ure News 11 - Gibraltar Ornithological & Natural History Society

sun and thus a higher rate of evaporation, will contain
many fewer stomata than the lower surface. In an
attempt to further reduce water loss, the stomata may
lie inside grooves formed on the leaf-surfaces, and in
some species the leaves actually curl inwards, reducing
water loss by evaporation even further. This is the
case of the sea knotgrass Polygonum maritimum and
several of the grasses found in the habitat. Others,
such as the sea spurge Euphorbia paralias, have
closely overlapping leaves towards the same aim.
The mobility of the dunes is also a problem, as
plants will have difficulty in rooting, and if they manage
to do so they may get smothered by sand. But
here the presence of marram grass Ammophila arenaria
is important. This grass forms dense clumps
which provide obstacles to the movement of the sand,
and is thus an essential component in stabilising and
consolidating the dune system.
Many other attractive species are found on this
habitat, and also further inland, including the middle
slopes of the Faro promontory and even the Cape
headland. Among these are: the shrubby pimpernel
Anagallis monelli with its striking violet-blue flowers;
the large-flowered knapweed Centaurea sphaerocephala;
the aromatic sea chamomile Anthemis maritima;
the beautiful prickly thrift Armeria pungens and
the parasitic dense-flowered broomrape Orobanche
densiflora. From the carrot family, there are the tall
Thapsia villosa subsp. maxima and the tiny
Pseudorlaya pumila, which usually lies half-buried in
the sand. In the more marshy areas among the
dunes, there are small stands of sharp rush Juncus
acutus and sea rush Juncus maritimus.
The surface of the sand dunes is often crisscrossed
by the tracks left behind by numerous beetles
and also by the Spiny-footed Lizard Acanthodactylus
erythrurus. This is more evident in the morning when
the sand has been dampened by the night dew and
is undisturbed. The Spiny-footed Lizard is so-called
Rock platform along shoreline
Centaurea sphaerocephala
because of the spines on its digits, which help it to
walk across the sand. Acanthodactylus lizards are
most diverse in desert regions and some species have
highly developed spines to cope with the problem of
running along sand dunes. Beetles walking along
sand dunes are most often darkling beetles (family
Tenebrionidae). Most residents of Gibraltar will be
familiar with tenebrionid beetles. These are mainly
large, black species with hard exoskeletons that prevent
the loss of moisture. Thus, they do extremely well
Juniperus oxycedrus subsp. macrocarpa
in arid habitats such as dunes and deserts.
Particularly common species in dune habitats include
Pimelia fornicata, Pachychila germari and a range of
Tentyria species.
The vegetation of the upper parts of the Faro
promontory is quite different to that on the dunes
nearer the shoreline. Here it forms a fairly dense
scrub of low shrubs growing on the sand, the roots of
which often lie exposed on the surface, criss-crossing
the more open areas and footpaths. There are several
species of shrubs, including olive Olea europea;
narrow-leaved phillyrea Phillyrea angustifolia; lentisc
Pistacia lentiscus; prickly buckthorn Rhamnus
lycioides subsp. oleoides; rosemary Rosmarinus officinalis;
shrubby scorpion vetch Coronilla valentina
subsp. glauca; and two species of juniper: prickly
juniper Juniperus oxycedrus subsp. macrocarpa, and
Phoenician juniper Juniperus phoenicea. Of the
species of rockrose present, the most abundant are
Halimium commutatum, which has rosemary-like
leaves and Halimium halimifolium, which has broader,
grey leaves. As can be expected, the exotic and
invasive Hottentot fig Carpobrotus edulis is present in
many places.
The Faro comprises a good promontory from
which to watch seabirds, particularly when onshore
(westerly) winds blow during the spring and autumn
migration periods. Morning watches are easiest during
sunny days since the sun is in your eyes in the
afternoons. As elsewhere along this coast, passage
of Gannets Morus bassanus, Cory’s Shearwaters
Calonectris diomedea, gulls and terns can be impressive.
Its location on the Atlantic coast makes it a likely
site at which rarer species may turn up. The Great
Shearwater Puffinus gravis has been seen here in
autumn for example. Off the town of Barbate itself,
whale-watching tours take place as there is a resident
population of Killer Whales Orca orca offshore.
To the south of the Faro lie the impressive sea
cliffs of the ‘Tajo de Barbate’. These hold a colony of
Yellow-legged Gulls Larus michahellis, as well as
Jackdaws Corvus monedula and a pair of Peregrines
Falco peregrinus. Until recently, these cliffs also supported
a large colony of Cattle Egrets Bubulcus ibis
and a few pairs of Little Egrets Egretta garzetta.
These have moved away to nest in nearby La Janda,
however.
For the present, this coastline is in pristine condition,
and free from the type of intensive touristic
developments that afflict other coastlines in the area,
especially along the Costa del Sol. But for how long,
one can only speculate. It doesn’t take much to imagine
some developer eyeing the large expanse of
clean, sandy beaches and making plans to “improve”
the area with new roads, hotels, etc. The recently
designated ‘Parque Natural del Estrecho’ does not
stretch this far north. Every effort should be made to
conserve all of what is still a coastline of exceptional
importance to wildlife of all forms.
Silene littorea
Halimium halimifolium
GIBRALTAR NATURE NEWS
13