Terms such as cloud forests usually evoke images of far-off places
at high altitude, such as the Andes of South America or the land
of ‘Gorillas in the Mist’ in central Africa. A similar ecological
counterpart is the escarpment juniper forest of the Asir Mountains
in south-west Saudi Arabia. Many readers may remember surprising
images of beautiful forested areas in Michael McKinnon’s TV series
‘Arabia – Sand, Sea, Sky’.
Within the Kingdom, the NCWCD Raydah Reserve near Abha is probably
the best example of the juniper forest that once covered much
high altitude (above1800 m) ground. Raydah is unique as it encompasses
a complete ecological cross-section through various vegetation
zones, since it falls steeply from the rim of the escarpment at
2750 m to the floor of Wadi Jaw, 4 km away at 1250 m. The contrast
in climate can be tremendous: cool, damp, cloudy and very temperate
at the top, to hot, oppressive tropical conditions at the bottom.
Extensive tree coverage is naturally of limited occurrence in
Arabia, a peninsula dominated by extremely arid deserts. Although
we can find open acacia woodland in many wadis, the junipers at
Raydah form a forest with trees reaching 15-20m. Juniper forest
is most lush at the top of the escarpment on north or west facing
slopes, with the trees draped in Usnea, a grey-green lichen. As
one descends, a wider variety of trees occurs, with olive, Nuxia,
pistachio and acacia all common in places. The forest peters out
at about 1700 m in a zone of orange flowered buddleia and tree
aloes. Scrub and open grassland dominate the more open, south
facing slopes.
The forest is a very important place for birds and other less
conspicuous wildlife, ranging from mammals to molluscs. To date,
just over 100 birds species have been recorded in the Reserve
but, given that about 500 have been recorded in the Kingdom, diversity
of species per se is not what attracts ornithologists. The uniqueness
of Raydah is that it is just about the only place in Arabia where
virtually all our endemic terrestrial birds occur together. As
a group, the world-wide distribution of these birds spans only
the mountains in south-west Saudi Arabia, Yemen and parts of Oman.
The remainder of the resident avifauna is dominated by tropical
African species and it is the co-existence of these two groups
that explains why NCWCD gives high priority to the study and conservation
of Raydah’s birds.
Amongst the many things we need to know are the particular habitats
these birds prefer, what they eat, how long they live, how far
they move, their breeding rates and seasonal abundance. In addition
to the resident birds, a variety of migrants use the Reserve at
different times of the year: a small number of African species
arrives in spring to breed in south-west Arabia, with many more
passing through in spring and autumn en route between Eurasian
breeding areas and their wintering areas in Africa. Another small
group is the winter visitors and European species such as Song
Thrush, Black Redstart, Blackcap and Chiffchaff which can be common
in the junipers.
Food and habitat are often good ways of dividing bird communities
into smaller units. Although not numerous, several species of
birds of prey are present in the forest and associated mountain
cliffs. The two largest breeding species are the Short-toed Eagle
and the Long-legged Buzzard (often the distinctive black form):
both eat mostly snakes and lizards, which they catch basking in
more open areas. Smaller raptors include Barbary Falcon, Kestrel,
both hunting small birds or rodents in open areas, and the Shikra,
an African sparowhawk which catches small birds by pursuit through
and over the forest.
The two endemic Arabian partridges, whose diet mostly comprises
grass seeds, are often conspicuous birds, perching on prominent,
rocky knolls and calling loudly. The slightly smaller Philby’s
Rock Partridge*, with a grey cap, is most frequent at the top
of the escarpment, whereas the larger Arabian Red-legged Partridge*,
with more bold black and white head and facial markings, usually
occurs at middle or lower altitudes.
Most medium and small sized birds are either insectivores or ‘vegetarians’
(e.g. granivores, frugivors or nectarivores). Different species
occur in the more open areas, natural or man-made, and the forest
itself. Areas along the paved road at the top of the escarpment
or, for example, around the terraced farm in the centre of the
Reserve are good places to see open-area species. The African
Rock Bunting is a typical breeding species at the top; though
often unobtrusive, it has a short, powerful song. The two serins,
Arabian* and Yemen*, are inconspicuous, dull-coloured, seed-eating
finches. The latter typically occurs on steep open slopes, whilst
the former prefers open woodland and scrub. The Arabian Waxbill*,
bright and delicately marked and with a blood red eye-stripe,
is the smallest member of the finch family to occur at Raydah
and is most common in grassy and scrub areas. Two iridescent jewels
in the avifauna are the nectar-drinking Palestine Sunbird, which
regularly inhabits scrub areas at mid altitudes, and the Shining
Sunbird which is prevalent nearer the wadi. Other, insectivorous,
birds of higher, more open areas include the South Arabian Wheatear*,
the Little Rock Thrush and the felix race of Stonechat.
Larger non-passerine birds in the forest include the Arabian Woodpecker:
this species is naturally insectivorous, though on occasions it
will sap-suck. It seldom occurs in junipers but is more frequently
seen in acacias where it digs most of its roosting and nesting
holes. Three less common dove species breed in the Reserve; all
are largely frugivorous, thriving on juniper berries and olive
fruits. The Olive Pigeon, a large dark grey bird with bright yellow
legs and bill is probably resident although it was only discovered
in Arabia about ten years ago. Both the Dusky Turtle Dove (dark
grey-brown, but its inner wing feathers have beautiful, rich red-brown
edgings), most easily detected by its low-pitched ‘cooing’, and
the Bruce’s Green Pigeon, an exquisitely coloured African dove,
are breeding visitors to the mountain forests and wadis of south-west
Arabia.
Warblers and flycatchers are generally insectivores: the Yemen
Warbler* is a dull, grey-brown bird with very skulking habits,
though it can often be seen in junipers, climbing up the trunks,
probing and pecking at the bark for insects in the same manner
as a tree-creeper. It can be located by its very harsh, piercing
rattling-laughing call. The Brown Woodland Warbler is one of the
most vocal birds in the forest and will sing at any time of the
day, sounding somewhere in between a Willow Warbler and Chiffchaff.
Plumage is green-brown with a vivid yellowish wing panel. The
African Paradise Flycatcher is, without doubt, the most impressive
bird of the forest. Again, it is often highly vocal and, once
the call is known, pairs or groups can be located easily, usually
beneath the canopy along drainage lines and stream valleys. The
typical plumage is a chestnut brown body with an iridescent blue-black
head and bright blue eye ring. Males have spectacularly long brown
or white tails and streamers. They appear very acrobatic during
aerial pursuits to catch butterflies and moths. Two of the most
abundant forest frugivores are the Yemen Linnet * and Yemen Thrush*.
The linnets are perhaps the first eye-catching species that you
are likely to encounter at Raydah, flitting above the canopy,
singing, displaying and pursuing neighbours between March and
July. They are recognizable by their trilling song and prominent
white wing patches against a chestnut, grey and black plumage.
The thrush is a little harder to pick up and, despite general
brown-black plumage, it has distinctive yellow-orange bill and
legs and an orange underwing only seen in flight. They are normally
seen in juniper trees with good berry crops.
Some forest species are more generalist feeders, apparently using
both fruit and insects, depending on their seasonal availability.
These include the warbler-like White-breasted White-eye and the
widespread Yellow-vented Bulbul. A final mention should be made
of one other endemic species that occurs at Raydah: The Asir Magpie*,
a scarce resident in the forest, superficially like the European
or North American races but with a startlingly different call.
Some of the most interesting birds at Raydah are entirely nocturnal:
half an hour’s listening around dusk can usually reveal three
or four species that are seldom recorded during daytime. The Reserve
supports two nightjar and three owl species. The Plain Nightjar
has a long drawn-out churring call typical of many nightjars,
whereas the Mountain Nightjar has an evocative, whistling call
‘Wee-oo-wee-weerr’ and was only discovered in Arabia a few years
ago. The Senegal Scops Owl is the most numerous owl and its short
‘purrp’ call often echoes around well-forested areas around sunset.
Hume’s Tawny Owl and Spotted Eagle Owl are also present but are
not such regular contributors to the sunset chorus.
Much of our time researching the bird populations is devoted to
catching and marking resident species. All birds caught are ringed,
weighed, measured and inspected for brood patches (proof of breeding
activity in females) and moult. Some conspicuous species are also
fitted with colour rings by which we can identify individuals
without the need to retrap them. Many birds caught in spring 1992
were still present and breeding in the same locations three years
later: included are some of the larger species such as the Yemen
Thrush and Yellow-vented Bulbul, but also small species weighing
20 grams or less, e.g. Palestine Sunbirds, Brown Woodland and
Yemen Warblers, White-breasted White-eyes and Arabian Serins.
In contrast, the Yemen Linnets appear to be very mobile and are
seldom faithful to a particular location except for the duration
of the current breeding season. Several breeding or wintering
migrants also seem site-faithful; for example Dusky Turtle Doves
return to the same location to breed having over-wintered on the
Tihama and a Black Redstart was trapped in two consecutive winters
near the top of the Reserve. Presumably this bird must have bred
in the interim somewhere in central Asia. The overall strategy
of many juniper forest birds seems to be one of longevity, whilst
breeding at relatively low rates, with clutches or broods of two
or three typical.
The Raydah Escarpment is a unique environment, home to most of
Arabia’s endemic birds. We are only beginning to discover its
secrets and there is still much to be learned.
(*indicates an endemic species)