assume that the ecology of England is anything other than a study of artefacts, of species overcoming the extensive modifications we perpetrate, so that we are seeing the result of enforced habitat and dietary changes as a pragmatic response for survival. Thus, for instance, the diet of barn owl changed significantly over the second half of the twentieth century, with a decrease in common shrew (Sorex araneus) no change in its major prey of the field vole (Microtus agrestis) but an increase in pygmy shrew (Sorex minutus) wood mouse (Apodemus sylvaticus) yellow-necked mouse (Apodemus flavicollis) and bank vole (Myodes glareolus) the changes reflected in the varying populations of these small animals resulting from agricultural practices (16). I have pointed to the artefact of the non-native rabbit being a major part of wildcat diet in Scotland (17) but it also dominates the diet of foxes, with the additional artefact of non-native pheasants as the major bird species taken (18). Then there is the obsession with coppicing in England, a practice that is not carried out across much of the range of dormice in continental Europe, and yet they are there in that woodland. A clue to this may come from a study in Lithuania, which noted that the living conditions for dormice became better when mature forest stands thinned out naturally, and understorey developed in gaps naturally formed in the forest (19). This just screams at me that our woodlands, even those that the conservation industry bemoan have lacked management, are so devoid of woodland species through previous centuries of management, and are just not mature enough to exhibit the range of natural processes that have been characterised across continental Europe.
The importance of dead wood in natural forests
Species dependant on dead and decaying wood are a characteristic of ancient, old growth forests in continental Europe, such as lichens, fungi and invertebrates, as well as the forest specialist woodpeckers that prey on those invertebrates and which, along with some owls and bats, find nesting homes in that dead wood. Dead wood in parts of the stems or branches of standing trees, as well as standing and fallen dead trees are indicators for naturalness in ancient forests, as are old trees (>200 years) with rough bark structures, severe crown damage, large cavities, clefts in the stem, open bark gaps and bark bags (20). Standing and fallen dead wood is created by tree mortality, which in natural forests is caused by fire, wind, snow breakage, drought, competition, insects and pathogens (21). Many species associated with dead wood do not make a living directly on the dead wood, but on other species that consume dead wood. A fungal community develops after tree death and a large number of saproxylic beetle species feed on the fungal mycelium, or on the decaying wood. In turn, many parasitic insects live on wood living beetles.
Mould filled bark bags arise from dead bark on dead or living trees, where the bark is partially lifted and filled up with mould between the bark and stem (20). These mould filled bark bags are variously used as nesting sites by tree creepers (Certhia spp.) (23) and as breeding sites or roosts for two rare and threatened bats, the Barbastelle (Barbastella barbastellus) (24) and Bechstein's bat (Myotis bechstein) (25) (all three species being native to British woodlands as well). They are also used by insects, both as hiding places and breeding nests, in particular by various species of beetle, such as skin (Dermestidae spp.) comb-claw (Alleculidae spp.) and Clown beetles (Histeridae). The foraging ecology of insectivorous woodpecker species is based on gleaning and probing for bark-dwelling and boring insects like the beetles (26). The Middle Spotted Woodpecker (Dendrocopos medius) and the long-beaked white-backed woodpecker (Dendrocopos leucotos) are more often associated with the deadwood of deciduous forest, whereas throughout its range, the three-toed woodpecker (Picoides tridactylus) is found in old coniferous (spruce) forests (27) but all three predatory woodpeckers use standing deadwood for roosting or nesting (28).
The dependence of woodpecker species on large areas of long-lived forest with the characteristic properties of natural processes makes them indicator species for other species associated with unmanaged forests rich in older trees and dead wood (29). Woodpeckers also play a keystone role in forests through the provision of cavities for a range of secondary cavity users, such as other birds and sometimes small mammals such as dormice (30). Their trophic function places them as a top predator, a positioning that in the case of the three-toed woodpecker, exemplifies a contribution to the natural regulation of bark beetle populations in coniferous forests (31). The European spruce bark beetle (Ips typographus) a conifer detrivore, can if unchecked periodically build up large populations, resulting in the death of many trees in a few years. In production forests, this is met with aggressive pest management programs that involve either extensive harvesting of beetle-infested trees or chemical control. However, in natural unmanaged forests, predation of these beetles and their larvae by the three-toed woodpecker delays and lessens bark beetle outbreaks in spruce (Picea spp).
The Ural owl (Strix uralensis) is one of the largest cavity-nesting bird species in Europe, its presence an indication of older forests that have a high availability of dead trees with natural holes, such as hollow trunks as well as wide cracks and large hollows created through wind damage breaking off branches and crowns (32). The owl hunts from tree perches overlooking forest openings, like bogs and water courses, the main prey being small woodland mammals, such as bank voles (33). Although it may use deserted raptors nests made of sticks, the lack of large standing deadwood and tree cavities limits the numbers of Ural owls, which accept these structures for breeding more readily than stick nests (32).
As resident bird species, owls and woodpeckers have higher vulnerability to habitat changes that decrease naturalness, such as the characteristics of managed forests where there is removal of deadwood, loss of mature deciduous trees and the introduction of coniferous trees (20). Logging in the Białowieża Forest, Poland, leads to reduced volumes of deadwood, as well as reduced numbers of white-backed woodpecker (34) as well as three-toed woodpecker (35). However, greater numbers of these woodpeckers are found in the unmanaged, strictly protected forest of the Białowieża National Park (36). There is very little deciduous forest older than 30 years in parts of Sweden, particularly of aspen (Populus tremula) and birch (Betula spp.) and this has been accompanied by a gradual, natural overgrowth with spruce, resulting in a decline of the white-backed woodpecker by 80% over the last 20 years, so that it has now become assessed as Critically Endangered (37).
Old growth woodland and natural processes
There is evidence from across Europe that periods of absence of management intervention in woodland, coupled with density-dependent mortality and low-severity canopy disturbances (wind and snow) promotes greater abundance of natural processes based on species richness, abundance and diversity of birds, saproxylic beetles and fungi; as well as the number of special tree structures related to the natural processes of senility, decay and death; and in the volumes of deadwood (20, 38-41). Unsurprisingly, there are not too many similar studies in Britain, except for a survey of quantities of deadwood that we do have following non-intervention in ancient woodlands, the scarcity of fallen dead wood and standing dead trees being explained by the lack of woodland sites in Britain that have been left undisturbed over the last 100 years (42); a study that seeks to show the value of species diversity in plantation woodland compared to semi-natural woodland (43); and an interesting study of old spruce stands in the British uplands, which suggested that old-growth features can begin to develop after 80–100 years, conferring substantial benefits to species-groups such as hole-nesting birds, mammals (e.g. red squirrel), bryophytes, lichens and fungi (44). Based on the likelihood of wind damage, it was suggested that ~50 per cent of the current land area in upland Britain could support large patches (50–100+ ha) of old growth.
Perhaps it’s the length of time needed to wait for old-growth features, the impatience to be seen to be in control, and which means that the conservation industry eschews anything that takes a long term view, or which has a horizon longer than its lifetime. Gardening for nature gives the industry its quick returns, satisfying funders and matching the hyperbole of its mastery in the cause of its choices of biodiversity (think coppicing). You will not therefore be surprised to know that the conservation industry are always seeking short cuts, if it seems they can deliver another show of mastery. Thus the products of old growth can be manufactured: ringing the bark of trees can eventually kill them, and this was the approach taken in 2005 in plantations of the native Scots pine on the National Trust for Scotland’s estate at Mar Lodge (45). Eight years after ring-barking, a quarter of the trees had snapped off, half had lost 60-90% of their branches and a third had lost more than 50% of their bark. Almost all of the trees showed signs of wood boring invertebrates, like bark and long horn beetles, and three quarters were used by woodpeckers. The control trees remained largely structurally unchanged and none were colonised by saproxylic invertebrates or woodpeckers.
There is a study in the forests of Białowieża National Park, Poland, that I hope one day will be possible here. It set out to determine the influence of wolves on the patterns of browsing by deer, and how this affected tree regeneration, an as yet uncommon investigation in Europe of a trophic cascade mediated by a large carnivore (46). As you would expect, the browsing intensity of tree saplings was lowest inside a wolf core area where predator presence was highest, than in the remainder of the wolf pack’s home range. However, browsing intensity was further reduced in areas where there were larger volumes of dead wood, more so in the wolf core area compared to outside it. The explanation for the effect of deadwood was that the three-dimensional structural chaos in areas of high dead wood was acting as an “ungulate escape impediment”, the deer recognising that the physical difficulties in egress would slow their escape from attack. The deer thus avoid those areas because the perceived risk from predation is much greater - another aspect of a behaviourally mediated trophic cascade.
We have the deer – we now need the dead wood and the wolves.
Mark Fisher 10 January 2015
I try to use sources in reference lists that are open to free access, but there a number here that aren’t. Drop me an email.
1) Reynolds, S.H. (1929) The Giant Deer. A monograph of the British Pleistocene Mammalia, Vol. 3, Pt. 3. London: Palaeontographical Society
(2) Staggering attraction at Leeds City Museum, Yorkshire Evening Post 1 August 2008
(3) Worman, C.O’D. and Kimbrell, T. (2008) Getting to the hart of the matter: Did antlers truly cause the extinction of the Irish Elk? Oikos 117: 1397-1405
(4) Stuart, A.J. and Lister, A.M. (2012) Extinction chronology of the woolly rhinoceros Coelodonta antiquitatis in the context of late Quaternary megafaunal extinctions in northern Eurasia. Quaternary Science Reviews 51: 1-17
(5) Vislobokova, I.A. (2012) Giant Deer: Origin, Evolution, Role in the Biosphere. Paleontological Journal 46: 643–775
(6) Bright, P.W. (1993) Habitat fragmentation—problems and predictions for British mammals. Mammal Review 23: 101–111
(7) Roe Deer (Capreolus capreolus): About wild deer
(8) Roe deer, Species ecology, Best Practice Guides, The Deer Initiative
(9) Overview: About wild deer, The Deer Initiative
(10) Amori, G., Hutterer, R., Kryštufek, B., Yigit, N., Mitsain, G., Meinig, H. & Juškaitis, R. 2008.Muscardinus avellanarius. The IUCN Red List of Threatened Species. Version 2014.3
(11) S1341 - Common dormouse (Muscardinus avellanarius) Supporting documentation for the Third Report by the United Kingdom under Article 17 on the implementation of the Directive from January 2007 to December 2012. Conservation status assessment. European Community Directive on the Conservation of Natural Habitats and of Wild Fauna and Flora (92/43/EEC)
(12) Bright, P., Morris, P and Mitchell-Jones, T. (2006) The dormouse conservation handbook. Second edition, English Nature
(13) Bright, P.W. and Morris, P.A. (1995) A review of the dormouse (Muscardinus a vellanarius) in England and a conservation programme to safeguard its future. Hystrix 6: 295-302
(14) Common Dormouse species action plan. A Biodiversity Action Plan for Hertfordshire
(15) Juškaitis R. (2008) The Common Dormouse Muscardinus avellanarius: Ecology, Population Structure and Dynamics. Institute of Ecology of Vilnius University Publishers, Vilnius
(16) Love, R.A., Webbon, C., Glue, D.E. and Harris, S. (2000) Changes in the food of British Barn Owls (Tyto alba) between 1974 and 1997. Mammal Review 30: 107-129
(17) The third dimension is the last refuge of the wild. Self-willed land December 2014
(18) Baker, P., Furlong, M., Southern, S. and Harris, S. (2006) The potential impact of red fox Vulpes vulpes predation in agricultural landscapes in lowland Britain. Wildlife Biology 12: 39-50
(19) Juškaitis, R. and Šiožinytė, V. (2008) Habitat requirements of the common dormouse (Muscardinus avellanarius) and the fat dormouse (Glis glis) in mature mixed forest in Lithuania. Ekológia (Bratislava) 27: 143–151
(20) Winter, S., Flade, M., Schumacher, H., Kerstan, E. and Möller, G. (2005) The importance of near-natural stand structures for the biocoenosis of lowland beech forests For. Snow Landscape Research. 79:127–144
(21) Jonsson, B.G., Kruys, N. & Ranius, T. 2005. Ecology of species living on dead wood – Lessons for dead wood management. Silva Fennica 39: 289–309
(23) Treecreeper (Certhia familiaris) British Trust for Ornithology
(24) Bechstein’s bat (Myotis bechsteinii) Bat Conservation Trust
(25) Barbastelle bat (Barbastella barbastellus) Bat Conservation Trust
(26) Kosński, Z. and Winiecki, A. (2005) Factors affecting the density of the middle spotted woodpecker Dendrocopos medius: a macrohabitat approach. J Ornithol 146: 263–270
(27) Czeszczewik, D., Walankiewicz, W., Mitrus, C., Tumiel, T. Stański, T., Sahel, M. and Bednarczyk, G. (2013) Importance of dead wood resources for woodpeckers in coniferous stands of the Białowieża Forest. Bird Conservation International 23: 414-425
(28) Lõhmus, A., Kinks, R. and Soon, M. (2010) The Importance of Dead-Wood Supply for Woodpeckers in Estonia. Baltic Forestry 16:76-86
(29) Roberge J.-M., Angelstam P. (2006) Indicator species among resident forest birds – A cross-regional evaluation in northern Europe. Biological Conservation 130: 134–147
(30) Roberge, J-M, Agelstam, P.and Villard, M-A. (2008) Specialised woodpeckers and naturalness in hemiboreal forests – Deriving quantitative targets for conservation planning. Biological Conservation 141: 997-1012
(31) Fayta, P., Machmerb, M.M. and Steegerb, C. (2005) Regulation of spruce bark beetles by woodpeckers—a literature review. Forest Ecology and Management 206: 1–14
(32) Lõhmus, A. (2003). Do Ural Owls (Strix uralensis) suffer from the lack of nest sites in managed forests? Biological Conservation 110:1-9
(33) Obuch, J. Danko, S., Mihók, J., Karaska, D. and Šimák, L. (2013) Diet of the Ural owl (Strix uralensis) in Slovakia. Slovak Raptor Journal 7: 59–71
(34) Czeszczewik, D and Walankiewicz, W. (2006) Logging affects the white-backed woodpecker Dendrocopos leucotos in the Białowieża Forest. Annales Zoologici Fennici 43: 221-227
(35) Wesołowski, T., Czeszczewik, D., Rowiński, P., (2005) Effects of forest management on three-toed woodpecker Picoides tridactylus distribution in Białowieża Forest (NE Poland): conservation implications. Acta Ornithologica 40, 53–60
(36) Walankiewicz, W. Czeszczewik, D. Tumiel, T. and T. Stański, T. (2011) Woodpeckers abundance in the Białowieża Forest – a comparison between deciduous, strictly protected and managed stands. Ornis Polonica 52: 161–168
(37) ArtDatabanken (2011) Vitryggig hackspett (Dendrocopos leucotos) Rödlistan, ArtDatabanken, Sveriges lantbruksuniversitet
(38) Laiolo, P., Rolando, A. & Valsania, V. (2004) Responses of birds to the natural re-establishment of wilderness in montane beechwoods of North-western Italy. Acta Oecologica 25 (2004) 129–136
(39) Svoboda, M., Fraver, S. Jandaa, P., Bace, R. & Zenáhlíkováa, J. (2010) Natural development and regeneration of a Central European montane spruce forest. Forest Ecology and Management 260: 707–714
(40) Vandekerkhove, K., De Keersmaeker, L., Baete, H., Walleyn, R. (2005) Spontaneous re-establishment of natural structures and related diversity in a previously managed beech forest in Belgium after 20 years of non intervention. Forest Snow & Landscape Research 79:145–156
(41) Fichtner, A., Lüderitz, M., Mielke, G.. Sturm, K. and Rickert, C. (2013) Natürliche Waldentwicklung in norddeutschen Laubwaldgesellschaften: Impulse für den Waldnaturschutz.Jahrbuch des Naturwissenschaftlichen Vereins für das Fürstentum Lüneburg 45:57-70
(42) Kirby, K.J., Reid, C.M., Thomas, R.C. and Goldsmith, F.B. (1998) Preliminary estimates of fallen dead wood and standing dead trees in managed and unmanaged forests in Britain. Journal of Apllied Ecology 35: 148-155
(43) Quine, C.P. and Humphrey, J.W. (2010) Plantations of exotic tree species in Britain: irrelevant for biodiversity or novel habitat for native species? Biodiversity and Conservation 19: 1503-1512
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