British Birds |
VOL. LI FEBRUARY No. 2 1958 BRITISH BIRDS THE BIRDS OF TIREE AND COLL By J. MORTON BOYD (Department of Zoology, Glasgow University*) (Plates 18-20) THE islands of Tiree and Coll, Inner Hebrides, lie totally within the vice-county Mid Ebudes (103). Situated between Mull and the Barra Isles, they stretch some 45 miles S.W. into the ocean from Ardnamurchan, the most westerly headland of the Scottish main land. Their geographical position, and separate scale maps of each, are shown in Figs. 1, 2 and 3. This work is concerned with records of all species of bird observed, from the earliest literature to the present day, not only on Tiree and Coll, but also on all islands and rocks between and including Eilein Mor, N.E. of Coll, and Skerryvore, S.W. of Tiree. The islands are a low undulating platform of Lewisian gneiss masked extensively by raised beach material and wind-blown sand. The sand deposits are particularly widespread in Tiree and S.W. Coll, but in N.W. Coll there are considerable tracts of bare rock. The terrain rises to its highest point (460 feet) in Ben Hynish, Tiree. The principal ecological divisions of the islands are: (i) an intertidal zone, including extensive beaches of shell-sand inter spaced with rocky shores trenched by eroded dykes, and fringed with skerries; (ii) grazed sand-dune systems landward to the shore sand, and moorland altered by salt-spray landward to the rocky shores (the only substantial sea-cliffs are at Ceann a'Mhara, Tiree); (iii) machair or sea-meadow, and cultivated calcareous grassland covering wide tracts of Tiree and S.W.
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