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Urkiola nature parks flora and fauna



Grove of Holm oaks


Holm oak on a rocky place with a goat (Increase the size in a new window)


The big tooth shaped rocks that form the north face of the Park: Ezkubaratz, Mugarra, Artaun-Egirotz, InunganeLeungane, the dark green vegetation contrasta con el blanco de las calizas arrecifales. Son los encinares que con sus 377 Ha. ocupan un 6 % de la superficie del Parque Natural de Urkiola, siendo la segunda formación forestal autóctona en extensión.

Tree in a deciduous wood (Increase the size in a new window)

The presence of these forests, of clear Mediterranean characteristics, in a rainfall environment such as Bizkaia, is an aspect that has always surprised both travellers and naturalists, visiting this area. As these forests are like an evergreen island in the world of ducidious forests. These are the only natural forests of the Cantabric slopes, whose leaves refuse to follow the rhythm set out by the seasons.

Holm oak wood seen from the extended hillside in the east of Ezkubaratz. (Increase the size in a new window)

Climbing up the elongated oriental slope of Ezkubaratz, the grove of Holm oaks resists the climatic variations experienced throughout time.

The origin of this "arrhythmia" is based on a series of climatic oscillations, which have taken place after the last glaciations. During the Quaternary era, a series of periods have been characterized by a diversity of climate, one of these called the Xerothermic, is characterized for having a dryer and hotter climate than the present one. During the mentioned era the Mediterranean vegetation took over the valley of the Ebro, crossing the hills that separated the waters, and subsequently scattering abundantly through the Cantrabic Coast. With the change of climatic conditions - becoming colder and humid -, as it is at present, such species were forced to retract to drier and hotter environments in order to survive.

The Holm oaks (Quercus ilex), accompanied by other species, moved to the rockiest locations, fundamentally the limestone area, where the filtering character of the rocks and the scarcity of soil allowed them to emulate the situations that existed here when they first arrived. This preference has been the main reason that has allowed them to survive throughout civilization changes. Relegated to dirty and skeletal domains, its dominance was barely envied by man, as it was difficult to transform to cultivating or pasture fields such a poor area. Not even the spreading of the pine tree or the eucalyptus affected them the same it affected the grove of oaks. This does not mean that this resource was not put to good use, apart from being valued as grazing fields for goats and the likes, the grove of Holm oaks was always a good source of coal and wood for the home. For this purpose the forest were exploited as if it was a type of herbaceous vegetation. The grove of Holm oaks was literally cut down, cutting them very near the stem. After this handling the shrubs sprouted from the base, they were allowed to grow for some years, and then the operation was once again repeated. At present the lowering in demand for use, as firewood substituted by fossil fuels, has been responsible for the disappearance of this exploitation. But their footprint still endures in the inextricability of these forests, where the trees branched out from a very low level, being all of these of modest height, less than 4 m.

If we take notice of the trees and the shrubs that make up the grove of Holm oaks we can detect in them a lot similarities. The leaves, apart from its perennial character, are similar in shape, starting with the strawberry tree (Arbutus unedo) going on to the laurel (Laurus nobilis), passing by the Rhamnaceae (Rhamnus alaternus) or the labiérnago (Phyllirea latifolia), they are shiny and furless, except the Holm oak, that has a dense fluff on the reverse side, apart from this, they all produce fleshy fruits that are eaten and dispersed by the various bird species.

Many of these characteristics repeat themselves with the lianas and reeds, which take up any free space available in the forest. Each species finds its own way around the slopes, by means of ring-like attachment as is the case of the Black bryony (Tamus communis), or the Prickly Ivy (Smilax aspera), the wild madder (Rubia peregrina) that doubles its steam and uses its small ), that adheres to the ground by means of adventitious roots, even though most of the times it can be found spread out amongst the rocks on the ground. Other plants lack the special adaptations for these doings, like the Dog rose (Rosa sempervirens) or the raspberries (Rubus sp.), use other types of strategies, as can be detected when going deeper into the forest. Its thorns are ready to trap any person or animal that goes near them. Here also appear some ducidious shrubs like the Hawthorn (Crataegus monogyna) or Dogwood (Cornus sanguinea).

Under this brush grow some plants directly on the forest ground, such as the fern Black Splenwort (Asplenium adiantum-nigrum) or the Italian Arum (Arum italicum) with its enormous flower heads and its notorious red fruit, the Liverleaf (Hepatica nobilis),and also the violet (Viola gr. sylvestris).

The Butcher´s broom (Ruscus aculeatus), is a shrub seen frequently in this type of forest. Resulting very interesting the adaptation of its sprouts, which have turned into leaves, leaving the original leaves reduced to mere scales facing the wrong side. The flower situated on the lower side of these cutting hedge-type leaves, or false leaves, are of a beautiful violet colour and very small, therefore it is very surprising to see the size the fruit attains, bigger than a cherry and of a bright red colour. The beautiful leave-flower contrast is one of the main reasons for its massive use as Christmas decoration, in substitution of the Holly, whose commercialisation is becoming a serious threat to this species.

Black maidenhair. (Increase the size in a new window)

Of perennial characteristics as is the case with all other plants in the grove of Holm oaks, the Black Splenwort (Asplenium adiantum-nigrum subsp. onopteris) avoids the cooler areas.

Branch of a strawberry tree with fruits. (Increase the size in a new window)

The madrono tree (Arbutus unedo) is one of the few species of our flora that flowers twice a year.

The strawberry trees or the madrona trees deserve to be mentioned separately, they sprout where the grove of Holm oaks has been trimmed or burnt, healing the clear openings in the forest. Its flower composition is similar to the grove of Holm oaks, with the difference that the dominating species is the madrona tree, and the presence of plants belonging to meadow is of less importance. Its extension in the Park is evident, being located in the same area as the grove of Holm oaks.

Holm oak wood ecosystem in Urkiola: Holm oak; Cuckoo Pint; Butcher’s Broom; Strawberry Tree; Blue Tit; Woodpigeon; Green Woodpecker; Common Whitethroat; Badger and Shrew. (Increase the size in a new window)


The vertebrae community that has settled in this type of xeric forest in Urkiola´s Nature Park is strongly conditioned mainly due to two reasons that will now be described. In the first place the existence of a very characteristic type of climate typical of the mild European environments, that strongly conditions the settling in of Mediterranean origin. The other reason is related to the development level presented by the masses of grove of Holm oaks in Urkiola. A combination of environmental factors (implementation is of a very poor level) combined with the human factor (continuous utilization of these trees for domestic uses) makes the actual formation of this type of forest not very adaptable to welcome a fauna of a certain size, especially the day type birds of prey.

The woodpeckers that have a higher representation in the forest areas of Urkiola, is on the one hand, the Green Woodpecker, Picus viridis. With the scarcity difference that presents the Great Spotted Woodpecker, Dendrocopos major, the other woodpecker resident in the Park, this bird is distributed throughout the totality of the Park; inclusively he has been spotted living in the beech trees that with difficulty climb up the rocky areas. Its unreserved character makes it easier to spot him in any ecological niche present in Urkiola; perhaps it is in the Cantabic grove of Holm oaks where it is more difficult to spot him due to the closeness of the vegetation. Nevertheless its characteristic sounds can frequently be heard in between the Holm oaks. It is a bird of an important size - measures around 30 cm - of attractive plumage. Its back is of an olive green colour, and its chest is yellow. The regimes and rectrices (tail feathers) are dark, white spotted, and chest feathers are greenish grey. Both male and female have a red crest and very bright yellow eyes. Even though they insect larvae, rotten wood termite (as is the case for all woodpeckers), the fundamental part of its diet is obtained by eating ants, they do so by trapping them with their sticky tongue. For this they come down to ground frequently; therefore the most frequent way to observe them is when they take off in flight from the ground, when in the presence of any observer.

Common flycatcher perched on a branch (Increase the size in a new window)

Urkiola Park with limestone crenellations in the background. (Increase the size in a new window)

The grass field plantation prosperous in the grove of Holm oaks in Urkiola, provide an adequate habitat for the construction of nests for the chiffchaff bird (Phylloscopus collybita).

During the cold season the Cantábric grove of Holm oaks supply the fauna lodged in them with a good cover against the climatologically adverse conditions. At present the new tree plantations also carry out, to a certain point, a similar role.

Even though the great hunting tradition established throughout the centuries with regards to the Wood Pigeon, Columba palumbus, in the Basque Country, the nesting of this type of species is of a scarce nature, without having any influence the extraordinary hunting pressure exerted on them. The hunting is concentrated uniquely on migrating birds. Their nesting inside the Park limits, following the tendency applicable to the rest of country, is very scarce; very few couples settle in Urkiola. The majority of these, seems that they nest in the disperse, existing spots, of the grove of Holm oaks, as in the south-western area of the Park, the area that posses the better spots of deciduous forests, they have not seen. On the other side in the disperse grove of Holm oaks, that prosper in one of the parks boundaries (the Dima area), here it is very common to observe them. It is quiet a biggish bird, with the blue colour being more predominant than the grey, and a wine coloured breast: When in flight the two strip on the wings and the black fringe on the tail end are quiet obvious, and less visible are the white spots, on both sides of the neck. As is the case with all pigeons its basic feeding habits is exclusively based on digesting all types of seeds, from cultivated (wheat, barley, etc.) up to beechnut and acorn, this being the feed of the migrating species.

One of the most attractive looking birds and also one of the most abundant, in leafy forest environments is the common Blue Tit, Parus caeruleus. The upper part of the head, the wings and the tail are of a light blue colour, the sides of the head white, and the breast as well as the abdomen is yellow. The back is grey, and he also a black frock/bib. In the park it occupies the Beech Tree forest, in the countryside and naturally in the grove of Holm oaks. The presence of this bird species in between the spots of coniferous is practically anecdotic. In spring time the more dense groups of the common Blue Tit, inside Urkiola can be found in between the Holm oaks, because this type of tree supplies them with numerous holes where they can construct their nests. Its feeding habits are assured throughout the major part of the year, they eat all types of insects offered by the grove of Holm oaks. During the cold months, it forms groups with other bird species in order to go travel through forest, countryside and urban parks; in this period faced with a shortage of insects they forced to complement their diet with seeds. Amongst the songbirds (small sized birds) the common Blue Tit, is possibly the species that is most affected by the practical absence of oak trees from the Park.

Tree-stump surrounded by grass. (Increase the size in a new window)

Stones of a certain size, or as it is in this particular case a tree stump are normally used by the thrush bird to brake the snail shell in order to extract the edible matter. These are the plodders (the tireless worker).

Inside a forest area, where dense bushes or blackberry bush appear, the possibility of it being occupied during the nesting period, by some whitethroat species is high. On the edges of the grove of Holm oaks spots, with a bush presence, normally hidden away between the bushes is found the Blackberry whitethroat, Sylvia communis. Its presence in Urkiola never reaches high numbers. It is a species with dullish colour plumage, having a combination of grey, white and brown feathers. During the spring and summer seasons goes into the depths of the grove of Holm oaks, also one couple or other to be found around the countryside.

The badger, Meles meles, is the biggest Mustelidae that lives in the Park. Its presence is directly related to the forest areas, due to its small size, makes credible its permanent presence in the countryside. Nevertheless he is highly attached to the farming areas, due the rich food resources that these supply. It is an animal with a substantially different physiognomy from the rest of the Mustelidae family that live in Urkiola. Contrary to these of stocky and fast body characteristics, this badger is a compact animal, well filled and heavy, even though when under threat, reaches a reasonable running speed. With the mentioned body characteristics it is easily understandable that its life is bound to ground level, with few possibilities of living a tree life. During the day it remains in subterranean burrows, built with a great number of galleries, therefore with an important overlapping in the internal distribution, and these are usually utilised and passed down from generation to generation. With the arrival of dusk their feeding period begins. It is a characteristic of this mammal to run through all the tracks previously established, night after night, and during these nocturnal trips he will ingest all types of food, from worms (of great importance in his diet) up to small animals (like frogs and mice, etc.) going on to fruit and those situated in the proximity of cultivated fields, with regular visits to these. The head is white with two thick black stripes, starting at the snout, going through the eyes and ears (these are white) and finishing at the neck. The fur on the dorsal area is grey same for the belly part (neck, abdomen and paws) is very dark or black.

The micro mammals maintain a very low profile in this biological niche. One of these is the Millet Shrewmouse, Sorex coronatus, this is a small animal that barely surpasses 10 cm in height (the tail alone has 6 cm), that like the rest of this type of species posses a long snout which is disproportional to the rest and total size of the body. The ears are, on the contrary, short protruding very little from its fur. The adult species are of a dark brown colour on the dorsal area and slightly lighter on the sides.

Upper part of the body of a jay. (Increase the size in a new window)

An exclusively forest species, the Jay bird (Garrulus glandarius), also lets his lout cry be heard through the grove of Holm oaks of the Park.

The high metabolism of these animals forces them to have an hyperactivity with regards to the food resources of such a level that in practice it means being constantly eating throughout the 24 hours of the day, with intervals in between lasting approximately one and a half hours. During this period it can ingest food with a weight equivalent to his corporal mass. Their prey consists of worms and insects found in the soil.

Luis Viera (Geología).
José Miguel Olano, Francisco Solván y Josetxo Riofrío (Vegetación y fauna).
José Ramón Aihartza (Murciélagos).
Elena Barrena y Miren Ayerbe (La huella humana).
Servicio Central de Publicaciones del Gobierno Vasco.
Year edited:
Page extracts:
98-105 (both inclusive).

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