Species

Justification
Although this species has a small range, it is thought to be stable and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Taxonomic source(s)
AERC TAC. 2003. AERC TAC Checklist of bird taxa occurring in Western Palearctic region, 15th Draft. Available at: http://www.aerc.eu/DOCS/Bird_taxa_of _the_WP15.xls.
Cramp, S.; Perrins, C. M. 1977-1994. Handbook of the birds of Europe, the Middle East and Africa. The birds of the western Palearctic. Oxford University Press, Oxford.
Sibley, C. G.; Monroe, B. L. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, USA.

Taxonomic note
Loxia crossbills are conifer seed specialists for which there is an increasing body of evidence to show that bill morphology and overall body size, the main morphological features by which forms vary, are intimately linked to the cone structure and size of the particular conifer species (or mosaics of species) upon which they feed. There is also increasing evidence that different populations of crossbills show differences in flight and excitement calls which co-vary with bill shape, and hence with the distributions of their main food sources (e.g. Borras et al. 2008, Edelaar 2008a, 2008b). This evidence is especially well developed in the case of the Scottish Crossbill Loxia scotica by Summers et al. (2002, 2007) to support treatment of L. scotica as a species distinct from both Common Crossbill L. curvirostra and Parrot Crossbill L. pytyopsittacus. In particular, Summers et al. (2007) present data to show that, in areas of broad sympatry in Scotland, these forms largely breed assortatively. Although they do show some degree of hybridisation, in the view of Summers et al. (2007) this is insufficient not to warrant recognition as species, despite overlaps in morphology and the lack of any genetic differentiation. Some uncertainty remains regarding the status of this form, and an alternative approach is to regard different vocal types as components of a single resource-polymorphic species. Assortative mating by voice-type could prove to be a consequence of post-pairing vocal copying. More generally, increasing numbers of vocal types are being discovered among sympatric populations of crossbills whenever sufficiently detailed studies are carried out. The American Ornithologists' Union (BirdLife's taxonomic source for North America) has yet to recognise any of the nine North American 'vocal types' as species, although the case for the first of these was made over twenty years ago (Groth 1988). Nevertheless, given the evidence currently available and associated uncertainties, BirdLife continues to follow the Association of European Rarities Committees in treating L. scotica as a species distinct from L. curvirostra and L. pytyopsittacus.

Distribution and population
Loxia scotica occurs in Scotland, UK, where it is mainly restricted to the eastern Highlands within which core areas are Nairn, Moray and Banff, extending down into lower Deeside, and in Sutherland (Summers and Buckland in press). It is likely that there are shifts in the distribution of the population in response to regional fluctuations in the cone crops of conifers, particularly those of Scots pine Pinus sylvestris (Tucker and Heath 1994, I. Bainbridge and R. Summers in litt. 1999). The population size was estimated at 1,500 adult birds in the early 1970s and at estimate of 300-1250 pairs in 1988. Surveys during 1995-2003 using an apparently diagnostic excitement call to locate the species found it in 94 woods during the breeding season (Summers et al. 2004), but as birds are likely to move seasonally and this study was carried out over several years it is hard to be sure how much duplication is involved. Using the same diagnostic excitement call, a recent study has estimated its population to number 13,600 post-juvenile individuals (Summers and Buckland in press).

Population justification
A survey using playback has estimated the population at 13,600 mature individuals. This roughly equates to 20,000 individuals in total.

Trend justification
The population is suspected to be stable in the absence of evidence for any declines or substantial threats.

Ecology
It inhabits both semi-natural stands of Scots pine Pinus sylvestris and conifer plantations.

Threats
Suitable semi-natural habitat has declined from approximately 15,000 km² to fragments totalling 160 km² over the last 5,000 years. However, the amount of plantation woodland has increased substantially during the 20th century.

Conservation actions underway
A UK Biodiversity Action Plan is being implemented. A survey was conducted in 2008 to assess the current population size (Summers and Buckland in press).

Conservation actions proposed
Carry out further studies to establish whether L. scotica is best adapted to native Scots pine or to plantations of non-native species (and therefore establish the degree of threat it faces).

Related state of the world's birds case studies

• In Europe, species with ranges that both contract and shift are likely to be most at risk

References
Tucker, G. M.; Heath, M. F. 1994. Birds in Europe: their conservation status. BirdLife International, Cambridge, U.K.

Summers, R. W.; Jardine, D. C.; Dawson, R. J. G. 2004. The distribution of the Scottish Crossbill, 1995-2003. Scottish Birds 24(2): 11-16.

Summers, R. W.; Dawson, R. J. G.; Phillips, R. E. 2007. Assortative mating and patterns of inheritance indicate that the three crossbill taxa in Scotland are species. Journal of Avian Biology 38(2): 153-162.

Summers Ron W.; Buckland Stephen T. 2011. A first survey of the global population size and distribution of the Scottish Crossbill Loxia scotica. Bird Conservation International 21(2): 186-198.

Further web sources of information
Action Plan for the Scottish Crossbill in Europe

Detailed species account from Birds in Europe: population estimates, trends and conservation status (BirdLife International 2004)

View photos and videos, and hear sounds of this species from the Internet Bird Collection

Text account compilers
Calvert, R., Capper, D., Symes, A.

Contributors
Bainbridge, I., Summers, R.

IUCN Red List evaluators
Butchart, S., Symes, A.

Recommended citation
BirdLife International (2013) Species factsheet: Loxia scotica. Downloaded from http://www.birdlife.org on 24/05/2013. Recommended citation for factsheets for more than one species: BirdLife International (2013) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 24/05/2013.

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

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