An historical account of the social and ecological causes of Capercaillie Tetrao urogallus extinction and reintroduction in Scotland

Abstract

The capercaillie is the largest member of the grouse family extant in Scotland. This species is reported to have become extinct during the 1700s. It is also reported to have been reintroduced to Scotland from Sweden during the 1800s. There have been many assertions made about the underlying causes of the decline of the species; however the specific causal factors remain unknown. The reintroduction of the capercaillie to Scotland in the 1800s is the only successful reintroduction of a grouse species ever to have occurred in the world. The specific factors behind the success of the reintroduction also remain unknown. This thesis examines the extent to which a selection of historical documentary evidence can help to establish both the causes of the 18th century decline of the capercaillie in Scotland and the successes of the 19th century reintroduction.

The methodology of this thesis incorporates facets from the fields of both environmental science and history. The methodology includes three steps. The first step involves the selection of a series of potential critical factors that may have been responsible for the decline of the species in the 1700s; these critical factors were selected from the present day understanding of the ecology and the behaviour of the capercaillie. The second step of the methodology includes the surveying of a series of historical documentary sources. From these surveys historical observations of the species were gathered. The historical documentary sources selected for examination in this thesis include what are referred to here as ‘primary historical source material’ and ‘secondary historical source material’.

The majority of the primary historical source material was gathered from the hand written manuscripts of the Breadalbane estate, held at the National Archives of Scotland (NAS) and the Atholl estate held at the Blair Castle Charter Room in Blair Atholl. Other select primary historical source material consulted to a lesser extent, due to time constraints, includes the Forfeited Estates (1745) Inventory and the Baron Court Records for Strathspey and Urquhart (1617–1683) from the Grant estate muniments; both held at the NAS. The secondary historical source material was gathered from published and edited literary collections that include historical accounts of the species. The third and final step of the methodology involves the synthesis of both the historical and environmental information in order to establish to what extent the causes of both the decline of the species in the 1700s and success of its reintroduction in the 1800s can be realised.

The findings from this thesis assert that the capercaillie was resident in Scotland from, at least, the end of the Medieval. Moving forward from the Middle Ages this thesis presents observations of the capercaillie throughout the historical period. These observations of the capercaillie appear in many different historical accounts. In some instances these observations are fleeting and do not form the main subject of the particular document in question. In other instances accounts of the species are much more detailed and include references to the ecology and behaviour of the bird. The level of detail included in an observation aside, the frequency with which the species is referred to in the sample of historical documents suggests that sections of the Scottish human population were familiar with the species, in various locations and at various times throughout history.

By the 17th century the capercaillie is reported as beginning to become rare in some locations while still remaining comparatively abundant in others. The number of instances where the species is referred to as becoming rare in the historical documents increases between the 17th and the 19th centuries. Despite the reported scarceness of the species in Scotland from around the 17th century onwards, the capercaillie is recorded as persisting in Scotland until around the end of the 1700s. By the early 1800s the number of observations of the species in the secondary historical source material increases. All of the observations in the secondary sources from the early 1800s record the absence of the species from localities and regions of Scotland. No new evidence was found in either the primary or secondary historical source material to challenge the supposition that the capercaillie did become extinct in Scotland after 1785.

No detailed quantitative data was available for analysis of the decline of the species. Thus, to investigate the extent to which the historical accounts can help explain the specific causal factors of the reported decline, a synthesis of the environmental and historical data was necessary. The findings of this synthesis suggest that the naturally occurring Scottish population of capercaillie probably persisted in the form of a metapopulation. The two hundred years between the 17th and 19th century most likely saw the extinction of capercaillie sub-populations, before the loss of the overall population of capercaillie around 1785. The sample historical documentary evidence alludes to this pattern of local and/or regional extinction of sub-populations.

The cause or causes of the extinction of these sub-populations has focussed on five limiting or critical factors known to affect the species today. These five factors are climate change, particularly weather effects associated with the Little Ice Age, habitat loss and deterioration, disturbance, human hunting and predation by species other than humans also contributed to the species’ extinction. The extent to which these critical factors affected each sub-population would have varied between regions of Scotland occupied by the capercaillie in history. This thesis proposes that there was no single or combination of specific critical factors that were ultimately responsible for the decline of the capercaillie in Scotland during the 1700s. In some areas the capercaillie sub-populations would have most likely died out as a result of habitat loss and deterioration and climate change. Whereas in others predation and inbreeding may have been the critical factors responsible for the species’ demise.

More detailed information referring to the capercaillie was found in the historical documentary source material for the period post-extinction (i.e. 1800 onwards). Contrary to popular understanding numerous attempts to reintroduce the capercaillie to Scotland were carried out before the Marquis of Breadalbane’s successful programme in 1837. The historical documentary evidence reports early attempts to reintroduce the species to locations such as the Isle of Arran in 1807, on the Duke of Atholl’s estate in 1822 and on the Earl of Mar’s estate in 1824. None of these reintroduction programmes are reported to have been successful in establishing a ‘wild’ population. However, in some instances the captive rearing programmes initiated did bear some fruit and captive reared birds were sent from Dunkeld by the Duke of Atholl to Kenmore and were used in Breadalbane’s successful reintroduction in 1837.

The historical documents report two causes for the failure of these early reintroduction attempts. The first is the sudden death of captive birds, most likely as a result of choking due to stress as observed in recent rearing programmes (i.e. Moss 1986). The reintroduced Arran population is reported to have become extinct in this fashion. The second reported cause of failure is predation by species other than man. For example the entire population of birds brought to Scotland by the Earl of Mar were predated when released on his estate. This thesis offers two critical factors as explanations for the remarkable success of the capercaillie’s reintroduction to Scotland in the 19th century. The first is the method by which the reintroduction was carried out; specifically, the re-establishment of a series of capercaillie sub-populations in different regions of Scotland. It is proposed here that the second critical factor that made the reintroduction a success was the reduction of capercaillie mortality throughout their life-cycle to a very low level; brought about by the human control of predators.