Canarian Oystercatcher - Extinction

Extinction

This bird was last collected in 1913, and local fishermen and lighthouse keepers reported it had disappeared around 1940 (Hockey 1996), after a prolonged decline starting probably in the 19th century (Hockey 1987). It first – until the early 20th century – seems to have disappeared from Lanzarote, in accord with the general pattern of Canarian extinctions. By 1913, it was not reported to have been found outside the Chinijo Archipelago and Islote de Lobos in recent times (Bannerman 1963).

It is now considered extinct, because extensive surveys between 1956/57 and the late 1980s failed to find any evidence of the Canarian Black Oystercatcher's survival. It was officially declared extinct with publication of the 1994 IUCN Red List.

There have been sight records of altogether 3 black oystercatchers from the coast of Senegal, in 1970 (Jarry in Hockey 1987) and 1975 (Ziguinchor Region: de Ridder 1997), but these are very unlikely to refer to this species which was by all accounts a resident bird never recorded outside the Canaries archipelago on other occasions. Two fairly convincing records from Tenerife - apparently in July 1965 or 1968 at Puerto de la Cruz (Bannerman 1969), and in 1981 at El Médano (Kraft in Hockey 1987) -, on the other hand, could indicate that a small population managed to persist on uninhabited islets until the early 1980s, it is interesting to note that second-hand records from Tenerife also exists for the mid-19th century (Bannerman 1963). The Senegal records are nonetheless puzzling, as none of the black species of oystercatcher are known to occur even in the general area; melanism is known to occur occasionally in the Eurasian Oystercatcher (Stresemann 1927) which winters in the region; possibly the Senegal birds were such specimens.

Over-harvesting of intertidal invertebrates and disturbance by people was probably the main underlying cause of its decline (Hockey 1987), although predation by rats and cats has also been implicated. In addition, its eggs were said to be of exquisite taste and consequently much collected (Álamo Tavío 1975). Although oystercatchers generally have adapted to the commonplace loss of the first egg in their clutch to predators and readily re-lay lost eggs, if the present species' clutch was indeed only one, egg collecting would have had a major impact: collectors would have to disturb more breeding pairs per number of eggs gathered. Also, adult birds were apparently opportunistically shot together with more plentiful migrant waders in the winter months and sold as salmuera (preserved in brine) (Álamo Tavío 1975). It is unknown how far-reaching the direct impact of unsustainable agriculture practices, which led to widespread desertification especially of Lanzarote by the end of the 19th century (Hockey 1987), was. It might have altered local climate regimes, leading to increased pressure on intertidal habitat e.g. by increased flash floods causing silting of barranco mouths and delines in invertebrate populations there.

There exist apparently only 4 specimens (Bannerman 1963), three collected by Meade-Waldo in the BMNH and one collected by Bannerman in the World Museum Liverpool. The type specimen BMNH 1905.12.22.323 is a female shot at Jandía, Fuerteventura, on April 7, 1888 or 1889 (Bannerman 1963). About the same time in the next year, a couple was taken on Graciosa. From there is also the last known specimen – the male now in Liverpool – shot on June 3, 1913. It is not known what became of the specimen shot in April 1852, apparently also near Jandía, by Carl Bolle (Bolle 1855).