The area of this study is located in the northwest of Navarra at an altitude of between 600 and 400 metres.

These characteristics correspond to highland and so we would expect to find a clear predominance of oak and ash. In this case, however, what draws one's attention is the widespread presence of beech trees in the landscape.

They belong to the acidophilic Cantabrian-Basque class of beech tree (Saxifrago hirsutae-Fageto sylvaticae Sigmetum).

This type of vegetation is, in fact, more common in mountainous areas (heights of between 600-650 and 1600-1700 metres), but the high rainfall in this region means that it reaches far lower heights, generally between 400-500 metres; the tree even flourishes above 300 metres on the northwestern slopes nearest to Guipúzcoa.

The dominant species in this vegetation type is the beech tree (Fagus sylvatica).

The long, slender trunks of these trees make for unique woodland: dark, cool and high.

When there is enough water, the beech ousts other species by casting dark shadow and coming into leaf early. Very rarely does the beech share its space with other tree species, such as the odd sessile oak (Quercus petraea), birch (Betula celtiberica) or European rowan (Sorbus aucuparia).
The understory is also very poor. The shrub understory is stunted and generally consists of dispersed examples of holly (llex aquifolium) and common hawthorn (Crataegus monogina). The grass understory is not well covered either.

A good part of the old beech woods have been felled and the soil reforested with conifers such as Japanese larch (Larix kaempferi), Norway spruce (Picea abies) and Lawson's cypress (Chamaecyparis lawsoniana). The Japanese larch has been grown as a reforestation species above all in Guipúzcoa and the northernmost reaches of Navarra at over 400 metres and has met with varying success. The Norway spruce has been used for reforestation at slightly higher levels (500 metres), but, as this tree's root system is very superficial, not in areas exposed to strong winds.

The natural distribution area of Lawson's cypress is the western coast of North America, from Oregon to California. It has been used for reforestation, giving way to very dense formations which barely let any light past.

The disappearance of the acidophilic beech tree has led to the extension of smaller vegetation types, of which the borderline or pre-wood area is worthy of mention, basically consisting of shrub species such as common broom (Cytisus scoparius), blackthorn (Prunus spinosa), hawthorn (Crataegus monogina) and berry bushes (Rubus). There is also bracken (Pteridium aquilinum), birch (Betula celtibérica) and European rowan (Sorbus aucuparia), particularly in the areas nearest the mature woodland.

More common is the brush stage, consisting of heather and gorse, corresponding for the most part to Daboecio-Ulicetum gallii heathland.

This formation consists of a range of species from the heather family (Erica vagans, Erica cinerea and, on occasions, Erica tetralix and Erica ciliaris) and other species such as Daboecia cantábrica, Caluna vulgaris and bilberry (Vaccinum mirtillus). Completing the associated group and living alongside these members of the ericacea family, there is gorse (Ulex europaeus and Ulex gallii), Lithodora prostrata, Agrostis curtisii and Pseudarrhenatherum longifolium.

On occasions, intensive pastureland farming, combined with the use of fire, may lead to short, dense pastureland dominated by grasses such as Danthonia decumbens, Festuca nigra subsp. micropylla, Agrostis capillaris and sometimes even Nardus stricta.

Fields like these are highly cherished by man as they can maintain a good part of the sheep and horses bred in the area during the summer.

These pastures are, however, costly to maintain mainly because the intense rainfall leads to significant leaching of the bases and acidification of the soil, which naturally favours the development of heather and gorse.

In the same conditions (poor base soils, humid or hyperhumid precipitation zone and non-existent dry period in the summer) as the previous type (Cantabrian-Basque acidophilic beech), but at lower heights, we find Cantabrian-Basque, humid-hyperhumid, acidophilic oak vegetation.

It mainly consists of pedunculate oak (Quercus robur) with the odd tree such as a birch (Betula celtibérica), whitebeam (Sorbus aria), European rowan (Sorbus aucuparia) or Pyrenean oak (Quercus pyrenaica).

These woods give rise to far thicker undergrowth with an abundance of grass species, ferns and low thicket (heather), but the high rainfall in the Agiña area means that this veggetation is ousted by the beech trees to lower heights than usual, thereby falling beyond the area of study.

The animals which most catch the eye in the area are its birds and of these, the habitual presence of the Griffon vulture (Gyps fulvus) flying over the hills and perched on the rock shelf beneath the summit of Agiña is particularly worthy of mention.

Here, it is possible to see large groups of these birds (a gregarious species) calmly warming themselves in the sun for hours or with their wings spread out to dry after a storm.

The Griffon vulture is notable for its size (with a wing span of between 230 and 265 centimetre) and because its lack of fear of man means that it can often be found very near to fairly busy paths, It nests on cliff shelves.

The vultures observed near Agiña most probably belong to the breeding colony on the nearby mountain of Peñas de Aia, although they could come from somewhere else; there is another important breeding colony in Baztán and these birds can travel as far as 100 kilometres from their nests in search of carrion.

The presence of other birds of prey, such as the common buzzard (Buteo buteo) and the red kite (Milvus milvus), is also quite frequent.

These diurnal birds of prey are large (though smaller than the vultures) and, therefore, easy to see; the great distances they usually maintain and the speed at which they fly, however, often makes them hard for the inexpert eye to distinguish.

Members of the corvidae family, such as the carrion crow (Corvus corone corone) and the common raven(Corvus corax), can also often be seen.

These two species are very similar. In order to distinguish between them, observe the difference in size (the raven is larger) and the shape of the tail (the raven's is wedge-shaped).

There is also a wide range of small birds.

You can often find chaffinches (Fringilla coelebs), nuthatches (Sitta europaea), coal tits and stonechats (Saxicola torcuata). The first three are frequently found in woodland, while stonechats are more common in relatively open spaces with vegetation and at vantage pioints, making them easy to spot on the summit of Agiña.

Another great group to see is that formed by swifts (Apus apus), swallows (Hirundo rustica) and house martins (Delichon urbica).

These species are summer visitors.

One of their main points of interest is that they are almost continually on the trail of insects and if you stop for a moment on Agiña, they will fly over you again and again, often at very low heights.

Another striking bird is the great spotted woodpecker (Dendrocopos major). It is well known both for its abundance and due to its attractive black, white and red plumage which makes it hard to miss, be it in flight or still.

In the spring, it is easy to hear the short, sharp thumping noise it makes when it pecking tree trunks.