Mauritian salangans
| Mauritian salangans | ||||||||||||
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Mauritian salangans in La Possession , Réunion |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Aerodramus francicus | ||||||||||||
| ( Gmelin , 1789) |
The Mauritian Salangan ( Aerodramus francicus , Syn . : Collocalia francica ) is a species of bird from the family of sailors (Apodidae). The species belongs to the salangans and is one of the smaller representatives of this group with a body length of 10.5 centimeters. Like most salangans, the Mauritian salangan has the ability to echolocate , which enables it to visit the breeding colonies lying in caves. It occurs exclusively in Mauritius and Réunion , so it is endemic to these two Mascarene islands . The population is estimated at 10,000 to 20,000 individuals. Because of this relatively small total population and the narrowly limited distribution area, the species was included in the IUCN 's warning list ( near threatened ).
features
Appearance
The Mauritian salangan is a typical salangan with a gray-white rump and a slightly forked tail. The body length is approximately 10.5 centimeters, the wing length is between 108 and 117 millimeters, on average 112 millimeters. The weight is usually between 9.2 and 9.6 grams, gender-specific differences in size are not discernible. The legs are very short and black.
The black-brown top of the head and the brown ear covers, in conjunction with the significantly lighter gray-brown throat, give the impression of a head cap. The color of the upper side is dark brown like that of the top of the head, with the exception of the clearly lighter gray-white rump, which is very indistinctly differentiated from the surrounding darker plumage. The underside is quite light gray-brown, except for the somewhat darker under-tail-coverts. The top of the wings appears even darker than the rest of the top, especially on the outside. On the lighter underside of the wing, the wing feathers and large arm covers appear paler than the darker medium and small arm covers. The sexes are outwardly indistinguishable. The representatives of Réunion show certain differences compared to the conspecifics of Mauritius , they are darker colored, especially in the area of the under tail coverts. Possibly these differences could justify the recognition of different subspecies for the two islands.
Since the Mauritian salangan is the only species of salangan found on the Mascarene Islands, there are normally no problems with identification. The Mauritian salangane differs from the similar, somewhat larger Seychelles salangane in that it has somewhat shorter wings, a smaller beak, a somewhat darker underside and a significantly lighter rump.
Vocalizations
The gossiping cries of the Mauritian salangans can be heard especially near the nesting holes. Inside the cave, especially when the birds fly in or out, a constant sequence of clicks used for echolocation can be heard. Such clicks can occasionally also be heard outside the nesting holes.
distribution
The Mascarene Swiftlet is on the two Maskareneninseln Mauritius and Reunion endemic . Together with the closely related Seychelles salangan ( Aerodramus elaphrus ), it is the most western species of salangan. These two species represent a biogeographical peculiarity, as there is no other species of salangan within a radius of 2000 kilometers. The geographically next Salanganenart is in South India and Sri Lanka occurring Malabarsalangane ( Aerodramus unicolor ). The Mauritian Salangane is a resident bird ; there were supposed sightings in Madagascar, but these are dubious.
habitat
Mauritian salangans can be found in all habitats on the islands. Lava tunnels are typically used as nesting holes . Floor holes that allow access through the cave roof often serve as entrances. Sometimes a ditch has formed due to the collapse of the cave roof, which gives them access to the cave. The exit points of underground watercourses also serve as entrances. On Réunion, Mauritian salangans have also settled in a disused railway tunnel between Saint-Denis and La Grande Chaloupe .
Behavior and food acquisition
The activity of the birds is limited to times of daylight, although the animals are able to find their way in the dark of the nest caves by means of echolocation. The Mauritian Salangans also come back to their nesting sites in the caves outside of the breeding season and spend the night in pairs. As a rule, they arrive in the nest cavity less than 20 minutes and a maximum of 35 minutes after dark. In contrast, the Seychelles salangana is active long after dark; she has the significantly larger eyes.
The behavior of the Mauritian salanganese is typical for small species of sailors. When foraging for food, they can be found individually or in small groups, rarely larger swarms. When they do not hunt over inland lakes, they are usually more than 20 meters above the ground, only occasionally they fly lower. In good weather, they also look for food at significantly higher altitudes. In various studies on Mauritius and Réunion of a total of five bales of food that the adult birds had collected to feed their young, two-winged birds (Diptera) formed the main component of the diet with a share of 53 to 60 percent. Also detected with shares in part between 10 and 20 percent were Hemiptera (Hemiptera), dust lice (Psocoptera), beetles (Coleoptera) and Hymenoptera (Hymenoptera), arachnids were detected only in the collected Réunion bales, these were exclusively spiders ( Araneae), their share was 3 percent. In the bales of food examined in Mauritius, the size of the prey animals collected was remarkably uniform, between 1.6 and 3.2 millimeters, with a few exceptions, which were mainly swarming ants between 5.2 and 8 in size , 2 millimeters acted.
Reproduction
Mauritian Salangans breed all year round, in Mauritius, unlike all other land birds that occur there, no connection between breeding and seasons can be determined. Even within a colony, breeding does not take place synchronously. The nest is a self-supporting half-shell, which is attached like a console to more or less vertical surfaces in the area of the cave roof. The nest consists mainly of plant material or lichen , such as beard lichen . The “needles” of the casuarina are used as nesting material and, in the inland nesting caves, conifer needles are occasionally used . These components are stuck together with saliva, but the concentration of saliva is only high in the area of the nest base compared to other salangan species. If there is a loss of clutch, it takes four to six weeks until the new nest is ready and the eggs are laid, nest building takes longer after a breeding break.
The clutch usually consists of two eggs, these are chalk white and on average 19.4 × 13.0 millimeters in size. The incubation period lasts about 21 to 23 days, the young hatch largely synchronously and remain in the nest for 45 to 55 days. If the nests are not destroyed by humans, the breeding success is very high: in an investigation of two caves in Mauritius, the young hatched from 84 percent of the clutches and these, with a few exceptions, flew out. However, a significant proportion of the nests were vandalized and destroyed during the investigation. If the birds are undisturbed, two, possibly three broods per year can be assumed. With four nests observed, the break between two successive successful broods was three weeks.
Existence and endangerment
With 4400 square kilometers, the distribution area covers almost the entire island area of Mauritius and Réunion . The Mauritian salangan used to be more common on Mauritius than on Réunion, but now it is the other way around due to contrary developments. On Réunion the total number of adult individuals is estimated to be at least 10,000, an estimate on Mauritius came to a minimum of about 2,250 to 2,600 birds. Since the distribution area is small and the population is quite low, the species was included in the IUCN 's warning list . If the population trend were to develop negatively on Réunion as well, the classification in a higher protection category would be necessary.
Today the utilization of the nests for the " swallow's nest soup " no longer plays a role; in the 19th century this was still a smaller trade. But rumors still linger in the 21st century that the nests could be used to enhance the effects of cannabis . In addition, the caves in Mauritius are used for a wide variety of activities, such as illegal gambling. Some of the nests are also destroyed by vandalism or the birds are fumigated by burning car tires at the cave entrance. On Réunion, the planning of tourist development with canyoning and other cave tourism are a possible threat, and disturbances by cave explorers impair the breeding success of the birds. The designation of protected areas may be required.
Systematics
In 1970, all species of salangan originally assigned to the genus Collocalia were re-divided into three genera: All species that had the ability to echolocation were placed in the genus Aerodramus . Since then, however, it has been proven that the dwarf alangans ( C. troglodytes ) , which belong to the genus Collocalia , are also echolocating species. However, the monophyly of the species previously assigned to the genus Aerodramus has also been confirmed by molecular genetic studies.
The sister species of the Mauritian salangan, the Seychelles salangan , was considered by some authors as a subspecies of the Mauritian salangan. Morphological differences, different subspecies of the parasitic pine louse species (genus Dennyus ) and, above all, the results of molecular genetic studies speak against the combination of these two species . Using a molecular clock calibration of 2 percent per million years, the results of the study of mitochondrial DNA lead to the assumption that a common ancestral species of the Mauritius and Seychelles salangans split into the two separate species 500,000 years ago. It is also assumed that this parent species separated from the other salangan species about a million years ago.
literature
- Phil Chantler, Gerald Driessens: A Guide to the Swifts and Tree Swifts of the World . Pica Press, Mountfield 2000, ISBN 1-873403-83-6 .
- Anthony W. Diamond (Ed.): Studies of Mascarene Island Birds. Cambridge University Press, Cambridge 1987, ISBN 0-521-25808-1 .
- Anthony Cheke , Julian Pender Hume : Lost Land of the Dodo. An Ecological History of Mauritius, Réunion & Rodrigues. T & AD Poyser, London 2008, ISBN 978-0-7136-6544-4 .
- Josep del Hoyo , Andrew Elliot, Jordi Sargatal (Eds.): Handbook of the Birds of the World . Volume 5: Barn-owls to Hummingbirds . Lynx Edicions, 1999, ISBN 84-87334-25-3 .
Web links
- Aerodramus francicus onthe IUCN Red List of Threatened Species .
- Audio recordings and videos for Aerodramus francicus in the Macaulay Library of the Cornell Lab of Ornithology
Individual evidence
- ↑ Aerodramus francicus in the IUCN Red List of Threatened Species 2010.4. Listed by: BirdLife International, 2008. Retrieved June 2, 2011.
- ↑ a b c d e f Phil Chantler, Gerald Driessens: A Guide to the Swifts and Tree Swifts of the World . P. 128f.
- ^ Anthony William Diamond (Ed.): Studies of Mascarene Island Birds. P. 413f.
- ^ A b Nicolas Barré, Armand Barau: Oiseaux de la Réunion. Les Editions du Pacifique, Paris 2005, ISBN 2-87763-263-6 , pp. 160f.
- ↑ a b c d e f g h i Anthony S. Cheke: Mascarene Swiftlet Collocalia (Aerodramus francica (Gmelin 1788)). In: Anthony William Diamond (Ed.): Studies of Mascarene Island Birds. Pp. 161-171.
- ↑ a b Kevin P. Johnson, Dale H. Clayton: Swiftlets on islands: genetics and phylogeny of the Seychelles and Mascarene swiftlets. In: Phelsuma. No. 7, 1999, pp. 9-13 ( PDF; 425 kB ).
- ^ A b Anthony S. Cheke, Julian Hume: Lost Land of the Dodo. An Ecological History of Mauritius, Réunion & Rodrigues. P. 190.
- ^ Anthony William Diamond (Ed.): Studies of Mascarene Island Birds. P. 406.
- ↑ a b BirdLife International: Species Factsheet - Mascarene Swiftlet ( Aerodramus francicus ) . Retrieved June 11, 2011.
- ^ Henri A. Thomassen, Robert-Jan den Tex, Merijn AG de Bakker, G. David E. Povel: Phylogenetic relationships amongst swifts and swiftlets: A multi locus approach. In: Molecular Phylogenetics and Evolution. 37, 2005, pp. 264-277, doi : 10.1016 / j.ympev.2005.05.010 .
