Long-billed (Moreau's) Tailorbird: 2

Does competitive exclusion explain a disjunct distribution?
Stuart [15] speculated that Long-billed Tailorbird is sufficiently similar to two other species that probably share the same niche, that its restricted and disjunct distribution in the Njesi Plateau and East Usambaras could be explained by competitive exclusion. One of these species, Grey-backed Camaroptera (Bleating Warbler) Camaroptera brachyura, is sympatric with the tailorbird at most forest-edge sites, but not within interior forest gaps, which are occupied only by the tailorbird. Both share food resources in the lower strata, but the camaroptera also takes prey on the ground and rarely ventures above 3 m. This behaviour contrasts with that of the tailorbird, described above.
The other possible competitor mentioned by Stuart [15] is African Tailorbird Orthotomus [Artisornis] metopias. This is extremely rare in the Amani area but not uncommon at higher elevations on Nilo. As this species occurs on most of the intervening mountains between the East Usambaras and Njesi Plateau, but is rare in the Amani area, Stuart [l5] suggested that this might be due to competition with Long-billed Tailorbird. In intervening areas he suggested that metopias could have outcompeted its congener.
Both species occur in the Nilo area [6]: moreaui within a large glade at the forest edge and the fairly common metopias at the forest edge and interior. It is difficult to ascertain numbers of metopias in the Amani area during Moreau's times as no estimates were made. Nonetheless, he infrequently observed the species in the 1930s [12], but prior to and following Moreau's residence in Amani there were few if any reports [8, 14]. Despite an annual mist-netting programme, Newmark 10] has only sporadically captured a tiny number of metopias in Amani during the last two decades. Our current work has not produced any records (NJC pers obs), despite knowledge of its vocalisations. That metopias has declined is highly probable, but that this is due to competition with its congener as proposed by Stuart [l5] appears unlikely. As metopias occurs within the interior of moist, dense forest, usually above 1,000 m, it is probable that its population at Amani was always small and its purported decrease may relate to this factor or a rapid decrease in available habitat between the late 1800s and 1980s. Long-billed Tailorbird is segregated by habitat.

Unresolved taxonomy?
When Sclater [1] described moreaui he placed it within the genus Apalis, with a clause that several characteristic features (i.e. greater bill length and number of tail feathers) could warrant erection of a new genus. More recently the species has been considered a tailorbird Orthotomus [9, 17], which has gained adherence within the conservation community [4], but Birds of Africa places it in Artisornis. While it shares a number of morphological features with Asian tailorbirds [9], it is not known whether it also builds a distinctively sewn nest of leaves like that of other Orthotomus. To this confusion, we add our discovery that the individuals at Amani possess long filoplumes (Figs 1-2), a feature that has not been previously noted [1, 9,11,12,17]. Thus controversy surrounding its generic placement appears set to continue.

Long-billed (Moreau's) Tailorbird, Tanzania (N. J. Cordeiro)

Conservation status
Amani Nature Reserve was established in 1997 to provide greater protection to this biodiversity hotspot. Such status will enhance the survival possibilities for rarer animals and birds, including moreaui, which is widespread in the reserve. Our work has demonstrated that the species' population is not as low as feared and that it is also more widespread than previously believed. Even if this encouraging news is solely due to more thorough field work than has previously been conducted, the existence of this population is a positive development.
Nonetheless, there is still a pressing need to assess the species' distribution and numbers within the rest of the nature reserve and in surrounding forest at suitable elevations. A short detailed ecological study on territory sizes, foraging ecology and behaviour is planned for the future. It is envisaged that details of its habitat specificity will be obtained to gain a better understanding of how to manage for the species in the East Usambaras. We also plan to establish whether forest-edge habitats adjacent to wetlands are preferred over drier areas.
Many years elapsed without any sightings of this skulking bird in the East Usambara Mountains, and it has not been reported from other Eastern Arc mountains that possibly hold suitable habitat. We consider that there is a strong possibility of finding it in the Udzungwa Mountains, particularly in more level areas at similar altitudes.

Acknowledgements
We thank the Conservator of Amani Nature Reserve, C Sawe, and East Usambara Conservation Area Management Programme Manager, E Nashanda, for logistical support of the population study and NJC's research in the East Usambaras. Support for NJC's presence in Amani came from the Wildlife Conservation Society, New York (WCS), Garden Club of America, Chicago Zoological Society, Chapman Memorial Fund, Explorers Club, Sigma Xi and a fellowship from the University of Illinois at Chicago. The Tanzanian Commission for Science and Technology kindly permitted NJC's research. B Munisi, M Joho, V Gupta and R Muna provided essential field assistance. C & T Challange assisted in other aspects of the research project and C. McBride and J. McEntee shared some observations. David Moyer of WCS was instrumental in providing advice and support during our research concerning this bird. We thank David Moyer and Peter Lack for their comments on an earlier draft of this paper.

To download a copy of the relevant East Usambara Conservation Area Programme report (No.47), please refer to the internet site www.usambara.com. At this site one can also find an updated list of 342 birds of the East Usambara Mountains. A checklist of the East Usambara avifauna is available for sale at the Amani Nature Reserve Visitor's Centre in Sigi.

Further reading

1. Benson, C.W. 1945. A new race of Long-billed forest warbler from northern Portuguese East Africa. Bull. Br. Ornithol. Cl. 56: 19.
2. Benson, C.W. 1946. A collection of birds from near Unangu, Portuguese East Africa. Ibis 88: 240-241.
3. Britton, P. L., Stuart, S.N. and Turner, D.A.1984. East African endangered species. Proc. V Pan-African Ornithol. Congr: 679-688.
4. Collar, N.J., Crosby, M.J. and Stattersfield, A.J. 1994. Birds ta Watch 2. the world list of threatened birds. Cambridge, UK: BirdLife International.
5. Collar, N.J. and Stuart, S.N. (1985) Threatened Birds of Africa and related islands: the ICBP/IUCN Red Data Book. Cambridge, UK: International Council for Bird Preservation.
6. Cordeiro, N.J. 1998. A preliminary survey of the montane avifauna of Mt Nilo, East Usambaras, Tanzania. Scopus 20: 1-18.
7. Cordeiro, N.J. 2001. Report on a pilot study of the Long-billed tailorbird O11hatamus moreaui Sclater in the East Usambara Mountains. Tech. Rep. 47. Dar es Salaam: East Usambara Conservation Area Management Programme & London, UK: Forestry and Beekeeping Division, Finnish Forest & Park Service, and Society for Environmental Exploration.
8. Friedmann, H. 1928. A collection of birds from the Uluguru and Usambara Mountains, Tanganyika Territory. Ibis 12: 74-99.
9. Fry, C.H. 1976. On the systematics of African and Asian tailorbirds (Sylviinae). Arnoldia 8: 1-15.
10. Newmark, W.D. 1991. Tropical forest fragmentation and the local extinction of understorey birds in the Eastern Usambara Mountains, Tanzania. Conserv. Biol. 5: 67-78.
11. Sclater, P.R. 1931. Three new birds from Amani Forest, in the Usambara District of Tanganyika, recently obtained by Mr. R.E. Moreau. Bull. Br. Ornithol. Cl. 51: 109-112.
12. Sclater,P.R.and Moreau,R.E.1933. Taxonomic field notes on some birds of north-eastern Tanganyika territory, Part 3. Ibis 13: 1-33.
13. Stattersfield, A.J. and Capper, D.R. 2000. Threatened Birds of the World. Cambridge, UK; BirdLife International & Barcelona: Lynx Edicions.
14. Stuart, S.N. and Hutton, J.M. 1978. The avifauna of the East Usambara Mountains, Tanzania. Unpublished report of the Cambridge Ornithol. Expedition to Tanzania, 1977
15. Stuart, S.N. 1981. An explanation for the disjunct distributions of Modulatrix orostruthus and Apalis (or Orthotomus) moreaui. Scopus 5: 1-4.
16. Turner, D.A. 1978. Interim report on the endangered birds of the Usambara Mts. Unpublished manuscript.
17. White, C.M.N. 1960. Further notes on African warblers. Bull. Br. Ornithol. CI. 80: 147-152.
18. Zimmerman, D.A., Turner, D.A. and Pearson, D.J. 1996. Birds of Kenya and northern Tanzania. Lon- don, UK: A. & C. Black.