New fossil records of choughs genus Pyrhocorax in the Canary Islands: hypotheses to explain its extinction and current narrow distribution

Authors: Juan Carlos Rando

E-mail: jcrando@ull.es

Published: Volume 54(2), December 2007. Pages 185-195.

Language: English

Keywords: Island biogeography, Canary Islands, extinction, palaeontology, Pyrrhocorax graculus and Pyrrhocorax pyrrhocorax

Summary:

Aims: To describe the new fossil records of the genus Pyrrhocorax in the Canary Islands. The main goal will be to use these data to discuss about the possible scenario of colonization and extinctions events of this genus in the canary archipelago. Specifically, the possible causes affecting the current narrow distribution of the red-billed chough in the Canary Islands are discussed. Actually this species only breeds in La Palma, the most north-westerly island of the archipelago.

Location: Four caves in three islands (La Palma, Tenerife and La Gomera) of the Canary archipelago.

Methods: Fossil bones where identify through the combination of biometric and morphologic traits, and using Discriminant Function Analysis (DFA).

Results: The bones studied were contrasted with both red-billed chough Pyrrhocorax pyrrhocorax and alpine chough P. graculus. Bones of the alpine chough were found on both Tenerife and La Palma, the highest islands in the Canary archipelago. These are the first records for this bird in the Canary Islands. On the other hand, the fossil record shows that red-billed chough was distributed at least on La Palma, Tenerife and La Gomera.

Conclusions: It is suggested that the colonisation of choughs could be related to climatic changes affecting to the distribution of mainland biota during the Upper Pleistocene period. Alteration of island ecosystems by human arrival is also suggested asan hypothesis to explain local extinctions in the Canaries, such as has been proposed in other insular environments. Two main hypotheses to explain the current narrow distribution of red-billed chough are discussed: (i) It is the result of the survival of a part of the ancestral pool of choughs living in the Canary Islands; (ii) It is a direct consequence of new colonisation and/or reintroduction event.

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