2. BIRDS OF PREY: STATUS AND THREATS IN KENYA- Njoroge
Peter.
Summary
Kenya has over70 diurnal birds of prey (raptors) in addition to 19 nocturnal birds of prey
(owls). They are classified into 4 distinct families –Falconidae (falcons), Acciptridae (diurnal
birds of prey except falcons), Tytonidae (barn owls) and Strigidae (typical owls). This rich
diversity of birds of prey is due to Kenya’s position across the equator, the variety of habitats
and also being in the migratory flyway. Most of the birds of prey in Kenya are residents;
however about 30 species are palaearctic or afrotropical migrant species.
None of the diurnal species is endemic, but Sokoke Scops Owl was until recently only known
from Arabuko-sokoke forest in Kenya. A total of nine species are listed in the IUCN Red List
of Threatened Species, several of them as endangered the second highest threat category. A
further nine species are listed as near-threatened. Threats to birds of prey in Kenya range
from habitat destruction and fragmentation, collision and electrocution by powerlines and
wind farms to persecution and poisoning. In a recent case study around the Masai Mara
National Reserve, a decline of 25% of the population of scavenging birds of prey was
recorded in about 20 years. As a result some species e.g. Egyptian Vulture (once a common
bird in the Mara) are now close to extinction.
Conservation organizations such as the National Museums of Kenya, Raptor Working Group
of the EANHS and the Peregrine Fund are at the forefront of implementing various
conservation actions and this includes development of species action plans, advocacy for
review of policy and legislation, awareness campaigns including development of con
servation partnerships with the energy industry.
Introduction
Birds of prey are birds that hunt for food primarily via flight, using their keen senses,
especially vision. They are defined as birds that primarily hunt other vertebrates, including
other birds though a large majority of them will take invertebrates as well. Their talons and
beaks tend to be relatively large, powerful and adapted for tearing flesh. Some species also
also highly adapted to scavenge and eat carrion. In most cases, the females are considerably
larger than the males. The term "raptor" is derived from the Latin word rapere (meaning to
seize or take by force) and may refer informally to all birds of prey, or specifically to those
that hunt during the day (diurnal birds of prey).
Birds of prey occur worldwide and live on every continent except Antarctica, with the highest
diversity occurring in tropical regions. They inhabit most terrestrial habitats grasslands,
7
desserts, sea coasts, rainforests, woodlands, agricultural, suburban and some urban areas.
They are found at most elevations, from coastal areas at sea level to the tops of mountains.
Birds of prey important role in African cultures.
They feature prominently in traditional war stories, as clues during hunts and their molted
feathers have been used in making arrows. For example Kikuyu’s believe that seeing the
white chest of an Augur Buzzard early in the morning heralds a day of good fortunes.
In the ecosystem birds of prey play a significant role including pest control, disease control,
waste removal and facilitate nutrient recycling. Because of their predatory nature, often at
the top of the food chain they face distinct conservation concerns.
In Kenya two types of birds of prey, the diurnal birds of prey (raptors) and nocturnal birds of
prey (owls).
The diurnal birds of prey in Kenya
The diurnal birds of prey that occur in Kenya occur in two families, falconidae and
accipitridae.
The family falconidae, includes all falcons. Falcons are medium-sized birds of prey with long
pointed wings. Most are particularly swift flyers. Falcons do not build their own nest but will
appropriate the old nests of other birds; but, sometimes, they lay their eggs on cliff ledges or
in tree hollows. Nineteen species of falcons are known to occur in Kenya, 10 of them being
Palaearctic migrants i.e. visitors from the northern hemisphere during the northern winter.
Family Accipitridae, is a family of small to large birds with strongly hooked bills and
variable morphology based on diet. A great deal of diversity exists among the accipitridae.
They eat fish, mammals, birds, bats, invertebrates, carrion and some will also eat fruit. They
nest on cliffs, in trees or sometimes on the ground and lay between 1 to 9 eggs. Physical size
is also quite variable within this group, with wingspans ranging from 50cm to 3m. Sixty
species occur in Kenya (see appendix 1), with 16 of them being palaearctic migrants
Nocturnal Birds of prey in Kenya
Nocturnal birds of prey fly and hunt in the dark. Their sense of hearing is very acute, and they
can detect and identify precisely the subtlest sounds. Their flight is extremely quiet in
comparison to their diurnal relatives. In Kenya, nocturnal birds of prey occur in two families
Tytonidae (barn owls) and Strigidae (typical owls).
Tytonidae are medium to large sized owls with large heads and characteristic heart-shaped
faces. They also differ from Strigidae in structural details relating in particular to the sternum
and feet. This family this family is represented in Kenya by only two species the Grass Owl
(Tyto capensis) and the Barn Owl (Tyto alba).
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Strigidae family is the larger of the two families of owls. The characteristic facial disk in
strigid owls is circular rather than heart-shaped and their eyes relatively larger. There are 17
species under this family that occur in Kenya, with one Otus scops being a palaearctic
migrant.
Trends in conservation status
As top predators, raptors are often sensitive indicators of change in the environment,
particularly the presence of toxins. Two decades ago only 6 birds of prey were listed in the
IUCN red list of threatened species as compared to today’s 18 bird species (see table
below).This does not necessarily mean that levels of threat of drastically increased over the
period but may reflect our increased knowledge about birds of prey during the period. In a
Critical
Endangered
Vulnerable
Near
Threatened
Data
Deficient
Total
20
years
ago
0
0
4
2
0
6
Today
(2013)
0
3
6
9
0
18
Table 1: Number of threatened birds of prey 20 years ago as compared to numbers threatened
in 2013
report by Watson and Munir (1998) on the state of ecological knowledge and conservation
status of raptors of East Africa, 60% of the 79 dirurnal raptors and 23 owl species in the
regions had no information on distribution, population trends, abundance breeding biology
and feeding ecology.
Status
Over the preceding 20 years the conservation status of some birds of prey species has
changed, with more species added to the IUCN Red list of threatened species (table 2.0).
Nearly 65% of vulture populations over the last two decades have been lost mainly through
the illegal use of pesticides to poison wildlife. Today 6 out of the eight vulture species that
occur in Kenya are listed as threatened or near-threatened and one of the non-threatened
species Lammergeier Gypaetus barbatus is very rare in Kenya with only a single confirmed
pair. Three charismatic species of eagles are now listed as near threatened, Martial Eagle
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Polemaetus bellicosus, Crowned Eagle Stephanoatus coronatus and Bateleur Terathopius
ecaudatus, while the iconic Secretarybird Sagittarius serpentarius is now listed as a
vulnerable species. In addition smaller and previously common species such as Augur
Buzzards have lost foraging ground as a result of horticultural expansion and their breeding
population is down by 60% in Kenya’s southern Lake Naivasha area. Owls have also been
affected with populations of the “endangered” East African endemic Sokoke Scops Owl in
Kenya’s Arabuko Sokoke forest. The African Crowned Eagle and other forest dependent
raptors are not only faced with rapidly fragmenting forest cover but also a new threat of being
persecuted and eaten by humans in places like Cameroon’s Ebo forest.
Table 2.0: List of the threatened birds of Prey in Kenya in 2013 (IUCN 2013)
Common Name
Species
IUCN Category
Sokoke Scops-owl
Otus ireneae
EN
Lappet-faced Vulture
Torgos tracheliotos
Vu
White-headed Vulture
Trigonoceps occipitalis
VU
Greater Spotted Eagle
Aquila clanga
VU
Eastern Imperial Eagle
Aquila heliaca
VU
Egyptian Vulture
Neophron percnopterus
EN
Hooded Vulture
Necrosyrtes monachus
EN
White-backed Vulture
Gyps africanus
EN
Rueppell's Vulture
Gyps rueppellii
EN
Secretarybird
Sagittarius serpentarius
VU
Saker Falcon
Falco cherrug
EN
Pallid Harrier
Circus macrourus
NT
Taita Falcon
Falco fasciinucha
NT
Crowned Hawk-eagle
Stephanoaetus coronatus
NT
10
Martial Eagle
Polemaetus bellicosus
NT
Red-footed Falcon
Falco vespertinus
NT
Sooty Falcon
Falco concolor
NT
Southern Banded Snake-eagle
Circaetus fasciolatus
NT
Case Study: Major declines in the abundance of vultures and other scavenging raptors
in and around the Masai Mara ecosystem, Kenya
CASE STUDY: The Decline of Vultures in Masai Mara Region (Source: Munir,
V., Kendall, C. Njoroge, P. & Thomsett, S. (2010).
Numbers of large eagles and scavenging birds were counted during two
periods : early (1976-88) and recent (2003-05) using road counts across
three land use types in the Masai mara region i.e. i) the reserve ii) buffer
zone, the mara dispersal zone iii) the grazed zone. This was for purposes of
assessing how numbers of large eagles and vultures changed over time in
the region. Their results showed staggering declines in abundance
for seven of eight scavenging raptors surveyed (see graph above). No
Egyptian vultures were seen during recent transects and the species is
virtually extinct in Kenya. By comparing trends between the ungulate
migration and non-migration season among the three land use types
(reserve, buffer, and grazed) and among the species surveyed to establish
the causes of declines in scavenging raptors; large declines were found
during the ungulate migratory period suggesting that most scavenging
raptor species are declining well beyond the area of study. For all species,
except Hooded vultures, substantial declines outside of the reserve indicate
an important role of land use change in causing observed declines. In
addition, significant declines of populations of Gyps species in the reserve
itself, especially during the migration season, provide evidence that human
activities occurring in other parts of the species’ range such as poisoning of
carcasses may be causing their decline. As a result of this study’s
recommendations African white-backed, Rüppell’s, and Hooded vultures
status in the IUCN Red list of threatened species were upgraded
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Threats
Changing land-use patterns, livestock overgrazing and the intensification of agriculture
combined with Africa’s rapidly growing population have all substantially reduced the
distributional ranges of charismatic raptors such as the Martial Eagle, African Hawk Eagle
and Secretary bird, all of which have been pushed out of former ranges. This problem is more
apparent for forest species some of which require huge home ranges.
Pesticides such as Organo-chlorines are still present in Lakes Naivasha and Baringo. High
levels of heavy metal (lead and mercury) have also been found in Lake Naivasha. Lead has
also been documented in the Introduced Common carp, which has human health implications.
These lead to declines in population of African Fish Eagle around Lake Naivasha. Already
numbers of Augur Buzzards have have reduced by 60% around the lake.
Poisoning has become a major problem for large eagles and vultures and is largely a
consequence of human-wildlife conflicts. Eagles and vultures inadvertently feed on poisoned
carcases left out for predators (lions, Hyenas and Wild Dogs). Vultures are obligate
scavengers, tending to congregate in large numbers at a carcass and are therefore are more
risk from poisoning than other large eagles. The poison of choice in East Africa is Furadan
(available in crystal and liquid form) and its derivatives. Vultures have been known to travel
incredibly long distances covering four East African countries and this makes them
vulnerable to the effects of poisoning not only secondary effects from carcasses laced to kill
predators but also deliberate efforts by poachers to eliminate vultures and erase all clues that
could lead authorities to them. Poisoning of birds of prey also occurs in rice growing areas in
Kenya (Bunayala and Mwea) when they consume ducks or other congregatory birds killed by
poisoning by poachers for illegal bush meat. Though this has some public health implications
the authorities have shown little efforts to contain the problem.
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Figure 1.0 Vultures poisoned with Furadan at a carcass
Collision and electrocution by electricity transmission and distribution infrastructure: This
is a problem resulting from use of non-bird friendly infrastructure. With the projected growth
of kenya’s economy (vision 2030) this problem can only grow. Though we do not know how
many birds of prey are killed in this way, reports from elsewhere that Electrocution of birds
on overhead lines is an important cause of unnatural mortality of raptors, storks and other
species in South Africa (Eskom-EWT Strategic Partnership Central Incident Register,
unpublished data), and has attracted plenty of attention in Europe, USA and South Africa
(APLIC 1994; van Rooyen & Ledger 1999, Bevanger 1998). Electrocution occurs when a
bird is perched or attempts to perch on the electrical structure and causes an electrical short
circuit by physically bridging the air gap between live components and/or live and earthed
components (van Rooyen 2004). Thoughit is easy to mitigate for bird electrocution before
installation of transmission lines, this is rarely done in Kenya even though later costs in
outages are higher than “retrofitting”. Mitigation of existing infrastructure is usually achieved
through insulating certain components on the poles to make them “bird friendly”. Mitigation
of new infrastructure is best achieved by designing infrastructure with clearances large
enough to accommodate the relevant bird species, or where relevant hardware components
are out of reach to birds. Returning to existing infrastructure to ‘retrofit’ dangerous structures
is generally more difficult and costly than simply building ‘bird friendly’ structures from the
outset. A collision occurs when a bird in mid flight collides with the overhead cables.
Collisions are the biggest single threat posed by overhead transmission (>132kilovolts) power
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lines to birds in southern Africa (van Rooyen 2004). Mitigation of existing power lines
involves marking the line with anti-collision marking devices to increase their visibility to
birds. These devices are fixed to the conductors or earth wires at five or ten metre intervals
along the line and have proven partially effective (measured post marking reduction in
collisions of approximately 60-80% have been recorded by various studies in Jenkins et al, in
prep) in reducing bird collisions (Jenkins et al, in prep).
Mitigation of new power lines is
best achieved through correct routing of the lines to avoid sensitive areas and flight paths, in
combination with line marking. Once again, mitigation is more cost effective to implement at
construction than after line commissioning, as specialized methods are required for line
marking on live lines. Birds can cause electrical faults on electrical infrastructure through
several mechanisms: bird streamers; bird pollution; and nesting. This is a business impact as
it affects the quality of electrical supply to customers. Birds are very seldom injured or killed
through this interaction. A bird streamer is a long stream of excrement, which when produced
by a bird perching on an electrical pole or pylon, may bridge the “air gap” between live and
grounded hardware – thereby resulting in a short circuit (Taylor, Vosloo, Wolmarans, Britten,
Naidoo, Hoch, & van Rooyen, 1999
(a)
(b)
Figure 1 a &b. The unsafe ‘T’ type (a) of pole configuration very common in Kenya and
the relatively safe inverted ‘T’ type (b)
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Wind farms are starting to dot the African landscape and Kenya will have the largest wind
farm in Africa with over 350 wind turbines on the eastern shores of Lake Turkana. The Great
Rift Valley is a major migratory route for raptors and other palaearctic migrant birds. With
the wind farms will come thousands of kilometers of power lines that are also known to kill
raptors from electrocution and collision (above).
Bibliography
Munir, V., Kendall, C. Njoroge, P. & Thomsett, S. (2010). Major declines in the abundance
of vultures and other scavenging raptors in and around the Masai Mara ecosystem, Kenya.
Biological conservation. , 746-753.
Del Hoyo, J., Elliott. & Sargatal, J. eds. (1994) . Handbook of the Birds of the World. Vol. 2.
New World Vultures to Guineafowl. Lynx Edicions, Barcelona.
East African Wildlife Society. (2012). Swara, The voice of conservation in East Africa.
October - December| 2013: 04
Van Rooyen, C.S. and Ledger, J.A. 1999. Birds and utility structures: Developments in
southern Africa in Ferrer, M. & G. F.M Janns (eds) Birds and Power lines. Quercus: Madirid,
Spain, pp 205-230.
Van Rooyen, C.S. and Taylor, P.V. 1999. Bird Streamers as probable cause of electrocutions
in South Africa. (EPRI Workshop on Avian Interactions with Utility Structures 2-3
December 1999. Charleston, South Carolina)
Appendix 1: list of all birds of prey in Kenya and their IUCN status
IUCN
threat/Migratory
Common Name
Species
status
Falconidae: falcons
Pygmy Falcon
Polihierax semitorquatus
Lesser Kestrel
Falco naumanni
PM; Vulnerable
Common Kestrel
Falco tinnunculus
pm,
Greater Kestrel
Falco rupicoloides
Fox Kestrel
Falco alopex
Grey Kestrel
Falco ardosiaceus
Dickinson's Kestrel
Falco dickinsoni
Red-necked Falcon
Falco chiquera
PM;
Red-footed Falcon
Falco vespertinus
Threatened
Amur Falcon
Falco amurensis
PM
15
Near
Eleonora's Falcon
Falco eleonorae
PM
PM;
Near
Sooty Falcon
Falco concolor
Threatened
Eurasian Hobby
Falco subbuteo
PM
African Hobby
Falco cuvieri
Lanner Falcon
Falco biarmicus
Saker Falcon
Falco cherrug
PM; Endangered
Peregrine Falcon
Falco peregrinus
Pm
Barbary Falcon
Falco pelegrinoides
PM
Taita Falcon
Falco fasciinucha
Near Threatened
Secretarybird
Sagittarius serpentarius
Vulnerable
Osprey
Pandion haliaetus
PM
African Cuckoo Hawk
Aviceda cuculoides
European Honey Buzzard
Pernis apivorus
Bat Hawk
Macheiramphus alcinus
African Black-shouldered Kite
Elanus caeruleus
African Swallow-tailed Kite
Chelictinia riocourii
Black Kite
Milvus migrans
African Fish Eagle
Haliaeetus vocifer
Palm-nut Vulture
Gypohierax angolensis
Lammergeier
Gypaetus barbatus
Egyptian Vulture
Neophron percnopterus
Hooded Vulture
Necrosyrtes monachus
White-backed Vulture
Gyps africanus
Near Threatened,
Rüppell's Vulture
Gyps rueppellii
Near Threatened,
White-headed Vulture
Trigonoceps occipitalis
Vulnerable
Lappet-faced Vulture
Torgos tracheliotus
Vulnerable,
Short-toed Snake Eagle
Circaetus gallicus
PM,
Beaudouin's Snake Eagle
Circaetus beaudouini
Vulnerable,
Black-chested Snake Eagle
Circaetus pectoralis
Brown Snake Eagle
Circaetus cinereus
Southern Banded Snake Eagle
Circaetus fasciolatus
Western Banded Snake Eagle
Circaetus cinerascens
Bateleur
Terathopius ecaudatus
Western Marsh Harrier
Circus aeruginosus
African Marsh Harrier
Circus ranivorus
Accipitridae: diurnal birds of prey other than falcons
16
PM,
am, pm,
Endangered
Near Threatened
PM,
PM;
Pallid Harrier
Circus macrourus
Threatened
Montagu's Harrier
Circus pygargus
PM
African Harrier Hawk
Polyboroides typus
Dark Chanting Goshawk
Melierax metabates
Eastern Chanting Goshawk
Melierax poliopterus
Gabar Goshawk
Micronisus gabar
African Goshawk
Accipiter tachiro
Shikra
Accipiter badius
Levant Sparrowhawk
Accipiter brevipes
Little Sparrowhawk
Accipiter minullus
Ovambo Sparrowhawk
Accipiter ovampensis
Eurasian Sparrowhawk
Accipiter nisus
Rufous-breasted Sparrowhawk
Accipiter rufiventris
Great Sparrowhawk
Accipiter melanoleucus
Near
PM
PM
Kaupifalco
Lizard Buzzard
monogrammicus
Grasshopper Buzzard
Butastur rufipennis
AM
Common Buzzard
Buteo buteo
PM,
Mountain Buzzard
Buteo oreophilus
Long-legged Buzzard
Buteo rufinus
Augur Buzzard
Buteo augur
Lesser Spotted Eagle
Aquila pomarina
PM
Greater Spotted Eagle
Aquila clanga
PM; Vulnerable
Tawny Eagle
Aquila rapax
Steppe Eagle
Aquila nepalensis
PM
Eastern Imperial Eagle
Aquila heliaca
PM; Vulnerable,
Verreaux's Eagle
Aquila verreauxii
Wahlberg's Eagle
Aquila wahlbergi
African Hawk Eagle
Aquila spilogaster
Booted Eagle
Aquila pennata
Ayres's Hawk Eagle
Aquila ayresii
Martial Eagle
Polemaetus bellicosus
Long-crested Eagle
Lophaetus occipitalis
Cassin's Hawk Eagle
Spizaetus africanus
Crowned Eagle
Stephanoaetus coronatus
Tytonidae: barn owls
17
PM
Am
PM
Near Threatened
Grass Owl
Tyto capensis
Barn Owl
Tyto alba
Strigidae: typical owls
Sokoke Scops Owl
Otus ireneae
African Scops Owl
Otus senegalensis
Eurasian Scops Owl
Otus scops
Northern White-faced Scops Owl
Ptilopsis leucotis
Southern White-faced Scops Owl
Ptilopsis granti
Cape Eagle Owl
Bubo capensis
Spotted Eagle Owl
Bubo africanus
Greyish Eagle Owl
Bubo cinerascens
Verreaux's Eagle Owl
Bubo lacteus
Pel's Fishing Owl
Scotopelia peli
African Wood Owl
Strix woodfordii
Pearl-spotted Owlet
Glaucidium perlatum
Red-chested Owlet
Glaucidium tephronotum
African Barred Owlet
Glaucidium capense
Abyssinian Owl
Asio abyssinicus
Short-eared Owl
Asio flammeus
Marsh Owl
Asio capensis
18
Endangered
PM
VP