Document kdo2LqGE6r242MRd9g1vne3B

.'TV j--2*2*idA 'diklttP* *&,.*.*C>i,i .-. -.. .--..v _ ~- MATURE VOL 231 JUNE 18 1971 i Sokal. R-, and Sncavh, P. H. A., Principles of Numerical Taxonomy, 72 and 226 (Freeman, San Francisco and London, 1963). : Anderson, N- G., Nature, 227, 1346 (1970). j Sprigg, R. C., Trans. Roy. Soc. South Austro!., 71, 212 (1947). * Glr.ess.ner, M. F., and Wade, M., Palaeontology, 9, 599 (1966). Glaessnrr, M. F., Bull. Geol. Soc. Amer., Notes and Discussions (in the press, 1971). Gfacssner, M. F., Biot. Rev., 37, 467 (1962). ' Simkiss, K., Biol. Rev., 39, 487 (1964). 467 The age and body weight of control and PCB-loaded birds were compared, and no significant differences were found. Both groups had gained weight equally by comparison with birds weighed immediately after trapping at Falsterbo'0. Table 1 Organochlorina Residues (ng/g Fresh Weight) in Bteest Muscles of Robins Effect of PCB on Nocturnal Activity in Caged Robins, Erithacus rubecula L. Chlorinated hydrocarbons are a recognized threat to popula tions of wild birds, but their precise mode of ecological action is largely unknown. They arc, however, known to have a thinning effect on the egg shell1 -2,*a*nd they react with some hormones5-*, thus affecting the endocrine balance of the body. Such findings suggest that these substances may exert a profound influence on the activity and behaviour of contaminated animals, but little attention has been devoted to this aspect. The migratory activity of birds is governed chiefly by the interplay of hormonal systems5-6,*a*n*d* *the orientation of the migrants is a highly relined instinct pattern. This suggests that the nocturnal activity of affected migratory birds might be a suitable indicator of the possible ecological effects of organochlorines. The robin, Erithacus rubecula L., in Sweden is almost com pletely migratory, moving exclusively by night. Its main flight direction during the autumn migration is SW-SSW. Robins were trapped at Falsterbo Bird Station (55 23' N, 12 50' E) in the last week of September 1970. They w-ere kept singly in opaque plastic containers under a natural light-dark, rhythm and were fed mealworms and berries ad lib. Beginning on October 2, twenty-eight robins were given one extra meal worm each day, injected with 5 pg of `Clophen A50', a poly chlorinated biphenyl (PCB). These worms were marked with a small dot of red dye to enable us to determine whether the worm had been eaten; in a few cases it was not taken. Eighteen robins were kept in identical conditions but were not given worms containing PCB. The experiments were performed between 1900 and 2100 on October 21 and 22 (within the normal migratory period of Swedish robins) on birds which had eaten eleven to thirteen PCB-loaded worms. The experimentally contaminated and control birds were placed singly in'Emlen funnels under the open sky at a site 20 km east of Lund, where no artificial light sources interfered. During the first night the sky was overcast, and the experiment was discontinued after 35 min because of rain. During the second night, cloud-cover was approxi mately 1/8, and the experiment was continued for 75 min as planned. The evaluation of the activity sums and of the mean vectors of the birds followed the procedures described by Rabbi'-', On the first occasion, twenty PCB-loaded and twelve control birds were tested, and on the second, nineteen and eleven birds, respectively. With a few exceptions, the same individuals were used in both experiments. The average activity sums were compared separately for each night using a Mann-Whitney U test (two-tailed). The average activity on the first night was much higher in the PCB-loaded birds than in the controls, but the difference was not quite significant. On the second night, when the experi ment ran for a longer period, the average activity of the PCB-loaded birds was significantly higher than that of the controls (Pc 0.05). The dispersion of the mc^n vectors was greater on the overcast night of October 21 than on the follow ing night which was cloudless. No significant differences between PCB-loaded and control birds with respect to direction or dispersion were detected on either night. The direction was the same as the supposed standard migratory direction of Swedish robins. pg of PCB ingested Birds fed with PCB 60 55 65 35 60 55 Control birds -- p,p'-DDE 95 96 75 64 91 56 72 69 70 66 p,p'-DDT 7 25 25 24 22 2 23 27 30 26 PCB 375 467 341 164 365 287 120 70 90 51 The breast muscles of six PCB-loaded birds and four control birds were analysed by gas chromatography for organo- chlorine content (Table 1). The apparatus consisted of a Varian Aerograph 204 gas chromatograph equipped with electron capture detectors, and three different columns using SF 96 (4%), QF I (8%) and SF 96/QF I (3:1) as the stationary phases on GasChrom P (100/120 mesh) were utilized. The iden tity of the more important compounds detected was also con firmed by chemical techniques. The PCB level in the experi mentally contaminated birds was four times that found in the controls, the difference being statistically highly significant, but it was in unexpectedly low concentration, indicating that much of it had been excreted or stored elsewhere than in the breasi muscles. Both groups of birds were also analysed for p,p'- DDE and p,p'-DDT, but no significant differences were - detected. . These results demonstrate an effect of organochlorine residues on the activity patterns of the bird. Gwinner" demonstrated a correlation between the degree of migratory activity (restlessness) and the distance between the breeding and wintering quarters in different warbler species of the genus Phythscopus. A quantitative change in such activity therefore assumes great ecological significance. The rapid mobilization of fat during migration is also an important aspect of this - problem12-*15*. PCB compounds occur widely in the global ecosystem and. like other chlorinated hydrocarbons, they accumulate in food chains1*-15. Their effects, even at the relatively low levels used in these experiments, indicate that they arc important environmental contaminants. S. Ultstrand A. SoDERGREN Department of Animal Ecology, Ecology Building, University of Lund, S-223 62 Lund _ Zoological Laboratory, University of Copenhagen, Universitetsparken 15, >26-2100 Copenhagen J. Rabol DSW 025532 Received March 29, 1971. ' STLCOPCB4009487 468 NATURE VOL, 231 JUNE 18 1 Ratclifle, D. A., J. Appl. Ecol., 7, 67 (1970). 7 peaka.ll, D. B., Science, 168, 592 (1970). 5 Peakall, D. B., Nature, 216, 505 (1967). 4 Lincer, J. L., and Peakall, D. B,, Nature, 228, 783 (1970). ' * Furnor, D. S., Proc. -V/ V Intern. Orn. Cong. Oxford, 1966, 107 (Blackwell, Oxford and Edinburgh, 1967). 6 Berthold, 1>., Zooi. Jb. Syst., 96, 491 (1969). 7 Rabbi, J., Orn. Scant!., 1, 27 (1970). * RabOl J., Dansk Orn. For. Tidsskr., 64, 118 (1970). Svcnsson, L., Identification Guide to European Passerines (Nal- urliisl. Riksmus., Slockliolm, 1970). 10 Scot!. R. E., Vdr Fdgeh., 24, 156 (1965). 11 Gwinncr, E,, J.f. Orn., 109, 70 (1968). 17 Helms, C. VV,, Amer. Zooi., 8. 151 (1968). 13 Hussell, D. J. T,, Auk, 86, 75 (1969). 14 Riscbrough, R. W.. Rieche, P., Peakall, D. B_, Herman, S. G., and Kirven, M. N., Nature, 220, 1098 (1968). 15 Jensen, S., Johnels, A. G., Olsson, M., and Olterlind, G., Nature, 224, 247 (1969). Skua Numbers and Conservation Problems at Cape Hallett, Antarctica The flora and fauna of Antarctica ate often considered to be secure, principally because of international treaty obligations. Nevertheless, several people have already drawn attention to conservation problems1 "3, which are underlined by my own work on the decline of the South Polar skua (Catharacta maccormicki) at Cape Hallett (lat. 72 18'S, long. 1707 19' E). During the two austral summers of 1967-68 and 1968-69, l made an intensive study of the decline of the skua and of skuapenguin feeding relationships, which will be published in full later. Data gathered by Dr T. S. Choate in the 1966-67 season arc also incorporated in this report. Because of the scarcity of suitable coastal building sites, man sometimes competes directly with nesting birds for space. In December 1956, for example, when the joint United StalesNcw Zealand station was established, 3,318 juvenile and at least ' 4,900 adult Adelie penguins (Pygoscelis acleiiae) were removed from the Hallett rookery4, and at that time the breeding popu lation was probably between 56,000 and 62,000 pairs5. Although indications of the size of the resident skua breeding population are available4-6, the first census was of 181 pairs in the 1960-61 season7. Census records in subsequent seasons reveal a drastic decline in the numbers of skua pairs breeding; these are 162 pairs in 1963-64 and 147 pairs in 1965-66 (per sonal communication from F. C. Kinsky); 113 pairs in 1966-67 (personal communication from T. S. Choate); 105 pairs in 1967-68 and 98 pairs in 1968-69 (my own work). Thus there has been a 54% decline during, nine seasons. Census records of (he Adelie penguin breeding population made by Choate (1967-68) and Westerskov (1968-69) indicate a decrease of a similar magnitude during the same period (personal communi cation from Choate and K. E. Westerskov). The decrease in the number of skuas during and between the three seasons studied was determined from the recovery records of banded birds. During this period 95-98% of the breeding population and many non-breeding birds were marked with numbered monel-metal bands. There was no significant loss of these bands. The mean annual loss of breeding skuas was 18% compared with 6% for a stable population of skuas at Cape Crozier (personal communication from R. C. Wood). This result for the Hallett skuas probably represents a perma nent loss of birds rather than sporadic return or breeding. Of the fifty breeding birds lost between 1966-67 and 1967-68, for example, only one was recovered in the 1968-69 season and as a non-breeder. During the three seasons, twenty-three skuas, including eight breeding birds, were found dead or dying. The cause of death was established in only six cases, all resulting from human activities (wing breakages or ruptured crops caused by the ingestion of corn cobs). No breeding birds disappeared \ out trace. Seasonal losses are therefore only slightly gri than might be expected for a stable population. High setts mortalities, however, have been recorded, In 1965-66 Ki recorded the deaths of thirty-three adult skuas. He until three of these, and discovered that they had been poisone ingesting parts of lead battery plates. Figures for fledgling production (chicks fledged/fen breeding) during the period of the decline tire heterogene 59/156 in 1959-60 (ref, 6), 116/181 in 1960-61 (ref. 7), 36 in 1966-67 (personal communication from Choate), 41/K 1967-68 and 24/98 in 1968-69 (y2 = 21.2, P< 0.001). If, 1 ever, the 1960-61 data are removed from the calculation significant deviation remains (x2 = 3.57, P> 0.25) and resulting mean annual figure of 0.34 fledglings per bree female compares favourably with the value of 0.33 for fled] production at the stable Cape Crozier colony (personal t munication from Wood). The high tledgling produr in 1960-61 was probably, therefore, unusual, and this r meter does not seem to have changed significantly durim period of the decline. The effect of any alteration in fledi production on the decline could, however, be recorded after 5-6 yr, the approximate age of first breeding. I conclude that the decline of the skua population has be result of adults abandoning the Hallett colony as a bre>area. This decline has coincided with a period of human u pation and with the decline of the Adelie penguin popula on which skuas prey and scavenge for food. The declir penguins has itself been established as resulting directly I human disturbance (personal communication from Choate Westerskov). Thus although the skua decline has beet ultimate consequence of human activity, the relative import of direct disturbance as distinct from the penguin decline proximate cause requires evaluation. This aspect oT the s which has provided new information about the relation between skuas and penguins will be published later. In spite of suggestions by several workers for the elinilna of possible sources of poisoning and the reduction of dist ance to both penguins and skuas, this ignominious situalioi continued virtually for a dccude. Holdgute3 points out l although the agreed measures for conservation under Antarctic Treaty are comprehensive and therefore should require significant future amendment, three areas for impr ment remain, especially with regard to specially prole localities or species. These areas are the perfection of application oT the agreed measures, the development of pus schemes for management and the adoption of cducati means to ensure that all personnel visiting Antarctica are a1 of the need for conservation. This report should serv endorse Holdgate's suggestions Tor the improvement of coi vation in the Antarctic, particularly as Cape Hallett is class as a specially protected area. I thank Dr T. S. Choate, Mr F. C. Kinsky, Mr R. C. \\ and Dr K. E. Westerskov for valuable information. Brian R. Johnsti Zoology Department, University of Otago, Dunedin, New Zealand DSW 025533 Received March II; revised April 15, 1971. 1 Stonehouse, R., N7, Set. Rev., 23, 3 (1965). 2 Shimoizumi,.!., Antarctic F(d/|jyr(edii. by Holdgaie. M. W. j. 2 (Academic Press. London, 1970). 5 Holdgale, M. W., Antarctic Ecology (edit, by Hoklgate, M. 2, 924 (Academic Press. London, 1970). 1 Eklund, C. R., Bird-llantlinv, 32, 283 (1961). 5 Reid, B. E.. Nolornis, 15, 193 (1968). 6 Reid, H. E., NZ DSIR Antarctic Div. Rep. (1961). 7 Maher, W. J., Nat. Hist., 75. 42 (1966). STLCOPCB4009488