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Ingestion of plastic debris by Laysan Albatrosses and Wedge-tailed Shearwaters in the Hawaiian Islands
Volume 18/Number 61J/June 1987 C;dkins. I). (1985). Sleller sea Item entanglement in marine debris. Unpuhl. ntanuseripl. Alaska DepI. lqsh and Game. A~cttorage, AK. Cooper, C. F & Stewart, B. S. (19821. The perils of success: impliealions of increasing marine mammal pnpulati{ms in the Southern Califi~rnia Bight. l'n)e. Ocean Studies Symposium. Asihmmr, Calif., 7-1(l Nnv. 19N2. Ci,oper, C. E & Stewart, B. S. (1983). Demography of northern elephant .seals, 1911-1982. Science 219, 969-971. l)el-ong, R. L. (1982). Population bioh,gy of northern fur seals at San Miguel Island. Calih~rnia. I'11.I). Dissertalion, University of Califi)rnia, Berkeley. CA. beLong. R. L & An|anvils, G. A.. Jr. ( 19851. Impact (ff thc 1 9 8 2 - t 9 8 3 El Nifio on the northern fur seal population at San Migncl Island. Abslr. 6th Bienn. C o a l Biol. Mar. Mature, 2 2 - 2 6 Nt~v. 1985. Vancouver. British Columbia. Canada. DeMastcr. 13. E, MillcL D. J., Goodman, D.. DeLong. IL L & Stewart. 13. S. (1982). Assessment of California sea lion-fishery interactions. 7h~t~,c At. Am. II~ldl. A'al. R~:~.Coati 47, 253-276. Fowler, C. W. (1985). An evaluation of the n)le of entanglement in population dynamics of northern fur seals on the Pribilof Islands. In
Pn)~; Bbrkshop on lhe l~te and hnpac't of Marine Debris. NOAA Tech. Memo. NMFS-SWFC-54. (R. S. Shomura & H. O. Yoshida, cds). pp. 291-307. Honolulu, ItawaiL Fowler, C. W. (19861. Marine debris and northern fur seals: a ease study. Mar. Ibllut. Bull. 18,326-335. Itanan. D. A. (19861. Califi)rnia Dcparlmenl of Fish and Game coastal marine mammal study, annual report lot the period July 1. 1983June 3(I, 1984. NMFS/SWFC Admire Report L J - 8 6 - 1 6 . Nati~mal Marine Fisheries Service. La Jolla, CA. 1to(livid. 1t. (19851. Set gill and trammel net observations in ecmral Califi~rni~. Report to the US Marine Mammal Commi~,sion. Con• tract No. MM2911 (1891-2. Henry, M. E. (19851. Observalions of gill and trammel net fishing activities between Pt. Buchon and Pt. Sur. Califi)rnia. June-August 1985. Report to the US Marine Mammal Commission. Contract MM33(1951 I - 8 . Huber0 H. R. (I 984). The effects of El Nifio on the sea lion pt)pulations of the Pt. Reyes National Seashore. Proceedings of the Second Bienn. Conf. on Science in Nat. Parks. 5 - 7 Sept. 198.1. Univ. of Calif., Davis. CA. Kuzin. A. E., Maminov, M. K. & Perlov. A. S. (19841. The number of plnnipeds and sea otlers on the Kurll Islands. In Mammals of the Far East (V. E. Rodin. A. S. Pcrlov. A. A. Berzln. G. M. Gavrilov. A. 1. Shevchenko, N. S. Fadeev & E. B. Kucheriavenko, cds), pp. $4-72. TINRO. Vladivostok.
L~mghlin. T. 1L. f;earin. P. J.. beLong. I,L L. & Merrick. R. L (1981"~). Assessment of net entanglement on northern se~ lions in the Aleutian Islimds, 25 June-15 July 1985. NWAFC I'mcessed Report. 8(~(12. National Marine Fisheries Service, Seattle. WA. L~mghlin. T R.. Rugh. D. J. & Fiseus. C. FI. (1984). N~rlhern sea li
MarirJel~olh,ionlhdletin.V{U.lg. No.M].pp.339-343.1987.
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ngestion of Plastic Debris by . aysan Albatrosses and Wedge-taded Shearwaters in the Hawaiian Islands D. MICHAEL
FRY,* STEWART
1. F E F E R t
and LOUIS
SILEO:I:
* D e p a r t m e n t o f A v i a n Sciences, Unitersio, o f California, Davis, C A 95616; "~Office o f Refitges a n d Wildlife Resources, U S F W S , P O B o x 50167, Honoh~ht, H [ 96850; e N a t i o n a l Wildlife Health Laboratory, U S F B ~ , 6006 S c h r o e d e r Rd., M a d i s o n , IVi 5371L U S A
Surveys of Lays~n Albatross and Wedge-tailed Shearwaters on Midway and Oahu Island, Hawaii, identified a high proportion of birds with plastic in the upper gastrointestinal tract, representing hazards to the health of adult birds and their chicks. Fifty Laysan Albatross chicks were examined for plastic items lodged within the upper digestive tract. Forty-five (90%) contained plastic, including 3 chicks having proventricular impactions or ulcerative lesions.
Plastic items in 21 live albatross chicks weighed a mean of 35.7 g chick-I (range 1-175 g). Four dead birds contained 14-175 g (mean 76.7 g). Two of four adult albatross examined contained plastic in the gut. Laysan albatross chicks have the highest reported incidence and amount of ingested plastic of any seabird species. Twelve of 20 adult Wedge-tailed Shearwaters (60%) contained plastic particles 2-4 mm in diameter, impaclion did not appear to be a significant hazard for adult 339
Marine Pollution Bulletin
shearwaters. Shearwater chicks ~ere not examined. Chemical toxicity of plastic polymers, plasticlzers and antioxidant addilh'es is low, although many pigments are toxic and plastics may serve as vehicles for tile adsorption of organochtorine pollutants from sea •,~ater, and the toxicity of plastics is unlikely to pose significant hazard compared to obstruclian and impaction of the gut.
1982 and 1983 on Midway Island (28'N, 177"W) to investigate a series of disease and lead poisoning incidents with albatross chicks. Necropsies were conducted on apparently healthy chicks, chicks with wing-droop syndrome, and dead chicks. Tissues were collected for residue analysis of lead and mercury. The association between lead poisoning and wing-droop syndrome is presented elsewhere (Sileo & Fefer, in prep.). During the 1982 and 1983 investigations, we recorded the presence and quantity of plastic in the gastro intestinal (GI) tracts of necropsied birds. Wedge-tailed Shearwaters were collected in the courlship phase of the breeding season in May, 1984, on Manana Island, a small volcanic cone 1.2 km offshore from Oahu, Hawaii (2I'I',1, 158"W). Ten pairs of adult birds were collected as part of a field study on oil toxicity (Fry et aL, 1986). Complete gross necropsies were performed on each bird.
Persistent plastic items floating on the ocean present hazards to ninny species of marine birds that eat them. Plastics ingestion by seabirds is worldwide, and the number of species known to be ingesting plastic has markedly increased in the past ten years. Ingestion of plastics by seabirds was first documented (Kenyon & Kridler, 1969) in Laysan Albatross (Diomedea immutabills), a seabird species at high risk from plastics consumption. Results Procetlariiform and Charadriiform birds (albatrosses, shearwaters, fulmars, petrels, phalaropes, auklets, and Plastic ingestion by Laysan A lbatrosses puffins) are the groups most frequently found with plasTable 1 presents the numbers of Laysan Albatrosses tics in their upper digestive tracts (van Franeker, 1983; sampled and the numbers with plastics in the prevenlriDay et aL, 1985). Day et aL (1985) documented inges- culus. During the surveys of 1982 and 1983, 90% of tion of plastics by 50 species of seabirds and have chicks surveyed had plastic fragments, toys, bottle caps, closely examined correlations between feeding habits or cigarette lighters in their upper GI tract. Four adult and ingestion of plastics. Surface-feeding species, espe- Laysan Albatross were examined, and two contained cially those feeding on squid, fish eggs, and pelagic plastic. In July 1983, 24 albatross chicks were examined crustaceans are at greatest risk. From analysis of plastic for plastics, and the plastic debris was weighed and the particle sizes and colours, Day et aL (1985) concluded volume determined. Table 2 presents the amounts of that most species of seabirds that ingest plastic are plastics within the proventriculus of 19 live chicks selective in the sizes and colours of plastics and that collected for study and of 5 freshly dead chicks most ingested particles tend to resenable normal prey collected within the colony. Sevenleen of 19 (89%) live items. chicks contained plastic, and 4 of the 5 dead chicks Two classes of plastic debris appear to present the (80%) contained plastic. The mean weight and mean greatest hazard to sea birds. The most commonly volume of plastics was 35.7 g and 39.3 cc in live chicks, collected plastic particles in the marine environment are and 76.6 g and 85 cc in dead chicks. Two o f the live small bits of polyethylene, polypropylene and poly- chicks (containing 158 g and 175 g plastic) had styrene 1-5 mm in diameter that are apparently either impacted proventriculi. Starvation complicated by raw pellets from manufacturing sources or small weath1 ered fragments of plastic trash (Carpenter et aL, 1972; Incidence of plastic ingestionTABLE by Laysan Albatross chicks, Midway Colton et aL, 1974; van Franeker, 1983; Day et aL, Island. North Western Hawaiian Islands. 1985). These were commonly found by Day et aL Date Number of chicks with plaslie (t985) in a varieiy of small plankton-feeding seabirds. (No./No. examined) % The second class of plastic debris presenting risks to Aug. 1982 3/4 75.0 16/17 94.1 seabirds includes small manufactured items and frag- Apr. 1983 MaY t983 5/5 10t,) ments with dimensions as large as 20 x 80 mm. Large July 1983 21/24 87,5 birds such as albatrosses, feeding on large prey, are at 45/50 90,0 risk principally from these larger pieces of debris Totals floating on the ocean surface. 2 This report documents the increasing frequency of Quantity of plastic ingested by TABLE Laysan Albatross chicks. Midway Island, ingestion of plastic by Laysan Albatrosses and the Hawaii. July, 1983. Live and dead chicks were examined for incidence of plastics. detrimental effects on chicks that are fed plastics by adults. Additionally, we report a high incidence of Live chicks Dead chicks plastic ingestion by Wedge-tailed Shearwaters (Puffinus ;,1o. : 'h plastic/Total 17/19 4/5 pacificus), a species not previously known to ingest ~ t . . . , f :~stlc: mean 35.7 g 76.7 g plastics. range 1-t58 g 14-175 g '~
Study Locations and Methods
Surveys of Laysan Albatross were conducted during 340
Vc. ,,:~~=z,,~,~ aean :.~n~e
. . . . . . . . . . . . :";;:
49.8 g
69.t g
39.3 cc 1-175 cc 54.1 ce
85,0 c c 15-188ec 73.5 ee
Vt~lumcIll/Number6B/Julle 1987 impaction could have been the cause of death in the impacted dead dlick. Four chicks examined had proventricular ulcerations. Large plastic fragments appeared to be the direct cause of severe, chronic inflammatory lesions in the rnuseularis and mucosal I:mfin~l propria ~fone of the birds, and plastic may have caused minor chronic ulcerative lesions in the other t Ittee. The prevalence and severity {)f plastic obstruction of the upper G1 tracts of chicks varied widely. Laysan Albatross chicks weighing 2-3 kg contained, on average, 36 g of plastic, amounts not appearing to cause obstruction or interference in digestion or assimilation of food. Only chicks containing as much as 175 g had impacted preventrieuli whicl~ resulted in partial obstruction of the gut. Olher facmt.~ a/}~,ctit~galbatross chick cottdition and sltrt'il,a! Severe debilitation occurred in many albatross chicks as a consequence of ingesting lead from paint fragments peeling off military buildings on Midway Island. Paint chips were ingested along with plastics and other foreign ohjects in the vicinity of albatross nests. Chicks from nests adjacent to abandoned buildings developed a wing-droop syndrome and were unable to fledge. Ten of 12 chicks suffering from droop-wing syndrome had indications of lead poisoning (Stied & Fefer, in prep.). Lead and mercury content of weathered paint samples collected from buihlings was very high, with a mean lead concentration of 84,000 ppm and a mean mercury concentration of 40 ppnt. Plastic hlgestim: by adult Wedge-roiled Shear~ters Necropsies of shearwaters revealed plastic pellets and fragments in 12 of 20 birds. Plastics were rounded pellets or irregularly shaped fragments 1-3 mm thick and 2-7 ram long. Most shearwaters containing plastic had 2-6 fragments within the gizzard, but one male contained a total of eleven 3-4 mm diameter pellets distending the ventriculus and one additional 4 mm diameter fragment in the proventriculus. The majority of plastic items lodged within the gizzards were rounded pellets of polyethylene or polyproplylene 2-3 turn in diameter similar to those identified in other reports (Day, 1980; Day et al., 1985) as raw pellets used in the fabrication of manufactured goods. Approximately 20% of the plastic particles were worn polystyrene fragments~white, yellow, blue, or green--and apparently representing fragments of broken manufactured items. Fourteen of 20 shearwaters had numbers of small squid beaks within their gizzards. Beaks were roughly triangular in shape, 1-2 tara in longest dimension and 0.2-0.5 ram thick. The number of squid beaks ranged from 1-3 beaks in five birds up to several dozen in each of two birds. There was a negative correlation between the presence of squid beaks and the presence of plastic within the gizzards (P ~ 0.02, Fishers exact test). The incidence and amount of plastic was equal in both sexes (6 female, 6 male) and independent of the extent of subcutaneous fat and gonadal maturation. The
condition of the gonads of both males and females was characteristic of the courtship phase of the breeding season preceding the period of rapid yolk formation. Since our focus was on breeding pairs, our sample criteria automatically excluded nonbreeding birds, thereby precluding meaningful correlation between presence of plastic and delayed maturation of gonads. Discussion Plastic ingestion by La3.~an AIbatross chicks The rcsuhs presented here dcmonstrale thai a 't,,trry high proportion of chicks of albatrosses breeding in the North Western Hawaiian Islands (NWHI) ingest plastics during the pre-fledging period when they are dependent upon food brought to the breeding colony by parents. Floating plastic items are ingested by adult albatrosses and regurgitated to chicks along with normal food items. Albatrosses feed primarily on squid, fish, and masses of fish eggs floating at the water surface. Flying fish (family Exocoetidatt) lay egg masses on flotsam, including plastic, which may tend to encourage the gathering of plastic by albatrosses. The variability in amounts of plastics in albatross chicks was high, with some birds containing little or no plastic and others containing more than 150 g. Large amounts of plastic appeared to cause impaction of the upper GI tract and interfered with passage of food through the digestive system. The sub-lethal effects of plastic impaction and minor ulceralions may contribute to reduced resistance to disease and lowered post fledging survival, Some fragments of plastic ingested by albatross chicks are picked up directly by the chicks in the litter of the breeding colony. Plastic fragments are abundant on the ground at Midway Island and other NWHI breeding colonies. Plastic litter is most common on beaches where it is deposited by ,,,,'ave action, but small pieces are common in the albatross colonies as parts of castings regurgitated by resident albatrosses. Laysan Albatross fledglings ingest many types of foreign materials when they reach a size large enough to move from the nest (chick weights greater than 2 kg). The phenomenon of pica, the behaviour of ingestion of indigestible foreign matter, is not unique to albatrosses, but has been described for other species of avian chicks, including eagles, vultures, and ibis (Koford, 1953; Halliwetl et aL, 1973; Dobbs & Benson, 1984). The extent to which pica by Laysan Albatro:~s chicks contributes to ingestion of plastics and impaction has not been determined, and it is possible that pica may be partly a consequence of association of plastic items with food fed to chicks by adults, The small sample of 4 adult albatrosses surveyed here indicated half of the birds contained plastic during the period when these birds were actively feeding chicks. It is probable that adults transfer the bulk of the plastic to their chicks when feeding them by regurgitation. The high amounts of plastics in chicks probably represents the accumulation of indigestible items collected and regurgitated by adults throughout the breeding season (Kenyon & Kridler, 1969; Pettit ez aL,
341
Maritl¢ Pollution Bulletin
1981). Chicks appear to retain indigestible items in their proventriculi for long periods. Pettit et al. (1981) inadvertently monitored retention of foreign objects by albatross chicks after feeding small radio transmitters to adult albatrosses and having them regurgitate the transnfitters to chicks. The chicks did not regurgitate the transmitters for at least 40 days.
Wedge-tailed Shear,~ters Sixty percent of the adult Wedge-tailed Shearwaters surveyed carried small plastic pellets and fragments in their gizzards and provenlriculi. The pieces were much smaller (2--7 ram) than items carried by albatrosses and none of the breeding shearwaters in this study appeared debilitated by the plastics. One shearwater which contained 12 pieces had a distended gizzard, although there was no evidence that this volume of plastic was causing obstruction of the gut. There was a negative correlation between the presence of squid beaks and the presence of plastic within the gizzards. The cause of the negative correlation is unknown, but perhaps may be related to foraging habit differences such that 'squid-specialists' did not encounter much plastic. An alternative explanation could be that birds not finding sufficient squid may be opportunistically taking random items including plastic. Adult shearwaters ingest numerous small fragments of plastic, but at the rates and volumes documented here, it is not likely that they are at high risk. Regurgitated pellets of indigestible materials were not observed in the breeding colony, however, and we do not know whether shearwaters regurgitate indigestible material from their gizzards when the volume becomes large. If adults ingest plastics frequently, the risk to shearwater chicks fed plastic could be significant, as it appears to be with albatross chicks.
Ingestion of plastics by other Pacific species Both Laysan and Black-footed (D. nigripes) Albatrosses ingest plastics. The endangered Short-tailed Albatross (D. albatms) must also be considered at high risk because much of its distribution overlaps with Laysan and Black-footed Albatrosses and its foraging range is near Japan and across the Pacific in areas of high density of plastic debris. This species, which was thought to be extinct in 1949, now consists of not more than 300 birds breeding on Torishima Island (30*N, 140"E) 580 km south of Tokyo, Japan, and perhaps breeding on Minami-Kojima (26"N, 124"E) 200 km northeast of Taiwan (Hasegawa & DeGrange, 1982; Rice, 1984). The occurrence of plastics in chicks of seabirds has been reported only for Laysan, Black-footed (D. nigripes), and Wandering Albatrosses (D. exulans) (Kenyon & Kridler, 1969; Pettit et aL, 1981; Furness, 1983), and Leach's Storm-petrel (Oceanodroma leucorhoa) (Rothstein, 1975). The incidence of plastics consumption by Wedge-tailed Shearwater chicks has not been investigated, but it is likely that chicks receive regurgitated plastics from adults since 60% of adults surveyed contained plastics in their gizzards. Adult 342
birds of more than 50 species of seabirds have been recorded ingesting plastic (Day et aL, 1985), and it is probable that chicks of many species subsequently receive plastics regurgitated by adults, but there are no data for chicks of other species. Research is under way to quantify the consequences of plastic ingestion by chicks of albatrosses, and to determine the extent of plastics ingestion by adults and chicks of other species of Hawaiian seabirds.
htcreasing plastic pollution in the North- Western Hau~iian Islands The amount of plastic pollution on NWHI beaches has increased in the past 15 years and relatively large quantities of a variety of debris including fishing nets, floats, boxes, bottles, manufactured plastic items, and fragments of a diversity of sizes and types are now found on beaches. Comparisons of descriptions of plastics on beaches in the report of Kenyon & Kridler (1969) and Fisher (1975) with the report of Pettit et aL (1981) and observations made during this study indicate there has been an increase in tile amount of plastic debris collected by albatrosses and brought to breeding colonies. Numerous small indigestible items are now found within the albatross breeding colonies away from the beaches. Fisher (1975) reported that during his 13 year study of Laysan Albatross on Midway Island (1960-I973) foreign objects such as plastics were not usually found in colonies away from tidal action. Tile debris is apparently from the Orient as indicated by markings on the items. Pettit et al. (1981) identified 108 of 109 plastic articles in carcasses of albatross chicks as having been manufactured in Japan. The distribution of plastic trash appears to be much more abundant in the NWHI than on other remote islands of the central Pacific (S. Fefer, unpublished observations) and it is probable that much of the plastic found on NWHI beaches has been carried by the Kuroshio Extension. The most likely source of the majority of the plastic is land-based discharge. The incidence of plastic ingestion by albatross chicks appears to have increased since 1966 when Kenyon & Kridler (1969) determined that 74% of dead albatross chick carcasses found at Pearl and Hermes Reef (28°N, 176"W, 160 km east of Midway Island) contained plastic, with 8 pieces being the greatest number in any one carcass. Pettit et aL (1981) examined only 4 dead chicks on Midway Island in 1980, and all contained plastic. The indigestible material in the stomach of one dead chick appeared to have contributed to obstruction of the upper GI tract which prevented food from passing into the intestines. The carcasses of dead chicks weather over the course of the year into collections of foreign objects surrounded by skeletal remains. Fisher (1975) suggested the potential problem of recycling of foreign objects by Laysan Albatross chicks as he speculated that foreign objects in the skeletal/remains of albatross chicks from previous years might effect successive generations of chicks when they wdre consumed again.
Volume I/~/Number 6B/June 1987
R L s ~ to species h~ other m¢,as
The distribution of plastics in the world's oceans is not tmiform and seabirds foraging in areas of high plastic occurrence are obviously at greater risk than birds foraging in low density areas. The greatest density of large plastic dehris found in the Norlh Pacific by Dahlberg & Day (1985) was in the North Pacific Current at latitudes 30*N-40*N. The North Pacific Current and the Kuroshio Extension are prime feeding areas for Laysan, Black-footed, and Short-tailed Albatrosses. Several species of albatross from southern oceans have been reported to ingest large fragments of plastics (see review by Day el aL, 1985), but with lower frequency than Laysan Albatross, presumably because of the lower density of floating plastics in the southern heluisphere. Small plastic debris (principally raw polyethylene and polypropylene pellets) such as that ingested by shearwaters, of 2-5 mm diameteL appears 1o be distributed worldwide (Gulf of Alaska, Day et al., 1985; Sargasso Sea, Carpenter & Smith, 1972; Cape Basin of the South Atlantic Ocean, Bourne & lmber, 1982), but with higher densities in large oceanic gyres such as the Gulf of Alaska and the Sargasso Sea (Day et al., 1985; Carpenter & Smith, 1972). Most of the small plastic pellets in waters surrounding the main Hawaiian Islands (2300 km southeast of Midway Island) are carried south-westward on the California Current and its extension into the North Equatorial current. The origin of these petlels has been assumed to be inadvertent loss during production and ocean transport (Day et aL, 1985). The foraging habits of birds and the characteristics of their prey play a dominant role in determining risk from plastics. The species at risk from large fragments and plastic items 2-10 cm in length are albatrosses and perhaps boobies, frigate birds, and pelicans, although the latter species have not been recorded as ingesting plastics. The species at greatest risk from small plastic pellets are plankton-feeding birds such as shearwaters, petrels, prions, phalaropes, and auklets. A high proportion of Parakeet and Cassio's Auklets in the Gulf of Alaska and the Aleutian lslands~ingest plastics (Day et aL, 1985). In the S o u t h A t l a d i i c and South Pacific Oceans, several species of prions (small surface-feeding procellarids) ingest similar raw polyethylene pellets (Bourne & Imber, 1982; Furness, 1983). Ingestion of plastic does not, necessarily, present risk to adult birds. Plastic polymers, plasticizers, and antioxidant additives are not very toxic, although many. pigments are toxic and pla.stics may serve "as vehicles ,'for the adsorption of organochlorine pollutants from sea water. Carpenter et al. (1972) reported PCBs and DDT adsorbed to plastic pellets in the Atlantic Ocean, and Fisher (1973) has documented occurrence of persistent organochlorine p011utants in Laysan Albatross, but the sources of pollutants may well have been the food chain
rather than ingestion of plastics. The currently available evidence suggests that plastics appear to present risks only when they are consumed in sufficient quantity 1o cause physical obstruction or ulccratkms of stomachs of 0irds. The risk of plastic ingestion and impaclion in chicks of many species of seabirds may be different from the risks to adults. Albatross chicks appear to be at greater risk than adults, because of their high rates of ingestion and apparent low frequency of regurgitative casting of indigestible material, h is possible that chicks of other procellariids are at similar risk.
Bourne, W. R. P. & tmber. M. J. (1982). Plastic pellets collected hy a prion on Gough I~land, central ~mth Atlantic Ocean. Mar. F,d[ut Hull 13, 20-21. Carpenter, E. J. & Smith, K L. Jr. ( 1972}. Plastics on the Sargasso Sea surface, Science ! 75.124t J- 1241. Carpenter, l-.J..Anderson. S. J.,llarvey, G. R., Miklas. H. P. & Peck, II. B. (1972). Polyst)'rene spherules in coastal waters. Science 178, 749-750. Colton, J. 13. J r., Knapp, E 1). & Burns, B. R. (1974). Plastic particles in surface waters of the northwestern Atlantic. Science 1 8 5 , 4 9 1 - 4 9 7 . 1)ahlbcrg. M. L. & Day, R. H. (1o85). Obscrvatiom, of man-made objects on the sudacc of the north Pacific Ocean. In t'toceeding~ of the Bbrl~hop on the Fate and hnpacl of Marine Debris, 2 6 - 2 9 Novemher, 1984. t|onolu|u, I'lawaii (R, S. Shomura & H. O. Yoshida. eds). US Dept. of Commerce. NOAA Tech. Mere. NMI'-S. NOAA-TM -N M FS~SWFC-54. Day. R. H. (1980). The occurrence and charactefislies oi" plastic p~fllution in Alaska's marine birds. MS Thesis. University of Alaska, Fairbanks. Day, R. H., Wehle, D. H. S. & C o l c m a n . IL C. (1985). Ingestion of plastic pollutants by marine birds. In Proceedings of the Bbrkshop tm the Fate and Impair of Marine Debris, 2 6 - 2 9 November. 1984, Honolulu, Hawaii (R. S. Shimura ~ H. O. Yo~hida, eds), pp. 3 3 4 3,":,6. US Dept. of Commerce, NOAA. Tech. Mere. N M F S - N O A A TM-NMFS-SWFC-54. Dobbs, .1. C. & Benson, E C. t1984). Behavioural and metalx~lie resg~mses to ff~,d deprivation in the Cape Vulture. In Proceedings of the Second Symposi*mt on African t'reditory Binls (J. M. Mcndelsohn & C, W. Saps ford. cds), pp. 211-214. Natal ~3ird CMb. Durban. Fisher, t4. L 41975). Mortality and survival in lhe Lays.an Albatross. Diomedea imvm*tabilis I~cific Science 29, 279-300+ FD'. D. M.. Swenson, J. Addiego. L. A., Grau. C. R, & Kang, A. (1986). Reduced reproduction of Wedge-tailed Shear~aters e x p o ~ d to single doses of weathered Santa Barbara crude oil. An'h. Edviron. Cowtam. ToxicoL 15..153-463. Furness. B. L. (1983). Plastic panicles in three procellariiiorm sea birds from the Benguela Current, South Africa. Mar. l~a/lut. Bull 14, 3 0 7 308, Ha|liwclt, ~V H.. Graham, D. L. & Ward, E P. (1973). Nutritional diseases in birds-of-prey. Z Zou Atdm. Med. 4. 18-20. Hasegawa, H. & DeGrange. A. R. (1982). The Short-tailed Albatross { Diomedea albamts), its status, distribtttion, and natural histo~', Am. Birds 36, 806-814. Kenyon, K. W. & Kridler, E. (1969). Laysan Albatross s~,'allow indigestible manet. Auk 86, 339-343. Koford. C. B. (1953). The California Condor, pp. 55-59. Dover Publications, New York. Pettit, T. N.. Grant. G. S. & Whitlow. G. C. (! 981 ). Ingestion of plastics by Laysan Albatross. Auk 98, 839-841. Rice. D. W. (1984), Albatrosses. In Seabints o f Eastern Abrth Pacific and Aft'tic Water~ (D. Haley, ed.), pp. 32-41. Pacific Search Press, Seattle. Rothstein, S. I. (1973). Plastic particle pollution of the surface of the Atlantic Ocean: Evidence from a seabird. Condor 75, 344-345. van Franeker, J. A. 0 9 8 3 ) . Plastics---een bcdreiging your zeevogels. NedeHaods Stookoli~lachtoffer.Onder~oek fNSO) 4, 41-61.
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Pn)~; Bbrkshop on lhe l~te and hnpac't of Marine Debris. NOAA Tech. Memo. NMFS-SWFC-54. (R. S. Shomura & H. O. Yoshida, cds). pp. 291-307. Honolulu, ItawaiL Fowler, C. W. (19861. Marine debris and northern fur seals: a ease study. Mar. Ibllut. Bull. 18,326-335. Itanan. D. A. (19861. Califi)rnia Dcparlmenl of Fish and Game coastal marine mammal study, annual report lot the period July 1. 1983June 3(I, 1984. NMFS/SWFC Admire Report L J - 8 6 - 1 6 . Nati~mal Marine Fisheries Service. La Jolla, CA. 1to(livid. 1t. (19851. Set gill and trammel net observations in ecmral Califi~rni~. Report to the US Marine Mammal Commi~,sion. Con• tract No. MM2911 (1891-2. Henry, M. E. (19851. Observalions of gill and trammel net fishing activities between Pt. Buchon and Pt. Sur. Califi)rnia. June-August 1985. Report to the US Marine Mammal Commission. Contract MM33(1951 I - 8 . Huber0 H. R. (I 984). The effects of El Nifio on the sea lion pt)pulations of the Pt. Reyes National Seashore. Proceedings of the Second Bienn. Conf. on Science in Nat. Parks. 5 - 7 Sept. 198.1. Univ. of Calif., Davis. CA. Kuzin. A. E., Maminov, M. K. & Perlov. A. S. (19841. The number of plnnipeds and sea otlers on the Kurll Islands. In Mammals of the Far East (V. E. Rodin. A. S. Pcrlov. A. A. Berzln. G. M. Gavrilov. A. 1. Shevchenko, N. S. Fadeev & E. B. Kucheriavenko, cds), pp. $4-72. TINRO. Vladivostok.
L~mghlin. T. 1L. f;earin. P. J.. beLong. I,L L. & Merrick. R. L (1981"~). Assessment of net entanglement on northern se~ lions in the Aleutian Islimds, 25 June-15 July 1985. NWAFC I'mcessed Report. 8(~(12. National Marine Fisheries Service, Seattle. WA. L~mghlin. T R.. Rugh. D. J. & Fiseus. C. FI. (1984). N~rlhern sea li
MarirJel~olh,ionlhdletin.V{U.lg. No.M].pp.339-343.1987.
I)a25-32~X/~TSJ ()(I-~4U)t)
t~nntedin Grea!13ritain.
© ]v~7Pcr~armmJournalsLid.
ngestion of Plastic Debris by . aysan Albatrosses and Wedge-taded Shearwaters in the Hawaiian Islands D. MICHAEL
FRY,* STEWART
1. F E F E R t
and LOUIS
SILEO:I:
* D e p a r t m e n t o f A v i a n Sciences, Unitersio, o f California, Davis, C A 95616; "~Office o f Refitges a n d Wildlife Resources, U S F W S , P O B o x 50167, Honoh~ht, H [ 96850; e N a t i o n a l Wildlife Health Laboratory, U S F B ~ , 6006 S c h r o e d e r Rd., M a d i s o n , IVi 5371L U S A
Surveys of Lays~n Albatross and Wedge-tailed Shearwaters on Midway and Oahu Island, Hawaii, identified a high proportion of birds with plastic in the upper gastrointestinal tract, representing hazards to the health of adult birds and their chicks. Fifty Laysan Albatross chicks were examined for plastic items lodged within the upper digestive tract. Forty-five (90%) contained plastic, including 3 chicks having proventricular impactions or ulcerative lesions.
Plastic items in 21 live albatross chicks weighed a mean of 35.7 g chick-I (range 1-175 g). Four dead birds contained 14-175 g (mean 76.7 g). Two of four adult albatross examined contained plastic in the gut. Laysan albatross chicks have the highest reported incidence and amount of ingested plastic of any seabird species. Twelve of 20 adult Wedge-tailed Shearwaters (60%) contained plastic particles 2-4 mm in diameter, impaclion did not appear to be a significant hazard for adult 339
Marine Pollution Bulletin
shearwaters. Shearwater chicks ~ere not examined. Chemical toxicity of plastic polymers, plasticlzers and antioxidant addilh'es is low, although many pigments are toxic and plastics may serve as vehicles for tile adsorption of organochtorine pollutants from sea •,~ater, and the toxicity of plastics is unlikely to pose significant hazard compared to obstruclian and impaction of the gut.
1982 and 1983 on Midway Island (28'N, 177"W) to investigate a series of disease and lead poisoning incidents with albatross chicks. Necropsies were conducted on apparently healthy chicks, chicks with wing-droop syndrome, and dead chicks. Tissues were collected for residue analysis of lead and mercury. The association between lead poisoning and wing-droop syndrome is presented elsewhere (Sileo & Fefer, in prep.). During the 1982 and 1983 investigations, we recorded the presence and quantity of plastic in the gastro intestinal (GI) tracts of necropsied birds. Wedge-tailed Shearwaters were collected in the courlship phase of the breeding season in May, 1984, on Manana Island, a small volcanic cone 1.2 km offshore from Oahu, Hawaii (2I'I',1, 158"W). Ten pairs of adult birds were collected as part of a field study on oil toxicity (Fry et aL, 1986). Complete gross necropsies were performed on each bird.
Persistent plastic items floating on the ocean present hazards to ninny species of marine birds that eat them. Plastics ingestion by seabirds is worldwide, and the number of species known to be ingesting plastic has markedly increased in the past ten years. Ingestion of plastics by seabirds was first documented (Kenyon & Kridler, 1969) in Laysan Albatross (Diomedea immutabills), a seabird species at high risk from plastics consumption. Results Procetlariiform and Charadriiform birds (albatrosses, shearwaters, fulmars, petrels, phalaropes, auklets, and Plastic ingestion by Laysan A lbatrosses puffins) are the groups most frequently found with plasTable 1 presents the numbers of Laysan Albatrosses tics in their upper digestive tracts (van Franeker, 1983; sampled and the numbers with plastics in the prevenlriDay et aL, 1985). Day et aL (1985) documented inges- culus. During the surveys of 1982 and 1983, 90% of tion of plastics by 50 species of seabirds and have chicks surveyed had plastic fragments, toys, bottle caps, closely examined correlations between feeding habits or cigarette lighters in their upper GI tract. Four adult and ingestion of plastics. Surface-feeding species, espe- Laysan Albatross were examined, and two contained cially those feeding on squid, fish eggs, and pelagic plastic. In July 1983, 24 albatross chicks were examined crustaceans are at greatest risk. From analysis of plastic for plastics, and the plastic debris was weighed and the particle sizes and colours, Day et aL (1985) concluded volume determined. Table 2 presents the amounts of that most species of seabirds that ingest plastic are plastics within the proventriculus of 19 live chicks selective in the sizes and colours of plastics and that collected for study and of 5 freshly dead chicks most ingested particles tend to resenable normal prey collected within the colony. Sevenleen of 19 (89%) live items. chicks contained plastic, and 4 of the 5 dead chicks Two classes of plastic debris appear to present the (80%) contained plastic. The mean weight and mean greatest hazard to sea birds. The most commonly volume of plastics was 35.7 g and 39.3 cc in live chicks, collected plastic particles in the marine environment are and 76.6 g and 85 cc in dead chicks. Two o f the live small bits of polyethylene, polypropylene and poly- chicks (containing 158 g and 175 g plastic) had styrene 1-5 mm in diameter that are apparently either impacted proventriculi. Starvation complicated by raw pellets from manufacturing sources or small weath1 ered fragments of plastic trash (Carpenter et aL, 1972; Incidence of plastic ingestionTABLE by Laysan Albatross chicks, Midway Colton et aL, 1974; van Franeker, 1983; Day et aL, Island. North Western Hawaiian Islands. 1985). These were commonly found by Day et aL Date Number of chicks with plaslie (t985) in a varieiy of small plankton-feeding seabirds. (No./No. examined) % The second class of plastic debris presenting risks to Aug. 1982 3/4 75.0 16/17 94.1 seabirds includes small manufactured items and frag- Apr. 1983 MaY t983 5/5 10t,) ments with dimensions as large as 20 x 80 mm. Large July 1983 21/24 87,5 birds such as albatrosses, feeding on large prey, are at 45/50 90,0 risk principally from these larger pieces of debris Totals floating on the ocean surface. 2 This report documents the increasing frequency of Quantity of plastic ingested by TABLE Laysan Albatross chicks. Midway Island, ingestion of plastic by Laysan Albatrosses and the Hawaii. July, 1983. Live and dead chicks were examined for incidence of plastics. detrimental effects on chicks that are fed plastics by adults. Additionally, we report a high incidence of Live chicks Dead chicks plastic ingestion by Wedge-tailed Shearwaters (Puffinus ;,1o. : 'h plastic/Total 17/19 4/5 pacificus), a species not previously known to ingest ~ t . . . , f :~stlc: mean 35.7 g 76.7 g plastics. range 1-t58 g 14-175 g '~
Study Locations and Methods
Surveys of Laysan Albatross were conducted during 340
Vc. ,,:~~=z,,~,~ aean :.~n~e
. . . . . . . . . . . . :";;:
49.8 g
69.t g
39.3 cc 1-175 cc 54.1 ce
85,0 c c 15-188ec 73.5 ee
Vt~lumcIll/Number6B/Julle 1987 impaction could have been the cause of death in the impacted dead dlick. Four chicks examined had proventricular ulcerations. Large plastic fragments appeared to be the direct cause of severe, chronic inflammatory lesions in the rnuseularis and mucosal I:mfin~l propria ~fone of the birds, and plastic may have caused minor chronic ulcerative lesions in the other t Ittee. The prevalence and severity {)f plastic obstruction of the upper G1 tracts of chicks varied widely. Laysan Albatross chicks weighing 2-3 kg contained, on average, 36 g of plastic, amounts not appearing to cause obstruction or interference in digestion or assimilation of food. Only chicks containing as much as 175 g had impacted preventrieuli whicl~ resulted in partial obstruction of the gut. Olher facmt.~ a/}~,ctit~galbatross chick cottdition and sltrt'il,a! Severe debilitation occurred in many albatross chicks as a consequence of ingesting lead from paint fragments peeling off military buildings on Midway Island. Paint chips were ingested along with plastics and other foreign ohjects in the vicinity of albatross nests. Chicks from nests adjacent to abandoned buildings developed a wing-droop syndrome and were unable to fledge. Ten of 12 chicks suffering from droop-wing syndrome had indications of lead poisoning (Stied & Fefer, in prep.). Lead and mercury content of weathered paint samples collected from buihlings was very high, with a mean lead concentration of 84,000 ppm and a mean mercury concentration of 40 ppnt. Plastic hlgestim: by adult Wedge-roiled Shear~ters Necropsies of shearwaters revealed plastic pellets and fragments in 12 of 20 birds. Plastics were rounded pellets or irregularly shaped fragments 1-3 mm thick and 2-7 ram long. Most shearwaters containing plastic had 2-6 fragments within the gizzard, but one male contained a total of eleven 3-4 mm diameter pellets distending the ventriculus and one additional 4 mm diameter fragment in the proventriculus. The majority of plastic items lodged within the gizzards were rounded pellets of polyethylene or polyproplylene 2-3 turn in diameter similar to those identified in other reports (Day, 1980; Day et al., 1985) as raw pellets used in the fabrication of manufactured goods. Approximately 20% of the plastic particles were worn polystyrene fragments~white, yellow, blue, or green--and apparently representing fragments of broken manufactured items. Fourteen of 20 shearwaters had numbers of small squid beaks within their gizzards. Beaks were roughly triangular in shape, 1-2 tara in longest dimension and 0.2-0.5 ram thick. The number of squid beaks ranged from 1-3 beaks in five birds up to several dozen in each of two birds. There was a negative correlation between the presence of squid beaks and the presence of plastic within the gizzards (P ~ 0.02, Fishers exact test). The incidence and amount of plastic was equal in both sexes (6 female, 6 male) and independent of the extent of subcutaneous fat and gonadal maturation. The
condition of the gonads of both males and females was characteristic of the courtship phase of the breeding season preceding the period of rapid yolk formation. Since our focus was on breeding pairs, our sample criteria automatically excluded nonbreeding birds, thereby precluding meaningful correlation between presence of plastic and delayed maturation of gonads. Discussion Plastic ingestion by La3.~an AIbatross chicks The rcsuhs presented here dcmonstrale thai a 't,,trry high proportion of chicks of albatrosses breeding in the North Western Hawaiian Islands (NWHI) ingest plastics during the pre-fledging period when they are dependent upon food brought to the breeding colony by parents. Floating plastic items are ingested by adult albatrosses and regurgitated to chicks along with normal food items. Albatrosses feed primarily on squid, fish, and masses of fish eggs floating at the water surface. Flying fish (family Exocoetidatt) lay egg masses on flotsam, including plastic, which may tend to encourage the gathering of plastic by albatrosses. The variability in amounts of plastics in albatross chicks was high, with some birds containing little or no plastic and others containing more than 150 g. Large amounts of plastic appeared to cause impaction of the upper GI tract and interfered with passage of food through the digestive system. The sub-lethal effects of plastic impaction and minor ulceralions may contribute to reduced resistance to disease and lowered post fledging survival, Some fragments of plastic ingested by albatross chicks are picked up directly by the chicks in the litter of the breeding colony. Plastic fragments are abundant on the ground at Midway Island and other NWHI breeding colonies. Plastic litter is most common on beaches where it is deposited by ,,,,'ave action, but small pieces are common in the albatross colonies as parts of castings regurgitated by resident albatrosses. Laysan Albatross fledglings ingest many types of foreign materials when they reach a size large enough to move from the nest (chick weights greater than 2 kg). The phenomenon of pica, the behaviour of ingestion of indigestible foreign matter, is not unique to albatrosses, but has been described for other species of avian chicks, including eagles, vultures, and ibis (Koford, 1953; Halliwetl et aL, 1973; Dobbs & Benson, 1984). The extent to which pica by Laysan Albatro:~s chicks contributes to ingestion of plastics and impaction has not been determined, and it is possible that pica may be partly a consequence of association of plastic items with food fed to chicks by adults, The small sample of 4 adult albatrosses surveyed here indicated half of the birds contained plastic during the period when these birds were actively feeding chicks. It is probable that adults transfer the bulk of the plastic to their chicks when feeding them by regurgitation. The high amounts of plastics in chicks probably represents the accumulation of indigestible items collected and regurgitated by adults throughout the breeding season (Kenyon & Kridler, 1969; Pettit ez aL,
341
Maritl¢ Pollution Bulletin
1981). Chicks appear to retain indigestible items in their proventriculi for long periods. Pettit et al. (1981) inadvertently monitored retention of foreign objects by albatross chicks after feeding small radio transmitters to adult albatrosses and having them regurgitate the transnfitters to chicks. The chicks did not regurgitate the transmitters for at least 40 days.
Wedge-tailed Shear,~ters Sixty percent of the adult Wedge-tailed Shearwaters surveyed carried small plastic pellets and fragments in their gizzards and provenlriculi. The pieces were much smaller (2--7 ram) than items carried by albatrosses and none of the breeding shearwaters in this study appeared debilitated by the plastics. One shearwater which contained 12 pieces had a distended gizzard, although there was no evidence that this volume of plastic was causing obstruction of the gut. There was a negative correlation between the presence of squid beaks and the presence of plastic within the gizzards. The cause of the negative correlation is unknown, but perhaps may be related to foraging habit differences such that 'squid-specialists' did not encounter much plastic. An alternative explanation could be that birds not finding sufficient squid may be opportunistically taking random items including plastic. Adult shearwaters ingest numerous small fragments of plastic, but at the rates and volumes documented here, it is not likely that they are at high risk. Regurgitated pellets of indigestible materials were not observed in the breeding colony, however, and we do not know whether shearwaters regurgitate indigestible material from their gizzards when the volume becomes large. If adults ingest plastics frequently, the risk to shearwater chicks fed plastic could be significant, as it appears to be with albatross chicks.
Ingestion of plastics by other Pacific species Both Laysan and Black-footed (D. nigripes) Albatrosses ingest plastics. The endangered Short-tailed Albatross (D. albatms) must also be considered at high risk because much of its distribution overlaps with Laysan and Black-footed Albatrosses and its foraging range is near Japan and across the Pacific in areas of high density of plastic debris. This species, which was thought to be extinct in 1949, now consists of not more than 300 birds breeding on Torishima Island (30*N, 140"E) 580 km south of Tokyo, Japan, and perhaps breeding on Minami-Kojima (26"N, 124"E) 200 km northeast of Taiwan (Hasegawa & DeGrange, 1982; Rice, 1984). The occurrence of plastics in chicks of seabirds has been reported only for Laysan, Black-footed (D. nigripes), and Wandering Albatrosses (D. exulans) (Kenyon & Kridler, 1969; Pettit et aL, 1981; Furness, 1983), and Leach's Storm-petrel (Oceanodroma leucorhoa) (Rothstein, 1975). The incidence of plastics consumption by Wedge-tailed Shearwater chicks has not been investigated, but it is likely that chicks receive regurgitated plastics from adults since 60% of adults surveyed contained plastics in their gizzards. Adult 342
birds of more than 50 species of seabirds have been recorded ingesting plastic (Day et aL, 1985), and it is probable that chicks of many species subsequently receive plastics regurgitated by adults, but there are no data for chicks of other species. Research is under way to quantify the consequences of plastic ingestion by chicks of albatrosses, and to determine the extent of plastics ingestion by adults and chicks of other species of Hawaiian seabirds.
htcreasing plastic pollution in the North- Western Hau~iian Islands The amount of plastic pollution on NWHI beaches has increased in the past 15 years and relatively large quantities of a variety of debris including fishing nets, floats, boxes, bottles, manufactured plastic items, and fragments of a diversity of sizes and types are now found on beaches. Comparisons of descriptions of plastics on beaches in the report of Kenyon & Kridler (1969) and Fisher (1975) with the report of Pettit et aL (1981) and observations made during this study indicate there has been an increase in tile amount of plastic debris collected by albatrosses and brought to breeding colonies. Numerous small indigestible items are now found within the albatross breeding colonies away from the beaches. Fisher (1975) reported that during his 13 year study of Laysan Albatross on Midway Island (1960-I973) foreign objects such as plastics were not usually found in colonies away from tidal action. Tile debris is apparently from the Orient as indicated by markings on the items. Pettit et al. (1981) identified 108 of 109 plastic articles in carcasses of albatross chicks as having been manufactured in Japan. The distribution of plastic trash appears to be much more abundant in the NWHI than on other remote islands of the central Pacific (S. Fefer, unpublished observations) and it is probable that much of the plastic found on NWHI beaches has been carried by the Kuroshio Extension. The most likely source of the majority of the plastic is land-based discharge. The incidence of plastic ingestion by albatross chicks appears to have increased since 1966 when Kenyon & Kridler (1969) determined that 74% of dead albatross chick carcasses found at Pearl and Hermes Reef (28°N, 176"W, 160 km east of Midway Island) contained plastic, with 8 pieces being the greatest number in any one carcass. Pettit et aL (1981) examined only 4 dead chicks on Midway Island in 1980, and all contained plastic. The indigestible material in the stomach of one dead chick appeared to have contributed to obstruction of the upper GI tract which prevented food from passing into the intestines. The carcasses of dead chicks weather over the course of the year into collections of foreign objects surrounded by skeletal remains. Fisher (1975) suggested the potential problem of recycling of foreign objects by Laysan Albatross chicks as he speculated that foreign objects in the skeletal/remains of albatross chicks from previous years might effect successive generations of chicks when they wdre consumed again.
Volume I/~/Number 6B/June 1987
R L s ~ to species h~ other m¢,as
The distribution of plastics in the world's oceans is not tmiform and seabirds foraging in areas of high plastic occurrence are obviously at greater risk than birds foraging in low density areas. The greatest density of large plastic dehris found in the Norlh Pacific by Dahlberg & Day (1985) was in the North Pacific Current at latitudes 30*N-40*N. The North Pacific Current and the Kuroshio Extension are prime feeding areas for Laysan, Black-footed, and Short-tailed Albatrosses. Several species of albatross from southern oceans have been reported to ingest large fragments of plastics (see review by Day el aL, 1985), but with lower frequency than Laysan Albatross, presumably because of the lower density of floating plastics in the southern heluisphere. Small plastic debris (principally raw polyethylene and polypropylene pellets) such as that ingested by shearwaters, of 2-5 mm diameteL appears 1o be distributed worldwide (Gulf of Alaska, Day et al., 1985; Sargasso Sea, Carpenter & Smith, 1972; Cape Basin of the South Atlantic Ocean, Bourne & lmber, 1982), but with higher densities in large oceanic gyres such as the Gulf of Alaska and the Sargasso Sea (Day et al., 1985; Carpenter & Smith, 1972). Most of the small plastic pellets in waters surrounding the main Hawaiian Islands (2300 km southeast of Midway Island) are carried south-westward on the California Current and its extension into the North Equatorial current. The origin of these petlels has been assumed to be inadvertent loss during production and ocean transport (Day et aL, 1985). The foraging habits of birds and the characteristics of their prey play a dominant role in determining risk from plastics. The species at risk from large fragments and plastic items 2-10 cm in length are albatrosses and perhaps boobies, frigate birds, and pelicans, although the latter species have not been recorded as ingesting plastics. The species at greatest risk from small plastic pellets are plankton-feeding birds such as shearwaters, petrels, prions, phalaropes, and auklets. A high proportion of Parakeet and Cassio's Auklets in the Gulf of Alaska and the Aleutian lslands~ingest plastics (Day et aL, 1985). In the S o u t h A t l a d i i c and South Pacific Oceans, several species of prions (small surface-feeding procellarids) ingest similar raw polyethylene pellets (Bourne & Imber, 1982; Furness, 1983). Ingestion of plastic does not, necessarily, present risk to adult birds. Plastic polymers, plasticizers, and antioxidant additives are not very toxic, although many. pigments are toxic and pla.stics may serve "as vehicles ,'for the adsorption of organochlorine pollutants from sea water. Carpenter et al. (1972) reported PCBs and DDT adsorbed to plastic pellets in the Atlantic Ocean, and Fisher (1973) has documented occurrence of persistent organochlorine p011utants in Laysan Albatross, but the sources of pollutants may well have been the food chain
rather than ingestion of plastics. The currently available evidence suggests that plastics appear to present risks only when they are consumed in sufficient quantity 1o cause physical obstruction or ulccratkms of stomachs of 0irds. The risk of plastic ingestion and impaclion in chicks of many species of seabirds may be different from the risks to adults. Albatross chicks appear to be at greater risk than adults, because of their high rates of ingestion and apparent low frequency of regurgitative casting of indigestible material, h is possible that chicks of other procellariids are at similar risk.
Bourne, W. R. P. & tmber. M. J. (1982). Plastic pellets collected hy a prion on Gough I~land, central ~mth Atlantic Ocean. Mar. F,d[ut Hull 13, 20-21. Carpenter, E. J. & Smith, K L. Jr. ( 1972}. Plastics on the Sargasso Sea surface, Science ! 75.124t J- 1241. Carpenter, l-.J..Anderson. S. J.,llarvey, G. R., Miklas. H. P. & Peck, II. B. (1972). Polyst)'rene spherules in coastal waters. Science 178, 749-750. Colton, J. 13. J r., Knapp, E 1). & Burns, B. R. (1974). Plastic particles in surface waters of the northwestern Atlantic. Science 1 8 5 , 4 9 1 - 4 9 7 . 1)ahlbcrg. M. L. & Day, R. H. (1o85). Obscrvatiom, of man-made objects on the sudacc of the north Pacific Ocean. In t'toceeding~ of the Bbrl~hop on the Fate and hnpacl of Marine Debris, 2 6 - 2 9 Novemher, 1984. t|onolu|u, I'lawaii (R, S. Shomura & H. O. Yoshida. eds). US Dept. of Commerce. NOAA Tech. Mere. NMI'-S. NOAA-TM -N M FS~SWFC-54. Day. R. H. (1980). The occurrence and charactefislies oi" plastic p~fllution in Alaska's marine birds. MS Thesis. University of Alaska, Fairbanks. Day, R. H., Wehle, D. H. S. & C o l c m a n . IL C. (1985). Ingestion of plastic pollutants by marine birds. In Proceedings of the Bbrkshop tm the Fate and Impair of Marine Debris, 2 6 - 2 9 November. 1984, Honolulu, Hawaii (R. S. Shimura ~ H. O. Yo~hida, eds), pp. 3 3 4 3,":,6. US Dept. of Commerce, NOAA. Tech. Mere. N M F S - N O A A TM-NMFS-SWFC-54. Dobbs, .1. C. & Benson, E C. t1984). Behavioural and metalx~lie resg~mses to ff~,d deprivation in the Cape Vulture. In Proceedings of the Second Symposi*mt on African t'reditory Binls (J. M. Mcndelsohn & C, W. Saps ford. cds), pp. 211-214. Natal ~3ird CMb. Durban. Fisher, t4. L 41975). Mortality and survival in lhe Lays.an Albatross. Diomedea imvm*tabilis I~cific Science 29, 279-300+ FD'. D. M.. Swenson, J. Addiego. L. A., Grau. C. R, & Kang, A. (1986). Reduced reproduction of Wedge-tailed Shear~aters e x p o ~ d to single doses of weathered Santa Barbara crude oil. An'h. Edviron. Cowtam. ToxicoL 15..153-463. Furness. B. L. (1983). Plastic panicles in three procellariiiorm sea birds from the Benguela Current, South Africa. Mar. l~a/lut. Bull 14, 3 0 7 308, Ha|liwclt, ~V H.. Graham, D. L. & Ward, E P. (1973). Nutritional diseases in birds-of-prey. Z Zou Atdm. Med. 4. 18-20. Hasegawa, H. & DeGrange. A. R. (1982). The Short-tailed Albatross { Diomedea albamts), its status, distribtttion, and natural histo~', Am. Birds 36, 806-814. Kenyon, K. W. & Kridler, E. (1969). Laysan Albatross s~,'allow indigestible manet. Auk 86, 339-343. Koford. C. B. (1953). The California Condor, pp. 55-59. Dover Publications, New York. Pettit, T. N.. Grant. G. S. & Whitlow. G. C. (! 981 ). Ingestion of plastics by Laysan Albatross. Auk 98, 839-841. Rice. D. W. (1984), Albatrosses. In Seabints o f Eastern Abrth Pacific and Aft'tic Water~ (D. Haley, ed.), pp. 32-41. Pacific Search Press, Seattle. Rothstein, S. I. (1973). Plastic particle pollution of the surface of the Atlantic Ocean: Evidence from a seabird. Condor 75, 344-345. van Franeker, J. A. 0 9 8 3 ) . Plastics---een bcdreiging your zeevogels. NedeHaods Stookoli~lachtoffer.Onder~oek fNSO) 4, 41-61.
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