THE SOCIAL SYSTEM OF THE TEXAS GREEN JAY DOUGLAS C. GAYOU • Divisionof BiologicalSciences, 105 TuckerHall, Universityof Missouri, Columbia, Missouri 65211 USA ABSTRACT.--Acces$otybirds were absent at the nests of Green Jays (Cyanocoraxyncas). However, young stayedin the family flock for one year. After the young from the following year fledged,the 1-yr-old young were forced from their natal territory by the breeding male. These young either dispersed into adjacent habitat or became floaters within their former territories until, possibly,a breeding position opened up in a family flock. The yearlings provided a significant amount of territorial defense, which freed the breedersof much of the energeticcosts inflicted on them by the stringent territoriality required in south Texas habitat. I proposethat southTexas Green Jaysrepresent an early stagein the evolutionarysequence of development of cooperativebreeding as a responseto environmental factors.The reten- tion of young on the natal territory without helping at the nest representsan evolutionary early step,heretofore only hypothesized,that may lead to a more complexcooperative system that includes helpers at the nest. Received3 September1985, accepted 28 January1986. NEW World Jays possessa wide variety of of the Texas population of Green Jaysare an- socialorganizations and breeding systemsthat ecdotal,and information on breeding biology range from territoriality by breeding pairs in in North America consistsprimarily of nest lo- the Blue Jay (Cyanocittacristata; Hardy 1961); cation,height, and compositionand clutch size through highly cooperativebreeding systems (Merrill 1878, Sennett 1878, Bendire 1895, Sut- in the Gray-breasted(Mexican) Jay (Aphelocoma ton et al. 1950). ultramarina;Brown 1963, 1970), the Tufted Jay I report here on detailed field observations (Cyanocoraxdickeyi; Crossin 1967), and the Flor- of the Green Jay'ssocial system and discussthe ida Scrub Jay (Aphelocomacoerulescens; Wool- evolution of helping behavior and territoriali- fenden 1975);to colonialismin the Pinyon Jay ty in the North American population. I also (Gymnorhinuscyanocephalus; Balda and Bateman comparethe socialsystems of the two disjunct 1972). The neotropical Green Jay (Cyanocorax Green Jay populations. yncas)has been most intensively studied in Co- lombia, South America where it occurs in METHODS AND MATERIALS groups of 3-9 individuals that defend stable territories all year (Alvarez 1975). Breeding is I studiedGreen Jaysat SantaAria National Wildlife cooperative,with membersof the group help- Refuge(NWR) locatedapproximately 12 km south of ing to feed and care for the young. Juvenile Alamo, Hidalgo Co., Texason the Rio GrandeRiver. The area is semiarid, with a mean annual rainfall of Green Jaysdo not disperseimmediately from 45 cm. Most of the precipitationoccurs in late spring the parental group but stay as helpers at the and early autumn. Autumn precipitation occasion- nestfor a minimum of one additionalbreeding ally is enhancedby the movementof a low-pressure season. center onshoreand into the Rio Grande Valley. The There is no published information on the so- mean temperaturein winter is 15.5øC,spring 20.5øC, cial system of the North American population summer 28øC, and autumn 27øC. The lowest recorded of the Green Jay,which occursfrom just north temperatureis -9øC and the highest43øC (Fleetwood of the Rio Grande River in southeast Texas 1973). south to north-central Honduras (Meyer de The refuge consistsof about 900 ha coveredmostly Schauensee 1966). References to the behavior by evergreen,dry subtropicalforest. All land adja- cent to the refuge has been cleared for agriculture and is subjectto intense aerial spraying of insecti- cides and herbicides. Thus, Santa Ana NWR has been • Presentaddress: 2307 Ridgefield, Columbia,Mis- an island of natural habitat for 30-40 yr. The most souri 65203 USA. common trees are elm (Celtis spp. and Ulmus crasi- 540 The Auk 103:540-547. July 1986 July1986] TexasGreen Jay Social System 541 folia), ebony (Pithecellobiumfiexicaule), anaqua (Ehretia flying in the open resultsin heavy useof travel anacua),mesquite (varieties of Prosopisjulifiora), hui- corridorsof dense vegetation. sache(Acacia farnesiana), and retama (Parkinsoniaacu- Three reports on Green Jay age at Santa Ana leata). Beneath the canopy is a dense understory of NWR exist. The first (Kennard 1975) gave the shrubsand thorny vines. age of an AHY Green Jay banded at SantaAna A total of 2,850 h of observations was made from NWR as 9 yr, 9 months at death. On 15 June April 1981 through June 1984. I followed three flocks of jays for the majority of time and observed one 1982,I live-trapped an AHY jay that was band- ed on 30 November 1972 at the same location. other flock only occasionally.Hereafter, the study flockswill be referred to as Ray's Group, Handicap This bird extended the minimum lifespan to 10 Group, Blue Group, and Willow Lake Group. As of yr, 0 months.This jay, releasedunharmed, has March 1984 a total of 133 after-hatching-year (AHY) not been resighted since. Finally, Clapp et al. Green Jayshas been banded within the refuge. Each (1983) discovereda SantaAna Green Jay record bird received one numbered metal USF&WS band extending the age record to 10 yr, 8 months. and up to four plastic colored leg bands. The plastic Theseage recordswere of Green Jaysbanded bands were cemented with Duco Cement and none and recaptured within the confines of this were lost during the study period. small refuge. As of late 1985, it was unknown The jays were captured in potter traps baited with bird seed. Each jay was banded, measured, and whether a significantnumber of banded jays weighed using a 300-g Pesolaspring scale.Each jay had ventured outsideof the refugeboundaries. was then released within 10 m of the capture point. Only one recordof dispersalbeyond the refuge I sexedGreen Jaysby mating behavior becauseI could exists.A female (banded 8 January 1982) was not discern any sexual differencesin plumage, size, found dead on 24 February 1983 south of Rey- or other characteristics.Sexing via laparotomieswas nosa,Tamaulipas, Mexico, 15 km west of Santa not attempted becauseof Alvarez's (1975) lack of suc- Ana NWR. cess with this method. Groupcomposition.--In south Texas, Green Jays Nine nests were located during the study period, lived in a family group that remained stable and the majority of time was spent observing nests from one breeding seasonto the end of the of Ray's Group and the Handicap Group. Observa- tions commenced when a nest was located and con- next. In the winter and spring a family group tinued until all young fledged. In 1981, 6-h nest ob- consistedof the monogamousbreeding adult servation periods were conducted for Ray's Group male and female and all surviving offspring after the young had hatched. In 1982 and 1983, 4-h from the previous year's reproductive effort. observationperiods per nest were conductedand were During and after the breeding season,the rotated for the study nests so that observationsin- family group size increasedby the addition of cluded some morning and afternoon study periods the young producedduring the current year's for all nests until young fledged. After the young reproductiveeffort. At this time the group size fledged,observations continued on a similar rotating basis for 2-3 weeks. peaked.Several weeks after the young fledged, the yearling jayswere driven out of their natal RESULTS territory by the adult breeding male. The fam- ily group size was then reduced to just the Generalobservations.--Green Jays were con- breedingpair and the currentyear's young. This spicuousand scoldedloudly during the entire group size is maintained until the next breed- year except for the spring and summer breed- ing season(Figs. 1 and 2, Table 1). ing season,when they became secretive and During the winter, the family group usually difficult to locate. At this time the adults and foragedtogether (>76%, n = 142).In the spring young rarely scolded or called when alarmed when the breeding pair was building the nest, but, rather, silently moved away. laying eggs,etc., the yearlingsspent almost all Adult Green Jaystended to avoid flying in of their time foraging together within the pa- open spaces.In 5 yr of observations,I saw only rental territory yet having little contactwith 5 jays fly 30-200 m in the open, and all 5 were the breeders. The breeding male and female juveniles. Adult Green Jays preferred to fly foraged within 100 m of the nest during this short distancesin dense understory until they time (>90%, n = 78). The yearlings joined in a arrived at their destination.When flying in the "greeting" behavior with the adult pair in the open, Green Jays had an undulating, wood- morning and at dusk before separating. pecker-like flight. The apparent avoidance of After the current year's young fledged, the 542 DOUGLASC. GAYOU [Auk, Vol. 103 Fig. 1. Composition of Ray's Group study flock, Fig. 2. Compositionof Handicap Group study 1981-1983.In the age classificationused in this study, flock, 1981-1983. by winter those individuals initially placed in the "juvenile" categorybecome "yearlings." territorial year-round, but exhibited a higher degree of territorial defense behavior during breeding male spent increasingamounts of time the spring and summer breeding season.The with the yearlings foraging and moving about territory boundarieswere defined through ob- the entire territory and only occasionallyre- servationsof daily group movements and of joined the femaleduring