'A nest record of Oberlander''s Ground Thrush Zoothera oberlaenderi'

2008·1.7 MB·

by  Thomas Gottschalk

A nest record of Oberlander’s Ground Thrush
Zoothera oberlaenderi
K
Thomas Gottschalk1andSaulAmpeireb
Observationd’un niddelaGrive d’OberlaenderZootheraoberlaenderi. Le 1 mars 2007, un nid
de la Grive d’OberlaenderZoothera oberlaenderi a ete decouvert dans la partie sud de la foret de
m
Bwindi, au sud-ouest de l’Ouganda. Le nid, place sur une branche a 5 de hauteur, contenait
trois oisillons. Les premieres photographies du nid, de la nichee, et d’un adulte de cette espece
menacee sont presentees.
Oberlander’s Ground Thrush Zoothera ober- (Urban et al. 1997, Collar 2005). A nest of Z
laenderi occurs in north-east Congo- oberlaenderi found in Bwindi byA. Twinomujuni
, &
Kinshasa and in western Uganda, and is known in May-June 1998 (Clement Hathway 2000),
solelyfrom afewsites in the formercountry (Ituri was constructed of ‘dry grasses, vegetation strips
Forest, Bondo-Mabe, Kamituga area, southern and plant fibres’, but was later destroyed by
Kivu and Semliki Valley) and two in Uganda squirrels.
(Semliki/Bwamba Forest and Bwindi Intheafternoonof1 March2007, in thewest-
Impenetrable Forest: Clement & Hathway 2000). ern sector ofBwindi Impenetrable Forest 2.5 km
The species inhabits primary lowland and transi- south of Buhoma, SA heard a ground thrush
tional forest at 700-1,620 m (Urban etal. 1997), singing in dense forest 12m away beside a stream
but is unknown from secondary forests (Collar (01°01’S 29°37’E; 1,492 m). Arriving in the area
2005). In Bwamba (Uganda), this thrush is from where the song emanated we observed the
known from tall stands of ironwood trees, groundthrushinflight. Initiallywewereunableto
Cynometra alexandri with a fairly open under- obtain good views, but after a while the bird flew
,
storey, and avoids areas with dense undergrowth to a tree, where we observed that itwas sitting on
m
(Urban etal. 1997). The species’ current status is a nest, 5 up in a Carapaglandiflora, andwhere-
unclear, e.g., only seven dated records have been upon we were able to identify the bird as an
published from Uganda since the 1960s (Carswell Oberlander’s Ground Thrush. Using a telescope
et al. 2005) including a female collected in the we saw the distinctive broken white eye-ring and
Itama area of Bwindi Impenetrable Forest, at the rufous-brown head (Figs. 1-2). The darkver-
1,616 m, byA. Williams, on 18June 1969 (Keith tical line through the eye was seen well on several
& Garrett 1994). Ffowever, the IUCN / BirdLife occasions. Both adults were bringing food to the
International (2007) currently treats Z. oberlaen- nest, suggesting that it contained nestlings. As
derias NearThreatened, despite the lackofrecent with Black-eared Ground Thrush Zoothera
published records, e.g., from the Semliki Valley cameronensis, which appears very shy at the nest
(Carswell etal. 2005). Urban etal. (1997) suggest- (Lindsell 2002), the Oberlander’s Ground
ed that the species may no longer be extant in the Thrushes departed the nest whenever we
Bwamba Forest of the Semliki Valley, owing to approached towithin 25 m.Afterc.1 hourobserv-
habitat degradation. Habitat loss may have also ing and photographing the birds, TG climbed the
caused its local extinction at Beni and Kamituga tree to photograph the nest, which was well con-
(Ituri, Congo-Kinshasa: Collar & Stuart 1985), as cealed on a small, wet branch covered by
the species appears sensitive to forest degradation liverworts and ferns. The open-cup nest was con-
(Plumptre 1997), which is extensive within its structed mainly of liverwort, Plagiochila, with a
small range (Collar2005). Moreover, conservation few fern stems visible inside the nest (Fig. 3). Dry
efforts are impeded by the fact that Oberlander’s grasses, which were mentioned from the first
&
Ground Thrush remains one of the least-studied recorded nest in Bwindi Forest (Clement
African birds, due to its elusive behaviourand tiny Hathway 2000), were not apparent. The nest
range; the species’ breeding habits are largely structure and its location resembled that ofa nest
unknown, and the eggs and nestlings undescribed of Abyssinian Ground Thrush Zoothera piaggae
250-BullABCVol15No2(2008) A nestrecordofOberlcinders GroundThrush: Gottschalk&Ampeire
Figure 1.AdultOberlander’s GroundThrushZoothera
oberlaenderijustpriortoleavingthe nest, Bwindi
ImpenetrableForest, Uganda, 1 March2007 (Thomas
Gottschalk)
Grive d’OberlaenderZootheraoberlaenderiadultejuste
avantdes’envolerdunid, Foretde Bwindi, Ouganda, 1
mars 2007 (Thomas Gottschalk)
Figure2.AdultOberlander’s GroundThrushZoothera
oberlaenderion thenest, Bwindi Impenetrable Forest,
Uganda, 1 March2007 (Thomas Gottschalk)
Grived’OberlaenderZootheraoberlaenderiadultedans
sonnid, ForetdeBwindi, Ouganda, 1 mars2007
(Thomas Gottschalk)
Figure3. NestandnestlingofOberlander’s Ground
ThrushZootheraoberlaenderi Bwindi Impenetrable
,
Forest, Uganda, 1 March2007 (Thomas Gottschalk)
NidavecoisillondelaGrived’OberlaenderZoothera
oberlaenderi, Foretde Bwindi, Ouganda, 1 mars2007
(Thomas Gottschalk)
On 10 February 2008 the same place was vis-
ited again. The one-year old Z. oberlaenderi nest
was still on the tree and in good condition. After
removing it from the small, unstable branch, the
following measurements were taken: external
diameter 140 mm, internal diameter 60 mm,
internal depth 40 mm.The areaofground shaded
bytrees and shrubs at middaywas estimated to be
m
10 around the nest. Canopy closurewas c.75%
and included trees up to 26 m high. The under-
storey layer (trees lower than 3 m) covered 40%,
the upper field layer (trees and shrubs <2-3 m)
50% and thelowerfield layer (shrubs >3 m) 50%.
Further data are required to elucidate the cur-
rent status ofOberlander’s GroundThrush. Such
data are particularly important given that
Oberlander’s Ground Thrush is an Albertine Rift
endemic and is confined to the few remnants of
primaryforest in this part ofEastAfrica.
found in Uganda, which was built ofloose green
moss and well concealed in dense foliage 5 m Acknowledgements
above ground (T. Butynski et al. in Urban et al. We thank Ron Demey, Guy Kirwan and three anony-
1997). The nests of Black-eared Ground Thrush mous referees for very helpful comments on earlier
and GreyGroundThrushZ.princeiare somewhat drafts ofthis note.
different, as they are constructed of dead leaves,
some twigs and dry bark (Brosset & Erard 1976, References
Lindsell 2002, Collar 2005). The nest held three BirdLife International 2007. Species factsheet:
unfeathered chicks with closed eyes. To our Oberlander’s Ground-thrushZoothera oberlaenderi.
knowledge, the photographs ofthe adult and the www.birdlife.org (accessed 9 March 2007).
nestarethefirsteverpublishedofthespecies (Figs.
1-3).
A nestrecordofOberlander’s GroundThrush: Gottschalk &Ampeire BullABCVol15No2(2008)-251
&
Brosset, A. Erard, C. 1976. Premiere description de Plumptre, A. J. 1997. Shifting cultivation along the
lanidification de quatre especes enforetgabonaise. trans-African Highway and its impact on the
Alauda44: 239-255. understorey bird community in the Ituri Forest,
Carswell, M., Pomeroy, D., Reynolds,J. &Tushabe, H. Zaire. BirdConserv. Intern. 7: 317-329.
&
2005. The BirdAtlas of Uganda. Oxford: British Urban, E. K., Fry, C. H. Keith, S. (eds.) 1997. The
&
Ornithologists’ Club British Ornithologists’ Birds ofAfrica. Vol. 5. London, UK: Academic
Union. Press.
&
ClemUeKn:t,ChP.ristoHpahtehrwaHye,lmR.. 2000. Thrushes. London, aDepartmentofAnimalEcology,JustusLiebig University,
IFZ, Heinrich-Buff-Ring 26-32, 35392 Giessen,
Collar, N. J. 2005. FamilyT&urdidae (thrushes). In del Germany. E-mail: [email protected]
HHaoynod,booJ.k, Eolfliotthte, BAi.rds ofChrtihsetieW,orlDd.. AV.ol.(ed1s0..) bPO Box 992, Kabale, Uganda. E-mail:
[email protected]
Barcelona: LynxEdicions.
&
Collar, N. J. Stuart, S. N. 1985. ThreatenedBirdsof Received 19 June 2007; revision accepted 31 May
Africa and Related Islands. Cambridge, UK: 2008.
International Council for Bird Preservation.
&
Keith, S. Garrett, K. L. 1994. Oberlander’s Ground-
Thrush Zoothera oberlaenderi in the Impenetrable
Forest, Uganda. Scopus 17: 141-142.
Lindsell, J. A. 2002. The first nest and egg records of
Black-earedGround-ThrushZootheracameronensis,
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252-BullABCVol15No2(2008) A nestrecordofOberlanders GroundThrush: Gottschalk &Ampeire