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Callitrichidae) numa ilha deflorestaAt&&a. Re- the role of infant-carrying in wild saddle-back vista Nordestina de Biologia 6: 105-l 37. tamarins (Sag&us ficicollis). Behav. Ecol. So- B~INSKI,S., AND P. E. Scorr. 1988. Association of ciobiol. 20:99-109. with monkeys in Costa Rica. Biotropica 20: IZAWA, K. 1978. A field study of the ecology and 136-143. behavior of the black-mantle tamarin (Suguinus BOINSKI,S., AND R. M. TIMM. 1985. Predation by nigricollis).Primates 19:241-274. squirrelmonkeys and double-toothedkites on tent- NEVILLE, M. K., K. E. GLAND~~,F. B~AZA,AND A. B. making bats. Am. J. Primatol. 9:121-128. RYLANDS. 1988. The howling monkeys, genus BROWN.L., AND D. AMAD~N. 1968. Eaales. hawks Alouatta, p. 349453. In R. A. Mittermeier, A. B. and falcons of the World. McGrawrHill, New Rylands, A. F. Coimbra-Filho, and G. A. Bou- York. chardet da Fonseca [eds.], Ecology and behavior DAWSON, G. A. 1976. Behavioral ecologyof the Pan- of Neotropical primates. Vol. 2. World Wildlife amanian tamarin, Sag&us Oedipus.Ph.D.diss., Fund-US, Washington, DC. Michigan State Univ.;East Lansing. SICK, H. 1984. Ornithologia Brasileira. Vol. 1. Edi- FERRARI. S. F. 1988. The behaviour and ecoloav of tora Universidade de Brasilia, Brasilia. the bully-headedmarmoset, CaZZ~~hriwfravice~(O. SIEGEL, C. E., J. M. HAMILTON, AND N. R. CASTRO. Thomas, 1903). Ph.D.diss., University College, 1989. Observations of the Red-billed Ground- London. Cuckoo (Neomorphuspucheranii) in association FERRAIU, S. F., AND M. A. LOPES FERRARI. In press. with tamarins (,S&&zs) in Northeastern Ama- Predator avoidancebehaviour in the bully-headed zonian Peru. Condor 91:720-722. marmoset, Cullithrixflaviceps.Primates. TERBORGH, J. 1983. Five New World primates: a Fomm, R. 1980. Observationsof the foraging as- study in comparative ecology. Princeton Univ. sociationof Double-toothed Kites and white-faced Press, Princeton, NJ. capuchin monkeys. Auk 97:94-98. WILLIS, E. O., AND Y. ONIKI. 1978. Birds and army GOLDIZEN, A. W. 1987. Facultative polyandry and ants. Annu. Rev. Ecol. Syst. 91243-263.

The Condor92783-788 0 The Cooper Ornithological Society 1990

SURVIVAL OF BREEDERS IN SANTA CRUZ ISLAND AND MAINLAND SCRUB POPULATIONS’

JONATHAN L. A-IWCOD~ Manomet Observatory,Box 936, Manomet, MA 02345

MARY Jo ELPERS U.S. Fish and Wildlife Service,Great Basin Complex, 4600 Kietzke Lane, Reno, NV 89502 CHAWS T. COLLINS Department of Biology, California State University,Long Beach, CA 90840

Key words: Scrub Jay; coerulescens; den 1974, Atwood 1980b, Verbeek 1973) other as- cooperativebreeding; survivorship; Santa Cruz Island. pectsof their socialbehavior vary dramaticallybetween populations.The Florida ScrubJay, A. c. coerulescens, The Santa Cruz (Aphelocomacoeru- has a well-developed system of cooperative breeding, lescensinsularis) is the most morphologically differ- in which groups of related birds defend year-round entiated member of the southern California Channel territories and nonbreedershelp raise offspringthat are Islands’ endemic avifauna (Johnson 1972). Further- not their own (Woolfenden and Fitzpatrick 1984). The more, its isolation from mainland Scrub Jay popula- principal factor associatedwith the of this tions provides an opportunity to examine various fac- social system is the lack of suitable breeding space tors associated with the species’ social evolution within the population’s rare, patchy, scrubhabitat (Atwood 1980b, Woolfenden and Fitzpatrick 1984). (Woolfenden and Fitzpatrick 1984). All suitable hab- Although ScrubJays in generalare permanently mo- itat always seemsto be occupiedby establishedbreed- nogamousthroughout their breeding range (Woolfen- ers,which preventsyoung, subordinate individuals from acquiring nesting space. Consequently, breeding by l-year-old Florida ScrubJays is extremely rare (wool- fenden 1974,1975; Woolfenden and Fitzpatrick 1978, I Received 15 December 1989. Final acceptance17 1984). April 1990. In contrast,western mainland ScrubJay populations 784 SHORT COMMUNICATIONS

TABLE 1. Annual survival rates of breeding Santa Cruz Island Scrub Jays (1975-l 985).

Annual Annual YG5.W n Deaths mortality n Deaths mortality Mean survival

1975 9 0.00 7 1 0.14 0.938 1976 18 0.00 16 1 0.06 0.971 1977 19 :, 0.05 19 1 0.05 0.947 1978 19 0.00 19 1 0.05 0.971 1979 19 ; 0.05 21 1 0.05 0.950 1980 19 0.00 21 : 0.14 0.925 1981 23 2 0.09 28 0.11 0.902 1982 38 6 0.16 42 4 0.10 0.875 1983 40 1 0.03 42 1 0.02 0.976 1984 42 : 0.05 42 2 0.05 0.952 1985 36 0.08 35 6 0.17 0.873 Total 282 16 0.05 292 24 0.09 0.935 + 0.04 sBased on numberof individualspresent during indicated year that died priorto the followingbreeding season. Thus, of 23 malespresent in 1981, two (0.09) died prior to 1982. Seetext for furtherdiscussion.

do not breed cooperatively (Pitelka 1951, Atwood habitat is saturatedis the frequencywith which young 1980b). Although few details have been publishedcon- individuals are able to acquire nesting territories. In cerning their socialbehavior or demography, the pres- relatively nonsaturated habitats, l-year-old breeders ence of yearling breeders in western mainland Scrub would be predicted to occur more frequently than in Jays has been documented by several investigators saturatedhabitats where suitable spaceis occupied by (Ritter 1972; Verbeek 1973; Elpers,unpubl. data), sug- established, older individuals. Data concerning this gestingthat in these populations suitable nesting hab- portion of our research will be presented elsewhere. itat frequently is available even to young individuals. Here we describeinformation concerninga secondim- Unlike the geographicallyand ecologically restricted portant and related aspect of Scrub Jay demography, Florida population, westernmainland ScrubJays occur namely, the frequencywith which establishedbreeders in a wide range of habitats throughout western North die, thereby creating vacancies in areas known to be America (Pitelka 1951). suitable nesting habitat. These resultsare summarized Like western mainland forms, Santa Cruz Island from studies of Scrub Jays on Santa Cruz Island (At- Scrub Jays also lack cooperative breeding (Atwood wood and Collins), the southern California mainland 1980b, 1980~).However, this subspeciesresembles the (Elpers),and Florida (Woolfendenand Fitzpatrick 1984, in that most first-year birds, as well unpubl. data). as some older individuals, fail to occupybreeding space and thereby attain reproductivestatus (Atwood 1980~). STUDY AREAS AND METHODS Nonbreeding Santa Cruz Island Scrub Jays do not re- Santa Cruz Island, located approximately 30 km from main on their natal territories and act as helpers, but the nearest mainland point, is the largest and topo- instead wander along the peripheriesof establishedter- graphically most diverse of the California Channel Is- ritories and in suboptimal habitatsuntil breedingspace lands, being approximately 249 km2 in area and rang- can be acquired (Atwood 1980~). ing elevationally from sealevel to 753 m (Power 1980). The demography of these populations in relation to It has been part of an island land mass since the early availability of breeding habitat is an important con- to mid-Pleistocene, althoughits degreeofisolation dur- sideration. One index of the extent to which breeding ing the lowered sea levels associatedwith glacial max-

TABLE 2. Annual survival rates of breeding California mainland Scrub Jays (198 l-l 985).

1981 6 0 0.00 8 3 0.38 0.786 1982 19 3 0.16 19 4 0.21 0.816 1983 25 5 0.20 26 0.19 0.804 1984 4 0.13 30 : 0.10 0.885 1985 ::, 5 0.17 33 3 0.09 0.873 Total 111 17 0.13 116 18 0.19 0.833 + 0.04 ’ ’ Basedon number of individuals present during indicated year that died prior to the followingbreeding season. See text and legendto Table 1 for furtherdiscussion. SHORT COMMUNICATIONS 185 ima was less than at the present time (Vedder and Howell 1980, Wenner and Johnson 1980). The sub- stantialmorphological divergence exhibited by the Santa Cruz Island Scrub Jay, in which linear measurements and body weights average approximately 20% larger than those of the adjacent mainland population (Pi- telka 1951, Atwood 1980a), suggestsan extended pe- riod of genetic isolation. No evidence existsfor current interchange between the mainland and island Scrub Jay populations (Pitelka 1951, Jones 1975). Principal vegetation types in the Santa Cruz Island study area, located near the University of California’s Channel Islands Field Station, include (a) dominated by scrub oak (Quercusdumosa) and laurel 1 2 3 4 5 6 7 tl 9 10 11 sumac (MuZosmaluurina), (b) coast live oak (Quercus YEARSAl=fER FIRST OBSERVED BREEDING ugrifoliu)woodland, (c) variably open thickets of mule- fat (Bucchurisglundulosu), (d) introduced Eucalyptus FIGURE 1. Survivorshiprates of breedingScrub Jays groves,and (e) open grassland.Additional descriptions from three populations. Regressionlines are weighted of the study area are provided in Yeaton (1974) and by sample sizes contributing to each year’s survivor- Atwood (1980b). ship estimate. See text for further discussion. Mainland California Scrub Jays were studied at the Starr Ranch Wildlife Sanctuary of the National Au- dubon Society,located approximately 12 km northeast 0.531, n = 5). Data presented by Fitzpatrick et al. of San Juan Capistrano in the coastal foothills of the (1988) also failed to indicate differential rates of mor- SantaAna Mountains. The approximately279-ha study tality between breedingmale and female Florida Scrub area is situated in a major canyon featuring an inter- Jays. Consequently,in order to increase sample sizes mittent stream. Southern oak woodland, dominated for the following comparisons between populations, by coast live oak and California sycamore (Platunus mortality data from both sexeswere pooled. rucemosu)characterizes the canyonbottom. Other ma- A Kruskal-Wallis test obtained significant differ- jor vegetation types of the surrounding hillsides and encesin annual mortality, calculatedas the percentage ridgesinclude (a) coastalsage scrub, dominated by Cal- of each year’s breedersthat died prior to the following ifornia sagebrush(Artemesia culifornicu), buckwheat nesting season,among the three study populations (F (Eriogonum fasciculutum), and laurel sumac and (b) = 11.56, P = 0.0004). Santa Cruz Island Scrub Jays chaparral, dominated by scrub oak and toyon (Het- had higher mean survivorship rates (X = 0.94, SD = eromelesarbutifoliu). 0.04, n = 11) than samples from either California (X Between 1975 and 1986 a total of 651 Santa Cruz = 0.83, SD = 0.04, n = 3) or Florida (X = 0.82, SD = Island Scrub Jays were uniquely color-banded; 439 0.09. n = 9: Woolfenden and Fitzoatrick (1984) (Tu- mainland California ScrubJays were similarly marked key’s studentizedrange test, P < 0.65; df = 22; analysis between 1980 and 1986. Determinations of sex and based on ranked data due to small sample sizes). An- breeding status were based on behavior, including nual survivorship rates of mainland California and vocalizations (Atwood 1978). Florida ScrubJays did not differ significantlyfrom one Divorce occursonly rarely in known ScrubJay pop- another (P > 0.05). ulations (Woolfenden and Fitzpatrick 1984; Atwood Linear regressionsof survivorship during the years 1980~; Elpers, unpubl. data). In the present analysis, following first documentationof breedingare presented when one member of a pair disappearedand was sub- in Figure 1. Following the approach of Woolfenden sequentlyreplaced by a new individual, the absentbird and Fitzpatrick (1984), samples sizes for the Santa was assumedto have died. In caseswhere both mem- Cruz Island data varied from five individuals that were bers of a pair disappeared, it was usually impossible identified as breeders in 1975 and which could have to distinguishbetween the scenariosof both birds dying potentially lived through 11 subsequentbreeding sea- more or less simultaneously and dispersal from the sonsto 103 individuals (including those five birds first study area of a widowed bird which failed to maintain observed in 1975) that could have been followed for its territory following the death of its mate. Data from one breeding season. In the data set from mainland instances in which both members of a pair vanished California, samples for each year cohort varied from were used, up to the year of disappearance,in calcu- six to 89 individuals. Becauseof these differences in lating rates of annual mortality (Tables 1 and 2). How- sample sizes and resultant variation in the reliability ever, birds belongingto “vanished pairs” were exclud- ofannual survivorship estimates,values were weighted ed from the regressionanalyses (Fig. 1). by the number of birds contributing to each estimate. Statistical analyseswere performed using SAS (ver- Since the proportion of survivors at year 0 (the initial sion 5.18) proceduresNPAR 1WAY, RANK, and GLM. year in which each bird was identified as a breeder) was by definition 1.00, the intercept of each line was RESULTS fixed at the origin. In comparisonsinvolving the Cal- No significant difference in annual mortality between ifornia mainland sample, which included only 5 years males and females were noted on Santa Cruz Island of survivorship data, only the first 5 yearsof data from (Table 1; P = 0.113, n = 11) or in the mainland study the longer-term studies in Florida and on Santa Cruz population (Table 2; Wilcoxon’s two-sample test, P = Island were used. 186 SHORT COMMUNICATIONS

During the time periods included in this study, an important source of avian mortality (von Bloeker breeding Scrub Jays on both Santa Cruz Island and 1967; Atwood, pers. observ.), and the diet of island mainland California exhibited relatively constantrates foxes has been describedas consistingprimarily of in- of survivorship (Santa Cruz Island, r* = 0.93, P = sectsand vegetablematter (Laughrin 1977). 0.0001; mainland California, r2 = 0.99, P = 0.0001). Stebbins (1966) mentions at least seven species of Similar results have been found in the Florida Scrub snakesthat prey occasionallyon birds or bird eggsand Jay (Woolfenden and Fitzpatrick 1984, Fitzpatrick et which occur on the southern California mainland ad- al. 1988). jacent to Santa Cruz Island: gopher snake (Pi&o&is In comparingthe slopesof regressionlines from each melanoleucus),racer (Coluber constrictor),coachwhip location (Fig. l), the Santa Cruz Island population (Masticophusflagellum), striped racer (IV. lateralis), showed a significantly higher survivorship rate than rosy boa (Lichanura trivirgata), common kingsnake both the mainland California ScrubJay (basedon data (Lampropeltisget&s), and western rattlesnake (Cro- from years l-5 only; F = 35.83; P = 0.001) and the talus viridis). df these, only gopher snakesand racers Floridapopulation(years l-l 1;F= 62.26,P=O.O001). occur on Santa Cruz Island (Savaae 1967). and their The survivorship rate of the Florida Scrub Jay was densitiesappear to be low compared to mainland sites. lower, though not significantly so, than that of the Francis et al. (1989) list nine speciesof snakesthat are mainland California population (years 1-5; F = 4.29, mobbed by ScrubJays in Florida, including two species P = 0.084). (coachwhip and indigo snake, Drymarchon corais) Using the slopesofthese regressionlines as estimates known to prey upon Scrub Jays. Florida Scrub Jays of mortality rates, we calculated annual survivorship ignored or killed and ate snakes ~60 cm in length with the equation (Francis et al. 1989); we have never seensnakes longer than approximately 45 cm on Santa Cruz Island. S, = emd, Raptors are also less diverse on Santa Cruz Island where S, representsthe proportion of an original sam- than on the mainland sites; Red-shouldered Hawks ple that survives y years after the first observedbreed- (Buteo Zirzeatus),Great Homed Owls (Bubo virgini- ing seasonand d representsthe instantaneousrate of anus), and screech-owls(Otus kennicottiiin California mortality (Caughley 1977). Based on this approach, and 0. asio in Florida) are absent from Santa Cruz Woolfenden and Fitzpatrick (1984) and Fitzpatrick et Island (Jones 1975). The only potentially significant al. (1988) calculated an annual survival rate of 82% avian nredatorson volant SantaCruz Island ScrubJavs for breeding Scrub Jays in Florida. Our calculations are migrant and wintering Sharp-shinned (Accipiter yield annual survivorship rates of 9 1% (e&.o94s)for the striatus)and Cooper’s (A. cooperiz)hawks, both of which Santa Cruz Island nonulation and 83% (em0.1s74)for the orobablv occur at lower densitieson Santa Cruz Island California mainland population. Thanon ihe adjacentCalifornia mainland (H. Lee Jones, pers. comm.): The relative importance of these two DISCUSSION sneciesas nredatorsof ScrubJavs on SantaCruz Island Once reproductive statushas been achieved, ScrubJays compared-with mainland California and Florida is un- are long lived in comparisonwith most passerinebirds. known. However, we note that male Sharp-shinned In fact, the annual survivorship rates reported here, Hawks are approximately 20% smaller in body mass ranging from 91-94% in breeding Santa Cmz Island than Santa Cruz Island Scrub Jays; although we have ScrubJays, 83% in the mainland California population, observed approximately 10 capture attempts by this and 82% in the Florida Scrub Jay (Woolfenden and species, we have never seen a Sharp-shinned Hawk Fitzpatrick 1984, Fitzpatrick et al. 1988) are among successfullytake a SantaCruz Island ScrubJay. On the the highest that have been describedfor any California mainland and in Florida, Sharp-shinned (Ricklefs 1973). Survivorship between males and fe- Hawks are more evenly matched in body size with males is comparable in all three populations. Scrub Jays, and may be a greater source of jay mor- The precise circumstances surrounding deaths of tality. breeding jays in all three populations were generally Regardlessof its cause,the lower rate of annual mor- unknown. However, we speculatethat higher rates of tality in the Santa Cruz Island Scrub Jay, when com- adult survivorship in the SantaCruz Island population pared with California mainland populations, contrib- reflect a relative absence of predators on the island utes importantly to habitat saturation of the island when compared with mainland sites. On the adjacent subspecies(Atwood 1980b, 1980~). The opportunity California mainland and in Florida, opossums(Didef- for nonbreedingindividuals to acquire suitable breed- phus marsupialis),striped skunks(Mephitis mephitis), ing space that has been left vacant through the death spotted skunks(Spilogaleputorius), bobcats (Lynx ru- of an establishedterritory holder occursless frequently fus), gray foxes (Urocyon cinereoargentaeus),raccoons on the island than on the California mainland. (Procyonlotor), longtail weasels(Mustela frenata), do- The absence of cooperative breeding in the Santa mestic cats (Felis catus),and (in western North Amer- Cruz Island Scrub Jay is not yet fully explained. In ica) coyotes (Canis Zatrans)are all potential or known both the Florida and Santa Cruz Island populations predators on Scrub Jay eggs, nestlings, fledglings, or breeding space is in short supply, and young or sub- adults (Burt and Grossenheider 1964, Francis et al. ordinate individuals must delay reproduction for sev- 1989). On Santa Cruz Island, potential mammalian eral years until they are able to acquire a suitable nest- predators are limited to the island fox (Urocyon littor- ing territory. However, the socialbehavior of thesetwo alis) and spotted skunk (von Bloeker 1967). Skunk populations differs markedly, with Florida Scrub Jays densitieson the island are so low as to be negligibleas having helpersat the nest, and SantaCruz Island Scrub SHORT COMMUNICATIONS 787

Jayshaving “floaters” that are not associatedwith any past’ which led to the initial evolution of helping be- established breeding territory. Two main hypotheses havior within the New World jays. However, we do may be suggestedto explain these contrasts. not know how quickly suchsocial systems may evolve. First, as postulated by Atwood (1980~) and Wool- Both Florida and Santa Cruz Island Scrub Jay popu- fenden and Fitzpatrick (1984), nonbreedingScrub Jays lations probably became separatedfrom westernmain- on Santa Cruz Island may be able to survive in areas land forms during the Pleistocene (Pitelka 1951, At- that are unsuitable for breeding territories, whereas wood 1980b, Woolfenden and Fitzpatrick 1984), but such“marginal” habitats are lessavailable to the Flor- the timing of thesetwo isolationsrelative to each other ida population. Woolfenden (1974) characterizedFlor- is unknown. Changesin ecologyand population struc- ida Scrub Jays as having “extremely narrow habitat ture may have resulted in the disappearanceof coop- tolerances,” and suggestedthat survivorship of non- erative breedingfrom ancestralwestern Scrub Jays sub- breedersin areas outside of suitable breeding habitat sequentto isolation of the Florida population but prior would be so low as to selectfor an alternative strategy, to the establishmentof the Santa Cruz Island deme. If namely, juvenile birds remaining on their natal teni- true, derivation of the insular form from noncooper- tories beyond the normal ageof dispersal(Woolfenden atively breeding ancestors,coupled with a relatively and Fitzpatrick 1984). On Santa Cruz Island, non- short period of genetic isolation, may be important in breeding individuals may be able to survive in mar- understandingits present social system. Even though ginal habitats or in limited areas of suitable habitat Santa Cruz Island ScrubJays are now characterizedby that are located in interstices between establishedter- habitat constraintsand population demography simi- ritories without incurring the increasedmortality rates lar to thoseof the cooperativelybreeding Florida Scrub postulated for such behavior in the Florida Scrub Jay Jay, suchselective pressures in and of themselveshave (Woolfenden and Fitznatrick 1984). Bv wanderins failed thus far to result in evolution of a comparable throughsuch unoccupied areas, nonbreeding Santa C& social system. Island Scrub Jays may be better able to search for potential territory openings. We especially thank G. E. Woolfenden for his in- A related factor may be the relative scarcityof pred- terest in our studies of western Scrub Jays, and for ators on Santa Cruz Island. Woolfenden and Fitzpat- making available unpublished data from the work in rick (1984) predicted that “Santa Cruz juveniles, while Florida. P. Peters contributed greatly to this project living and wandering through suboptimal habitat, ex- through her banding activites on Santa Cruz Island perience higher survival than would analogous,juve- from 1980-1983, as have various individuals who have nile dispersersin Florida.” Becausewe have generally participated in the fieldwork on SantaCruz Island. The been unableto distinguishdeath from dispersalin non- mainland California researchwould not have been pos- breeding Santa Cruz Island Scrub Jays, survivorship sible without the encouragementand support of D. R. data for floatersis presentlylacking. However, the low- Bontrager;additional field assistancewas provided by er levels of predation associatedwith the depauperate D. Toohey, P. Osborne, and S. Grebel. insular fauna may contribute to higher survivorship Work on Santa Cruz Island was made possible not only among breeding birds but also among non- through the cooperation of C. Stanton (Santa Cruz Is- breeding individuals. Furthermore, reduced predation land Company), L. L. Laughrin (University of Cali- pressureson Santa Cruz Island may decreasethe im- fornia SantaCruz Island Reserve),and The Nature Con- portanceof one of the main benefitsreceived by breed- servancy. Similar hospitality was provided on Starr ing pairs that allow auxiliary individuals to help. Wool- Ranch by J. B. Froke (National Audubon Society), and fenden (1978) and Stallcup and Woolfenden (1978) P. and S. Desimone. J. M. Hagan and B. A. Hamilton suggestedthat predator dissuasion was the principal provided valuable suggestionson early drafts of the form of help given by Florida Scrub Jay helpers to the manuscript:comments from G. E. Woolfenden and D. breederswith which they were associated,and Francis M. Power improved the final version. et al. (1989) showed that helpers contributed impor- Financial assistancewas provided to Atwood by the tantly to antipredator mobbing behavior. On Santa Frank M. Chapman Memorial Fund, the El Dorado Cmz Island, where predation pressureon Scrub Jays Audubon Society, W. R. Atwood, and Manomet Bird is lessthan in mainland areas,there may simply be less Observatory, and to Elpers by Sigma Xi and the El opportunity for nonbreeding individuals to help. Dorado Audubon Society. An alternative explanation of the contrasting social structuresof Santa Cruz Island and Florida ScrubJays LITERATURE CITED emphasizes the historical aspectsof evolution of so- ciality in the genusAphelocoma. Becausecooperative ATWOOD,J. L. 1978. The breeding biology of the breedingis a widespreadphenomenon among the New Santa Cruz Island Scrub Jav. Auhelocomacoeru- World jay lineage, including all three speciesof &he- lescensinsularis. M.A.the&,-California State locoma(Brown 1970, Pitelka 1951, Woolfenden 1975, Univ., Long Beach. Goodwin 1976), well-developed social behavior ATWOOD,J. L. 1980a. Body weightsof the SantaCruz seems likely to be an ancestral rather than a recent, Island ScrubJay. N. Am. Bird-Bander 4: 148-l 53. repeatedly derived characteristic. We concur with ATWOOD,J. L. 1980b. Breeding biology of the Santa Woolfenden and Fitzpatrick (1984) that present-day Cruz Island ScrubJay, p. 675-688. In D. M. Power ecologyand demographyare important in maintaining [ed.], The California Islands:proceedings of a mul- the social system of the Florida Scrub Jay, and that tidisciplinary symposium. Santa Barbara Natural these factors probably reflect the ‘ghost of selection History Museum, Santa Barbara, CA. 788 SHORT COMMUNICATIONS

ATWOOD,J. L. 1980~. Social interactionsin the Santa the California Islands. SantaBarbara Botanic Gar- Cruz Island Scrub Jay. Condor 82:440-448. den, Santa Barbara, CA. BROWN,J. L. 1970. Cooperative breeding and al- STALLCUP,J.A.,ANDG.E. WOOLFENDEN.1978. Fam- truistic behavior in the Mexican Jay, Aphelocoma ily statusand contribution to breeding by Florida ultramarina. Anim. Behav. 18:366-378. Scrub Jays. Anim. Behav. 26:1144-l 156. BURT, W. H., AND R. P. GROSSENHEIDER.1964. A STEBBINS, R. C. 1966. A field guide to western reptiles field guideto the mammals. Hot&ton Mifflin Co.. and amphibians. Houghton Mifflin Co., Boston, Boston, MA. MA. CAUGHLEY,G. 1977. Analysis of vertebrate popula- VEDDER,J. G., AND D. G. HOWELL. 1980. Topo- tions. John Wiley and Sons, The Pitman Press, graphic evolution of the southern California bor- Bath. derland during late Cenozoic time, p. 7-3 1. In D. FITZPATRICK,J. W., G. E. Woo -EN, AND K. J. M. Power [ed.], The California Islands: proceed- MCGOWAN. 1988. Sourcesofvariance in lifetime ings of a multidisciplinary symposium. Santa Bar- fitness of Florida Scrub Jays. Proc. XIX Int. Or- bara Museum of Natural History, Santa Barbara, nithol. Congr. (1986):876-89 1. CA. FRANCIS,A. M., J. P. Hm, AND G. E. WOOLFEN- VERBEEK,N.A.M. 1973. The exploitation system of DEN. 1989. Mobbing by Florida Scrub Jays:be- the Yellow-billed . Univ. Calif. Publ. Zool. haviour, sexual asymmetry, role of helpers and 99:1-58. ontogeny. Anim. Behav. 38~795-816. VON BLOEKER,J. C., JR. 1967. Land mammals of the GOODWIN,D. 1976. Crows of the world. Comstock southern California Islands, p. 245-263. In R. N. Publishing Associates,Ithaca, NY. Philbrick [ed.], Proceedingsof the symposium on JOHNSON.N. K. 1972. Oriain and differentiation of the bioloav of the California Islands. Santa Bar- the avifauna of the Ch&nel Islands, California. bara Bot&c Garden, Santa Barbara, CA. Condor 741295-315. WENNER, A. M., AND D. L. JOHNSON. 1980. Land JONES,H. L. 1975. Studies of avian turnover, dis- vertebrates on the California Channel Islands: persal and colonization of the California Channel sweepstakesor bridges?, p. 497-530. In D. M. Islands. Ph.D.diss., Univ. of California, Los An- Power [ed.], The California Islands: proceedings geles. of a multidisciplinary symposium. Santa Barbara LAUGH~UN,L. L. 1977. The Island Fox: a field study Museum of Natural History, Santa Barbara, CA. of its behavior and ecology. Ph.D.diss., Univ. of WOOLFENDEN,G. E. 1974. Nesting and survival in a California, Santa Barbara. nonulation of Florida Scrub Jays. Living Bird 12: PITEJXA, F. A. 1951. Speciation and ecologicdistri- 25149. bution in American jays of the genusAphelocoma. WCIOLFENDEN,G. E. 1975. Florida ScrubJay helpers Univ. Calif. Publ. Zool. 50:195464. at the nest. Auk 92: l-l 5. POWER,D. M. 1980. Introduction, p. la. In D. M. WOOLFENDEN,G. E. 1978. Growth and survival of Power [ed]., The California Islands: proceedings young Florida Scrub Jays. Wilson Bull. 90: 1-18. of a multidisciplinary symposium. Santa Barbara WOOLFENDEN.G. E.. AND J. W. F~TZPA~UCK. 1978. Natural History Museum, Santa Barbara, CA. The inheritanceof territory in group-breedingbirds. R~CKLE~,R. E. 1973. Fecundity, mortality, and avi- Bioscience28:674684. _ - an demography,p. 366435. In D. S. Famer [ed.], WOO-EN. G. E.. AND J. W. FIT~A~R~CK. 1984. Breeding biology of birds. National Academy of The Florida Scrub Jay: demography of a cooper- Science, Washington, DC. ative-breeding bird. Monogr. Popul. Biol. 20:1- Rtrrza, L. V. 1972. The breeding biology of Scrub 406. Jays. M.A. thesis, California State Univ., Chico. YEATON,R. I. 1974. An ecologicalanalysis of chap- SAVAGE,J. M. 1967. Evolution of the insular her- arral and pine forest bird communities on Santa petofauna, p. 219-227. In R. N. Philbrick [ed.], Cruz Island and mainland California. Ecology 55: Proceedingsof the symposium on the biology of 959-973.