Although a great deal has been written about the history, both human and biological, of the Mascarenes, there has been no synthesis of the available material from an ecological point of view; this chapter is an attempt to fill this gap. I make no apologies for covering ground familiar to Mascarene specialists, since there is at present no suitable introductory work for biologists new to the area; also much of the original material is rare, and even many of the secondary sources are not easily accessible outside the islands themselves.

Already known to Arab navigators, the Mascarenes were ‘discovered’ by Europeans in the early sixteenth century. The exact dates at which each island was first sighted by the Portuguese have long been a matter of debate, but are of little concern here as no useful accounts of Portuguese visits apparently survive. North-Coombes (1980b) reviewed the history of Portuguese movements in the Indian Ocean in the sixteenth century and concluded that they very rarely landed in the Mascarenes, and then probably only on Reunion. The most they appear to have left us by way of description is a note in 1728 that “Santa Apelonia” (=Reunion) had “plenty of fresh water, trees, birds and fish” (ibid.). The next description of the islands dates from the Dutch visit to Mauritius in 1598 (see e.g. Pitot 1905, Barnwell 1948). Réunion was described briefly by Verhuff in 1611 but the earliest adequate account is Tatton's in 1613 (Tatton 1625, Lougnon 1970). Only the scantiest accounts of Rodrigues exist prior to Leguat's 2-year stay on the island in 1691-3 (North-Coombes 1971).

Introduction

Rodrigues is the smallest and most ecologically devastated of the Mascarenes, retaining only three species of endemic land vertebrates from the wealth and diversity that existed there when the island was first discovered (North-Coombes 1980a, Chapter 1). The survivors are two birds, a warbler and a fody Foudia, considered here, and a flying-fox Pteropus rodricensis (Cheke & Dahl 1981). The ecological history of the island is reviewed in Chapter 1.

As the status of the Rodrigues Warbler Acrocephalus (Bebrornis) rodericanus was giving rise to “Very grave anxiety” with three-star rating in the Red Data Book (Vincent 1966), I lost no time in visiting Rodrigues after establishing the BOU Expedition's base in Mauritius. Since the distribution of my original report (Cheke 1974a) on the status of the endemic vertebrates, Rodrigues has been the focus of more biological and conservation interest than at any time since the famous Transit of Venus expedition of 1874 (Hooker & Günther 1879). Flying-foxes (Durrell 1977a, b) and Fodies (Cheke 1979a) have been captured for captive breeding, and all the species have been the subject of some further study (Cheke 1979a, 1980, Mungroo 1979, Carroll 1982a, b; C. G. Jones unpubl.). Particular recommendations for conservation of the vertebrates are to be found in a variety of reports already produced (Cheke 1974a, 1978a, b, 1980, Carroll 1982b, Jones & Owadally 1982a). This chapter discusses the general biology of the two birds.

I visited Rodrigues four times in 1974: 16-20 January, 25 February-13 March, 12-18 July and 12-15 December. Dr A. W. Diamond (AWD) and A. S. Gardner (ASG), visiting 4-15 February and 18-24 September 1975 respectively, have very kindly allowed me to use their observations.

I have been invited to introduce the book arising out of the BOU Mascarene Island Expedition because this project took place during my term of office as President of the BOU. I am pleased to take advantage of this gesture.

The BOU has a long tradition of ornithological exploration. During the latter part of the last century many distinguished members made important collections in remote parts of the world, and The Ibis in consequence was full of long faunistic lists. Such ventures were privately financed and leisurely in tempo. From time to time, the BOU organized its own larger-scale expeditions, financed at least in part from its own funds, notable examples being the Jubilee Expedition to Dutch New Guinea (1909-11) and the Centenary Expeditions to Ascension Island (1957-9) and the Comoro Islands (1958). The Jubilee Expedition was over-ambitious and failed to reach its final destination, though doing useful work in an alternative location. Both the Centenary Expeditions of 1958/9, however, were highly successful, thanks to the care with which they were organized and to the skilled leadership of Dr Bernard Stonehouse in Ascension and of C. W. Benson in the Comoros. Previous expeditions had been chiefly concerned with collecting, at a time when museum collections were still far from complete. This was, however, a diminishing requirement; concern for the conservation of rare species was gaining momentum and studies of birds in the field had emerged as the primary interest among ornithologists. Although limited collecting was necessarily involved in the Com oros in order to fill important gaps in existing material, both Centenary Expeditions concentrated on ecological and behavioural studies.

Mauritius Kestrel Falco punctatus (Temminck 1823; mangeur de poules (mañzer d'pul)

Introduction

The Mauritius Kestrel was a little-known falcon until the current series of studies on its biology was started in January 1973 by Dr S. A. Temple (Temple 1977a, McKelvey 1977c, 1978, Jones 1980d, Jones et al. 1981, Jones & Owadally 1982b). I have drawn widely upon the unpublished manuscript of Temple (1978c) and have endeavoured to bring it up to date in the light of recent research. (Some of the following material also appears in Jones & Owadally (1985) (Ed.).)

Taxonomy

Brown & Amadon (1968) placed the Mauritius Kestrel in a super-species with the European Kestrel F. tinnunculus, Moluccan Kestrel F. moluccensis, Australian Kestrel F. cenchroides, Madagascar Kestrel F. newtoni, Seychelles Kestrel F. araea, and perhaps the American Kestrel F. sparverius. They also regarded the Lesser Kestrel F. naumanni, Greater Kestrel F. rupicoloides and the Fox Kestrel F. alopex as being typical kestrels. Fox (1977) kept the above grouping but gave them sub-generic status. Cade (1982) kept the sub-genus, calling it tinnunculus, but considered F. rupicoloides and F. alopex to have diverged earlier from the rest of the group.

Sub-generic status for the typical kestrels is more desirable than placing them in a single super-species. Within Brown & Amadon's super-species, F. punctatus and F. araea are too divergent to justify such a close grouping. It would, however, be reasonable to place the kestrels which appear to be of recent radiation from F. tinnunculus, or a common ancestor, in a single super-species. These would be the allopatric F. tinnunculus, F. sparverius, F. newtoni, F. cenchroides and F. moluccensis.

Introduction

General

Already famous in the seventeenth century for the Dodo and the quality of its ebony, Mauritius is biologically the best known of the Mascarene Islands. However, ecological studies of the native biota date only from the 1930s, with Vaughan & Wiehé's pioneering work (1937, 1941) on the forests. The basic natural history of some of the birds has been known for two centuries, but no systematic ecological studies had been done before 1973 when Dr S. Temple and the BOU Expedition began work. Most of the native forest birds, all endemic or shared only with Réunion, had been considered endangered for over a century (E. Newton 1865b), so their study was overdue. The historical background of the abundance and distribution of Mauritian birds is given by Clark (1859), E. Newton (1861b), Carié (1904), Meinertzhagen (1912), Guérin (1940-53), Rountree et al. (1952) and Newton (1958a). Since 1973, numerous publications on the island birds and their conservation have appeared (e.g. Procter & Salm 1975, Cheke 1978a, Jones & Owadally 1982a, and others cited in appropriate places in the text), and F. Staub has written two books on the birds’ natural history and identification (in French, 1973a; revised in English, 1976). This paper gives the detailed results of the BOU Expedition's observations.

Expedition personnel were based in Mauritius. I was on the island from late September 1973 to late February 1975 except for absences in December 1973, late April to mid-May, June, August and November 1974, and mid-February 1975.1 also made short trips to Rodrigues on several occasions. I re-visited the island briefly in October 1978 under the auspices of the Jersey Wildlife Preservation Trust.

One of the aims of the BOU Mascarene Islands Expedition was to obtain as complete a record as possible of the voices of the endemic birds. To this end I spent the breeding seasons of 1973 and 1974 in the islands, and recorded all the endemic land-birds. This report is concerned solely with vocalisations and associated behaviour. Some comparisons are made, where appropriate, between the voices of Mascarene birds and related birds elsewhere.

Itinerary and methods

The dates of my visits to each island, and the study areas I used, are listed in Table 1.

In both seasons the breeding cyle of all species had begun, so I could not study the initial period when territories were being set up and pairs formed. For some species, the time spent in the islands was not long enough for me to be able to determine the behavioural context of all the calls recorded. The passerine species were easier than the non-passerines to observe and tape-record, so that results for them are more complete.

Weather conditions were better for recording in 1974 than in 1973, when frequent high winds and cyclonic disturbance gave rise to background noise. I spent an average of 11 hours per day in the field. On return each night, whenever possible, a primary edit was done, the edit books written up, and the tapes re-spooled onto 7-inch reels. ‘Playback’ tapes also were prepared to attract and stimulate certain species, especially Zosterops chloronothos, whose population density was so low in any given locality that playback proved very useful in helping to locate individuals and to hold them in an area for a short period.

Details of weights and measurements are brought together in this chapter to facilitate comparisons and for easy reference. The data are given in Table 1, the text being in effect a commentary on the table; some species do not require further comment. The location of the museum specimens used in this study is given in Table 3. Conventions in text tables are the same as in Table 1.

Mauritius Kestrel Falco punctatus

In Table 1 weights of captive Kestrels are from birds in good body condition with empty crops weighed by CGJ prior to feeding. These weights are similar to the few records from wild birds. Temple's (1978c) weights (male: 178 g; 2 females: 221 g, 240 g) were of wild-caught adults weighed later in captivity (Temple in lift, to CGJ); these weights are well above the weight range we have, but two overweight young females have reached 252 and 253 g in captivity. Egg weights from wild birds are a clutch weighed after 8 days of incubation; details of calculated weights in relation to egg shell thinning are given in Chapter 5.

Ecological correlates of linear measurements and comparisons with other species are given in Chapter 5. The measurements given in Table 1 are as found, and include museum specimens with worn wings and/or tail, but in the majority of 50 skins the extent of wear ranges only from 1 to 4 mm, only 7 approaching the 20 mm reported by Temple (see Chapter 5). Only 23 of the 50 museum specimens were gonadally sexed; the others have not been used in the table.

Four species of petrel breed in Reunion, two in the genus Puffinus and two in Pterodroma. A third gadflypetrel, Pterodroma arminjoniana, nests on Round Is., off Mauritius, and brings the total number of petrels nesting in the Mascarenes to five. Breeding stormpetrels (Hydrobatidae) are absent, and this is true for the Indian Ocean as a whole, where members of this family occur only on migration.

The two endemic gadfly-petrels, Pterodroma baraui and P. aterrima, were the subject of earlier papers (Jouanin 1963, Jouanin & Gill 1967, Jouanin 1970a) where I tried to bring together all information that was then known. It seems useful also to publish details of the two shearwaters, although they are common and widespread species, and to add some unpublished observations on the Pterodroma species made since my previous papers were published.

Wedge-tailed Shearwater Puffinus pacificus

The Wedge-tailed Shearwater is widely distributed throughout the tropical and subtropical parts of the Indo-Pacific region. The various described races are doubtfully tenable (Jouanin & Mougin 1979), although there are slight statistical differences in measurements (see Murphy 1951), and colour phases occur in more or less stable ratios in different areas; only the dark phase is known from the Western Indian Ocean.

Créoles who live up in the mountains in Réunion often report cries of nocturnal birds resembling babies crying. I have been given this information at Hellbourg and Dos d'Ane, and by A. S. Cheke (in litt., hereafter ‘ASC’) at St.-Joseph. Jadin & Billiet (1979) heard cries of this type at Pavilion, Petit Serré and from the road under the sea cliffs between St.-Denis and La Possession.

Background to the expedition (AWD)

In 1970 the Council of the British Ornithologists’ Union decided on a policy of promoting expeditions to study ecologically little-known endangered species (Mountfort 1970). The first proposed survey was to be in Cuba, but for various reasons this plan had to be abandoned. However, a timely visit to Dr D. W. Snow, then Chairman of the Research Committee, by Dr France Staub, then Chairman of the Mauritian National Section of the International Council for Bird Preservation, drew the Union's attention to the Mascarenes and the proposed expedition was formally announced in January 1972 (Ibis 114: 138). The IUCN Red Data Book vol. 2 (Aves) (Vincent 1966, partly revised 1971) listed 11 species or forms from the Mascarenes, four of which were given ‘three-star’ ratings, their rarity giving rise to ‘very grave anxiety’ as to their prospects for survival. None of these birds was well known biologically and there was thus a strong case for further investigation. The urgency of action and a plan for research had already been outlined by F. R. G. Rountree as early as 1950 (Rountree 1951), but it is doubtful whether his report was seen by many outside Mauritius, and the matter thus lay fallow for another 20 years, there being no one available locally to do the necessary work. Since 1950 the natural habitat has been substantially reduced, and the birds thus made rarer.

Coincidentally, and independently, Dr Stanley Temple then of Cornell University had put forward a project to study the endangered birds of prey in the Indian Ocean, with particular attention to the Mauritius Kestrel Falco punctatus, the rarest of them.

Chapter 1 has outlined the extent to which many endemic Mascarene Island birds have become extinct, probably during the last 300 years since man arrived on the islands. Thirty extinct species are recognised today (Cowles in press), but of these only five are known from skins preserved in museums and institutions throughout the world. Four of these species, the Mauritian Blue Pigeon Alectroenas nitidissima, the Mascarene Parrot from Réunion Mascarinus mascarinus, the Rodrigues Parakeet Psittacula exsul and the contentious Leguat's Starling Necropsar (Orphanopsar) leguati of unknown locality, are represented by a total of only eight skins. The Reunion Crested Starling Fregilupus varius was better represented by 24-25 skins, all documented by Hachisuka (1953), although fewer survive today (Chapter 1). The remaining 25 extinct species are known only from fossil bones discovered in caverns and deposits on the three islands. In number these range to well over 200 elements for the better known Solitaire of Rodrigues Pezophaps solitaria and perhaps the Mauritius Dodo Raphus cucullatus, but the remaining species are unfortunately known from very few bones or bone fragments.

Identifications based on the osteological evidence are in some instances substantiated by field descriptions and illustrations in journals of seventeenth- century voyagers to the islands. The visitors who added notably to early ornithological history were Leguat (1708), on Rodrigues in 1691, Dubois (1674), on Reunion 1671-2, and Van Neck, on Mauritius 1598 or 1599 (see Strickland 1848). The other voyagers were listed by Hachisuka (1953) and Cheke (Chapter 1). These brief accounts of the flora and fauna of the islands were compiled by people with little ornithological knowledge, but they do provide a most valuable and historical record of the lost avifauna of the islands.

The challenge of managing lands, resources, and people to sustain viable populations of large vertebrates and other taxa is enormous. Conservation biologists (e.g., Soulé, 1980; Frankel, 1983; 1984) have emphasized that few existing protected areas can provide this service for all desired species found within their bounds. However, most analyses of the ability of reserves to sustain viable populations (e.g., Soulé, 1980; Frankel and Soulé, 1981; Schonewald-Cox, 1983) consider each jurisdictional unit as a separate entity. This reflects a frequent lack of cooperation and the conflicting priorities and management practices that can exist in adjacent areas (Schonewald-Cox and Bayless, in press; Harris, 1984). The future of many species would not be nearly as bleak if managers who share species of concern would cooperate to minimize conflicts and reach mutual conservation goals.

The effectiveness of cooperation in attaining conservation goals has been demonstrated by The Nature Conservancy since its inception in 1951 (Jenkins, 1984). More recently, the value of cooperation was recognized in the first recommendation of the Terrestrial Animal Species Panel at the US Strategy Conference on Biological Diversity (US Dept. of State, 1982): ‘… identify, establish, and manage a worldwide system of national parks and other conservation areas to insure the perpetuation of all major ecosystem types and the diversity of organisms and processes they contain … in a way which promotes local economic development compatible with long-term ecosystem integrity and the sustained use of natural resources.’