RED GROUSE

The Irish Red GROUSE

BY DARREN ELLIS

The red grouse Lagopus lagopus scotica is a sub-species of the willow grouse L. lagopus. The willow grouse is a widely distributed bird with habitats ranging throughout the temperate, boreal and Arctic biogeographical zones of the Northern Hemisphere. Subspecies have developed genetic and morphological variations defined by climate, location and diversity of their habitats. The red grouse occupies upland heath and mountain blanket bog in Ireland and Britain and has been the subject of much research due to its cultural and economic importance as a game bird. It had been suggested historically that the Irish population of red grouse represented a sub-species distinct from the Scottish population, referred to at the time as Lagopus scoticus hibernicus but this classification remained unsubstantiated for almost 100 years. Initial observations of divergence were based on a paler plumage in the Irish bird, the evolution of which was considered to be due to the presence of a greater cover of purple moor grass Molinia caerulea in the grouse’ Irish habitat. Consequently though, it was deemed impossible to assign the correct taxonomic classification based on the plumage of a bird and the initial suggestion was later rejected with claims that plumage colour in the galliforme group of birds is largely dictated by the pigment melanin. In 2012, DNA investigation was conducted to test the theory that populations of red grouse existing in Ireland are genetically distinct from the British population. To "GROUSE reinforce the theory posed by a POPULATIONS ARE morphological distinction a GEOGRAPHICALLY WIDESPREAD IN THE UPLAND number of DNA samples from both Scottish and Irish populations were genotyped. It was found that the two populations

BLANKET BOGS were in fact significantly

OF IRELAND BUT genetically differentiated, POPULATIONS promoting the requirement for

ARE BECOMING INCREASINGLY ISOLATED DUE re-classification of the Irish red grouse as a separate sub-species, which would tentatively become known as L. lagopus hibernicus. TO HABITAT The discovery of Irish red grouse FRAGMENTATION." as an endemic sub-species may have acute consequences for the conservation of existing populations. Grouse populations are geographically widespread in the upland blanket bogs of Ireland but populations are becoming increasingly isolated due to habitat fragmentation. This problem is exacerbated by the limited dispersal of juveniles to other locations and as such, their tendency to remain in or return to the area of birth combined with loss of habitat is reducing genetic variability. In small isolated populations this loss of variability from inbreeding can result in depression of fitness which may lead to reduction in reproductive success and increased exposure to parasites and disease.

Translocation of grouse from Scotland to the Irish blanket bog habitats occurred in the past to bolster population numbers for game hunting. Due to a shared common ancestor these two populations are likely to have only a slightly different genetic profile and it is probable that hybridisation between the two resulted in only a minor shift in the existing genotype of the Irish sub-species. Therefore, it is unlikely that small numbers of Scottish birds in Ireland have radically altered the Irish gene pool and may have even enhanced the genetic profile throughout regions where introductions took place. However, continued stocking of Irish populations with Scottish and UK birds would most certainly alter the native lineage over time and could pose a threat to native populations through hybridization, which can dilute the local gene pool leading to localised extinctions or loss of local adaptations.

Efforts to mitigate future extinctions are made difficult by limited knowledge related to the misidentification and misclassification of endemic species. Without identifying separate sub-species accurately and classifying them so, it is not possible to understand the true rate of extinctions or indeed the mitigation measures required to prevent them.

In some quarters the Irish subspecies is still considered to be that of the same species as the Scottish variety. However, in Annex II of The EU Birds Directive, both sub-species are recognised as distinct. Modern day DNA investigations allow us to identify formerly unknown species populations and implement appropriate measures for their conservation.

In 2010 it was estimated that Irish red grouse numbers had reduced drastically by at least 50% over the preceding 25 years. Such was the negative population trend that the species was placed on the Birds of Conservation Concern in Ireland (BoCCI) Red List in 1999, a designation under which it currently remains. Historic habitat management and predator and parasite control which bolstered grouse populations for game hunting are much less common in Ireland. Plantation forestry and continued overgrazing in the grouse’s upland habitats are fundamental obstacles to the species success. Sympathetic grazing regimes and the opening up of habitat corridors between isolated populations are essential to facilitate mixing of the gene pool resulting in increased fecundity and proliferation of healthy populations of the Irish red grouse.

Results from the National Red Grouse Survey 2021/22, which took place this year, will provide an up-to-date insight on the status of red grouse populations and the current state of their habitats. The implementation of this survey will provide a golden opportunity to reassess the landscape measures and conservation actions required to reverse the decline of this unique species.