The Fuerteventura Stonechat Project 1985.

Abstract

Listed as "Rare" in the recently revised ICBP/IUCN Bird Red Data Book (Collar and Stuart 1985), the Fuerteventura Stonechat Saxicola dacotiae is confined to the arid island of Fuerteventura in the eastern Canary Islands. It is one of four endemic birds currently found in the archipelago, and until recently one of the least known. Since its discovery in the late 19th century, information on the population and its pattern of distribution has been fragmentary. Collar and Stuart (1985) provide a concise review of references to the species, but, apart from a recent qualitative study by Collins (1984), the chat has received little scientific attention.

The chat remains one of the most restricted species in the Western Palearctic. Despite the presence of similar habitat, it has never been recorded from Lanzarote which lies only 11 km to the north-east of Fuerteventura. Bannerman's records (Bannerman 1913) on the islets of Allegranza and Montaña Clara to the north of Lanzarote are anomalous and have never been repeated.

This project was launched to provide an up-to-date assessment of the state of the chat population and examine the need for conservation measures. Before the present study, the majority of the population was believed to be patchily distributed near the coast. Following a general survey of the island's avifauna in 1979 (Shirt 1983) when up to 35 pairs were located, Collar and Stuart (1985) suggested a total population of 50-150 pairs. This figure was not based on a comprehensive census, being derived only from observations of the species' scarcity across its known range. Collins (1984) shared this view, proposing a figure of 100-200 pairs. Fewer casual observations on a similar survey in 1984 (Osborne 1986), led us to believe that the chat was, at least, temporarily absent from sites where it should have been found. We were anxious to find out if the species' future was really threatened or whether it had simply been overlooked.

A project team of nine ecologists from Britain and the Canary Islands worked on Fuerteventura from 18 February to 11 March for a total of 16 man-weeks. Our visit was timed to coincide with the start of the breeding season, and we arrived to find what was being described by islanders as the wettest spring for a decade. Most birds were already breeding and the chats were very conspicuous; calling noisily and frequently making aerial sallies to catch insects. We had four main objectives: (1) to obtain an accurate estimate of the population, (2) to establish a baseline census for subsequent population monitoring of population trends, (3) to map the distribution of the population and (4) to conduct a preliminary investigation of the species' habitat requirements.

Apart from being one of the few Western Palearctic species which merited treatment in the revised ICBP/IUCN Bird Red Data Book, the chat is also likely to be listed for inclusion in the revised version of Annex 1 of the EEC Wild Birds Directive (following Spain's entry to the European Economic Community in 1986). In view of this it became important that we obtained an accurate figure for the population. Eventually, data on the size of the breeding and non-breeding populations and their distribution will be needed for elaborating criteria in order to rank the importance of sites on the island, and for their subsequent designation as Important Bird Areas (IBA) in. accordance with existing EEC legislation. As the chat is endemic to Fuerteventura any areas holding a significant proportion of the population will be of high conservation priority within the EEC. To further the possible designation of IBAs, we also collected observations on other rare bird species on the island. This data does not feature in the report, but has been made available to the appropriate interested authorities. All other bird records are presented in the form of a systematic list (Appendix I).

Fuerteventura is the second largest island (1653 sq km) in the archipelago, but the least populated. The dessication of Fuerteventura is a comparatively recent state. Five centuries ago the island retained good woodland cover and lush grassland (Collar 1983), but now the landscape is an arid mixture of stony plains, sand dunes and eroded mountain ranges. Low rainfall and overgrazing by the numerous goats prevent revegetation and ensure that the cycle of desertification continues. Collar and Goriup (1983) and Osborne (1986) complement this report, and a broad review of the geology, history and biota is contained in the former.