DISTRIBUTION AND PROVENANCE OF FOSSIL AVIFAUNA ON SAN MIGUEL ISLAND

DANIEL A. GUTHRIE

Joint Science Program, Claremont McKenna, Scripps and Pitzer Colleges, Claremont, CA 91711 [email protected]

ABSTRACT—The avian species abundance from 19 Pleistocene vertebrate sites on San Miguel Island include fauna from new sites not previously listed. The provenance of material at most sites was from nearby nesting colonies of seabirds. One site was a roost for barn owls, which included many small birds in their diet. Proximity to bald eagle bones and comparison to avian material from a recent eagle nest on San Miguel Island suggest that remains of most non-nesting marine birds found at some sites were brought there by eagles.

Keywords: avifauna, bald eagles, California, Pleistocene, San Miguel Island

INTRODUCTION At Simonton Cove, fossil material is found along the sides of several wide canyons (localities To prevent loss of valuable faunal material to 6, 7, 16; Fig. 1). Although most material was the forces of erosion, San Miguel Island has been deposited through erosion from higher levels, some surveyed periodically to salvage exposed bone complete skeletons have been recovered from this from Pleistocene sediments. Collections were area suggesting these individuals may have made in 1980, 84, 85, 88, 90, 94, 96, 98, and 2002. burrowed into the sides of these canyons to nest. To date approximately 17,000 bones from 61 Presence of eggshell and of incompletely formed species have been recovered. All material has been bones of immature birds further support this idea. catalogued and is in the collections of the Santa At Cuyler Harbor (locality 10; Fig. 1), Barbara Museum of Natural History (Santa sediments just above the east end of the beach were Barbara, CA; Appendix 1). The locality for each formed by erosion from higher levels which specimen was identified by a number (Fig. 1). deposited a mixture of bone, snail shells and Descriptions and maps of each locality are on file fragments of marine mollusk shells. There is a at the Santa Barbara Museum of Natural History layer of tar sand in these deposits about 60 feet and at the headquarters of Channel Islands above sea level, which either indicates seepage National Park, Ventura, CA. from inland sources on San Miguel Island or Exposed sediments containing fossil material deposition on the beach from offshore oil seeps. occur along the north coast of San Miguel Island Although these deposits yielded many fossils in the (Fig. 1). Most of these sediments were formed by 1980s, most of this area is currently inaccessible as erosion of sea cliffs washing material to lower it is covered by dunes and sand blown upward from levels toward the north shore of the island. In some Cuyler Beach. areas, such as at localities 8, 14, 15, 17, 18, 19, Localities 4, 12, 21 and 22 (Fig. 1) are the only narrow gullies have cut through these deposits, areas to produce fossils on the upper surface of the exposing nearly vertical sections of bone-bearing island. The bones in these localities were buried by sediments. These fragile bones, including bird sand blown inland from upwind beaches. At skulls, were deposited without breakage at these locality 12, although skeletal material is localities due in part to the nature of the sediments, disarticulated, bones are concentrated in a small which consist of fine grained soil and wind blown area. The presence of complete skulls and nearly sand. The number of intact bones suggests that the complete eggshells indicates rapid in situ burial. distance of transport from the site of death to the Most of this site, which produced a rich collection site of deposition was not great. of skeletal material in the 1980s, is now buried by 36 GUTHRIE

bones), and three species of Alcidae; an extinct puffin (Fratercula dowi, 8,202 bones) and extant Cassin’s auklet (Ptychoramphus aleuticus, 4,160 bones) and ancient murrelet (Synthiboramphus antiquus, 2,042 bones). Although none of these species currently nest on San Miguel, based on the abundance of these species in discrete areas (Appendix 1) and the presence of eggshells and undeveloped bones of immature individuals, it is believed that these four species once had nesting colonies on the island. Figure 1. Pleistocene vertebrate fossil localities on San Migu Bones and eggshell fragments of C. lawi were Island, CA. especially abundant at localities 10 and 12, and it is believed that these areas were once major nesting shifting sand dunes. At localities 4, 21 and 22, sites for this species. Extant species of geese build bones are widely scattered and worn, indicating nests on the ground, often protected by grass and that these bones were either on the surface for an shrubs. Since C. lawi was flightless, its presence in extended period before burial or were eroded out of these areas, which are connected to the ocean by a the deposits well before collection. Additional gradually sloping shoreline, seems reasonable. comments on the geology of these sediments can Chendytes lawi remains are scarce at other coastal be found in Johnson (1980) and Guthrie (1993). localities on San Miguel Island, likely due to the Radiocarbon dating of bone from these cliffs separating upland from beach areas. deposits indicates ages varying between 12,000 The three species of alcid usually construct and 40,000 BP (before present). The more recent burrows in soft soil. The presence of a few dates were obtained from localities 4 and 12 on the articulated skeletons and also of disarticulated upper terrace of the island, while older dates were skeletons (but with bones closely associated) obtained from lower strata at localities 7 and 10 appear to be from individuals that died in burrows. (Guthrie 1992). Nearly complete skeletons of F. dowi have been Material found on the surface along the sides recovered from locality 7 as have egg shell of canyons and gullies may have fallen from higher remains. The area is rich in skeletal remains of this levels or have been deposited at the site of species, many of which were not fully developed, discovery. Thus, bones occurring side by side in indicating they were young. Deposits at locality 10 the deposits may have originally come from and localities 17, 18, 19 consist almost entirely of different layers and be of differing ages. However, material washed down from higher levels, as the completeness of fragile skeletal elements evidenced by the completely disarticulated nature indicates a short distance of transport for most of of the skeletal material and some pre-depositional the material, and allows some interpretation about breakage of fragile elements such as skulls. its provenance. There appear to be three main However, the abundance of material from these mechanisms by which avifaunal remains were locations, including many bones of immature incorporated into these deposits: from seabird individuals, indicates nearby nesting of F. dowi. colonies, by owls, and by bald eagles. Each of Remains of the two smaller species of alcid, these will be discussed below. Cassin’s auklet and ancient murrelet, were more abundant at localities 6, 15 and 16 than were remains of F. dowi, which is rare at the latter two NESTING COLONIES localities. This suggests separation in nesting location between these species. The rarity of alcid Four species are extremely well represented in remains at locality 12 indicates separation of the San Miguel Island deposits. These are an nesting areas on the island between these species extinct flightless goose Chendytes lawi (1,836 and C. dowi. AVIFAUNA FOSSILS 37

BARN OWLS white-winged scoter (Melanitta fusca), Brandt’s cormorant (Phalacrocorax penicillatus), sooty Owls are often responsible for transporting shearwater (Puffinus griseus) and Cassin’s auklet skeletal material of small taxa to their roosting or (Collins et al. 2005). The frequency of these species nesting sites. At locality 20, a thin but rich layer of mirrors their presence around San Miguel Island bones dated to 7,300 BP includes a few barn owl (Collins et al. 2005). Species poorly represented in bones and extremely abundant remains of barn owl material from this nest include shorebirds and gulls. prey. The most common prey item at locality 20 is In an earlier paper (Guthrie 1993) I suggested deer mouse (Peromyscus maniculatus), but ornate that the bones of seabirds not nesting on the island shrew (Sorex ornatus) alligator lizard (Gerrhonotus but incorporated into the deposits probably were multicarinatus) and birds form significant from beached carcasses that had been blown inland components of the deposit. Although the avian by the strong northwest winds. It now seems more material from this deposit has not been completely likely that these remains were brought inland by identified and tabulated, well represented species bald eagles. Several remains of bald eagles were include Cassin’s auklet, burrowing owl (Athene found in Pleistocene deposits on San Miguel Island cunicularia) and many passerine species, including (Appendix 1). A partially articulated skeleton of a island residents (western meadowlark, Sternella bald eagle was found at locality 16 and 12 eagle neglecta; song sparrow, Mesospiza melodia; bones were found at locality 7. A majority of the horned lark, Eremophila alpestris) and wintering non-nesting marine birds found on San Miguel species (white-crowned sparrow, Zonotrichia Island came from these localities. At locality 16, leucophrys). bones of marine birds were found concentrated At the Daisy Cave archeological site on the very close to the bald eagle skeleton, suggesting eastern end of San Miguel Island (just above that this was either a nest site or a perching site for locality 23), barn owl bones are found below eagles. ledges located above the entrance to this rock The only evidence of predation on bones from shelter along with numerous remains of species the eagle nest at Ferrelo Point is punctures in sterna considered their prey. The extinct mouse of Brandt’s cormorant, rhinoceros auklet, white- Peromyscus nesodytes occurs frequently in the winged scoter and large gulls, the spacing and lower layers of this deposit, but disappeared about pattern of which correspond to the foot structure of 8,000 BP (Guthrie 1980). At this time bones of P. bald eagle. Such puncture wounds could be from maniculatus first appear in the deposits and active predation, or from an eagle’s attempt to remains of Xantus’s murrelet (Synthiboramphus stabilize a carcass while tearing feathers or meat hypoleucus), Cassin’s auklet and of passerine birds from the bones. Larger sterna were found only become increasingly common. rarely in the Pleistocene San Miguel Island deposits and there is, therefore, no direct evidence of eagle predation. However, similarity in BALD EAGLES composition between the avifauna from the Ferrelo Point nest (Collins et al. 2005) and that from Recent analysis of the nest of a bald eagle from Pleistocene deposits associated with eagle remains Ferrelo Point on San Miguel Island (Collins et al. (locality 16; Appendix 1) is suggestive of eagle 2004, 2005) revealed a wide range of marine birds involvement in the formation of the assemblage. in the diet of island eagles. Although bald eagles The Pleistocene avifauna composition from are often considered to prey predominately on fish, localities with eagle remains was similar to that birds can account for a high proportion of their prey found in the Ferrelo Point nest in that both had high items in some areas (Buehler 2000). Eagles usually numbers of oceanic species (alcids, shearwaters, carry food items to the nest during breeding season ducks) and low numbers of shorebirds. A major or eat on nearby perch sites (Buehler 2000). difference between the faunas is substitution of Remains from the Ferrelo Point nest show that rhinoceros auklet in the modern fauna for rhinoceros auklet (Cerorhinca monocerata) was Pleistocene F. dowi. However, these species are the most common avian prey item, followed by identical in size, and F. dowi is the probable 38 GUTHRIE ancestor of the modern rhinoceros auklet (Guthrie bones of the three alcids away from suspected et al. 2000). Other differences included the greater nesting colonies. Bones of many other species of abundance of ancient murrelet in the Pleistocene birds may also be present in the deposits because of deposits. Thus, it seems that eagles may have bald eagle predation or scavenging. brought remains of oceanic species, especially the three species of alcids thought to nest on San Miguel Island, inland to eat, incorporating their ACKNOWLEDGMENTS remains in to the deposits. The suspicion that eagles fed on alcids at San Miguel Island in the My deep thanks to the editor of the 2005 past suggests that these species were incorporated Proceedings and two anonymous reviewers, whose into Pleistocene deposits by at least two different comments greatly improved this paper. mechanisms. The presence of the three species of nesting alcids in small numbers at some sites may be an indication not of nesting but rather of REFERENCES scavenging and/or predation by raptoral birds. The remains of red-tailed hawk (Buteo Buehler, D.A. 2000. Bald Eagle (Haliaeetus jamaicensis), crested caracara (Polyborus plancus) leucocephalus). In: Poole, A. and F. Gill (eds.), and peregrine falcon (Falco peregrinus) are also The Birds of North America, No. 506. The found more frequently at sites believed to have Birds of North America, Inc., Philadelphia, PA. been frequented by bald eagles. This may be Collins, P.W., D.A. Guthrie, T.C. Rick and J. evidence of successful competition and predation Erlandson. 2004. Food habits of bald eagles by eagles on these species. that nested historically at San Miguel Island Bones of island fox (Urocyon littoralis) were based on prey remains excavated from an very rare in the Ferrelo Point nest (Collins et al. historic nest site. Santa Barbara Museum of 2005). The few remains of island fox found in Natural History Technical Reports – No. 2. Pleistocene deposits on San Miguel Island come Santa Barbara, CA. 34pp. from localities where eagle remains occur Collins, P.W., D.A. Guthrie, T.C. Rick and J.M. frequently but whether this is due to predation or Erlandson. 2005. Analysis of prey remains scavenging by eagles cannot be determined from excavated from an historic bald eagle nest site the material. on Santa Miguel Island, California. Pages 103– 120. In: Garcelon, D.K. and C.A. Schwemm (eds.), Proceedings of the Sixth California SUMMARY Islands Symposium. National Park Service Technical Publication CHIS–05–01, Institute Deposits on San Miguel Island have yielded for Wildlife Studies, Arcata, California. more species of birds than any other coastal deposit Guthrie, D. 1980. Analysis of avifaunal and bat in California (Jefferson 1991) and possibly from remains from midden sites on San Miguel the Pacific rim. Due to burial by wind-blown sand island. Pages 689–702. In: Power, D. (ed.), and short distance of transport between site of The California islands: Proceedings of a death and site of deposition, this material is in an multidisciplinary symposium. Santa Barbara excellent state of preservation. Based on the Museum of Natural History, Santa Barbara, frequency of occurrence in the deposits and the CA. presence of bones of immature individuals and of Guthrie, D.A. 1992. A late Pleistocene Avifauna eggshells, three species of alcid (F. dowi, Cassin’s from San Miguel Island, California. Pages 319 auklet and ancient murrelet) and an extinct goose –327. In: Campbell, Jr., K.E. (ed.), Papers in (C. lawi) are believed to have once nested on San Avian Paleontology Honoring Pierce Brodkorb. Miguel Island. Distribution of bones of these Science Series No. 36. Natural History Museum species in the deposits suggests some separation of of Los Angeles County, Los Angeles, CA nesting colonies. Predation and/or scavenging by Guthrie, D. 1993. New Information on the bald eagles may account for the occurrence of Prehistoric Fauna of San Miguel Island, AVIFAUNA FOSSILS 39

California. Pages 405–416. In: Hochberg, F.G. Jefferson, G.T. 1991. A catalogue of late (ed.), Third California Islands Symposium: Quaternary vertebrates from California: Part Recent Advances in Research on the California one, non marine lower vertebrate and avian Islands. Santa Barbara Museum of Natural taxa. Natural History Museum of Los Angeles History, Santa Barbara, CA. County, Technical Report 5: 1 – 59 pp. Guthrie, D., H. Thomas and G. Kennedy, 2000. A Johnson, D.L. 1980. Episodic vegetation stripping, new species of extinct late Pleistocene puffin soil erosion, and landscape modification in (Aves: Alcidae) from the southern California prehistoric and Recent historic time, San Channel Islands. Pages 525–530. In: Brown, Miguel Island, California. Pages 103–121. In: D.R., K.L. Mitchell and H.W. Chaney (eds.), Power, D. (ed.), The California Islands: Proceedings of the Fifth California Islands Proceedings of a multidisciplinary symposium. Symposium. U.S. Dept. of Interior, Minerals Santa Barbara Museum of Natural History, Management Service, Pacific OCS Region Santa Barbara, CA. (published as CD) MMS 99–0038, Camarillo, CA. 40 GUTHRIE Locality number (see Fig. 1) ed between 1980 and 2002. and between 1980 ed San Miguel Island, collect 0002 1 00 0 0000 1 0100005 0121 5 00 0 0000 9 02100021 0 0000 8 01000550 2010 0915 0408 5 00 2 0002 1 2 0 01000024 1000118 0 0 0 0 4 00000 1 0 00 0 0 3 0000 10 0 29 0000001 0002 1 00 0 1000 0 0000004 0 0 2060106 0 0 0 0 2 00003 1 1 00 0 0 0 0000 01 2 28 01300010 0000 1 00 6 0100 0 1000009 omnlo00 0 00 3 0 00 0000 1 1 0100 0010002 0 0000008 loon0201 loon0000 common Pacific grebe otenfla00 4 01 1 0001 4 01000118 0 00 2 0000 0 0000002 grebe0000 fulmar0401 0 00 0 0000 3 0020005 eared grebe 0 00 0 0000 0horned 0000003 0 0short-tailed albatross gannet0000 1northern sooty 1heron0300 shearwater black-vented shearwater 1short-tailed shearwater 0fork-tailed storm-petrel 0ashy storm- petrel blue 2brown pelican 5 10 2 0200 4 3 00000018 extinct 0 0 Brandt’s 8cormorant 0pelagic 0cormorant 0 goose0005 0great 8 0white-faced ibis 0 0 California 0condor 0 0 0snow 0 0 0 0 0 0 0 1 0 0 0 0 17 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 8 0 0 0 0 1 sp. western/Clark’s Gavia immer Gavia pacifica Aechmophorus Podiceps nigricollis Fulmarus glacialis Puffinus opisthomelas Puffinus tenuirostris furcata Oceandroma Oceanodromas homochroa Phalacrocorax pelagicus Podiceps auritus Phoebastria albatrus Puffinus griseus Pelicanus occidentalis reyna Morus Phalacrocorax penicillatus Ardea herodias Plegadis chihi Gymnogyps californianus Chen caerulescens Scientific nameScientific Gaviiformes Order Name Common 2Order Podicipediformes 4 5 6 7 8 9 10 11 12 14 15 16 17 18 19 21 22 23 total Order Procellariiformes Pelecaniformes Order Order Ciconiiformes Anseriformes Order Appendix 1Appendix on bones from sites avian of Tabulation . AVIFAUNA FOSSILS 41 tween 1980 and 2002. and tween 1980 Locality number (see Fig. 1) land, collected be land, collected 0001 0 00 0 0000 2 0000003 0003 3 00 1 1000 1 0000009 0000 1 00 1 0000 0 0000002 0000 1 00 0 0000 0 0000001 0000 0 00 1 0000 1 0000002 0000 0 00 1 0000 1 0000002 0000 0 00 0 0000 1 0000001 0002 0 00 0 0000 2 0000004 avian bones from sites on San Miguel Is sites bones from avian aaagoe01100 0 5 0 0 0 20 3 53 0 0 210 5 00 1 03001900000033 2 0 00 00 7 0 1000 0000 goose00012100 1 3 01000113 0000003 hawk0302 3 01022111000029 scoter0000 1200 falcon0000 Canada white-fronted goose white-winged eagle0009 scoter surf 0 0 00 00 0 red-breasted 0 0000 0000 0 0 0100002 0000001 merganser gooseextinct 1bald 17 1red-tailed 00 0 1 5000 1 0000008 crested caracara 7 0 godwit0001 0 00peregrine 0 1000 2 0 0000003 00 1 0000 9 0 1 0000001 American gull0001 kestrel 0 0black-bellied 6 turnstone0001 21plover semipalmated 1003plover 7 35black 0000 1oystercatcher 00 0 592 0000 0 0 0000001 willet 0whimbrel0000 0 knot 5marbled 0 127 0black 0 6 0sanderling0000 1 9 0red 0 phalaropered 0 0California 0 1 0 1ring-billed gull 2 0 0 0 Bonaparte’s 0 0 2gull 0 0 0 1836 3 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 1 0 0 17 0 0 0 0 0 0 0 0 0 0 0 0 12 1 0 0 0 2 0 0 0 0 2 0 0 0 0 0 0 0 18 0 2 Branta canadensis Branta Melanitta fusca Melanitta perspicillata Chendytes lawi Charadrius semipalmatus bachmani Haematopus Catoptrophorus semipalmatus Anser albifrons Anser serrator Mergus Haliaeetus leucocephalus Buteo jamaicensis plancus Polyborus peregrinus Falco sparverius Falco squatarola Pluvialis phaeopus Numenius Limosa fedoa Arenaria melanocephala alba Calidris Calidris canutus fulicaria Phalaropus californicus Larus delawarensis Larus philadelphia Larus Order Falconiformes Order Order Charadriiformes Scientific nameScientific Name Common 2 4 5 6 7 8 9 10 11 12 14 15 16 17 18 19 21 22 23 total Appendix 1 (Continued). Tabulation of Tabulation Appendix 1 (Continued). 42 GUTHRIE tween 1980 and 2002. and tween 1980 Locality number (see Fig. 1) land, collected be land, collected 0012 1913019011202042 901021620 0100 1 00 1 0000 1 0000004 0000 2 00 0 0000 0 0000002 0000 0 00 1 0000 0 0000001 0300 3 00 0 0100 3 00000010 0100 0 00 0 0000 1 0000002 0000 1 00 0 0000 0 0000001 avian bones from sites on San Miguel Is sites bones from avian herring, and glaucous-winged gulls. and glaucous-winged herring, utdpfi0 0 1 00 2 0000 0 0000004 0 00 0 0001 2 0000003 owl0000 puffin01 6 0 00 00 2 1 0100 0100 0 0 0000009 0000003 2 00 0 owl0001 0000 0 5 0000004 00 0 0000 2 11000012 Xantus’s owl0102 murrelet aukletCassin’s 2 00 0 0000 0 0000002 raven0000 puffinextinct 1 149tufted 83 7 lark0000 491 1307 62barn 358 sparrow0002 589burrowing 3372 8 110extinct 0 0 711 1279common 40 28song 141 48horned 112 0 31white-crowned 359sparrow 13western 840meadowlark 707 57 839 102 87 83 742 1 80 4 166 2569 258 6 4260 0 160 0 8202 31 4160 3155 143 810 126 419 2075 790 999 110 207 292 44 17099 omnmre11120 0 2 0 0 0 11190 0 0 2 390 murre01015172 black-legged kittiwake common pigeon guillemot ancient murrelet 0 32 1 549 365 2 Ptychoramphus Ptychoramphus aleuticus neglecta Sternella Fratercula dowi Fratercula cirrhata Tyto alba cunicularia Athene Asio priscus corax Corvus melodia Melospiza alpestris Eremophila Zonotrichia leucophrys S. hypoleucus S. Larus spp. (large)* Larus Rissa tridactyla Uria aalge Synthiboramphus antiquus Cepphus columba Cepphus Order Strigiformes Order Passeriformes Order Totals Scientific nameScientific Name Common 2 4 5 6 7 8 9 10 11 12 14 15 16 17 18 19 21 22 23 total Appendix 1 (Continued). Tabulation of Tabulation Appendix 1 (Continued). * This category may include western,