Atitlan divers

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Atitlan divers
Systematics
Class : Birds (aves)
Order : Grebes (Podicipediformes)
Family : Grebes (Podicipedidae)
Genre : Podilymbus
Type : Atitlan divers
Scientific name
Podilymbus gigas
Griscom , 1929

The atitlan diver ( Podilymbus gigas ), also known as the poc after its characteristic reputation , was a bird in the grebes family . He was the closest relative of the binding diver ( Podilymbus podiceps ), however, was almost twice as large as this. It was endemic to Lake Atitlán in Guatemala at an altitude of 1700  m . Thanks to the research of the American biologist Anne LaBastille , the course of the decline has been quite well documented. LaBastille studied this species for over 25 years. She also wrote a book about her experiences at Lake Atitlan with the title "Mama Poc".

Features and way of life

The Atlantic diver reached a length of 46 to 50 cm. The reputation and appearance were quite similar to that of the tie diver. The top of the plumage was dark brown in color with dashed flanks. The underside was dark gray with white flecks. The head was almost black. The neck was dark brown in spring and mottled white in winter. The legs were slate gray. The eyes were brown. The Atlantic diver had very small wings with a length of 12 to 14 cm and was unable to fly.

The large, strong beak, the color of which varied from white in spring to brown at other times of the year, had a black vertical band in the middle. He was equipped with strong muscles and adapted to the cracking of crustaceans. This food specialization is unique among grebes. Crustaceans were extremely common in Lake Atitlán before the introduction of alien fish. In addition to crustaceans, the Atitlan divers also ate small fish and, to a small extent, aquatic insects.

The clutch consisted of 4 to 5 white eggs that were erected in the thick reeds. Both parents took part in raising the young.

Endangerment and extinction

The decline of the Atlantic diver began in 1958 when sport anglers released the black bass ( Micropterus dolomieu ) and the largemouth bass ( Micropterus salmoides ) in the lake. The predatory fish that were introduced increased so much that the diet of the Atitlánt divers decreased dramatically. The perches also ate the young birds. This and the destruction of the reed belts led to a drastic decline in the population from 200 in 1960 to only 80 in 1965.

In 1966, Anne LaBastille started a large-scale campaign to save the Atitlan diver. Through their efforts, a small protected area was created. In 1969 efforts were made to build an electricity station on the lake, which would have lowered the lake by 13 m and completely destroyed the reeds. This plan has not been put into practice, so that the population was able to recover to 210 individuals in 1973. At that time, however, there were two new threats. Holiday homes were built along the lake, and the population increased so much that the reed belts decreased even further. Another danger was the spread of the tie diver on Lake Atitlán. There was not only increased food competition between the two species, but also hybridization and thus a depletion of the gene pool.

In February 1976 there was a major earthquake in Guatemala. During this quake, the lake bed broke and an underwater runoff caused the water level to drop by over 6 m. The diving reserve was now on dry land and thousands of reeds had to be replanted to save the Atitlan divers. In 1982 this action was abruptly interrupted when Edgar Bauer, a longtime companion and supporter of Anne LaBastille, was murdered by strangers.

By 1980, 60% of the reed belt on the lake had been destroyed. In 1983 the number of divers had dropped to 32 animals. To the great horror it was found that most of the surviving birds were hybrids and were no longer able to reproduce. In 1989 only two copies were counted. When these two remaining birds also disappeared, the Atitlan diver was officially declared extinct.

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