Distribution and population size of Chapin’s Flycatcher Muscicapa lendu in Kakamega Forest, Kenya

2006·2.6 MB·

by  Simon Nganda Musila

,
Distribution and population size of Chapin’s Flycatcher
Muscicapa lendu in Kakamega Forest, Kenya
SimonNgandaMusila MuchaiMuchaneandKariukiNdanganga
*,
Distribution et taille de la population du Gobemouche de Chapin Muscicapa lendu dans la
foret de Kakamega, Kenya. Le Gobemouche de Chapin Muscicapa lendu classe comme
,
Vulnerable par BirdLife International (2000, 2004), est parmi les especes les plus menacees au
Kenya, vu le peu de foret ombrophile encore presente. De novembre 2002 a fevrier 2003, nous
avons etudie sa distribution et la taille de sa population dans la foret de Kakamega, Kenya.
m
L’espece a ete recherchee le long de 123 transects de 300 x 40 dans cinq lambeaux de foret.
Dix-sept oiseaux (13 individus solitaires et deux couples) ont ete vus dans trois fragments:
Isecheno, Ikuywa et Buyangu. Nous n’en navons pas trouve dans la Reserve Naturelle deYala ni
dans la Reserve Nationale de Kisere. La densite de lapopulation aete estimee a environ un indi-
vidu pour 20 ha, et la population entiere a environ 200 individus. Les gobemouches ont ete
observes ades hauteurs de 12-22 m, principalementsurdes branches sans feuilles, dans unezone
de grands arbres (hauteur moyenne 27 m), avec une couverture devoute de 32%. Ladiminution
et la fragmentation du milieu forestier sont sans doute responsables du petit nombre d’oiseaux
recenses. Le degre d’isolement des fragments forestiers pourrait conduire a des accidents gene-
tiques oudemographiques. Nous suggerons queles fragments actuels doiventetremieuxproteges
et qu’il serait tres utile de planter des corridors pour connecter ces fragments, avec bien sur des
essences indigenes. II est recommande de continuer a etudier l’ecologie de l’espece afin de pren-
dre les mesures de conservation appropriees.
Summary. Among the most threatened species of Kenya’s remaining rainforest is Chapin’s
Flycatcher Muscicapa lendu a species currently listed as Vulnerable by BirdLife International
(2000, 2004). BetweenNovember2002 and February2003, westudiedits distribution andpop-
ulation status in Kakamega Forest, Kenya. The species was searched for along 125 transects of
m
500 x 40 in five forest fragments. Seventeen birds (13 singles and two pairs) were sighted in
three fragments, Isecheno, Ikuywa and Buyangu, but we failed to find it in Yala Nature Reserve
andKisereNationalReserve. Populationdensitywasestimatedatc.1 birdper20ha, andtheover-
all population estimated at c.200 birds. Flycatchers were recorded perching at 12-22 m, mostly
on bare branches oftall indigenous trees with mean canopy height of27 m and mean canopy
cover of32%. Habitat loss, particularly through forest fragmentation, is possibly the main cause
ofthe small population size. That forest fragments are distant from each other could make the
species vulnerable to genetic or demographic disasters. We recommend improved forest manage-
ment practises to ensure retention oftall indigenous trees, and connecting forest patchesviacor-
ridorsofplantedindigenoustrees. Furtherstudiesarerequiredinorderto understandthisspecies’
ecology and formulate appropriate conservation measures.
C
hapin’s FlycatcherMuscicapa lendu is a scarce Kakamega Forest is an Important BirdArea (IBA)
and globally threatened (Vulnerable), range- of 18,300 ha and the only true tropical lowland
restricted species (BirdLife International 2000, rainforest in Kenya, which was formerly part ofa
2004), known only from the Itombwe Mountains contiguous forest ecosystem that included the
and Lendu Plateau in eastern Democratic Nandi-Tinderet blockand stretched as far asWest
Republic of Congo, Bwindi Impenetrable Africa (Blackett 1994).
National Park in Uganda, and Kakamega and Chapin’s Flycatcher appears to be rare
North Nandi Forests in western Kenya, with an throughout its range and intensive pressure on its
unconfirmed sight record from Nyungwe Forest, habitat implies that its small population is proba-
Rwanda (BirdLife International 2000, 2004). blydeclining (BirdLife International 2000, 2004).
162-BullABCVol13No2(2006) ChapinsFlycatcherinKakamegaForest, Kenya:Musilaetal.
Little is known concerning the current status of Methods
the species, and no adequate ecological data on In November 2002, we conducted a three-week
which to base effective conservation measures are reconnaissancevisitto all fivestudysites.Thevisit
available. was used mainly to familiarise ourselves with
Between November 2002 and February 2003, Chapin’s Flycatcher’s identification features,vocal-
we undertook a study of Chapin’s Flycatcher in isations, behaviour and general habitat choice.
Kakamega Forest to (1) determine its distribution Local bird guides were interviewed and searches
within the forest fragments, (2) estimate its popu- for the birds were conducted. We also tested the
lationdensity, and (3) investigateitspreferredveg- effectiveness of playback of Red-chested Owlet
etation characteristics. Such data should serve as a Glaucidium tephronotum calls for attracting our
base forfuture ecological studies and conservation study species.
programmes. The main field workwas undertaken from 17
January to 25 February 2003 (40 days) in
Study area Isecheno, Ikuywa, and Buyangu forest fragments,
Kakamega Forest (00°10’-00°21’N 34°47’- where Chapin’s Flycatcherweresighted duringthe
34°38’E) lies at 1,300-1,700 m altitude. Mean reconnaissance. Birds were searched for along
mm
annual rainfall is 2,000 and temperature existing trails, which were used as transect routes.
m m
10.6-27.7°C (Blackett 1994; for a detailed In total, 125 transects of500 length and 40
description see Kokwaro 1988). width were sampled during mornings
Th)e human population in the forest’s environs (07.00-11.00 hrs) and evenings (16.00-17.00
is rapidly increasing and its activities have frag- hrs) bythree observers using binoculars at aspeed
mented the once-contiguous forest into several ofc.300 m/h. Red-chestedOwletcallswereplayed
patches that are decreasing in extent. These forest
fragments include Isecheno (310 ha) and Yala
nature reserves (1,000 ha), Ikuywa River Forest
(1,450 ha), Kakamega National Reserve (4,457
ha, comprising Buyangu and Kisere fragments),
Malava East (75 ha) and Malava West (25 ha)
2(F0i0g0.)1). The IBA, although suffering from ongo-
ing degradation, fragmentation and destruction,
still provides suitable habitat for Chapin’s
Flycatcher, theequallygloballythreatenedTurner’s
Eremomela Eremomela turneri and 194 forest-
dependent bird species (BirdLife International
Hartlaub’s Turaco Tauraco hartlaubi and
.
Fine-banded Woodpecker Campethera tullbergi
have disappeared since the forest became discon-
nectedfromNorthNandi ForestIBA, andYellow-
mantled Weaver Ploceus tricolor has not been
recorded for many years (Bennun & Njoroge
2001
.
Our study concentrated on the forested areas
of Isecheno, Ikuywa (including Lirhanda Hill),
Yala Nature Reserve and Kakamega National
Reserve (Buyangu and Kisere). Surveys were not
conductedinMalavaEastandMalavaWestdueto
logistical difficulties and because theymainlycon-
sist ofexotic tree plantations.
Chapin’sFlycatcherinKakamegaForest, Kenya:Musilaetal. BullABCVol13No2(2006)-163
for two minutes at the start and end of each as Antiaris toxicaria Celtis africana, Albizia gum-
,
transect. mifera Olea capensis Cordia abyssinica and Fagara
, ,
Onlypositivelyidentified Chapin’s Flycatchers spp. The remaining four encounters were in sec-
were noted and their perch height estimated. ondaryforestdominatedbyMaesopsiseminiitrees.
Perchpositionwas recordedas: bare branch, inside Chapin’s Flycatchers did not react to playback of
canopyoredgeofcanopy. Behaviourwas recorded Red-crested Owlet calls.
as flying or perching quietly. Canopy height and Birds were more often (^=13) observed perch-
percentage ofcanopy cover within a 20-m radius ing quietly on bare branches within the canopy
were noted. Similar habitat data from random than on foliage or at canopy edges. Perch height
points in the same study fragments are available was 12-22 m (mean 17 m) on trees with a mean
(Gibbon 1991, Oyugi 1998, Brooks etal. 1999) height of 27 m and mean canopy cover of 32%
and we tested for differences in habitat structure (n=15). Canopyheightandcanopycoveratpoints
between the random points and those where where birds were observed differed significantly
Chapin’s Flycatcher was detected. The population (Analysis ofVariance (ANOVA), df=28, F=17.4,
density of flycatchers in each fragment was esti- P<0.001 and df=28, F=12.9, P=0.001 respective-
matedbydividingthe numberofbirds seen bythe ly) from those ofthe random points.
total area sampled by the transects.
Discussion
Results
Our results confirm that Chapin’s Flycatcher is a
Chapin’s Flycatcher was recorded in three of the scarce resident in Kakamega Forest (Zimmerman
five surveyed forest fragments (Table 1, Fig. 1). In et al. 1996). It is easily overlooked due to its
Isecheno birds were sighted within the inconspicuous plumage and behaviour, and this
‘Zimmermangrid’ andsurroundingforest, includ- may have affected population density estimates.
ing the Pump House trail; and in Ikuywa, at For instance, it can be reasonably assumed that
Ikuywa River bridge and upstream. One bird was most individuals thatweobservedas isolated indi-
recordedinforestaroundLirhandaHillduringthe vidualswere, infact, paired. ItdiffersfromAfrican
reconnaissance but not subsequently. In Buyangu, Dusky Flycatcher Muscicapa adusta, by being
the species was found along the Isiukhu River and
slightly larger with yellow gape corners, is less
in a forest patch behind theviewpoint at Buyangu vocal and is a forest-interior species unlikely to
Hill. In total, 17 individuals, comprising 13 sin- occur in highlydisturbed forest or nearhabitation
gles and two pairs, were recorded. We estimated (Zimmerman etal. 1996, Urban etal. 1997).
population density at 0.03 birds/ha (one bird per
20 ha). Localdistribution
Chapin’s Flycatcher appears to prefer tall During the present study, Chapin’s Flycatcherwas
indigenous tree species. Eleven ofthe 13 sightings found in the same forest fragments (Isecheno,
were made in the mid and upper canopy ofpri- Ikuywa and Buyangu) where previously recorded
maryforest, especiallyin tall indigenous trees such (Brooks et al. 1999), suggesting that its distribu-
Table 1. Estimated%areaofsuitableChapin’s FlycatcherMuscicapalendu(CF) habitatand numberof
birds detected atthestudysites.
Tableau 1. Estimationdu pourcentagede lazoneconvenantau GobemouchedeChapin Muscicapalendu(CF)
et nombre d’oiseauxdetectesdans lessitesetudies.
Forest Size %suitable Numberof Transects CF
fragment (ha) habitat transects withCF counted
Isecheno 310 70 37 9 10
Ikuywa 1,450 60 39 3 4
Buyangu 4,000 50 31 3 3
Yala 1,000 60 12 0 0
Kisere 457 80 6 0 0
Totals 7,217 60 125 15 17
164-BullABCVol13No2(2006) Chapin’sFlycatcherinKakamegaForest, Kenya:Musilaetal.
tion within Kakamega has changed little. In nous trees) in KakamegaForest, basedon ourfield
Isecheno, oneindividualwasseenin 1997 (Brooks observations and existing publications (Kokwaro
etal. 1999), andten duringthe presentstudy.The 1988, Blackett 1994, Oyugi 1996, 1998, Bennun
&
presenceandstrictsurveillanceofforestguardshas Njoroge 1999, Brooks et al. 1999). Assuming
protected a near-pristine indigenous and presum- that the species is restricted to such habitat, only
ablysuitablehabitat. In Ikuywa, abreedingrecord 60% ofthe indigenous forest, i.e. 4,330 ha, would
was reported by Stevenson (1991), an indication be suitable for it. Extrapolating our population
that suitable habitat formerly existed. However, density estimate to this area gives a very crude
over the years this forest has been heavily logged population estimate ofc.200 birds. Although this
and currently the interior is open with only scat- may be a significant underestimate (see comment
tered trees. Nevertheless, we still found four fly- above concerning the likelihood that most indi-
catchers here. In Buyangu, one individual was viduals that we recorded were paired), due to the
sighted in December 1996 (Brooks et al. 1999) species’ unobtrusiveness, its population must still
and we observed three. Numbers in this fragment be small and threatened. The species’ scarcity can
may increase in future because offorest regenera- be attributed to intense human activities, mainly
tion, facilitated by constant surveillance by Kenya logging, charcoal production, firewood collection,
Wildlife Service rangers (Mutangah et al. 1992, encroachment and overgrazing by cattle, which
Oyugi 1996). have continued to fragment the once-contiguous
There are no historical records in theYala and forest ecosystem. Fragmentation of Chapin’s
Kisere fragments and we did not find the species Flycatcher population in distant forest patches
there. AlthoughYalahas ahigh closed canopyand makes thespecies prone to local extinctions dueto
healthy tree population structure (Oyugi 1996), its greater vulnerability to demographic and envi-
its 20-year isolation (1972-2002) has probably ronmentalvariation, and loss ofgeneticvariability
hindered recolonisation from the nearest forest (Gaston 1994, Newmark 1999, Rodrigues &
patches (Ikuywa and Isecheno). However, Brooks Gaston 2002). Chapin’s Flycatcher may therefore
et al. (1999) suggested that the flycatcher’s mon- be unable to persist long term in these forest frag-
tane affinities may properly explain the lack of ments, and may eventually be extirpated unless
records from this lower altitude fragment. The conservation action to prevent further destruction
closedcanopyofindigenous treesat Kisere (Oyugi ofits habitat is taken.
1998) mayconstitute suitable habitatfor Chapin’s
Flycatcher and a local guide reported having seen Recommendations
one. We may have missed the species as surveys Our findings indicate that Chapin’s Flycatcher is
were conducted in this fragment on just one day rare and its population small and probablydeclin-
forthreehoursandthereforefuturesurveysshould ing. To ensure maintenance ofaviable population
tryto establish its presence or absence. we recommend the following:
Fivespecimens taken in KakamegaForesthave Improvement of forest management practises
been traced in two museums, the National to reduce the loss ofindigenous vegetation.
Museums of Kenya, Nairobi (one collected in Connecting all existing fragments of
1963), and the United States National Museum, Kakamega Forest via corridors ofplanted indige-
Washington DC (four collected in 1963), but the nous tree species, to enhance avian dispersal
fragments where theywere taken are not specified between forest patches and reduce the possibility
(Brooks etal. 1999). oflocal extinctions.
Conducting additional ecological studies of
Population status breeding and population dynamics, territory size
BirdLife International (2000, 2004) estimated the and territoriality, and dispersal.
global population of Chapin’s Flycatcher at Developmentofcontinuous monitoringofthe
2,300-10,000 individuals and declining. Table 1 species in the region, by members of the Site
presents estimates of the area ofpotentially suit- Support Groups (SSG; linked to the IBA conser-
able habitat for Chapin’s Flycatcher (tall indige- vation programme ofNature Kenya).
ChapinsFlycatcherinKakamegaForest, Kenya:Musilaetal. BullABCVol13No2(2006)-165
Acknowledgements Gibbon, M. 1991. Kakamega Forest Sight Survey.
Financial assistance was generously provided by the Nairobi: Kenya Indigenous Forest Conservation
African Bird Club Conservation Fund. The Programme.
Department of Ornithology, National Museums of Kokwaro,J. O. 1988. ConservationstatusofKakamega
Kenya, provided equipment for the survey. Titus Forestin Kenya, the eastern relicofEquatorial rain
Imboma and Nicholas Shikuyenze assisted data col- forest ofAfrica. Monogr. Systematic Bot. Missouri
lection in the field, and Alfred Owino made useful Bot. Gard. 25: 471-489.
comments to the studyproposal. Mutangah, J. G., Mwangangi, O. & Mwaura, P. K.
1992. Kakamega Forest Vegetation Survey Report.
References Nairobi: Kenya Indigenous Forest Conservation
Bennun, L. & Fanshawe,J. 1997. Usingforest birds to Programme.
evaluate forest management: an East African per- Newmark, W. D. 1999. Tropical forest fragmentation
spective. In Doolan, S. (ed.) African Rainforestand and local extinctions of understorey birds in the
the Conservation ofBiodiversity. Proceedings ofthe eastern Usambara Mountains, Tanzania. Conserv.
Limbe Botanic Garden 17—24 January 1997. Biol. 5: 67-78.
Oxford: EarthWatch Europe. Oyugi, J. O. 1996. Kakamega Forest is dying. E. Afr.
Bennun,L. &Njoroge, P. 1999.ImportantBirdAreasin Nat. Hist. Soc. Bull. 26(3/4): 47-49.
Kenya. Nairobi: Nature Kenya. Oyugi, J. O. 1998. Tropical forest fragmentation and
Bennun, L. & Njoroge, P. 2001. Important BirdAreas avifaunal population changes in Kakamega Forest,
in Kenya. In Fishpool, L. D. C. & Evans, M. I. Kenya. M.Phil. thesis. Eldoret: Moi University.
&
(eds.) ImportantBirdAreas inAfrica andAssociated Rodrigues, A. S. L. Gaston, K. J. 2002. Rarity and
Islands: Priority Sites for Conservation. Newbury: conservation planning in geopolitical units.
Pisces Publications & Cambridge, UK: BirdLife Conserv. Biol. 16: 672-682.
International. Stevenson, T. 1991. Kakamega Forest Tourism
BirdLife International 2000. Threatened Birds ofthe Consultancy. Nairobi: Kenya Indigenous Forest
World. Barcelona: Lynx Edicions & Cambridge, Conservation Programme.
&
UK: BirdLife International. Urban, E. K., Fry, C. H. Keith, S. (eds.) 1997. The
BirdLife International 2004. Threatened Birds ofthe Birds ofAfrica. Vol. 5. London, UK: Academic
World2004. CD-ROM. Cambridge, UK: BirdLife Press.
International. Zimmerman, D. A., Turner, D. A. & Pearson, D. J.
Blackett, H. L. 1994. Forest Inventory Report No. 3: 1996. Birds of Kenya and Northern Tanzania.
Kakamega. Nairobi: Forest Department/Kenya London, UK: ChristopherHelm.
BrooIknsd,iTg.enMo.u,sPFiomrems,tSC.onL.se&rvaOtyiuogni,PJr.oOg.ra1m9m9e9..Time NOarntiitohnoalolgy,MuPsOeuBmosx 4o0f658K,enyGaP,OD0e0p1a0r0tmNeanitrobio,f
lag between deforestation and bird extinction in
Kenya.
tropical forest fragments. Conserv. Biol. 13:
*Corresponding author: E-mail: kbirds@africaonline.
1140-1150.
Gaston, K. J. 1994. Rarity. New York: Chapman & [email protected]
Hall. Received 15 April 2004; revision accepted 29 May
2006
166-BullABCVol13No2(2006) ChapinsFlycatcherinKakamegaForest, Kenya:Musilaetal.