Rolland diver
| Rolland diver | ||||||||||
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Rolland diver ( Rollandia rolland ) |
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| Rollandia rolland | ||||||||||
| ( Quoy & Gaimard , 1824) |
The white-tufted grebe ( Rollandia rolland ) is a kind from the family of grebes . It is a relatively small, dark-colored grebe with conspicuously elongated, white tufts of feathers on the sides of the head. The Rolland diver is found only in South America and the Falkland Islands. There are three subspecies.
The IUCN classifies the Rolland diver as 
(= least concern - not endangered) because of its large distribution area .
Appearance
The Rolland diver is between 24 and 36 centimeters tall. The nominate form is the largest subspecies and reaches a body length between 33 and 36 centimeters. The wing length is 12.9 to 14.5 centimeters. Rolland divers weigh between 262 and 269 grams. Males tend to be slightly larger and have a slightly longer beak than the females.
The Rolland diver is predominantly black on the upper side of the body, with the plumage shimmering bottle green. The underside of the body is copper-brown, the flanks are chestnut-colored with isolated black spots. The elongated white feathers on the head run from the eye to the back of the head and form a white triangle on the sides of the head. Individual black feathers in between give this triangle a somewhat striped look. Towards the end of the breeding season, the plumage is usually a bit faded, the black parts of the body then appear more brown, the belly more cinnamon-colored. The eyes are bright dark purple, the beak is black. The feet and legs are blackish with yellow dots on top.
In the plain dress the throat is whitish, the throat is matt red-brown and the belly is light cinnamon-colored. The sides of the head are still whitish. Not yet sexually mature birds have brownish sides of the head, a whitish belly and a more yellow-brown neck.
voice
The Rolland diver is a little shouting rag diver who is usually not audible during the winter months. Croaking and growling calls can only be heard from a short distance. The sound repertoire includes a sharp jarrh or jrrh that can be heard when the Rolland divers are startled. If you feel threatened, a chourrh or hrrr can be heard. A buzzing jrrmmmmm can be heard during mating . The young birds have a similar repertoire of calls to the adults, but the pitch is slightly higher.
distribution
The range of the Rolland Diver is 4.8 million square kilometers. It stretches from northwestern Peru, Bolivia, Paraguay and the south of Brazil to Tierra del Fuego . The species is also found in small numbers in the Falkland Islands. The Rolland diver can often be found on lakes in the South American highlands at altitudes between 2,500 and 4,500 meters.
habitat
The Rolland diver uses a wide range of wetlands, but prefers to be found in waters that have a tight mosaic of areas densely overgrown with aquatic plants and open water areas. The typical habitat includes empty channels between swamps overgrown with reed plants. It is also often found on lakes and ponds that have dense floating vegetation. Where it competes with the flightless Titicaca diver for suitable habitat, it prefers to stay in these floating plant zones. In regions where small lakes and ponds dry out during the dry season, Rolland divers occasionally gather in thousands on larger lakes outside of the breeding season.
Way of life
The Rolland diver is very adaptable when it comes to food. It usually eats aquatic insects and their larvae, as well as small fish. He prefers to find his food in the twilight hours in the evening and in the morning.
During the breeding season, the Rolland diver is very territorial and vigorously defends its territory. During this time it is mainly in the plant belt and looks for most of its food there. Rolland divers who feel insecure typically lean their necks back and then look around while turning their heads. The tail is set up. Often they remain half submerged and motionless in the floating vegetation.
According to the current state of knowledge, Rolland divers enter into a relationship of several years. They prefer to build their nests in the reed belts along open waters. In Peru, Rolland divers can brood all year round, but usually most eggs are laid between October and December. The clutch usually consists of two eggs. The eggs are initially ivory in color, but become stained very quickly as they brood. The chicks remain mostly in the nest during the first week and are then gradually taken away by the adult parent birds. The breeding season and the nestling duration have not yet been investigated in detail.
Internal system
There are three subspecies. The nominate form endemic to the Falkland Islands is twice heavier than individuals of the subspecies Rollandia rolland chilensis . Of these, around 750 to 1,400 still occur on the Falkland Islands. The subspecies Rollandia rolland morrisoni is slightly heavier than R. r. chilensis and has a more powerful bill. It occurs exclusively on Lake Junín in central Peru. The subspecies R. r. chilensis is limited to the rest of mainland South America.
Duration
The population is estimated by the IUCN at 100,000 to 110,000 sexually mature individuals.
supporting documents
literature
- Josep del Hoyo et al .: Handbook of the Birds of the World. Volume 1: Ostrich to Ducks. Lynx Edicions, 1992, ISBN 84-87334-10-5 .
- Jon Fjeldså: The Grebes . Oxford University Press, 2004, ISBN 0-19-850064-5
- Hadoram Shirihai: A Complete Guide to Antarctic Wildlife - The Birds and Marine Mammals of the Antarctic Continent and Southern Ocean , Alula Press, Degerby 2002, ISBN 951-98947-0-5
- Robin and Anne Woods: Atlas of Breeding Birds of the Falkland Islands , Anthony Nelson, Shorpshire 1997, ISBN 0904614-60-3
Single receipts
- ↑ BirdLife Factsheet on Rolland Diver , accessed December 5, 2010
- ↑ Fjeldså, p. 144
- ^ Shirihai, p. 237
- ↑ Fjeldså, p. 144
- ↑ Fjeldså, p. 145
- ^ Shirihai, p. 237
- ↑ BirdLife Factsheet on Rolland Diver , accessed December 5, 2010
- ↑ Fjeldså, p. 145
- ↑ Fjeldså, p. 146
- ^ Woods, p. 38
- ↑ Fjeldså, p. 146
- ↑ Woods, p. 39
- ^ Shirihai, p. 237
- ↑ BirdLife Factsheet on Rolland Diver , accessed December 5, 2010
Web link
- Rollandia rolland inthe IUCN 2013 Red List of Threatened Species . Listed by: BirdLife International, 2012. Retrieved February 2, 2014.