White-tufted Grebe
Rolland - divers ( Rollandia rolland )
The Rolland - divers ( Rollandia rolland ) is a species of the family of grebes. It is a relatively small, dark-colored grebes with conspicuous elongated, white feather tufts 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 - divers because of its large distribution area as the uncritical ( least concern ).
Appearance
The Rolland - diver reaches a height 24-36 inches. The nominate subspecies is the largest and reaches a body length of 33-36 inches. The wing length is 12.9 to 14.5 inches. Rolland - divers weigh 262-269 grams. Males tend to be slightly larger and have a slightly longer beak than females.
The Rolland - diver is on the body top predominantly black, the plumage shimmers bottle green. The body bottom is copper brown, the flanks are chestnut -colored with scattered black spots. The elongated white feathers on the head extending from the eye to the back of the head and form the sides of the head a white triangle. Single black feathers give this triangle between a slightly striped appearance. Towards the end of the breeding season the plumage is usually somewhat faded, the black parts of the body work then brownish, rather cinnamon belly. The eyes are bright dark purple, the beak is black. The feet and legs are blackish with yellow dots on the top.
In Plain Dress throat is whitish, the throat is dull reddish brown and the belly is pale cinnamon. The sides of the head are still whitish. Immature birds have brownish head sides, a whitish belly and a more yellow-brown neck.
Voice
The Rolland - diver is a little ruffreudiger grebes, which is not usually heard during the winter months. Croaking and growling calls are audible to humans only from a short distance. According to the repertoire heard a sharp jarrh or jrrh that is heard when the Rolland - divers are startled. Do they feel threatened is a chourrh or hrrr to hear. During mating jrrmmmmm a humming can be heard. The young birds have a similar Rufrepertoire like the adult, but the pitch is slightly higher.
Dissemination
The distribution area of the Rolland - diver is 4.8 million square kilometers in size. It extends from the north-west of Peru, Bolivia, Paraguay and southern Brazil until after the Tierra del Fuego. The species also occurs in small numbers before in the Falkland Islands. The Rolland - diver is often found in lakes of the South American highlands at altitudes of 2500-4500 meters.
Habitat
The Rolland - diver uses a wide range of wetlands, but is preferably present in such water bodies that have a tight mosaic of densely vegetated with aquatic plants and open water bodies. For typical habitat include unvegetated channels between overgrown with reed plants swamps. He is also commonly found in lakes and ponds that have a dense floating plants vegetation. There, where it competes with the flightless Titicaca divers to suitable habitat, he considers himself preferred to floating plants in these zones. In regions where small lakes and ponds dry up during the dry season, to Rolland - Divers gather outside the breeding season, sometimes by the thousands on larger lakes.
Way of life
The Rolland - divers is with respect to its food very adaptable. He eats normally aquatic insects and their larvae, and small fish. His food he seeks preferably in the twilight hours of the evening and the morning.
During the breeding season the Rolland - diver is very territorial and vigorously defended his territory. He keeps himself in this time mainly in crop belt on and studied there and most of its food. Rolland - divers who feel insecure, typically lean your neck back slightly and then ogle at their head turning area. The tail is set up there. They often remain half submerged and motionless in the floating plants vegetation.
Rolland - divers go according to the current state of knowledge a perennial pair-bonding. They build their nests preferably in the reed belts along open waters. In Peru, Rolland - divers can proceed to breed all year round, but usually most clutches are laid in the period October to December. The nest usually consists of two eggs. The eggs are off-white, early, however, are in the course of breeding very quickly spotted. The chicks remain during the first week mostly in the nest and are then gradually taken away by the adult parent birds. The incubation period and the nestling period to date are not thoroughly investigated.
Inside systematics
There are three subspecies. The endemic in the Falkland Islands nominate is twice heavier than individuals of the subspecies Rollandia rolland chilensis. From this come about 750-1400 prior to the Falkland Islands. The subspecies Rollandia rolland morrisoni is slightly heavier than R. r. chilensis and has a strong trained beak. It comes exclusively at Junín Lake in central Peru before. The subspecies R. r. chilensis is limited to the rest of the South American mainland.
Stock
The population is estimated by the IUCN on 100000-110000 mature individuals.