These woods consist almost exclusively of a single, tree species: Beech (Fagus sylvatica).
They are distributed over the mountainous areas in the northern half of the community, where precipitation exceeds 800 mm. a year: mountains of the ?divide? and the Sierras of Aralar, Urbasa and Andia, all homes to large beech woods.
Historically, the beech tree has naturally gained ground over the oak. Beech woods have also been exploited by man for many centuries, although their mountain locations have saved them from massive disruption. Many beech woods are still commercially exploited in the modern day.
Beech woods are fairly homogenous woods, very few tree and bush species accompanying the beech tree. A few service trees, elms and maples appear, albeit sparsely.Birds
The homogeneity of beech woods makes for an unwelcoming habitat, especially in winter, when many birds abandon these woods, particularly their higher, more exposed reaches. Consequently, the variety of species is not normally very great and the density of birds does not normally exceed 50 birds/10 Ha. at the most. Some of the species inhabiting beech woods are, however, very interesting.
The more characteristic species include the Common Buzzard, Sparrowhawk, Iberian Green Woodpecker, Black Woodpecker, Great Spotted Woodpecker, Robin, Mistle Thrush, Blackbird, Firecrest, Short-toed Treecreeper, European Nuthatch, Great Tit, Coal Tit, Marsh Tit, Blue Tit, Crested Tit, Eurasian Jay and Common Chaffinch. Rather scarcer are the Woodcock, Common Woodpigeon, White-backed Woodpecker, Tree Pipit (in clearings), Blackcap, Garden Warbler, Short-toed Treecreeper, Citril Finch and Common Bullfinch.Among nocturnal species, the Tawny Owl is worthy of special mention.
Winter can also bring significant groups of Redwing and Brambling.