Preliminary survey of Wattled Ibis Bostrychia Carunculata in Bale Mountains NarionaPark Ethiopia, with notes on abundance, habitat and threats

2006·2.6 MB·

by  John Hughes

Preliminary survey of Wattled Ibis Bostrychia carunculata in
Bale Mountains National Park, Ethiopia, with notes on
abundance, habitat and threats
John Hughes
Inventaire preliminaire de l’lbis caroncule Bostrychia carunculata dans le Parc National des
Monts Bale, Ethiopie, avec notes surl’abondance, le milieu et les menaces pesant sur 1espece.
Un inventaire preliminaire de l’lbis caroncule Bostrychia carunculata a ete realise dans la partie
nord-estduParcNationaldesMontsBale, Ethiopie, enjanvier2005. Pendantenviron 100heures
d’observations sur le terrain, utilisant des transects et des comptages par point dans une zone de
27 km~, au moins 246 ibis ont ete notes. La densite d’lbis caroncules etait de 10 individus par
km~ etdes groupes de22-93 oiseauxonteteobserves surcinqsites. Dans lazone d’etudeles Ibis
caroncules dorment dans des arbres et evitent les cultures de cereales. Les problemes du surpa-
turage etlacouped’arbres, notes anterieurement, sonttoujours presents, tandis que des nouvelles
menacespotentiellescomprennentl’erosiondessols, ledefrichementpourl’agricultureet1extrac-
tion d’eau.
Summary. The results ofa preliminary survey ofWattled Ibis Bostrychia carunculata, conducted
inthenorth-easternpartofBaleMountainsNationalPark, Ethiopia, inJanuary2005, arereport-
ed. Duringc.100 hours offieldwork, usinglinetransects andpointcounts in an areaof27 km«,
at least 246 ibises were recorded. Wattled Ibises occurred at a density of 10 individuals per km~
and at five sites groups of22—93 birds were observed. In the studyareaWattled Ibises roosted in
trees and avoided cereal farmland. Previously recorded threats ofover-grazing and tree-cutting
still exist, whilst potential new threats include soil erosion, conversion to agriculture and extrac-
tion ofgroundwater.
W
attled Ibis Bostrychia carunculata is endem- Study area and methods
ic to Ethiopia, where it is locally common Thesurveywasconductedinthenorth-eastcorner
in thehighlands at c.1,500-4,100 m (Brown etal. of Bale Mountains National Park (06°30’N
1982, Matheu & del Hoyo 1992). No precise 39°55’E). The Bale Mountains have been identi-
quantitative details are available; Birdlife fied as a biodiversity hotspot by Conservation
International (2004) estimates the population at International (Mittermeier et al. 2004) and the
10,000-25,000 individuals and considers the park is an Important Bird Area (EWNFIS 2001).
species as Least Concern. This paper reports on a Five 10x10 km squares along the Didola-Delo
14-day survey ofWattled Ibis conducted in Bale Mena road and one 10x10 km square within the
Mountains National Park, c.400 km south of parkwere selected as the study area (Fig. 1). Half
Addis Ababa, during a visit to Ethiopia from 13 ofthe survey was conducted inside the park and
January to 2 February 2005. Additional observa- the other halfaround the outer perimeter.
ttioonasndwefrreommatdheeosntutdhyeajroeua.rnMeyyfariommAisddtiosmAabkaebaa PosiEtqiouniipnmgeSnytstceomns(iGstPeSd) orefceaiveGramromdienl G1l2obNaol
modest contribution to a more precise estimate of 36155001, 8x42 binoculars and the Bale
the species’ population, its habitat preferences and Mountains Trekking map 1/200,000 Digital
threats to its survival. The surveywas designed to Impressions Pic. It should be noted that the nor-
be repeatable as a whole or in parts, and to facili- thing grid lines are labelled incorrecdy on this
tate comparison ofpopulations between years and mthaep.1/T5h0e,0s0u0rvteoypoagreraapihsiccoavlermeadppininmgorseerideestaEilTbHy
sites. 4 (DOS 450) Sheets 0739 D4 and 0740 C3
SurveyofWattledIbisinBaleMountainsNationalPark:Hughes BullABCVol13No2(2006)-157
58 59 60
Figure 1. Studyareaandkeysites.Thestudyareais400 kmsouthofAddisAbabain theEthiopianHighlands along
thedirtroadlinkingDodolaandDeloMena. Itcomprisessix 10x10 kmsquaresandincludes thetownsofGoba, Robe
and Dinsho.Thefivesites markedwithastareachheld22-93WattledIbisesBostrychiacarunculata. Thedottedline
marks theboundaryofthenationalpark.
Zoned’etudeetsitesprincipaux. Lazoned’etudeestsitueea400 kmausudd’AddisAbabasurleshautes terres ethiopi-
enneslelongdelapistereliantDodolaaDelo Mena. Elleconsisteensixcarresde 1Ox10 kmetcomprendlesvillesde
Goba, RobeetDinsho. Lescinqsitesmarques d’uneetoilecontenaientchacun22-93 Ibis caronculesBostrychiacarun-
culata. Laligne interrompuemarquelalimiteduparenational.
Edition 1 SMGI/DOS 1976. All GPS observa- line transects were carried out bya single observer
tions and map references refer to UTM grid zone on foot amounting to 15.5 hours. Only Wattled
37 and to the Adindan Datum. Before the survey Ibises were counted. The birds surveyedwere usu-
commenced the GPS was set to the Adindan ally seen feeding on the ground in flocks (Fig. 2).
datum and GPS coordinates were compared with Ibis flyingacross the transectlinewere not record-
the map grid reference to confirm compatibility. ed. Shortage oftime and the rapid movement of
the vehicle prevented close scrutiny, so immatures
Survey methodsThe surveywas undertaken using were included in the survey. Small ibises with
modified line transects (traversed either on foot, flesh-coloured legs and without wattles were
horseback or by four-wheel-drive vehicle) and assumed to be juveniles/immatures. To maximise
point counts (Bibby 1992). Eight line transects, the encounter rate, the more detailed transect sur-
varying in length between 6 and 30 km with a vey on horseback, conducted at the end of the
width of 100 m either side, were surveyed by two studyperiod, avoidedagriculturallandandkeptto
observers (Table 1). Transects were surveyed on valleybottomswhere sightings ofibiseswere more
average four times (range 1-8).The total length of likely.
transects was 1 16 km and the area surveyed 23.2 Pointcountswere undertakenatfivelocations.
km551. The survey effort split between two At threeofthese, countswere made onlyonce, for
observers amounted to 37.4 hours. In addition, periods of30-60 minutes. The remaining two, in
158-BullABCVol13No2(2006) SurveyofWattledIbisinBaleMountainsNationalPark:Hughes
Table1. Summaryoflinetransects.
Tableau 1. Apergu destransects.
Line Length Area Numberof Totalobs Totalnumber Minimum Habitat Sightings Ibisper
transect (inkm) (ha) timestransect time(hrs) ofibisseen numberofibis type perhourof kmsq
surveyed onallsurveys alongtransect observation
1 6 120 2 2 0 0 G1 0 0
2 13 260 8 8 0 0 HI 0 0
3 30 600 6 12 158 58 HI &G1 13.2 9.7
4 7 140 3 3 74 30 G1 24.6 21.4
5 25 500 4 8 49 22 H1&G1 6.1 5.5
6 8 160 1 4 31 31 G1 7.8 19.4
7 12 240 6 28.4 324 93 G1 11.4 38.8
8 15 300 2 7.5 13 7 G1 1.7 2.3
Totals 116 2,320 mean4 72.9 649 241 8.9 10.4
Robe and at the park headquarters, were at camp M2 Giant Lobelia-A/c/^mz7/4-tussock grass
m
locations, where itwas convenient to make counts moorland, 3,800-4,100
atdawnandatdusk. Despitethepointcountloca- FI/ F3Hageniaforestand]\miper-Podocarpusfor-
tion in Robe being in the middle oftown, ibises est, 2,400-3,200 m
were recorded flyingto and from roosts.The loca- G1 Highland grassland, 1,800-2,750 m
tion at the park headquarters was surrounded by (reaching 3,400 m in theWeb Valley)
Hagenia and juniper trees and ibises roosting in D4 Cliffs and gorges, mainly bare rock
these trees were recorded on most mornings and A5 Highland streams and marshes
evenings. To avoid duplication, birds at roosts H
were notincludedin thepopulation estimate.The 1 Cereal-based agriculture
area surveyed by point counts was 4.05 km~ and H2 Town and urban areas
the surveyeffortwas 28 hours. Threats A checklist produced by the Ethiopian
Although the surveywas conducted in the dry Wildlife and Natural History Society (1996) to
season, it did rain, but this did not significantly classify existing and potential threats to birds as
reduce visibility, which was generally good. The critical, major or low, was used in the survey.
wind was moderate. Surveyworkwas undertaken
Threats were identified by personal observations
in daylight, except at the roosts. and through discussions with local authorities.
HabitatEach time aWattled Ibiswas sighted, the
habitat in which it occurred was noted following Results
the classification ofUrban & Brown (1971), with Wattled Ibis proved easy to identify whilst travel-
two habitat types (HI and H2) added to take into ling in a vehicle, as the species is large with a dis-
account characteristics in the Robe area. The fol- tinctive profile and diagnostic white wing-patch,
lowing habitats were encountered during the and prefers open areas. It is only likely to be con-
survey: fused with the Hadada Ibis Bostrychia hagedash,
Table2. Summaryofpointcounts.
Tableau 2.Aperpu descomptagesparpoint.
Point Area Obstime Numberof Min.number Habitat Sightings Ibisper
(ha) (hrs) sightings ofibisfeeding type perhour kmsq
1 100 0.5 0 0 G1 0 0
2 100 0.5 5 5feeding HI 10 5
3 100 20.0 8 0 H2 0.4 0
4 10 6.0 37 14roosting F1/F3 6.2 140
5 100 1.0 0 0 G1, D4&A5 0 0
Totals 405 28 49 5 1.8 n/a
SurveyofWattledIbisinBaleMountainsNationalPark:Hughes BullABCVol13No2(2006)-159
Table3. SizeoffeedingflocksofWattled Ibis Bostrychiacarunculatainthe Bale Mountain area.
Tableau 3.Tailledesgroupesd’lbiscaroncules Bostrychiacarunculataala recherchede nourriture
dans la zone des Monts Bale.
Flocksize Singleibis 2birds 3-9birds 10-19birds 20+birds
Numberofflocks 6 12 34 5 15
butthisspecies is uncommon and nonewas found ibises,wereidentified (Table4).Alllaycloseto the
in the study area. The call is a far-carrying honk- road and were relatively easy to access. As line
ing, uttered for 4-5 seconds on take-off Most transects and point count locations were chosen
birds seen had wattles ofc.5 cm in length with a opportunistically, the selection was not sufficient-
diameter ofc.0.5 cm. ly rigorous to permit a statistical analysis of the
Wattled Ibises were recorded on 82 occasions data. The survey was conducted in a very small
andatotalof698 birdswasobserved (Tables 1-2). geographical area (600 km~) and is thus not rep-
The minimum count (based on line transects and resentative ofthe Bale region or the total range of
point counts) was 246 adult and immature the species. GPS coordinates for the point count
Wattled Ibises. Most sightings were ofbirds feed- locations and the line transects (enabling repeat
ing in small or larger flocks (Table 3). surveys) are available from the author.
LocalabundanceThe areasurveyed totalled27.25 General habitat Wattled Ibises were most often
km~ or 4.5% ofthe study area. In the study area seen feeding in flocks of3-9 or 20+ birds (Table
Wattled Ibises were found at a densityof10 birds 3).Theyfedonagriculturallandthathadbeenleft
per km~. Five key sites, each containing 22-93 fallow for 1-2 years, in areas ofshort damp grass
(Gl) and in highland vegetation including rough
tussock grass (M2). They were frequently seen
Table4.Wattled Ibis Bostrychiacarunculatakeysites. close to villages and towns. In Addis Ababa, they
Tableau 4. Sites importantsde I’lbiscaroncule were seen feeding in the company of the locally
Bostrychia carunculata. morecommonSacredIbis Threskiornisaethiopicus.
Along the Dodola-Dinsho road they were seen
Site Gridcoordinates Flock Park feeding with Warthogs Phacochoerus aethiopicus.
size boundary
Sennetti Plateau 06°53’N39°54’E 22 Inside None was seen feeding in stubble, cornfields or
Nibisofa 07°06’N39°50’E 58 Outside freshly ploughed fields (HI) or in the extensive
WebValley 07°01’N39°44’E 93 Inside wheat fields surrounding the town of Robe. The
GaysayValley 07°07’N39°47’E 30 Inside
birds appearto preferlevelground; onlyoncewere
DishoLodgeroost 07°06’N39°48’E 14 Inside
they seen feeding on a slope. Only on rare occa-
sions were individuals observed near trees, except
when roosting. They were not recorded in scrub,
Table5Wattled Ibis Bostrychiacarunculata woodlandorforest (F1/F3), orinwater.Theyflew
roosting intrees. to theirtree roosts at 17.00-18.30 hrs anddepart-
Tableau 5. Ibiscaroncules Bostrychiacarunculata edat 06.30 hrs (Table 5), and appeared to roost in
au dortoir. pairs. No nests were found and no courtship dis-
DateandLocation Time plays observed. The species was more abundant
Departingroost Roosting within the National Park, but this is more likely
24January,DinshoLodge 18.00hrs 3 due to the fact that there are few cultivated areas
26January,DinshoLodge 06.30hrs 14
26January, DinshoLodge 17.15hrs 3 inside the park, rather than it offering any
26January, DinshoLodge 18.00hrs 4 protection.
27January,DinshoLodge 06.30hrs 6
27January.DinshoLodge 09.30hrs 2 Threats In generalWattled Ibises are notpersecut-
31 January,Nibisofa 09.10hrs 8 ed. The Oromo people who inhabit the Bale area
Totals 30 10
160-BullABCVol13No2(2006) SurveyofWattledIbisinBaleMountainsNationalPark:Hughes
Figure2. FeedingflockofWattledIbisesBostrychiacarunculata (CatherineHughes)
Grouped’lbis caronculesBostrychiacarunculataalarecherchedenourriture (CatherineHughes)
live in harmony with the birds. In the study area EthiopianWildlife andNatural HistorySociety (2001)
two threats could be classified as major: over- Ethiopia. In Fishpool, L. D. C. & Evans, M. I.
grazing and tree-cutting. Potential threats may (eds.) ImportantBirdAreas inAfrica andAssociated
come from soil erosion, conversion to agriculture Islands: Priority Sites for Conservation. Newbury:
(farmers from the north ofthe countryhave been Pisces Publications & Cambridge, UK: BirdLife
relocated to this area) and extraction of ground International.
&
water (small-scale extraction and irrigation has Matheu, E. del Hoyo, J. 1992. Family
started and there are plans to expand the process). AT.hr&eskSiaorrgnatiatlh,idJ.ae(e(disb.i)seHs)a.ndInbodoekl Hoofythoe,BJi.r,dsElolifottth,e
Acknowledgements World. Vol. 1. Barcelona: LynxEdicions.
I am grateful toXavier Oudard forhis notes on four Mittermeier, R. A., Robles Gil, P., Hoffmann, M.,
line transects that he completed on foot in the Web Pilgrim, J., &Brooks, T., Mittermeier, C. G.,
Valley on 31 January and 1 February 2003. I thank RLeavmiosirteeudx:,EJ.arth’dsaFBoinosloegciac,alGl.yA.RiBc.he2s0t04a.nHdotsMpoostts
Ken Wright, Simon Strickland and John Ash for
Endangered Terrestrial Ecoregions. Mexico City:
their helpful comments on a draft ofthis paper, and CEMEX.
Ron Demey and Guy Kirwan for their significant Urban, E. K. & Brown, L. H. 1971. A Checklistofthe
contribution to the finalversion.
Birds of Ethiopia. Addis Ababa: Addis Ababa
UniversityPress.
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SurveyofWattledIbisinBaleMountainsNationalPark:Hughes BullABCVol13No2(2006)-161