Archive for August 11th, 2006
ecologyasia.com
KUCHING: Sarawak has recorded a sharp increase in the population of wild swiftlets following the implementation of a sustainable management plan by the Forest Department for the harvesting of bird’s nest.Â
Researcher Dr Lim Chan Koon said the number of white-nest swiftlets in a cave in middle Baram, northern Sarawak, had shot up to 6,284 from 2,796 in 1997.Â
Dr Lim, who started the research on the breeding of swiftlets there five years ago, said that in another cave in Bukit Sarang, the swiftlet population had jumped to 660 from 396 in 2000.Â
Giving a talk on Sustainable Exploitation of a Natural Resource – Edible Bird’s Nest at the Malaysian Chemical Congress here, he said that under the first sustainable management plan introduced in 1998, no harvest of the product between January and April was allowed.Â
A second plan adopted two years later imposed a collection ban for any four continuous months, following which monthly harvests were permitted.Â
The four-month break allowed one complete breeding cycle of the swiftlets, including 30 days for nest-building, 25 days for incubation and between 45 and 49 days for the hatchings to grow until they leave the nest.Â
Dr Lim said uncontrolled and indiscriminate harvesting of bird’s nests over the years had caused a drastic decline in nest production and the wild swiftlets population in the Niah Cave.Â
“The swiftlet population there dropped from 1.7 million in 1935 to 200,000 in 1996 and 65,000 this year,” he added.Â
To arrest the sharp decline, the Forest Department imposed a four-month ban early this year on the collection of bird’s nest there.Â
The Niah Cave was once the state’s largest producer of black nests, with annual yields measured in tonnes. Â
Dr Lim said the government carried out two year-long comprehensive studies of the breeding of the black-nest and white-nest swiftlets in 1997 and 2000. Â
Of the five species of swiflets found in Sarawak, only three – black, white and glossy swiftlets – produce nests of commercial value. Â
Dr Lim said freshly collected white nests were worth between RM5,000 and RM7,000 per kilo in 1994. Â
He said commercial swiftlet farming in Sarawak had started where buildings with a cave-like environment were put up.
August 11th, 2006
springerlink.com
Donald R. Griffin1 and David Thompson1
(1)Â
The Rockefeller University, 10021Â New York, New York, USA
Received: 8 August 1981  Accepted: 7 December 1981 Â
Summary  The ability of cave dwelling swiftlets (Collocalia spodiopygius) to detect small cylindrical obstacles by echolocation was tested in a 3×9 m flight chamber. Although there was great individual variability, 6.3 mm obstacles were avoided much more often in total darkness than 1.5 wires (P<0.001). Flash photographs showed that the latter were avoided only by chance (about 50% misses). Obstacles 3.0 mm in diameter were avoided only slightly more often than 1.5 mm wires.
Even in the light these swiftlets avoided the obstacles in only about 75% of the trials, probably because gentle touches with the primary feathers caused little discomfort.
The 3.0 and 6.3 mm obstacles tended to be avoided more often on first encounters after they had been shifted horizontally by 10–30 cm, probably because the birds became more attentive.
References
Fenton MB (1975) Acuity of echolocation in Collocalia hirundinacea (Aves, Apodidae), with comments on the distributions of echolocating swiftlets and Molossid bats. Biotropica 7:1–7
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Griffin DR (1958) Listening in the dark. Yale University Press, New Haven, CT (reprinted 1974, Dover Publications, New York)
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Griffin DR, Suthers RA (1970) Sensitivity of echolocation in cave swiftlets. Biol Bull 129:495–501
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Griffin DR, McCue JJG, Grinnell AD (1963) The resistance of bats to jamming. J Exp Zool 152:229–250
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Henson OW, Schnitzler H-U (1980) Performance of airborne biosonar systems: II. Vertebrates other than microchiroptera. In: Busnel R-G, Fish JF (eds) Animal sonar systems. Plenum, New York, pp 183–195
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Jen PH-S, McCarty JK (1978) Bats avoid small moving objects more successfully than stationary ones. Nature 275:743–744
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Konishi M, Knudsen EI (1979) The oilbird: hearing and echolocation. Science 204:425–427
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Medway L, Pye JD (1977) Echolocation and the systematics of swiftlets, chap 19. In: Stonehouse B, Perrins C (eds) Evolutionary ecology. University Park Press, Baltimore, pp 225–238
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Neuweiler G, Moehres FP (1967) The role of spatial memory in the orientation. In: Busnel R-G (ed) Animal sonar systems, biology and bionics. Laboratoire de Physiologie Acoustique, Jouy-en-Josas, France, pp 129–140
Â
Smyth DM (1980) Studies on Echolocation in the grey swiftlet, Aerodramus spodiopygius. PhD thesis, James Cook University of North Queensland, Townsville, Australia
August 11th, 2006
nature.com
TOMÂ HARRISSON
Sarawak Museum, Kuching, Sarawak, Eastern Malaysia.
As a result of work initiated at the Sarawak Museum, Medway described and analysed the echo-location system of the cave dwelling “edible-nest swifblet”, Collocalia maxima, of Borneo1. Other work on C. salangana, which makes a moss nest (in Borneo), is as yet unpublished2; however, the taxonomy and nomenclature of all Collocalia are discussed by Medway3. The only other bird genus known to make use of echo-location is the central American oil-bird, Steatornis 4. In both genera the basic element is a loud click of short duration, comprising mixed frequencies, all audible to man.
1 Medway, Lord , Nature, 184, 1352 (1959). | ISI |
2 Novick, A. , Biol. Bull., 117, 497 (1959). | ISI |
3 Medway, Lord , Trans. Linnean Soc. (in the press, 1966).
4 Griffin, D. R. , Nat. Acad. Sci., 39, 884 (1953).
5 Medway, Lord , Ibis., 104, 45 (1962).
6 Smythies, B. E. , The Birds of Borneo, 68 (1960).
7 Cranbrook, Earl , and Medway, Lord , Ibis, 107, 258 (1965).
8 Marshall, A. J. , and Folley, S. J. , Proc. Zool. Soc. Lond., 126, 383 (1956).
9 Medway, Lord , Proc. Zool. Soc. Lond., 138, 313 (1962).
August 11th, 2006
ncbi.nlm.nih.gov
Thomassen HA, den Tex RJ, de Bakker MA, Povel GD.
Section of Evolutionary Morphology, Institute of Biology Leiden, Leiden University, Van der Klaauw Laboratory, The Netherlands. hthomassen@rulsfb.leidenuniv.nl
We recently reconstructed the troublesome swiftlet phylogeny using cytochrome-b mitochondrial DNA sequences. The relationship of the giant swiftlet (Hydrochous gigas) with swiftlets of the genus Aerodramus was, however, unresolved. In an attempt to clarify this issue, we now incorporated mitochondrial 12S rRNA and nuclear beta-fibrinogen intron 7 nuclear DNA sequences with the cyt-b sequences of six swiftlet, two swift, and one hummingbird outgroup species. A partition homogeneity (PH) test, used to determine the congruence of phylogenetic signal between two sets of sequences, suggested that cyt-b and Fib7 sequences were incongruent and therefore should not be combined. However, further analyses revealed that the apparent incongruence was probably due to the high amount of variation in cyt-b sequences. Separate and combined analyses of the three sequences unambiguously placed H. gigas as the sister-group of Aerodramus and supported monophyly of the swiftlets. These results were supported by analyses of combined NADH dehydrogenase subunit-2 (ND2) and cyt-b sequences of H. gigas in combination with sequences previously published by other workers. Recently, it was shown that the pygmy swiftlet (C. troglodytes)–in our phylogenetic analyses consistently placed with other, non-echolocating, Collocalia species–is in fact able to echolocate. Echolocation thereby lost its value to distinguish between different swiftlet genera. Furthermore, the phylogenetic distribution of echolocation can be explained either by its single evolution at the base of the swiftlets, with subsequent loss, or by independent evolution in Aerodramus and C. troglodytes. Because yet unpublished data suggest that only the auditory nuclei in swiftlet brains show adaptations to echolocation, the latter explanation seems the more likely one.
PMID: 16006151 [PubMed - indexed for MEDLINE]
August 11th, 2006
.ncbi.nlm.nih.gov
Lee PL, Clayton DH, Griffiths R, Page RD.
Department of Zoology, University of Oxford, United Kingdom.
Swiftlets are small insectivorous birds, many of which nest in caves and are known to echolocate. Due to a lack of distinguishing morphological characters, the taxonomy of swiftlets is primarily based on the presence or absence of echolocating ability, together with nest characters. To test the reliability of these behavioral characters, we constructed an independent phylogeny using cytochrome b mitochondrial DNA sequences from swiftlets and their relatives. This phylogeny is broadly consistent with the higher classification of swifts but does not support the monophyly of swiftlets. Echolocating swiftlets (Aerodramus) and the nonecholocating “giant swiftlet” (Hydrochous gigas) group together, but the remaining nonecholocating swiftlets belonging to Collocalia are not sister taxa to these swiftlets. While echolocation may be a synapomorphy of Aerodramus (perhaps secondarily lost in Hydrochous), no character of Aerodramus nests showed a statistically significant fit to the molecular phylogeny, indicating that nest characters are not phylogenetically reliable in this group.
PMID: 8692950 [PubMed - indexed for MED
August 11th, 2006