The Yelkouan (puffinus?) yelkouan W. R. P. Bourne, E.J. Mackrill, A. M. Paterson and P. Yesou n the classical Greek period, 2,500 years ago, two had Ialready given rise to immortal legends in the eastern Mediterranean. The Siren was reputed to lure seafarers to their doom by singing upon outlying rocks, a habit found in a variety of marine , but particularly characteristic of on misty nights. The larger of the area in particular, once known as the Mediterranean Shearwater and now as Cory's Shearwater, which still bears the local vernacular name Diomedee and scientific name Calonectris diomedea in memory of one of the Greeks who besieged Troy (Winthrope 1973), has a voice very like a foghorn. In contrast, the Halcyon was equally celebrated because it was never seen ashore, and thought to reproduce upon the surface of the sea in calm weather, which was named after it. This seems equally characteristic of a smaller species, long known as the Levantine Shearwater Puffinus yelkouan until it was reclassified early in this century as a race of the P. puffinus yelkouan, since it does not fly so well, and is prone to settle in flocks on the water far from its island breeding-places when the wind falls. Although the identity of these was forgotten over the years, and they were eventually considered to be all sorts of strange things, such as Gannets Sula bassana and Kingfishers Alcedo atthis (Yapp 1987), Win­ thrope (1973) reported that the name Halcyon is still used for the 'Levantine Shearwater' in its area of origin. There, it appears to have given rise via the modern Turkish 'Yelkouan' or 'Yelkovan', also used for the souls of the dead (Vian 1877, cited by Mayaud 1936), or 'spirit of the wind', and hence weathercock (Pierre Loti, cited in an annotation by J. Vielliard to Kumerloeve 1972), to the species' scientific name. In the last century, it was thought to wander to British seas, until N. F. Ticehurst (1908) noticed that one collected in Kent about 1865 and identified by John Gould as a new species was originally reported to be pink, and remained unusually dark, below. Witherby (1921) eventually showed that all the British specimens belonged to this form, which was described as a third race of the Manx Shearwater, P. p. mauretanicus, by Lowe (1921). A discussion between leading British ornithologists and some distinguished visitors, including Alexander Wetmore, Ernst Mayr and Sir Charles Fleming, under the chairmanship of Lowe, when C. B.

306 [Brit. Hints 81: :«)B-S19.July 1988] The 307 Ticehurst eventually located the breeding-place in the Balearic Islands, was summarised as follows (Anon. 1930): 'Mr Witherby called attention to the fact that he had personally examined almost every example of this which had been recorded as P. yelkouan in the British Isles. Practically every one turned out to be P. mauretanicus (Witherby 1921). He also stated that he was inclined to think P. mauretanicus would prove to be a separate species. The Chairman said he thought Mr Witherby was right, and he himself had been in doubt as to the position of P. mauretanicus as a of P. puffinus. He thought that in considering the question of its specific rank it was necessary to bear in mind that not long ago, geologically speaking, the Mediterranean consisted of two land-locked seas divided by a causeway whose remains were now represented by Italy, Sicily, Malta, Corsica and Sardinia. It seems possible P. mauretanicus originated in the western basin.' The structural differences between the European were then studied by Mayaud (1932), who found that, -while puffinus,yelkouan and mauretanicus are all very similar, the last two resemble each other, and differ from the first, in having a longer, lower skull with more powerful jaw muscles, and a long sternum, but proportionately short wing and tail adapted for more aquatic habits, while they differ from each other only in their average size and amount of marking below. He also remarked how the extreme forms, puffinus and mauretanicus, occur next to each other rather than at opposite extremities of the range of the group, as might be expected as the result of convergence in a similar environment and hybridisation if they were all conspecific, though he continued to treat them as the same species. In the next definitive check-list of the petrels, one of the two greatest authorities of the day, Mathews (1934), added three more very similar North Pacific races to P. puffinus. He was initially followed by the other main authority, Murphy (1952), who first went on to add two more

Fig. 1. Distribution of the Manx group of shearwaters Puffinus. Continuous arrows show direction of movement of the black-backed forms: A Manx Shearwater P. p. puffinus, B Townsend's Shearwater P. (p.?) auricularis, C NewelPs P. (p.?) newelli, H Hutton's Shearwater P. huttoni. Dashes show movements of the brown-backed forms: D Levantine Shearwater P. (y.?)yelkouan, E /3, (y.?) mauretanicus, F Black-vented Shearwater/5, (y.?) opisthomelas, G P. gavia. (Derived from Bourne 1982) All forms are illustrated by Harrison (1987), and mauretanicus and yelkouan will be dealt with in detail by Yesou et al. (in press) 308 The Yelkouan Shearwater races from New Zealand, but remarked that the group appeared to be divisible into contrasting black-backed and brown-backed forms every­ where that it occurred, but, when the New Zealand forms were shown by Harrow (1965) to differ markedly in their ecology, eventually concluded that yelkouan and mauretanicus are also 'more distinct from the Manx Shearwater than present nomenclature indicates' (Murphy 1967). When Bourne (in Ash & Rooke 1954) saw his first mauretanicus alongside nominate puffinus in 1953, he immediately thought that they differed in their 'jizz' as well as their markings. On reviewing the petrels for Palmer (1962), he soon developed growing doubts whether they should be considered conspecific when he observed how inconsis­ tently Murphy (1927, 1952) treated the very similar geographical variation of the smallest shearwaters, divided into two species, the P. assimilis and Audubon's Shearwater P. therminieri, and the Manx group, combined into one, P. puffinus. After examining both the European and the Australasian forms at sea and considering Murphy's (1967) terminal change of opinion, he eventually decided to reopen the matter (Bourne 1982), whereupon it emerged that the other three authors had arrived independently at similar conclusions.

Fluttering and Hutton's Shearwaters At this point, it may be useful to describe the extreme situation found in Australasia. The existence of local allies of the Manx Shearwater with more marked adaptations for diving, which include a reduction of the wings for use in swimming under water, resulting in a more fluttering type of flight similar to that of the (Brown et at. 1978), was noticed very early, in 1773-74 during Cook's second expedition. For a long time, only one form was recognised, the Fluttering Shearwater P. gavia, which has a brown back prone to fade and white underparts. It tends to feed socially inshore on shoaling , breeds early in the southern spring on islets around northern New Zealand, and later disperses as far as southeast Australia to moult (Serventy et at. 1971). The existence of a second, larger, dark-backed form with more markings on the sides of the body and underwing, and a very long, slender bill, Hutton's Shearwater P. huttoni, was noticed only in 1912, possibly because it disperses out to sea to feed. Even then, its status remained doubtful for over half a century, until eventually it was found to breed two months later in the spring, above the tree-line in the mountains of the South Island of New Zealand (Harrow 1965, 1976), and then migrate to moult during the winter in an area of upwelling which occurs off the northwest coast of Australia during the southeast monsoon (Shuntov 1968; Halse 1981). These are such dramatic differences that, clearly, the two forms must be treated as distinct species. Indeed, once their marks were worked out, they proved quite easy to tell apart at sea (personal observation, WRPB). A comparable situation appears to occur on a larger scale The Yelkouan Shearwater 309 among the similar but longer-winged shearwaters of the northern hemisphere. This has been obscured by their greater geographical variation, so that each type is represented by three forms spread across two oceans, where they have traditionally been classified in different ways: as one species in Europe, but as two or three in the Pacific. The resulting confusion has been increased by the fact that, here, it is the brown-backed forms which are the more heavily marked below.

Northern black-backed (Manx, Townsend's and Newell's) shear­ waters The Manx Shearwater P. p. piiffinus has acquired a misleading image in Europe as an inhabitant of northern seas, where it appears very 'lithe' {Cramp & Simmons 1977) and black-and-white, owing to the compara­ tively sharp division between the dark upperparts and white underparts as it swoops over stormy waters among stouter Fulmars Fulmarus glacialis. If, however, we consider the rest of its range, where it has been seriously affected everywhere by introduced predators, a different picture emerges. Thus, some still breed in the mountains of the Canaries, and the , and formerly bred in the consolidated coral sand-dunes of Bermuda, as far south as 30°N in the Atlantic; and two close allies, Townsend's Shearwater P. p. auricularis and Newell's Shearwater P. p. newelli, also breed in the mountains of the Revilla Gigedos and Hawaii, and one was found in the last century at Saipan in the Marianas, at 20°N in the tropical Pacific (Bourne 1982;Jehl 1982). Thus, possibly, this was originally a subtropical oceanic species—with a continuous range through the Strait of Panama before it closed some two million years ago—which has begun to spread north along the warm North Atlantic Drift only since the last ice-age. It has only recently colonised Newfoundland (Storey & Lien 1985), and has not yet reached the North and Barents Seas. These birds all lay rather late in the spring, in April and May, and appear to move south to moult in the winter, in the Pacific as well as the Atlantic (King & Gould 1967), where they may be unable to face the stronger competition from their more numerous southern allies south of the equator. Thus, so far, only the expanding Atlantic population is known to go farther south, where most appear to winter off eastern South America (Thomson 1965), some off southwest Africa (Lambert 1975), and a few individuals reach Australia and New Zealand (Tennyson 1986).

Northern brown-backed (Levantine, Balearic and Black-vented) shear­ waters Although it has been claimed that little is known about the Mediterranean representatives of the Manx Shearwater, large series have been discussed by Loomis (1919) and Mayaud (1932), and they are common birds in well- known seas. Basically, they resemble tubby, short-tailed Manx Shear­ waters with a rather bustling, fluttery flight, a brown back which fades markedly and then appears very patchy when the dark new feathers start to appear during the moult, and a variable amount of diffuse marking on 310 The Yelkouan Shearwater the underparts, which therefore often show less contrast with the upperparts (Yesou et al. in press). They tend to feed in groups on the water offshore, and lay early on offshore islets around the northern Mediterra­ nean when the marine divergences are best developed there, between February and April (Ovchinnikov 1966; Gallagher et al. 1981), dispersing north to moult where front-formation occurs offshore later in the summer. Nominate yelkouan is known to breed on offshore islets from the south coast of France and eastern Algeria west to the Aegean, and at least once in the Black Sea off Bulgaria (Cramp & Simmons 1977; Brichetti 1979; Ledant et al. 1981). It is slightly larger in its average dimensions than nominate puffinus (table 1), and has a browner back. Although it has been claimed that it may vary locally in shade, this may be due to variation in the amount of fading in different areas or age-groups (Yesou et al. in press), and little difference can be seen in 20 skins in fresh from Tunisia, Corsica, Italy, Sicily, Malta, Yugoslavia, Greece, and Turkey, the largest (wing 143 mm) from Malta in December. There is normally more diffuse pigment beneath the tail than on puffinus, and in about half it extends up the side of the body beneath the wing. One individual taken off Oran, Algeria, on 6th March 1873, with dimensions near the mean for this race (wing 134 mm), otherwise resembles the darker specimens of mauretanicus, and could belong to either form. Similar specimens taken later in the season show a variable amount of fading above. The birds normally appear to lay in March and April everywhere, and fledge their chicks by July. They appear to feed in coastal currents at this time, and 11 dated specimens out of 16 from the famous feeding-place in the current leaving the Black Sea through the Bosphorus were taken between March and June. Subsequently, many appear to move east and

166. Yelkouan Shearwater Puffinus yelkouan mauretanicus, Menorca, Spain, May 1985 (Ed Mackrilt) The Yelkouan Shearwater 311 north; a chick ringed off southern France in July was recovered off eastern Sicily a month later; an adult ringed in Malta in May was recovered in Greece in mid July; and two chicks ringed in Malta were recovered the following June and in August three years later off the north coast of the Black Sea. Tens of thousands congregate for much of the year, to feed on anchovies Engraulis encrasicolus in this last area, where a marine front is shown by infra-red satellite images, and it may serve as a nursery for young birds (Frank 1952; Van Impe 1975; Cramp & Simmons 1977; Brichetti 1979; Sultana & Gauci 1982; Jarry 1986; Department of Electronics, Dundee University). Subsequently, the old birds may return to the breeding area, since they start to visit the colonies off the south coast of France by November (Vidal 1965). Others, which may be largely immature, or displaced by hard weather, also appear to move south and east into the area where they are not yet known to breed. One newly fledged in the Royal Scottish Museum came ashore in Cyprus on 26th August 1969, and three adults were collected off the coasts of Israel and Egypt (where anchovies also occur in the Nile outflow) in September, three were taken there and two off Tunis in January, and six were taken off Tunisia in March. Some apparently occur off Tunisia and Algeria (where an unknown number breed) throughout the year (Brichetti 1979; Ledant et al. 1981), but reports of their occurrence farther west have not yet been substantiated by specimens. Hundreds, and sometimes thousands, of predominantly pale moulting birds, which seem likely to include at least a proportion of yelkouan, have, however, been reported mainly from boats in the as far west as Tangier Bay in some but not all summers in the past (Telleria 1981; dejuana & Paterson 1986; E. Garcia & C. Finlayson in lift.). Bourne also thought that the great majority of a flock of about a thousand moulting shearwaters seen from a submarine off Algeciras Bay on 11th September 1964, rather late in the season for mauretanicus, resembled yelkouan, though Mackrill and Paterson have failed to identify it from the shore, and it has never been proved to reach the Atlantic. The form mauretanicus may appear larger than yelkouan, and some are more heavily marked below, owing to the progressive extension of the pigment beneath the tail, which may already extend up the side of the body on yelkouan, on to the underwing and across the breast. This is most marked on an immature in the British Museum (Nat. Hist.) which was collected on Mallorca on 27th July 1927, which has much of the underparts 'powdered' with coffee-coloured pigment. Some thousands of pairs are known to lay in February and March in the Balearic Islands, when shearwaters have also been heard calling along the northeast coast of Spain (de Juana 1984). One skin in the BM (NH) was collected off Algiers on 24th February 1873, when the small dark bird of uncertain race reported above was taken off Oran on 6th March, and another in the Museum National d'Histoire Naturelle was taken off the mouth of the Moulaya River, eastern Morocco, on 15th March 1957. A few were seen off the Camargue, France, on 27th March 1961 (Erard 1962), and they are said to reach Corsica, Sardinia and Libya (Bundy 1976; Brichetti 1979), 312 The Yelkouan Shearwater though Thibault (1983) considered that more proof is required for at least Corsica. Some stay near the Balearic Islands all the year around, and small groups of moulting birds have also been observed off southeast Spain in summer (de Juana & Paterson 1986; AMP & EJM); it is not clear which form occurs off North Africa at this time. The bulk of the population start to leave the Mediterranean in May, with the peak at Gibraltar in late June (Telleria 1981), while a northward movement involving over 4,000 birds was seen near Lisbon in mid June 1983 (A. M. Teixeira in lift.). Some 10,000-15,000, which have included two juveniles ringed on Formentosa and Mallorca in the Balearic Islands one and three months before, then gather in the vicinity of a marine front off the west coast of France, where the old birds moult (Yesou 1985, 1986; Hemery et al. 1986). Moulting birds have been collected off Devon and Sark, in the , in August, and small numbers, which may include a high proportion of apparently immature dark birds, reach the northern limit of their range off Scotland and Scandinavia in September (Cramp & Simmons 1977), when they appear to accumulate in the vicinity of another front off northeast England (Witherby 1921; Hope Jones & Tasker 1982). Two moulting birds are also said to have been collected in False Bay, South Africa, on 29th September 1979 (Mackrill 1988). Thousands of birds have been seen leaving the Bay of Biscay around northwest Spain in September and October (Huyskens & Maes 1971), and two in fresh plumage in the BM (NH), collected off Portugal in October, which puzzled Ash & Rooke (1954) could have been taking part in this movement. Although Bourne detected only a few mauretanicus among the numerous shearwaters moulting in the Strait of Gibraltar in September 1964, Mackrill has seen them returning east there regularly from 19th October (Yesou et al. in press). This race also reappears at the breeding places from November (J. Mayol & J. Muntaner verbally), although some, possibly the darker immatures, appear to spend the winter in an area of upwelling with a rich food supply also frequented by Audouin's Lams audouinii from the Mediterranean (Beaubrun 1983) off west Africa (Mackrill in Yesou et al. in press), and continue to return through the Strait of Gibraltar into March (Pineau & Giraud-Audine in Mayaud 1982). Unfortunately, the Californian Black-vented Shearwater P. opisthamelas, which has normally been treated as a distinct species, appears to be one of the least-studied members of the group. Its skins are, however, intermedi­ ate in size and appearance between those ofyelkouan and mauretanicus, with a more marked tendency for dark markings to occur in a band across the breast, and, in common with the other North Pacific forms, it has a comparatively long tail (table 1). Its behaviour is apparently very similar to that of the Mediterranean forms, the birds feeding inshore, breeding on offshore islets in the south of their range early in the spring, and dispersing north to moult later in the summer (Palmer 1962).

Discussion A species has been defined as a group of organisms which interbreed Breeding oj Spanish Imperial Eagle 313 12 hours: during four feeds, both chicks procured a substantial amount of food; we saw them attack each other on six occasions, on some of which the smaller chick was the aggressor. Both young subsequently fledged. In 1978, we could establish only that two young fledged. In 1979, between 19th and 27th April, observations were again made over a period of 40 hours from a hide in a nearby tree. On 15th April, the three chicks weighed 206 g, 166 g and 104 g respectively. The largest chick was exceed­ ingly aggressive towards the other two. On 19th, it attacked the second largest 15 times and the smallest eight times; and, during feeds, it devoured over 46 morsels of flesh, whereas the second largest obtained only about 20 and the smallest only four. On 21st April, the chicks weighed 430 g, 250 g and 110 g respectively. On this day, the second largest chick suffered about 20 beak-blows from the largest and the smallest received three beak-blows from the largest and one from the second largest; in order to evade these attacks, both chicks retreated even farther to the rim of the nest, where as a rule they were not offered any food by the female. It was usually enough for the largest chick to threaten attack by raising its head to its full height for both smaller ones to be cowed. Frequently, the dominant chick not only struck with its beak, but would also tug and tear at its subordinate's down with vigorous head-shaking, and would even repeatedly pick up the smallest chick by its head and shake it, let it drop and pick it up again. The largest nestling demonstrated this behaviour not only at feeding times or when hungry, but also when its crop was full. On 23rd April, the smallest chick procured 20 morsels at one feed, after

154. Such broods of four Spanish Imperial Eagles Aquila (heliaca) adalberti are not infrequent: Spain, April 1973 (B.-U. Meyburg) 314 The Yelkouan Shearwater Table 1. Characters of the Manx Measurements: mean, standard deviation and range in mm all by WRPB. All dealt with in detail by Yesou et al, (in

Form Habitat Breeds Migrates Markings

EUROPE Manx Shearwater P N Atlantic S Atlantic Black, P. p. puffinus hills & isles Sep-Mar white Apr-May below Levantine S. C E Mediterranean Black Sea Browner, P. y. yelkouan cliffs & isles Jul-Oct? darker Mar-Apr? sides Balearic S. C W Mediterranean NW Europe Brown, P. y. mauretanicus cliffs & isles Jul-Oct dull Feb-Mar? below NORTH PACIFIC Newell's S. P Hawaii E tropical Black, P. p. newelii mountains Pacific? white May-Jun? Dec-Feb? below Townsend's S. P Revilla Gigedos Sedentary? Browner, P. p. auricularis mountains darker Feb-Mar? sides Black-vented S. C Baja California NW North Brown, P. y. opisthomelas isles America dull Feb-Mar? Jul-Oct? breast NEW ZEALAND Fluttering S. c North Island SE Australia Brown, P. gavia islets Feb-Aug? white Sep-Oct below Hutton's S. p South Island NW Australia Darker P. kuttoni mountains Mar-Sep? back, Nov-Dec? sides

It is notable that Mayaud (1932) had already remarked that mauretanicus, which regularly encounters puffinus when it migrates from the western Mediterranean into the Atlantic, shows a greater difference in size and appearance from it than does the eastern Mediterranean form yelkouan, which appears to migrate in the opposite direction into the Black Sea, where puffinus is absent. Subfossil remains about 30,000 years old, which apparently belong to another shearwater of the yelkouan group about one- third larger than the existing forms, have now also been found at a former colony on the low, desert island of Lanzarote in the eastern , close to a colony of puffinus in the mountains of the western island of Palma (C.J. O. Harrison, C. Walker and A. Martin, verbally and in lift.), so that the birds may have differed to an even greater extent when they bred in closer proximity during the last glaciation. An examination of the characteristics of the surviving members of the Manx group of shearwaters as a whole (table 1) indicates that, in all three areas where they occur, they can be divided into two types: dark-backed birds which tend to feed out at sea, nest late in the season in mountains inland, and migrate into or through lower latitudes to moult in the winter; and brown-backed birds which tend to feed inshore, nest earlier in the season on offshore islets, and disperse into higher latitudes to moult in the The Yelkouan Shearwater 315 group of shearwaters Puffinus forms are illustrated by Harrison (1987), and mauretanicus and yelkouan will be prep). Habitat: P = pelagic; C = coastal Measurements (mm) Ratios No. Wing Tail Culmen Tarsus W/Tl W/C W/Ts Ts/C

28 235±5.7 73.3+3.1 34.9±1.3 45.0±1.3 3.2 6.7 5.2 1.29 221-243 68-79 32-37 43-49

18 23215.6 70.1 ±3.0 36.0±1.5 45.1±1.5 3.3 6.4 5.1 1.25 220-243 63-74 34-74 43-48

17 246±5.6 72.7+2.1 38.5±1.9 47.9+1.4 3.4 6.4 5.0 1.24 234-254 68-76 35-43 46-50

3 239±7.8 82.0±2.6 33.0±2.0 46.0+1.7 2.9 7.2 5.0 1.39 230-245 79-84 31-35 45-48

10 230±4.8 76.3+1.9 32.7+1.5 45.4±1.3 3.0 7.0 5.1 1.39 225-237 74-79

13 240±5.3 79.2±2.9 36.8+1.8 45.1 + 1.6 3.0 6.5 5.3 1.23 231-252 72-83 33-39 43-49

10 206±5.7 59.8±2.2 33.3±1.6 42.1 + 2.4 3.4 6.2 4.9 1.26 198-213 58-64 30-35 40-45

12 220±5.3 65.4±2.9 36.0±1.0 42.2+1.1 3.4 6.1 5.2 1.17 212-230 61-71 35-38 40-44

summer. The local representatives of the two forms have normally been treated as distinct species in the North Pacific, and have recently been recognised as distinct in Australasia; yet, although a variety of good authorities listed earlier have repeatedly suggested that they may be distinct, they have always been treated as conspecific in Europe. Murphy (1952) has suggested that this situation arose because the birds' common ancestor evolved in the great Tethys Ocean, which once encircled the middle latitudes of the northern hemisphere in the early Tertiary period some tens of millions of years ago, and then dispersed in opposite directions around the world, through an ancient waterway between Eurasia and Africa to the east, and a more recent one between the Americas to the west, until the diverging extremes met and developed an overlapping distribution. This seems questionable because it would have provided little opportunity for the segregation of distinct stocks with different habits likely to provide isolating mechanisms when they came into contact again, and because the eastern waterway may have closed too soon, so we suggest the following modification to his hypothesis. It seems likely that the common ancestor of the black-and-white diving shearwaters originated in the Tethys Ocean, since, unlike most other groups of petrels, they still have a wider distribution in that area than in 316 The Yelkouan Shearwater the southern hemisphere, and it is known that shearwaters were well represented there in the past (Olson 1985). Their subsequent evolution may have resulted from the progressive disruption of that ocean to give rise to a series of temporarily isolated water-masses in central Eurasia in the middle Tertiary, and then the North Atlantic and Pacific Oceans as the result of the formation of the Isthmus of Panama at the end of the Tertiary, as follows:

1. Probably the first development was the isolation of the ancestor of the most distinct derivatives, the closely related Little P. assimilis and Audubon's Shearwaters P. Ihermbrieri^ in an increasingly warm environment in the Indian Ocean about 15 million years ago, from where they have dispersed throughout the warmer seas. 2. The ancestor of the coastal brown-backed shearwaters may then also have become isolated in one of the central Eurasian water-masses, probably but not necessarily the Mediterranean (since there were other enclosed seas farther east) when it was temporarily cut off and partly dried out to form a series of shallow saline lagoons with fertile margins about five million years ago (Busson et aL 1980). 3. Meanwhile, the original stock survived in the largest remaining fragment of the Tethys Ocean, to give rise to the pelagic black-backed shearwaters, which now have a transequatorial migration in the Atlantic, but a bipolar distribution in the comparable parts of the Pacific. 4. By the time the connections between the Atlantic, the Mediterranean and the Black Seas were restored towards the end of the Tertiary, their shearwaters must have developed a sufficiently different ecology, movements and especially annual cycles to remain distinct. 5. It remains debatable whether the Mediterranean form of brown-backed shearwater may have succeeded in spreading to the Pacific area around the coasts of the last remnant of the Tethys Ocean, which was warmer than the modern northern oceans and probably more congenial to it, before the final closure of the Isthmus of Panama about two million years ago (Schmidt-Effing 1980), or whether very similar brown-backed forms may also have evolved in much the same manner there in the region of the Gulf of California and New Zealand. If this analysis is correct, it would appear that these shearwaters have not only been familiar to man for rather a long time, but are in fact rather old European sibling species (much older than man), which originated during the formation of the continent. At least one of them, possibly both, has subsequently spread throughout the world, in much the same way that a Manx Shearwater P. puffinus ringed in Britain is still capable of reaching Australia (Thomson 1963), so that comparable pairs of oceanic and coastal representatives, and sometimes a third smaller ally as well, now occur in most warm, temperate seas. Most of these shearwater populations have well-established vernacular names, but, if the Mediterranean forms yelkouan and mauretanicus—which have been referred to individually as the Levantine and Balearic Shearwaters—are combined to form a distinct species, it becomes necessary to devise a distinctive vernacular name that will cover both of them collectively. In the circumstances, it seems a pity that the historic name Halcyon has become indissolubly linked to the kingfishers (though apparently still perpetuated in the Turkish vernacular and scientific name yelkouan), and that the attractive alternative 'Mediterranean Shearwater' was applied for many years to a race of another species, now rather inappropriately termed, for similar reasons, Cory's Shearwater. It may therefore be best to fall back on the unmistakable modern Turkish vernacular and scientific name and call the species Yelkouan Shearwater. The Yelkouan Shearwater 317 It remains debatable whether the North Pacific forms are closely related to the European ones, or have evolved independently, although they are apparently very similar, differing morphologically only in all having slightly longer tails (table 1). Clearly, there is also a need for the investigation of such factors as the birds' biochemistry, voices (Dr Claude Chappuis reports, verbally, that there is a difference between the calls of yelkouan and puffinus), and parasites (Timmermann, 1965, reported that they also differ in their , and Guiguen & Monnat, 1983, 1985, and Dr C. Guiguen (verbally) that they differ in their Siphonaptera), to elucidate the details of their relationships. Since the European scientific names are older and take priority, this will, however, not affect European nomenclature. The southern forms which live in a very different environment among a greater variety of competitors have diverged much more markedly, and clearly deserve to be treated as distinct species.

Acknowledgments We are indebted to many museums and their staffs for assistance with the examination of specimens, but especially the British Museum (Natural History), Tring; the Royal Scottish Museum, Edinburgh; the Museum National d'Histoire Naturelle, Paris; the American Museum of Natural History, New York; and the Dominion Museum, Wellington. J. F. Stephan of the Centre National de la Recherche Scientifique, France, has assisted the interpretation of geological events, and E. de Juana, A. Martin, J. Mayol, J. Muntaner, A. M. Teixeira, P. A. Zino and B. Zonfrillo, among others, have provided useful observations. Summary The classical Halcyon, whose true identity is indicated by its local vernacular and scientific name yelkouan, is a rather tubby, brown-backed sibling species of the Manx Shearwater Puffinus puffinus, with a short tail, a big bill, prominent feet, a variable amount of dark marking on the underparts, and a fluttery flight. It may have evolved in the Mediterranean when it was cut off from the other oceans about five million years ago, and has developed as a more coastal species. It feeds inshore, nests early in the spring on offshore islands, and then migrates into higher latitudes to moult later in the summer. It is divisible into two races in Europe, including the small, white-breasted nominate yelkouan ('Levantine Shearwater'), which breeds around most of the Mediterranean, appears to migrate northeast towards the Black Sea and has never been proved to visit the Atlantic, and the large, often darker- breasted mauretankus ('Balearic Shearwater'), which breeds in the Balearic Islands and migrates up and down the western coasts of Europe and Africa. An intermediate form of uncertain status which has usually been treated as a distinct species, the Black-vented Shearwater opisthome/as, behaves similarly off the west coast of North America, and a more distinct ally, the Fluttering Shearwater P. gavia, carries out similar movements between northern New Zealand and southeast Australia. The Manx Shearwater and various allies have a similar distribution, but tend to occur farther out to sea, nest in hills inland, and migrate into or through lower latitudes to moult in the winter. The Little P. a.ssimilis and Audubon's Shearwaters P. Iherminieri may also derive from another population of the same ancestral stock which was cut off earlier in the Indian Ocean and has now spread throughout the warmer seas. In order to avoid confusion with names which have been used in other ways, it is suggested that P. yelkouan could be referred to as the Yelkouan Shearwater. References ANON. 1930. (Discussion of P. p. mauretanicus). Bull Brit. Orn. CI. 50: 83-84. ASM, J., & ROOKF., K. B. 1954. Balearic Shearwaters off the Dorset coast in 1953. Brit. Birds. 47: 285-296. BKAUBRUN, P. C. 1983. Le Goeland d'Audouin (Larus audouinii Peyr.) sur les cotes du Maroc. I.'Oiseau 53: 209-226. 318 The Yelkouan Shearwater BOURNE, W. R. P. 1955. The birds of the Cape Verde Islands. Ibis 97: 508-556. 1982. The relationship of the Manx and Fluttering Shearwaters. Sea Swallow 31: 44-47. BRICHF.TTI, P. 1979. [Geographical distribution of breeding birds in Italy, Corsica and the Maltese Islands.] Natura Bresciana 16: 124-133. (Italian, English summaries) BROWN, R. G. B., BOURNE, W. R. P., & WAHI., T. R. 1978. Diving by shearwaters. Condor 80: 123-125. BROWN, W. L., & WILSON, E. O. 1956. Character displacement. Syst. Xooi 5: 49-64. Bl'NBY, G. 1976. 77K Birds of Libya. London. BUSSON, G., ROUCHY, J. M., NOEL, D., & GUILLEVIN, Y. 1980. Les depots salins, temoins insolites des mers fossiles. 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