ktill.rg\ *A(ll. IYSI. pp I Ill-((9 0 1981 by the Et.ologic,it Society of America

THE ECOLOGY OF TICK PARASITISM ON DENSELY NESTING PERUVIAN SEABIRDS'

DAVID CAMERONDUFFY? Depanmen! of Biolosy, Princeton University, fitncmn, Nfw Jersey 08544 USA

Absiracf. Densely nesting Guanay Cormorants (Phuluct-ocot-axhouguinviliti) , Peruvian Booby (Sdu variegafu), and Peruvian Brown Pehcan (Pelecunus occiciett~ulis thugus) deserted eggs and young in response to high densities of argasid ticks (Ornirhoilorus umbius). Alternative causes of desertion such as human disturbance, predation, disease, heat, and food shortage did not fit the evidence. Tick predators were less effective at controlling ticks than were frequent human harvestings of guano. A review of the avian and medical entomological literature indicates that ticks and other ectoparasites may be strong determinants of nesting success and of nest structure and duration of use. Key words colonid nesfins; ei.'fopurasnes:Ornithodoros amblus; Pelecanus occidentalis thagus; Phalacrocorax bougainvillii, Population replurioii, seabirds; Sula variegata, rieks.

tween 15 and 55 min. Related species (Anastos (957) Biologists have generally ignored the effects of par- can survive for many years as unfed adults, and this asitism on social animals (but see Smith 1968, Alex- is probably true for 0.amblus. ander 1974, Hoogland and Sherman 1976, Hoogland This species of tick is a vector for at least two ar- 1979). Among colonial seabirds, there is growing evi- thropod-borne viruses (arboviruses) designated " Hu- dence that ticks (Acari: Ixodoidea) cause desertions acho" and "Salinas" (Clifford et al. 1980), which were by nesting adults with resultant mortality of eggs and recovered from the Punta Salinas colony just east of Isla Mazorca, my primary study site. The effects of young (Feare 1976, King et al. 19770, h). This paper investigates the role of the argasid tick these arboviruses on the birds are unknown, but hu- Orni~hodorosumhlus in causing desertions of nests of mans suffer severe swelling, itching, and occasional the three main Peruvian guano birds: the Guanay Cor- gangrene and death following multiple tick bites (D. morant Phulucrucorax hu~iguinviilii,the Peruvian C. Duffy, personal com.municufion with various per- Booby or Piquero Suh vuriegata, and the Peruvian sonnel on the islands; Clifford et al. 1980). It is not Brown Pelican Peiecunus occidentaiis fhws. De- clear if all of these are the result of the tick bite itself, spite recent declines in numbers (Tovar 19781, these an arbovirus, or the low standard of medical attention three species still form some of the largest and densest which previously prevailed on the islands. I asked two questions in this study; To what extent colonies of birds (Murphy 1936, Duffy 1980). The col- onies have existed for millenia (Hutchinson 1950). are the ticks responsible for the desertions of nests by Dense, reliable populations of hosts offer excellent the three species of guano birds, and what limits the conditions for large numbers of parasites, because the numbers of ticks? difficult task of finding a host is virtually eliminated (Rothschild and Clay 1952). Ornirhodoros amblus was chosen for study from a variety of ectoparasites of the Study sires birds (Murphy 192 1) because it is large and abundant, I spent 6 mo (September 1977 to March 1978) on and LaValle (19 18) mentions ticks causing desertions Isla Mazorca (It023'S, 77'45'W, 11.6 ha) and between by guano birds, suggesting that at times it does have 14 February and 12 March 1979, I made trips of 1-7 d an effect on the hosts. to eight other islands: Isla Guanape Norte (08O32'S, Clifford et al. ( 1980) and Khalil and Hoogstraal ( 198 ( ) 78'58'W; 35 ha), Isla Macabi (07¡47'S 79*3OfW; 8 ha); have described some aspects of the life history of this Islas Lobos de Tierra (06¡28'S 80°50W; 1426 ha); 1s- tick. It has four to seven nymphal instars before ma- >as Ballestas Norte and Sur ( 13'44'S, 76'24'W; 32 ha); turity, each usually requiring a blood-meal. Females and Islas Chinchas None, Centro, and Sur (13'39'S, have a mean egg production of 457 in captivity, and 76¡25'W Norte: 64 ha; Centro: 66 ha; Sur: 27 ha). under artificial conditions the life cycle is completed in 63 to 401 d. Adults feed for only short periods be- Extent of deserf;'on.'s I used three methods to calculate the extent of de- ' Manuscript received 20 Apnl 198 1 ; revised 1 January 1982, sertion of nests by adult birds: (1) on Mazorca, I fol- accepted 9 March 1982. lowed the nest-by-nest pattern of desertion at 1 3 boo- Present address: Percy RtzPatrick Lnstitute of African Ornithology, University of Cape Town, Rondebosch 7700 by nesting sites; (2) on other islands, I estimated the South Africa extent of desertions from conversations with care- February 1983 TICKS AND SEABtRDS ill takers and by examination of empty nests; (3) at all Alternative agents of de'.ertiwns islands, the bimonthly census maps made by care- A number of other agents could have caused deser- takers (Nelson 1968) allowed an independent measure tions at the colonies. These include: predation, heat, of desertion over time. human disturbance, disease, and food shortage. Most Census records were also useful as an index of de- of these could be assessed through qualitative obser- sertions in past years. Ianalyzed all available records vations. Were predators present? Did desertions begin from three of the most important guano islands: Ma- on the warmer side of the island? What relation was zorca, Macabi, and Isla Don Martin (occasionally re- there between desertions and disturbed areas? Were ferred to as San Martin, I I¡01'S 77'40'W; 16.5 ha) there any symptoms of disease? For each breeding season, I compared the greatest To examine the possibility that shortage of food had area occupied by the three species during incubation led to the desertions, Imeasured the durations of 306 with the area occupied 2 mo later. Young take at least foraging trips by boobies over 10 d and 157 trips by 2 mo after hatching to leave the nest (10 wk for the cormorants over 5 d at Isla Mazorca. Idid not measure cormorant; 12 wk for the booby; and 12 wk for the the duration of pelican trips because this species is at pelican (Vogt 1942, D. C. Duffy, personal ohservu- least partially nocturnal (Vogt 1942, D. C. Duffy, per- nun), so any decrease in active nesting area was likely sow! ubser~~atiot~).I assumed that the longer the trip, to have been caused by desertions rather than by the the more difficult it was to obtain food. Vogt ( 1942) successful fledging of young. believed that trips of >6 h indicated food shortages and were predictive of desertions by nesting cormo- Behavior of she bid-i during desertion rants. Iassumed that the behavior of the birds would be indicative of the cause of the desertions. [ made qual- Limndons on the' numbers of sicks itative observations of the behavior of deserting and 1 concentrated on the two most likely controls on "normal" adults, noting nest attendance, ambulatory the increase of ticks on the islands: predation and guano behavior, and condition of plumage. harvesting by humans. On the assumption that preening serves at least par- On Lobos de Tierra, my field assistant and I col- tially to limi t ectoparasites (Rothschild and Clay 1952), lected five Tropidur~t.~sp. lizards from the edges of a. I recorded on Isla Mazorca the number of seconds per nesting colony of Peruvian Boobies. The collection minute that adults spent preening at nests in "healthy" was made between I000 and 1500 h. The lizards were areas and in areas where they were deserting. I made preserved in 95% alcohol within I h of collection. 88 I-min observations of boobies in both areas, 108 Stomachs were later dissected and the contents ana- such observations of cormorants in both areas, and lyzed by number of prey items per stomach, frequency 100 of pelicans, only at active nests. Idid not measure of occurrence, and percent of stomach volume. These preening at nests where pelicans were deserting be- data were compared with those compiled by Vogt ( 1939) cause most such desertions took place before I had from 12 Trupidurus taken on Isla Chincha Norte. opportunity to study them. Peruvian authorities harvest the guano at 1-3 yr in- tervals, removing all nests, trash, and guano accu- Ticks us she afens.~oj (if.'ifrlu)n.'i mulated. Dates of extraction are on file in the archives 1 did not actually count ticks feeding on birds be- of the Compania Administradora del Guano and PES- cause of the disturbance this would have entailed, the CA PERU in Lima. short feeding periods of adult and ny mphal 0.umhlus I compared the number of ticks on each island with (Clifford et al. 1980), and the possible bias which would the number of breeding seasons since the extraction have been introduced by any die! variations in feeding of guano. I used all samples taken from the nests of behavior of the ticks. recently deserted nests of Peruvian Boobies (Zone B) On every island, 1 took 500-cm3 scoop samples of in Tables I and 2. guano and debris from nests. 1 distinguished three cat- If ticks are limited by predators, then tick popula- egorles of nests based on proximity to areas with de- tions would be expected to go down with successive serted nests: (a) deserted nests >5 m from occupied seasons since extraction, as populations of the pred- nests : (b) deserted nests within I m of occupied nests; ators recover from the destruction caused by the last and (c) occupied nests at least 5 m from the edge of harvest. On the other hand, if the harvest itself is re- an active colony. Active nests were very rare in de- sponsible for controlling ticks, then ticks should in- serted areas as were empty nests in occupied areas. crease with each year since harvest Guano samples were sorted by hand on Mazorca. On the other islands, [ sifted guano through a screen or sorted it by hand when it was moist. Only adult and second-, third-, and tourth-instar nymphs were count- ed, since first-instar nymphs were too small and fast- Between late November and mid-January of 1977- moving for accurate tallies. I978 "375% of the 385 000 pairs of nesting Guanay Cor- I12 DAVID CAMERON DUFFY Ecology, Vol. 64. No I

TABLE1. Tick numbers on islands visited in. 1979 (means  SE) of 500-rnL samples of material from nests in three zones A from deserted nests at least 5 m from the nearest occupied nests; B.from deserted nests within I m of active nests; C. from active nests >5 m from deserted nests.

Nest location zone Percent Island Species deserting A 0 C No ticks per sample Macabi Pelican , -, Cormorant 21.8 Â 5.0 Booby 149.8 Â 60 2 Guanape Norte Booby 69.0 + 23.4 Lobos de Tierra Booby 95.2 Â 46.3 Ballestas Sur Booby . . Ballestas None Booby Chmcha Sur Booby Chincha Centre Booby

morants, Peruvian Boobies, and Peruvian Brown Pel- joined other adults roosting away from the nesting area. icans deserted their nests on Isla Mazorca, resulting Preening was a much more common behavior of adults in a loss of somewhere between 500 000 and 750 000 prior to desertion. Adult boobies spent 23% of each eggs and young. minute preening prior to desertions (i= 13.9 Â 0.2 The desertions began on the south side of the island s/min SE) compared to just 5% in apparently healthy during November in an area which was inaccessible areas (Y = 2.6 Â 0.2 slmin SE: n = 88 in each class). without causing major disturbance to the intervening Preening was also more frequent in cormorants (de- nesting area. During December and January, a line of serting adults, n = 108, x = 15.1 Â 0.2 shin; nonde- desertions worked its way northward, up the slope to sorting, n = 108, i = 2.2 Â 0.1 stmin). Pelicans at ap- the central ridge of the island and over onto the north- parently healthy sites spent 7% of each minute preening ern slope. By the middle of February, 75% of the north (n = 100, 2 = 4.5 Â 0.1 s/min). King et al. (1977b) slope had been deserted, although Peruvian Boobies found that adult pelicans in Mexico spent up to 68% and Guanay Cormorants had begun to renest on the of their time preening before deserting during an ap- south slope where the original desertions had taken parent tick infestation. place. Several subcolonies of pelicans deserted on the south side of the island; none did so on the north. The south- Desertions on other is/ands 1 visited eight islands in 1979. Five showed strong evidence of desertions (Table 1). The extent of deser- tion ranged from 5% on Isla Ballestas Sur to "10% on OOr m Isla Macabi. DON MARTIN

Desertions iti other years For three islands examined (Islas Mazorca, Macabi, and Don Martin), desertions were frequent (Fig. 1). 500 Out of 80 breeding seasons, 32 (40%) resulted in the OOr desertion of > 10% of the nesting area of the combined three species. Eleven of these occurred during years of the El Nino oceanic abnormality, which depresses Ill 0 the fish supply, (Quinn et al. 1978) and were probably caused by food shortage (Vogt 1940, 1942, Jordan 1964). Desertions occurred in 30% of the remaining 69 breed- ing seasons.

YEAR Desertions occurred nest by nest along a front (Fig. 2). At nests about to be deserted, adults appeared rest- FIG. 1 Percentage of nests being deserted per year at three guano islands from 1940 to 1978 (data derived from less. They frequently stood away from the nest, leav- original census sketches by Peruvian caretakers on the is- ing the contents exposed to seamist or sun. Some adult lands). Years of EL Nino events are indicated by X's at the boobies deserted their eggs and young at night and top of the figure. February 1983 TICKS AND SEAHI RDS [ i3

# EGGS OR YOUNG TABLE2 Aduh and nymphal tick abundmces (per 500-cm3 sample of nesting ma[er~aljin recently deser~edand in 0. NO. EGGS healthy areas of Isla Mazorca, 1978, (Mrans ? SF). 0 NO DATA

X DESERTED S~ec~es >I Healthv area Desened area

B No ticks per sample / '269 .. n .a 4/1 Gwmay Cormorant

Nest cup [0 9 9 2 0.7 42, I 2 5.0 Nes[ base I0 6,2 z 0,7 l7[,4 2 23.8 Peruvian Booby Nest cup I0 5.1 2 i.2 194.9 2 22.7 Brown Pel~can Nest cup I0 42,2 z 5,4 no data

P)~d~to~s-No Andean Condor ( Vlt11~1r~~t~pltit~s ) or Turkey Vulture (Curhu~f~.~(IUW) was seen on Mazor- ca during the study period, Vultures, and until re- cently, condors were shot on sight by the guards on the islands, The original accounts of thek causing de- sertions are al[ secondhand (Coker 1920, Murphy 1925, Vogt L942). Kelp and Band-tailed Gulls were never seen to attack nests defended by adults. No terrestriaL predators were present on Mazorca. Di*~oii*sc,.-Without extensive laboratory work, it is impossLble to prove that disease was not present. FIG.2. Deser~tonhat a booby subcolony on Mazorca be- However, the only pathoIogica1 condition 1 saw was a t ween 28 December I977 and 3 I January 1978, Mean distance between nests is 4.8 m. crusty appearance on the legs of a few young boobies in tickinfested area These crusts seemed to have been caused by guano st[ck[ng to the open wounds left by ticks. ern birds were on eggs, while the northern groups al- HII~OT~/i~~r~irh(~i~<~o.-Most of the colony was never ready had young and perhaps were more tenacious, disturbed until m~d-February.Desertions began in the Boobies and cormorants desened both eggs and young. area farthest from any human disturbance. Nests left unattended quickl y attracted Kelp and H

TI(^ -Densities of ticks were Iower Ln apparently healthy areas compared to areas where aduIts were deserting, on Mazorca (Table 2). Recently deserted nests (Zone B) on Islas Macabi, Guafiape Norte, Lo- bos de Tierra- and Chincha Centro all had higher tick levels than nests in apparently healthy areas (Zone C: F~bleI), TICKS / SAMPLE Combin~ngthe data from Tables I and 2, there was F[cr. 3. The relation between the percenrdge of A colony a Spearman Rank Correlation (r?)of ,97 (P < .Oi; n = deserting on an ~slandand the number of t~cks(tick samples 8: Fig. 3) between the extent of desertion and tick were taken from booby nests? includ[ng Mazorca), [Data from levels. Tables I and 2j, i I4 DAVID CAMERON DUFFY Ecology Vol. 64. No. [

I234567 DURATION (hl

F[G 4, Durations of foraging trips by Peruv~anBoobies and Guanay Cormorants on Mazorca tn 1978

FooJ J\~OHLIKP.-Cormorants, at least, tend to feed in immense groups of tens of thousands, which would BREEDING SEASONS SINCE presumably experience a similar feeding success GUANO HARVEST throughout the group. A food shortage would result in an abrupt, widespread desertion of nests rather than F~G.5, Tick abundance5 in re[ation to number of breed~ng seasons since last guano harvest. Data from all boohy sites the wave which was observed. sampled (Zone B Fable 11- deserted areas [Table ?I), (p3 = Vogt (1942) postulated that if each nesting cormo- 36: *t = 34: P < -051. rant or booby needed to feed once per day, then with =I2 h of daylight, durations of foraging of >6 h would be indicative of food shortages and predictive of mass desertions. In contrast, Guanay Cormorants and Pe- the desertions on the guano islands, S~milardeser- ruvian Boobies at Mazorca usuaLly spent <2 h foraging tions, not expla[nable by years of El Nifio, occurred (Fig. 4). in of breeding attempts over the years at the three isiands studied. Together, these facts suggest that ticks are a major cause of nesting fadure among the densely Vogt ( 1939) found that Tropiduru.s lizards from Isla nesting Peruvian guano birds. Chlncha Norte ate substant~alnumbers of ticks. [n Other explanations of desertions do not fit the avail- his satnples, they were the fourth commonest prey able data, Feeding trips were of very short duration by volume ( l4%), third commonest by number (2.4 per and desenions took place over months, not days. Water stomach), and t~edfor first pIace in frequency with temperatures are usually warmer dunng food short- which they were encountered in stomachs (5%). Ticks ages associated with El Niho (Murphy i936, Vogt i942). were even more prevalent in stomachs colIected from Sea surface temperatures were cooler than normal Isla Lobos de Tierra during the present study (volume (Duffy 1981). In summary, there was no evidence of 59%; 146 per stomach; 100% frequency). food shortage or ocranographic abnormality that might The comparison of the number of ticks in recently have caused the desertions. deserted Peruvian Booby nests (Zone B of Table 1; The two predators alleged to cause desertions were Table 2) with number of breeding seasons since the not present: the remaining two were never observed Ia5t guano barvest showed a gener~iincrease of the to attack defended nests. Human disturbance did not tick population with each successive year since har- occur in most of the colony, and desertions began in vest (Fig. 5; r$ = .36; H = 34; P < ,051. the area most distant from any human activity. Simi- lady desertions began on the coldest part of the is- land, The greater number of ticks in areas just recently A disease might have caused the desefl~ons,It would desefled, the greater frequency of preening among birds have to be a very virulent and infectious disease which about to desert, and the great number of ticks seen in attacked eggs or young but never adults. In addition< the colony all suggest that these ectoparasites caused adults, deserting eggs or young, would have to be gift- February I983 TtCKS AND SEABtRDS I IS ed with diagnostic skills which perceived symptoms in one species from a caretaker's garden on Lobos de eggs or young which appeared and behaved "norm~l- Tierra. Murphy (i92i) does not mention ants in his Iy" as far as 1 could determine. review of the islands' invertebrates, A final possibility is that the guano harvest controLs WHATLLML~S THE POPULAT~ONS OF TICKS'! tick populations. Every year or so, the guano is dug Some of the guano islands have been occupied by out with picks and shoveled down to bedrock. Brooms dense colonies of se4jirds for millenia (Hutchinson are used to sweep the rocks dean Feathers and car- 1950). Why doesn't every breeding season end up like casses are burned or thrown into the sea (Vogt 1942). [he one on Mazorca in 1977-1973? What limifs the For arthropods living in the guano, this results in an numbers of ticks? abrupt and almost complete disappearance of their There are a number of possibilities: the periodic habitat. Many aflhropods are undoubtedly bagged with crashes of the guano bird populations during El Nifio the guano and removed from the islands, Lizards may years might starve tick populations to such levels fhat escape this fate, but they are hunted by the guano they do not present a problem; ticks may have pred- extractors to supplement their food. ators that normally keep them under control; or human One can tesf the importance of ex tracf ion compared harvesting of guano every few years may be sufficient to predators in regulating tick numbers by looking at (at Ieast In this century) to keep tick numbers down. the size of tick populations with increasing yews since During El Niho years, there may be few hosts on the last guano harvesf. If predators are most Lmpor- the islands as birds undertake eruptive dispersals in tant, ticks should decrease as predators become more search of food (Vogt 1940). However, argasid ticks common with each successive year. On the ofher hand, such as Ort~ithodoro

TAB[.E3, A l~stof tick outbreaks from the literdture

T~ckspectes Host Location Effect Reference

Brown Pelican Texas colony desertion King et al. 19773 White Pelican Texas colony desertion

not reported

Wood Ibis ([his ih1,vl Kenya not reported Hoogstraal et al. I976 Sooty Tern Seychelles colony desert~on Feare I976 various species Johnston Atoll not reported Amerson and Shekon I976 Dry Tortugas not reported Denmark and Clifford I962

Brown Peltcan Mex~co colony desertton King et al. L977h various species Oregon not reported Cltfford et al I970 Galapagos not reported R~cel977:25

Galapagos possible desert~on Rice l977:36-38

Tunisia not reported Vermeil 1954: Hoogstral et al, 1976 France not reported Vermetl and Rebel 1976; Hoogstraal et al, I976 uarlous spp. Ire[and not reported Keirans et al. I976 guano b~rds Peru restricted nesting LaValle I918 guano b~rds Peru death of young, Vogt I942 anemia guano b~rds Peru human illness Hoogstraal et al. 1970; Clif- ford et al, [980 guano birds Peru desert~ons th~sstudy socotra Cormorant Arabian Gulf human illness Hoogstraal et al. I970 (f'h(~l(~cr~~cor<~,r8i- ~ro~~d((ri.~) Arabian Gulf possib[y restrtct nest ing

Prairie Falcon (Fill( (I death of young , ffl~~l<

Australia not reported Hoogstraal et al. I975 heronry Thatland not reported Hoogstral et al. 1975 heronry Tatwan not reported Hoogstrxd et al. I975 Scotland mortality directly and DIlfl~dnet XI. I978 through virus Bank Swallow mortal~tyof young Zolotov and Buker I976 uarlous seabirds not reported Murray and Vestjens I967 February I983 TICKS AND SEABIRDS

T~ckspecie5 Host Location Effect Reference

Common Murre British ChIumbia possible cause of Ballard and Ring I979 (L'rlu uu1h)e) death Brunnich's Murre USSR not reported Votyakov et al, I974 (Urid [om ~miu1 Clifc Swallow USA no effect Baerg I944 Ireland not reported Kelly and Walton I977

Australia weak< light young Johnstone et al, 1975

Farquak~rAtoll not reported Stoddard and Poore 1970

rooks and gulls USSR not reported

USSR not reported Andreev and Shcherbina I975 Ireland mot reported Evans 1971 unknown Australia death of young Reithmuller I93 I unknown Cape Cormorant Namibia not reported Berry 1975 (Phu!u~~r~)coruxco- pen$i.j-1 unknown Cape Cormorant South Africa not reported (Phulucrocor~~x cu- p~l?~is) unknown Crowned Cormorant South Acrica not reported Williams I978 (Phul~~c~ro~-~~rux coroflf/!l~h') unknown Brown Pelkcan Galapagos desertions

tation. Only 2 repon no effects. Unfoflunately 24 (52%) Plath (1919) concluded tkat birds with more densely give no information on possible effects, constructed nests have a higher load of parasitic Pro- Looking beyond just ticks and nesttng failure, x- ~ucdliphorufly larvae f han more loosely constructed toparasites may also ~nfluencegrowth of young, nest nests. structure, and nest and colony tenure. For exampLe, Ec[oparasites might also explain why landbirds typ- Moss and Kamin (1970) found that hrple Martins ically build additional nests when raising successive Progne mbis fledged larger clutches and hedvier young broods. in the absence of the martin rnife De~mun-vs

-liana with members of the Instituto del Mar (Callaoi, W. R. Coker, R. C. 1920. Habits and economic relations of the P. Bourne, H. Hoogstraal, G. Hunt, T. Price, D. Schneider, guano birds of Peru. Proceedings of the United States Na- R. Ricklefs, G. Watson, H. Zirnrnerberg, and especially the tional Museum 56:449-5 1 1 Princeton Pinhead Ecology Group. N. Atkins, C Gamba, C. Denmark, H. A., and C. M. Clifford. 1962. A tick of the Hays, E. Ortiz, B. Torres, and P. Yengle all helped with field Ornith<){Joros capensis group established on Bush Key, Dry work and census records. Grace Russell produced the illus- Tortugas, Florida. Florida Entomologis t 45: 139- 142. trations. Finally, the guards an the islands helped with their Duffy, D. C. 19SO. Comparative reproductive behavior and knowledge and hospitality. population regulation of seabirds of the Peruvian Coastal This study was supported by National Science Foundation Current. Dissertation, hnceton University. Prmceton, New gram DEB 77 16077; by the Organization of American States, Jersey, USA. by The International Council for Bird Preseruation (Pan -, 198 1. Seasonal changes in the seabird fauna of Peru. American) and by Princeton University. Ardea 69.109-1 13. I am deeply appreciative of the support and assistance of Duncan, J., H. Reid, R. Moss, J. Phillips. and A. Watson. all these individuals and organizations 1978. Ticks, Louping Ill and Red Grouse on moors in Speyside, Scotland. Journal of Wildlife Management 42: 500-505. LITERXIURE CITED Eddie, et at. 1970 (quoted by H. Hoogstraal and M. N. Kai- Alexander, R. D. 1974. The evolution of social behavior. ser. 1976. Ornithudot~os (Alectorobius) f:apmsis Neu- Annual Review of Ecology and Systematics 5: 325-383. mann (Ixoidea: Argasidae) parasmzing a human and birds Amerson, A. B., and P C. Shelton. 1976. The natural his- nesting on islands in East African lakes. Journal of Medical tory of Johnston Atoll, Central Pacific Ocean Atoll Re- Entomology 12 703-704.) search Bulletin 192: 1-479. Evans, P. G. H. 1971. The south-west Irish seabird popu- Anastos, G. 1957. The ticks or Ixodides of the U.S.S.R. a lations. Seabird Report 2:3540. review of the literature. Publicahon 548, Un~edStates Feare, C. J. 1976. Desertion and abnormal development in Public Health Service, Washington, D.C., USA. a colony of Sooty Terns Si~mufmcura infested by virus- Andreev, V. P..and A. A. Shcherbina 1975. New data infected ticks. Ibis 118. 1 12-1 L5. on importance of polyspecies colonies of Kara-Bogaz as Garcilaso de la Vega, Y. 1609. Primera parte de 10s ca- natural arbovirus foci. Translation I 140, United States Na- mentarios reales que tratan del origen de 10s Yncas, reyes val Medical Research Unit 3, Cairo, Egypt. que fueron del Peru, de su idolatria, leyes, y govierno en Ashburn, P M. 1947. 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