Working for birds in Africa

Discovery: A possible new taxon of rock thrush Monticola sp. from the limestone karst region of western Madagascar

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Male rock thrush
Monticola sp.
Kirsty J. Swinnerton
Male rock thrush
Monticola sp.
Kirsty J. Swinnerton

During June 1995, as members of a malacological expedition to the Tsingy de Bemaraha Nature Reserve, an area of limestone karst in western Madagascar, we established a base at the south edge of the reserve by the Manombolo River and close to Bekopaka village. From here we made sorties into the surrounding areas to look for snails but also taking the opportunity to look for birds and explore caves[3].

Late in the afternoon of 18 June 2 km north of the village of Kinajao, 11 km north-east of Bekopaka (19°24'S 44°48'E) we located a male rock thrush Monticola sp. perched on a boulder near the entrance of a cave. The light was poor and we were unable to get good views. Since we were aware that no rock thrushes had been recorded from the reserve [1] and it was outside the known range for all the Malagasy Monticola taxa [2, 5], we returned next morning to obtain better views of the bird. We relocated a pair of rock thrushes near to the area of the original sighting. The female was furtive and skulking, being difficult to keep in view for more than brief periods. The male, by contrast, was relatively confiding and perched prominently on bushes and rocks that, to judge by the accumulation of droppings, were regularly used. Both birds were seen at distances down to 2m in good light.

We were able to compare the birds with illustrations and descriptions of rock thrushes in Langrand2. The male did not match any of the taxa described, although the female was not, from our observations, separable from those of the Forest Rock Thrush Monticola sharpei sharpei and Mt. Amber Rock Thrush M. s. erythronotus.

The birds were on the edge of the Tsingy reserve next to the large limestone wall that, at this point, was c40 m high and were frequenting an area of scrub and disrupted canopy forest growing out of a steep boulder field at the base of the cliff.

We kept one or both of the birds in view for most of the two-hour observation period. They kept out of direct sunlight and spent much of the time actively foraging. The male caught a pale green caterpillar, c2.5 cm long, that it beat against a branch before consuming it. A hawk-moth, c5 cm long, was unsuccessfully attacked by the male and both birds were seen to descend to the ground to take small unidentified food items. Both were silent except for a brief quiet warble given by the male.

Two old nests in rocky recesses that we found were believed to belong to this pair. Both were a loose weave of roots and stems lined with leaves. The first nest was c25 cm in diameter and 12.5 cm deep and the cup, which was positioned toward the rear of the nest, was c10 cm across. The nest was set in a recess 45 cm wide and deep and 25 cm high above the nest. The second nest was similar but larger, an oval shape, c37.5 x 45 cm, again with the cup toward the rear of the nest, near the wall of the rocky recess.

We compared our photographs and field descriptions with study skins at the Natural History Museum (Tring). Details of the female agreed with those of Forest and Mt. Amber Rock Thrushes, as we had noted in the field. The male, however, possessed characteristics of both (Sinclair & Langrand [6] and Morris & Hawkins [4] recognise both as species-level taxa). The intense russet-coloured ventral plumage and the grey-blue head are similar to erythronotus while the dorsal colouring of grey-blue, becoming russet on the rump, is characteristic of sharpei. This record provides a record of what may be a new taxon of Monticola rock thrush in Madagascar.

Acknowledgements

We would like to thank Owen Griffiths who organised this expedition and the other team members, Greg Middleton and Vincent Florens. The staff of UNESCO Madagascar, particularly the Principal Co-ordinator Noeline Raondry made this field trip possible. Dr Robert Prys-Jones, Bird Section, The Natural History Museum, Tring, allowed us to examine the bird skins in his care.

References

  1. Bousquet, B. and Rabetaliana, H. 1992. Site du patrimoine mondial des Tsingy de Bemaraha et autres sites d'intérêt biologique et écologique du fivondronana d'Antalova. Evaluation et plan d'aménagement. UNESCO: Paris.
  2. Langrand, O.1990. Guide to the Birds of Madagascar. New Haven: Yale University Press.
  3. Middleton, G. 1996. The 1995 Australo-Anglo- Malagasy Speleo-Ornitho-Malacological Expedition, Tsingy de Bemaraha, western Madagascar. J. Sydney Speleological Soc. 40: 1-17.
  4. Morris, P. and Hawkins, F. 1998. Birds of Madagascar. A Photographic Guide. Robertsbridge: Pica Press.
  5. Rand, A.L. 1936. The distribution and habits of Madagascar birds: summary of the field notes of the Mission Zoologique Franco-Anglo-Americaine a Madagascar. Bull. Am. Mus. Hat. Hist. 75: 143-499.
  6. Sinclair, I. and Langrand, O. 1998. Birds of the Indian Ocean islands. Cape Town: Struik.

Gerald Durrell Endemic Wildlife Sanctuary, Black River; Mauritius.

Frank Hawkins has commented as follows. 'This population was first discovered in November 1994, by Ramanitra Narisoa Andriamboavonjy, while conucting field studies in Bemaraha. Brief details of the sighting were published (Ramanitra, N.A. 1995. Inventaire preliminare de l'avifaune du Tsingy de Bemaraha. Working Group on Birds in the Madagascar Region Newsletter 5 (1): 7-10). In July 1998, the ZICOMA team made a visit to this area and trapped a female Monticola, from which a blood sample was taken. Observations of its behaviour were made, as was a tape-recording of the song. A Malagasy student is now working on the taxonomy of Malagasy rock thrushes based on song structure, and we also await the results of DNA analysis of the blood samples. The important distinctions between this taxon and that of M. sharpei are: males have considerably less blue on the throat than sharpei and thus resemble M. erythronotus (see Morris & Hawkins[4]), except that they have a blue rather than reddish mantle, and the lower back is more rufous than in erythronotus. Both sexes are also much redder on the tail than M. sharpei (again like M. erythronotus). The female is rather more rufous than female sharpei, especially in the wide upper-breast band, although sharpei are rather variable in this feature. The female lacked the whitish upper-breast streaks of sharpei, another feature similar to erythronotus. However this population is much further removed from M. erythronotus than from M. sharpei, so it is very unlikely to be closely related to erythronotus.'

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