Ardeola 49(1), 2002, 39-49

NEW DATA OF FOSSIL BIRDS FROM EL HIERRO (CANARY ISLANDS): PROBABLE CAUSES OF EXTINCTION AND SOME BIOGEOGRAPHICAL CONSIDERATIONS J. C. RANDO* SUMMARY.—New data of fossil birds from El Hierro (Canary Islands): probable causes of extinction and some biogeographical considerations. A description of fossil birds from El Hierro (Canary Islands) is made. These bones are from Cueva de El Curascán, a volcanic tube in the Medium Volcanic Series on the Northeast of the island. Six specimens corresponding to four species have been studied. Two of these, a Petrel (Pterodroma sp.) and the Goshawk (Accipiter gentilis), are extinct in the Archipelago. They also represent the first palaeontological record of both species in the Canary Islands. The taxonomic status of the Petrel is discussed, as well as the possible origin and causes of extinction of both species, which seem to be different for each one, although in either case extinction seems to have been associated to the human occupation of the island. The bones discovered, like most of the palaeornithological findings on islands, show some of the diversity changes suffered by all insular ecosystems. This fact supports the idea that biogeographical analyses could have little reliability if recent extinction records are not taken into account. These affect a high number of species and, in the case of the Canary Archipelago, like in other oceanic islands, seem to be a direct consequence of a relatively recent human colonisation. Key words: Accipiter gentilis, biogeography, Canary Islands, El Hierro, extinction, fossil, Pterodroma sp. RESUMEN.—Nuevos datos sobre aves fósiles de El Hierro (Islas Canarias): probables causas de extinción y algunas consideraciones biogeográficas. Se hace una descripción de aves fósiles de El Hierro (Islas Canarias). Los fósiles descritos proceden de la Cueva de El Curascán, un tubo volcánico de la Serie Volcánica intermedia, situado en el noreste de La Isla. Parte del material estudiado pertenece a dos especies extintas en el archipiélago, un petrel (Pterodroma sp.) y el Azor Común (Accipiter gentilis). Estos restos constituyen los primeros registros paleontológicos de estas especies en Canarias. Se discute sobre su nivel taxonómico (en el caso de los petreles), posible origen y causas de extinción, que parecen diferentes para cada una de estas especies pero asociadas al poblamiento humano. Estos huesos, como la mayoría de los hallazgos paleornitológicos en islas, nos muestran una parte de los cambios de diversidad sufridos por los ecosistemas insulares. Estos hechos apoyan la idea de que los análisis biogeográficos podrían tener poca fiabilidad si no consideran los datos de extinciones recientes, las cuales afectan a un elevado número de especies. En el caso de Canarias, como en otros archipiélagos oceánicos, estas extinciones parecen ser consecuencia directa de una colonización humana relativamente reciente. Palabras clave: Accipiter gentilis, biogeografía, El Hierro, extinción, fósil, Islas Canarias, Pterodroma sp.

INTRODUCTION El Hierro, La Gomera and La Palma are a group of islands within the Canary Archipelago that display as a common characteristic the absence of non-flying terrestrial mammals in their native fauna. This circumstance is without doubt related to their geographic location, since they are the most westerly islands in the Archipelago and, therefore, the furthest away from the African coast (Figure 1). Other groups of vertebrates with a better dispersion capacity such as reptiles, bats and, especially, birds have

arrived to these islands. This fact makes them especially interesting from a palaeornithological point of view, as illustrated by the abundant examples of other islands without non-flying terrestrial mammals in their native faunas (Pacific Islands, New Zealand, Ibiza, etc.). These islands show, through their palaeontological sites, a different and more diversified fauna than the present one (James & Olson, 1991; Olson & James, 1991; Alcover & McMinn, 1992; Worthy & Holdoway, 1994). A common denominator of all these insular faunas is the high number of extinction events suffered by

* Museo de Ciencias Naturales (O.A.M.C.), Santa Cruz de Tenerife, Apartado 853, E-38003, Tenerife, Canary Islands, Spain. e-mail: [email protected]

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FIG. 1.—Geographic situation of the Canary Islands indicating (✸) the location of Cueva de El Curascán in El Hierro. [Situación geográfica de las Islas Canarias indicando (✸) la localización de la Cueva de El Curascán en El Hierro.]

these ecosystems as a direct consequence of human population (Milberg & Tyrbertg, 1993; Steadman, 1995; Worthy, 1999). Despite an incomplete fossil record, the palaeofauna from the Canary Islands shows large differences between the bird populations which inhabited the Archipelago in the relatively recent past (Upper Pleistocene – Holocene; see Alcover & McMinn, 1995; Rando et al., 1999) and those found today (Martín & Lorenzo, 2001). These differences are mainly based on the presence of extinct endemic species and species that had a different distribution from the current one. These data show an extinction process that probably began with the aboriginal arrival about 2500 years ago (Navarro et al., 1990), and which continues in our days. In the Canary Archipelago, like in other oceanic volcanic islands, the fossil record is mainly restricted to volcanic cavities created by different eruptive episodes. The bones that have been accumulated in caves by natural processes can be classified into various categories, which explain their presence in these places. They are related to the behaviour of the species or other biological characteristics (Alcover, 1992). Papers on fossil birds from the Canary Islands include the study of materials from the Upper Miocene in Lanzarote (García-Talavera, 1990) Ardeola 49(1), 2002, 38-49

and more recent bones from palaeontological sites in all of the islands (see Alcover & McMinn, 1995; Rando et al., 1999), except for Gran Canaria and El Hierro. In El Hierro, the smallest (269 km2) and most westerly island in the Archipelago (Figure 1), the volcanic cavities are abundant (Hernandez et al., 1991) due to their Medium and Recent geological series (less than 50000 years; Fuster et al., 1993). Some of these caves have provided important information about the fauna that inhabited the island (Izquierdo et al., 1989; López-Jurado et al., 1999; Mateo et al., 1999). However, in spite of the abundance of volcanic caves, only one paper has been published on bird bones from an archaeological site (Rando et al., 1997). The aim of this work is to describe the bird bones from Cueva de El Curascán, discuss the insular extinction process and draw a biogeographical interpretation of these remains. MATERIAL AND METHODS The material was collected in Cueva de El Curascán (UTM = 28R X: 0210400;Y: 3081850, data map WGS84), located in the Northeast of the island at about 300 meters above sea level (Figure 1). The tube is in the

NEW DATA OF FOSSIL BIRDS FROM EL HIERRO (CANARY ISLANDS)

Medium Volcanic Series, so that it is less than 50000 years old (Fúster et al., 1993). The cave is accessible through a cut produced in the construction of a road, so the birds had to access the inside through another entrance, probably no longer existent. It is a cavity with volcanic tubes at two levels, in whose interior sediment accumulation has not taken place, a reason why the bones were collected directly on the ground surface. The material (Appendix I) is kept in the Fossil Vertebrate Collection at the Museo de Ciencias Naturales of Santa Cruz de Tenerife (Canary Islands, Spain). Bones were compared to

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recent bird skeletons (see Appendix II) of this museum (TFMC), and also to material of the Vertebrate Collection at the Departamento de Biología Animal (Zoología) of the Universidad de La Laguna (Canary Islands, Spain) (DZUL), Museu de la Naturalesa de les Illes Balears (Ciutat de Mallorca, Balearic Islands, Spain) (MNIB), Museu Municipal do Funchal (Funchal, Madeira Island, Portugal) (MMF), and British Museum (Natural History) (Tring, UK) (BMNH). Measurements were taken as shown in Figure 2. The anatomical terminology follows Baumel et al., (1993).

FIG. 2.—Diagram showing the measurements used in this paper. The bones do not belong to the same species and are not to scale. 1: total length of skull; 2: height of the braincase; 3: maximum width of the skull; 4: interorbital width; 5: dorsal length of maxilla; 6: length of maxilla (from the jugal articulation); 7: length of culmen (from anterior edge of narinal opening); 8: width to culmen; 9: width of the nasofrontal joint; 10: internasal width; 11: length of the narinal opening; 12: height of the narinal opening; 13: total mandible length; 14: femur length; 15: tarsometarsus length; 16: tibiotarsus length; 17: humerus length; 18: ulna length; 19: capometacarpus length; 20: coracoid length; 21: coracoid width; 22, length of the carina sterni. [Diagrama con las medidas efectuadas en este trabajo. Los huesos no pertenecen a la misma especie y no han sido dibujados a escala. 1: longitud total del cráneo; 2: altura del cráneo; 3: máxima ancho del cráneo; 4: distancia interorbital; 5: longitud dorsal de la maxila; 6: longitud de la maxila (desde la articulación yugal); 7: longitud del culmen (desde el borde anterior de la narina); 8: anchura del culmen; 9: anchura de la articulación nasofrontal; 10: anchura de la barra internasal; 11: longitud de la narina; 12: altura de la narina; 13: longitud total de la mandíbula; 14: longitud del fémur; 15: longitud del tarsometatarso; 16: longitud del tibiotarso; 17: longitud del húmero; 18: longitud de la ulna; 19: longitud del carpometacarpo; 20: longitud del coracoides; 21: anchura del coracoides; 22: longitud de la carina sterni.] Ardeola 49(1), 2002, 38-49

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TABLE 1 Measurements (mm) of Pterodroma sp. bones from Cueva de El Curascán (El Hierro) and the two extant breeding species of Pterodroma of the Macaronesian region. Means ± SD, range and sample size (n) are given. Measurements as in Figure 2. [Medidas (mm) de los huesos de Pterodroma sp. de la Cueva de El Curascán y de las dos especies actuales de Pterodroma nidificantes en la Región Macaronésica. Se dan los valores medios ± SD, el rango y el tamaño de muestra (n). Las medidas fueron tomadas como se indica en la Figura 2.] Measurements

Fea’s Petrel [Petrel Gon-gon] P. feae

Skull length [Longitud del cráneo] Braincase height [Altura del cráneo] Skull width [Anchura del cráneo] Interorbital width [Distancia interorbitaria] Dorsal length of maxilla [Longitud dorsal de la maxila] Length of maxilla (from the jugal articulation) [Longitud de la maxila (desde la articulación yugal)] Length of culmen (from anterior edge of narinal opening) [Longitud del culmen (desde el borde anterior de la narina)] Culmen width [Anchura del culmen] Width of the nasofrontal joint [Anchura de la articulación nasofrontal] Internasal width [Anchura internasal] Narinal opening length [Longitud de la narina] Narinal opening height [Altura de la narina] Mandible length [Longitud de la mandíbula] Femur length [Longitud del fémur] Tarsometarsus length [Longitud del tarsometatarso] Tibiotarsus length [Longitud del tibiotarso] Humerus length [Longitud del húmero] Ulna length [Longitud de la ulna] Carpometacarpus length [Longitud del carpometacarpo] Coracoid length [Longitud del coracoides] Coracoid width [Anchura del coradides] Length of the carina sterni [Longitud de la carina sterni]

73.50 (1)

76.69 (1)

20.39 (1)

23.10 ± 0.66 (2) 22.64 – 23.57 30.09 (1)

Ardeola 49(1), 2002, 38-49

Madeira Petrel [Petrel Freira] P. madeira

28.61 (1) 10.00 (1)

Petrel from El Hierro [Petrel de El Hierro] Pterodroma sp.

37.02 (1)

33.08 (1)

9.99 ± 0.93 (2) 9.33 – 10.65 39.50 (1)

30.84 (1)

28.56 (1)

33.07 (1)

19.48 (1)

18.72 (1)

21.33 (1)

12.67 (1)

10.39 (1)

10.75 (1)

9.10 (1)

0.87 (1)

0.88 (1)

11.90 (1)

9.04 (1)

14.01 ± 0.48 (2) 13.67 – 14.35 11.56 ± 0.01 (2) 11.56 – 11.57 1.17 ± 0.06 (2) 1.13 – 1.21 11.76 (1)

3.19 (1)

2.92 (1)

3.09 ± 0.04 (2) 3.06 – 3.12

57.61 (1) 29.91 (1) 33.43 (1)

32.27 (1) 31.87 ± 0.22 (5) 31.58 – 32.14

35.39 (1) 55.98 (1)

85.86 (1)

28.88 (1)

87.91 ± 0.37 (2) 87.65 – 88.17 90.64 ± 0.72 (2) 90.13 – 91.15 44.53 ± 0.57 (3) 43.99 – 45.13 31.00 (1)

18.71 (1)

21.34 (1)

87.83 (1) 42.89 (1)

52.23 (1)

80.12 ± 4.35 (2) 77.04 – 83.20 83.25 ± 2.62 (8) 80.88 – 88.39 39.90 ± 0.77 (7) 38.96 – 41.32

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NEW DATA OF FOSSIL BIRDS FROM EL HIERRO (CANARY ISLANDS)

SYSTEMATIC PALAEONTOLOGY The material belongs to four species, two of them extinct nowadays in the Archipelago. Order Procellariiformes Family Procellariidae Pterodroma sp. (Petrel) Bones correspond to, at least, three adult specimens. The general morphology of the skull, as well as the postcranial skeleton, clearly indicates that it belongs to this genus. The skull is voluminous but short; the premaxilar is compressed laterally, but high; the depression of the fossa temporal is less developed than in Calonectris; the foramen orbitonasale are small (Warham, 1990); the lacrimal bone is perfectly fused to the frontal and mesethmoidal, without any noticeable remaining suture left between them (Figures 3 and 4); tarsometatarsus is small if it is compared with the body size (Imber, 1985; Figure 5). The only Fea’s Petrel (P. feae) from the Desertas Islands (Archipelago of Madeira) examined (MMF 24830) showed certain differences compared to the material from El Hierro. The skull of the Fea’s Petrel presents a depressio frontalis more noticeable than in El Hierro bones. The processus postorbitalisis is more developed in the Desertas specimen. The premaxilar is less robust and less compact in the Fea’s Petrel (Figures 3 and 4). The crista tomialis displays a greater development in the bones from El Hierro, forming a small channel in the outer edge of the ventral zone in the premaxilar bone; this structure is not perceptible in the Desertas bird. The joint of the lacrimal bone to the frontal generates dorsally a pointed-shaped structure which projects towards the posterior part of the skull, thus displaying a more developed and acute morphology in the Fea’s Petrel than in the material from El Hierro (Figure 3). Differences in the postcranial skeleton are basically in size (Figure 5; Table 1). Nevertheless, the impressio brachialis of the ulna is much more conspicuous in the bones from El Hierro than in the Fea’s Petrel. The comparison with skulls of the Madeira Petrel (P. madeira) has not been possible because of the lack of material. The available bones belong to birds depredated by rats, and collected in breeding areas on the Island of Madeira. The two premaxilars of this sample indicate a more

graceful morphology and smaller size than in the other two species examined (Figures 3 and 4). The postcranial bones (seven carpometacarpus, eight ulnas, two humerus and five tarsometarsus) present a lower size (Figure 5; Table 1), except in the length of one ulna (88.39 mm for MMF 31603), this value being similar to the length of the Fea’s Petrel’s ulna. A detail to emphasise is that, in spite of displaying a smaller length and a more graceful structure, four of the eight ulnas of Madeira Petrels present a development of impressio brachialis similar to that in the fossil bones from El Hierro. In summary, all skull and postcranial measurements show higher values in the bones from Cueva de El Curascán than in the other two species. The lowest are those of the Madeira Petrel, with the figures for the Fea’s Petrel examined placed in an intermediate position (Figures 3, 4 and 5; Table 1). Order Procellariiformes Family Procellariidae Calonectris diomedea (Cory’s Shearwater) Bones correspond to only one specimen, and present a similar morphology and size to that of the recent material of this species from the Canary Islands. Order Procellariiformes Family Hydrobatidae Oceanodroma castro (Madeiran Storm-petrel) The fossil remains (one bird only) can be differentiated from Leach’s Storm-petrel (O. leucorhoa) because the lamina of the ectethmoidale bone displays a greater development in the material from El Hierro; likewise, the processus postorbitalis is less prominent. Order Accipitriformes Family Accipitridae Accipiter gentilis (Goshawk) The material of this species belongs to one specimen only, probably a female. Since the skeleton is very fragmented, total lengths have been measured in two bones only (carpometacarpus [61.04 mm] and tarsometatarsus [80.46 mm]). This value is within the range of variation for the females of this species in Central Europe (tarsometatarsus: 79.7-86.2; SchmidtBurger, 1982), and is larger than the examined Ardeola 49(1), 2002, 38-49

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FIG. 3.—Comparison of the cranium of Petrels (Pterodroma sp.) from El Hierro, TFMC (VF 673 – VF 674) (A-B) with Fea’s Petrel (P. feae), MMF 24830 (C), and Madeira Petrel (P. madeira), MMF (26305 30500) (D-E). Dorsal view. Every square of the scale = 1 cm. [Comparación de los cráneos de los Petreles (Pterodroma sp.) de El Hierro, TFMC (VF 673 – VF 674) (A-B) con el Petrel Gon-gon (P. feae), MMF 24830 (C), y el Petrel Freira (P. madeira), MMF (26305 30500) (D-E). Vista dorsal. Cada cuadro de la escala =1 cm.]

FIG. 4.—Comparison of the cranium of Petrels (Pterodroma sp.) from El Hierro, TFMC (VF 673 – VF 674) (A-B) with Fea´s Petrel (P. feae), MMF 24830 (C), and Madeira Petrel (P. madeira), MMF (26305 30500) (D - E). Left lateral view. Every square of the scale = 1 cm. [Comparación de los cráneos de los Petreles (Pterodroma sp.) de El Hierro, TFMC (VF 673 – VF 674) (A-B) con el Petrel Gon-gon (P. feae), MMF 24830 (C), y el Petrel Freira (P. madeira), MMF (26305 30500) (D - E). Vista lateral izquierda. Cada cuadro de la escala =1 cm.]

specimens. Moreover, this material is morphologically similar to the bones of Goshawk excepted a few small differences, such as: a greater development of the processus procoracoideus, of the processus extensorius in the carpometacarpus, a fossa metatarsi I and a depressio radialis larger and deeper.

could have been trapped inside the cave, whereas the Petrels, Cory’s Shearwater and Madeiran Storm-petrel seem to have their origin in the reproductive activity of these birds inside the tube. Bones of Procellariiformes are very frequent in the Canary Islands in cavities located at a low altitude. Currently, Cory’s Shearwater is the most abundant bird of this group in the Canary Islands. Like Cory’s Shearwater, the Madeiran Storm-petrel is also present in all of the archipelagos in the Macaronesia, but is less abundant. In the Canary Islands it is restricted to small islets and cliffs, where predation by introduced mammals is very low or non-

DISCUSSION Bones of these two groups of birds (seabirds and raptors) found in Cueva de El Curascán show clearly different origins. The Goshawk Ardeola 49(1), 2002, 38-49

NEW DATA OF FOSSIL BIRDS FROM EL HIERRO (CANARY ISLANDS)

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FIG. 5.—Comparison of the bones of Petrels (Pterodroma sp.) from El Hierro (A``-G``, several specimens) with Fea’s Petrel (P. feae), MMF 24830 (A`-G`) and Madeira Petrel (P. madeira) (A-C and G, several specimens). Every square of the scale = 1 cm. A-A`` humerus, caudal view; B-B`` ulnas, cranial view; C-C`` carpometacarpus, ventral view; D`-D``coracoids, dorsal view; E`-E`` femurs, caudal view; F`-F`` tibiotarsus, cranial view; G-G`` tarsometarsus, dorsal view. [Comparación de huesos de los Petreles (Pterodroma sp.) de El Hierro, (A``-G``, varios individuos) con el Petrel Gon-gon (P. feae), MMF 24830 (A`-G`), y el Petrel Freira (P. madeira), (A-C y G, varios individuos). Cada cuadro de la escala =1 cm. A-A`` húmeros, vista caudal; B-B`` ulnas, vista craneal; C-C`` carpometacarpos, vista ventral; D`-D`` coracoides, vista dorsal; E`-E`` femures, vista caudal; F`-F`` tibiatarsos, vista craneal; G-G`` tarsometarsus, vista dorsal.]

FIG. 6.—Comparison of the bones of Goshwak (Accipiter gentilis) from El Hierro, TFMC VF 678 (A-E) with actual material of the same species, MNIB 12607 (A` and E`) and 9959 (B`-D`). Every square of the scale = 1 cm. A-A` carpometacarpus, dorsal view; B-B` femurs, cranial view; C-C` coracoids, ventral view; D-D` scapules, lateral view; E-E` carpometacarpus, dorsal view. [Comparación de los huesos de Azor (Accipiter gentilis) de El Hierro, TFMC VF 678 (A-E), con huesos actuales de la misma especie, MNIB 12607 (A` y E`) y MNIB 9959 (B`-D`). Cada cuadro de la escala =1 cm. A-A` carpometacarpos, vista dorsal; B-B` femures, vista craneal; C-C` coracoides, vista ventral; D-D` escapulas, vista lateral; E-E` carpometacarpos, vista dorsal.]

existent. The finding of bones of this species in new places on El Hierro mainland indicates a wider distribution in the past. The introduction of mammalian predators has probably forced them to breed exclusively in small islets (Roque Grande de Salmor) and cliffs of very difficult access (Delgado et al., 1989), as they do in the rest of the Macaronesia.

The Petrels The genus Pterodroma is present nowadays in several archipelagos of the Macaronesia (but not in the Canary Islands). Fea’s Petrel breeds in Bugio (Islas Desertas, Archipelago of Madeira), probably in Azores, and in the Cape Verde Islands. The Madeiran Petrel breeds only Ardeola 49(1), 2002, 38-49

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in the island of Madeira (Del Hoyo et al., 1992; Zonfrillo, 1993; Zino & Biscoito, 1994; Monteiro et al., 1996; Ratcliffe et al., 2000). The differences (in size and morphology; Table 1, Figures 3, 4 and 5) between the Pterodroma bones from El Hierro and the compared material from the two current breeding species of Pterodroma in the Macaronesian Region seem to indicate the possible existence of a differentiated breeding population of Pterodroma in the Canary Islands in the past. This point could be clarified in the future after studying more bones of these birds, and comparing them to skeletons of Fea’s Petrel from Cape Verde Islands and other Atlantic Petrels.

mens in the northern and eastern populations, and smaller in the southern and western ones (Snow & Perrins, 1998), and the length of the tarsometatarsus from Cueva de El Curascán, seem to indicate a relationship with the current populations in Europe. These populations could have suffered displacements to the South due to glacial conditions, perhaps during the Pleistocene-Holocene (Hewitt, 1999). The future discovery of more fossil material, and its comparison with specimens of several European populations, is however necessary to clarify the origin of the Goshawk bones found in El Hierro. EXTINCTION

The Goshawk Demographic and taphonomic causes are the main reasons for the poor samples of raptor bones in insular palaeontological records. The small populations of predators on the islands and the fragility of bird bones produce this scarcity (Alcover & McMinn, 1994). Sometimes, these records are limited to a single specimen. Therefore, the recent finding of Goshawk bones in El Hierro invite to think that, rather than an occasional record, it could represent a breeding species on the island. Moreover, in the palaeontological records of raptors from the Canary Islands there are data that would support this idea, due to the existence of several sites with the presence of raptor bones in low numbers in all of them (Rando, 1995; Rando & López, 1996; Rando, unpublished data). In this sense, indirect information would also support the possible past existence of Goshawk populations in the Archipelago. It is a non-specialised predator whose prey (reptiles, mammals and birds) varies depending on the season and the geographic region (Del Hoyo et al., 1994). The existence of potential prey like birds (e.g. Turdus, Coturnix, Columba, Corvus, etc., Matín & Lorenzo, 2001) and lizards of large size (Izquierdo et al., 1989; López-Jurado et al., 1999; Mateo et al., 1999), would have provided the necessary volume of prey for the existence of these birds. The origin of Goshawk bones from El Hierro is unknown. They could have arrived to the Archipelago from Europe or North Africa. The existence of size variation, with larger speciArdeola 49(1), 2002, 38-49

Apart from the genus Pterodroma, two extinct species of Puffinus are known for the Canary Islands (P. holeae and P. olsoni), both from palaeontological sites on the eastern islands (McMinn et al., 1990; Walker et al., 1990). The initial decline in the colonies of these birds could have been a consequence of the onset of the present interglacial phase (around 10000 years ago), which may have caused a change in the variety of marine organisms available as prey (Walker et al., 1990). Later, hunting by aboriginal people (Rando & Perera, 1994; Rando et al., 1996, 1997) and, especially, the massive presence of alien predators like cats (Felis catus) and rats (Rattus spp.) after the European conquest, produced strong changes in their populations. The activity of these mammals has been the main cause of extinction for many seabird species on islands worldwide (Burger & Gochfeld, 1994; see Zino and Zino, 1986 for the Madeira Petrel), as could have been for the species of petrel found in El Hierro. Habitat alteration and decrease in the number of potential prey due to the direct action of man have been suggested to explain the extinction of raptors on islands. The extinction of endemic owls from Mediterranean islands, such as Bubo insularis in Corsica and Sardinia, and Athene cretensis in Crete, which were also dependent on endemic mammals, was probably due to the eradication of the latter because of human activities (Alcover et al., 1992). In New Zealand, Harpagornis moorei (a genus close to Aquila) probably disappeared due to the alteration of its habitat and the extinction of its potential prey

NEW DATA OF FOSSIL BIRDS FROM EL HIERRO (CANARY ISLANDS)

due to human overhunting (Holdoway, 1989). In Hawaii, a species of the genus Circus, one of the genus Haliaeetus and four of Grallistrix (related to Strix) are known to be all extinct after the human arrival, which produced the eradication of most of their potential prey (mainly rails, ibises and ducks; James, 1995). In El Hierro, many potential prey for large terrestrial raptors such as endemic pigeons (Columba bolli and C. junoiae; Martín et al., 2000), giant lizards (Gallotia simonyi; Pérez-Melladoet al., 1999) and quails (Coturnix gomerae; Rando et al., 1997) are either endangered or even extinct, a fact that could have driven the hypothetical Goshawk populations of El Hierro to extinction. SOME BIOGEOGRAPHICAL IMPLICATIONS The theory of insular biogeography (McArthur & Wilson, 1967) was developed from present patterns of diversity. The sources from which such patterns were extracted are however very limited, as they are restricted to very short and recent periods of time. In this sense, palaeontological data, together with current data on diversity, are necessary to analyse biogeographic patterns that have taken thousands or million of years to develop (James, 1995). The image that we have on the diversity and biogeography of vertebrates in the archipelagos is at the moment partial, and it is changing with the increase in the number of palaeontological studies. The fossil record from the Canary Islands indicates that a significant part of the original ornithofauna is now extinct. Nowadays, there are seven breeding species of Procellariiformes in the Archipelago (Bulweri bulwerii, Calonectris diomedea, Puffinus puffinus, P. assimilis, Pelagodroma marina, Hydrobates pelagicus and Oceanodroma castro; Martín & Lorenzo, 2001), whereas at least three extinct species are known: Puffinus holeae (Walker et al., 1990), P. olsoni (McMinn et al., 1990) and Pterodroma sp. (this paper), so that at least 30% of the species in this group are extinct, and probably since a very recent time. A similar situation is observed in the family Accipitridae, which comprises four breeding species (Neophron percnopterus, Accipiter nisus, Buteo buteo and Pandion haliaetus; Martín & Lorenzo, 2001),

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and three extinct species (43%): Milvus milvus, eradicated only a few decades ago (Martín, 1987), Haliaeetus sp. (Rando, 1995) and Accipiter gentilis (this paper). Probably, with the advance of studies in this field, these proportions and those of other bird groups will change, which will result in a deeper knowledge and a better understanding of bird biogeography in the Canary Islands. ACKNOWLEDGMENTS.—To J.A. Alcover and B. Seguí of the Institut Mediterrani d’Estudis Avançats, J. M. Biscoito of the Museu Municipal do Funchal and J. Cooper and D. Smith of the British Museum (Natural History) for the loan of material for its comparison. A. Martín, P. Marrero, M. Nogales, F. Zino, P. Oliveira, J. Afonso, J.A. Lorenzo, J.D. Perera, R. Barone, S. Batista and R. Martínez helped me with different parts of the work. J.C. Illera and F. GarcíaTalavera made contributions to the first version. An anonymous referee made interesting comments on the original manuscript, and C. Solana improved the English version.

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NEW DATA OF FOSSIL BIRDS FROM EL HIERRO (CANARY ISLANDS)

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WORTHY, T. H. 1999. What was on the menu? Avian extinction in New Zealand. New Zealand Journal of Archaeology, 19: 125-160. WORTHY, T. H. & HOLDAWAY, R. N. 1994. Quaternary fossil faunas from caves in Takaka Valley and on Takaka Hill, nerthwest Nelson, South Island, New Zealand. Journal of the Royal Society of New Zealand, 24: 297-391. ZINO, P. A. & ZINO, F. 1986. Contribution to the study of the petrels of the genus Pterodroma in the Archipelago of Madeira. Boletim do Museu Municipal do Funchal, 38: 141-165. ZINO, F. & BISCOITO, M. J. 1994. Breeding seabirds in the Madeira archipelago. In, D. N. Nettleship, J. Burger & M. Gochfeld (Eds.): Seabirds on islands: Threats, case studies and actions plans, pp. 172-185. BirdLife International. Cambridge. ZONFRILLO, B. 1993. Relationships of the Pterodroma petrels from the Madeira Archipelago inferred from their feather lice. Boletim do Museu Municipal do Funchal, supl. 2: 325-331. [Recibido: 13-3-01] [Aceptado: 15-2-02]

APPENDIX I The bird bones from Cueva de El Curascán: Pterodroma sp. (Petrel) Specimen 1, TFMC VF 673: associated elements including cranium lacking palatal area and jugal bars, three fragments of mandible, both humerus, ulnas, radius, carpometacarpus, coracoids, tibiotarsus; left femur, right tarsometatarsus and left phalanx proximal digiti majoris; Specimen 2, TFMC VF 674: associated elements including cranium lacking palatal area and jugal bars, four fragments of mandible, left humerus, complete right and distal fragment of left ulna, radius, both carpometacarpus, left femur, left coraicoid, left scapule, left phalanx proximal digiti majoris, a fragment of synsacrum, sternum and one vertebrae; Specimen 3, TFMC VF 675: both humerus, right ulna, left carpometacarpus, fragment of right coraid, and a vertebrae. Calonectris diomedea (Cory’s Shearwater) TFMC VF 676: Cranium lacking premaxilla; both proximal fragments of the jaw and right phalanx proximal digiti majoris. Oceanodroma castro (Madeiran Storm-petrel) TFMC VF 677: Cranium lacking premaxilla and distal fragment of right tibiotarsus. Accipiter gentilis (Goshawk) TFMC VF 678: Fragment of cranium including nuchal area, foramen magnun and right temporal and occipital region, proximal fragment of right and left humerus, proximal fragment of left and distal fragment of right ulna, radius, both carpometacarpus, scapules and coracoids, left proximal phalanx of digiti majoris and both distal ones, three fragments of both femurs, two fragments of left tibiotarsus, complete left and two fragments of right tarsometatarsus, one carpi radial and one carpi ulnar bone, 15 pedal phalanx, and 7 vertebrae. APPENDIX II Comparative material examined: Pterodroma feae (Fea’s Petrel), MMF 24830; P. madeira (Madeira Petrel), MMF 26306, 26305, 30500, 31596, 31599, 31600, 31602, 31603, 31604, 26304. This last number includes remains of five birds; Calonectris diomedea (Cory’s Shearwater), DZUL 740, 1358, 1363, 1632; TFMC 18, 20; Oceanodroma castro (Madeiran Storm-petrel), DZUL 763, TFMC 121, 122; O. leucorhoa (Leach’s Storm-petrel), DZUL 2293; TFMC 130; Accipiter gentilis (Goshawk) MNIB 9959 female; 12607; Melierax metabates (Dark Chantinggoshawk) MBNH S/1954.30.29 female; M. canorus (Pale Chantin-goshawk) S/1984.99.4. Ardeola 49(1), 2002, 38-49