Steller's Jay Invasion on Southern Vancouver Island, British Columbia Andrew C. Stewart Michael G. Shepard British Columbia Ministry of 1241 Broad St. Environment, Lands and Parks Victoria, B.C., Canada W8W 2A4 Wildlife Branch 780 Blanshard St. Victoria, B.C., Canada V8V lX4 ABSTRACT Field observationsduring the autumnof 1992 indicated In BritishColumbia, some authors have suggested a largeSteller's Jay (Cyanocittastelleri) movement oc- that there may be a southwardmovement during curredon southernVancouver Island. The jayswere re- someyears (Swarth1922; McCabeand McCabe luctantto crosswide expansesof water. Bandingstud- 1928; Munro 1931; Munro and Cowan 1947; iesduring the winterof 1992/1993 suggestthat $teller's Canningset al. 1987). Autumninvasions by the Jays disperse and occupydiscrete winter territories.A review of literature and Christmas Bird Count data Steller's Jay have long been noted to occur on showed similar invasionshave occurred periodically southern Vancouver Island (Munro 1923, 1931; since at least 1913. Bent 1946; Guiguet1954). In the early autumnof 1992, a very large passage of Steller's Jays oc- curred on the coast of southwestern British Co- INTRODUCTION lumbia(Siddle 1993) and northwesternWashing- ton (Tweitand Gilligan1993). This movementwas Irruptivemigrations are knownfor severalspecies mostpronounced in the city of Victoria,located at the south end of Vancouver Island. A Christmas of NorthAmerican corvids. Significantmigrational movementsof the Blue Jay (Cyanocitta cristata) BirdCount (CBC) conductedthere on 17 Decem- have been documented in eastern North America ber 1992 resultedin a tally of 659 Steller's Jays, (Broun1941; Bent 1946; Stewart 1982) and more the highestever recordedin Canada. recentlyin the west (Weber1977; Smith1979). In the southwest,invasions by two coniferseed spe- The Steller'sJay is widely distributedthroughout cialists, the Clark's Nutcracker (Nucifraga VancouverIsland, inhabiting mid to low elevation columbiana) and Pinyon Jay (Gymnorhinus coniferousforests composed of western hemlock cyanocephala)have also been reported(Wescott ( Tsuga heterophylla),Douglas-fir ( Pseudotsuga 1964; Davis and Williams 1964; Goodwin1976). menziesi/),amabilis fir (Abies amabilis),grand fir Less well known are seasonal movementsby the (Abies grandis),western redcedar(Thuja plicata) Steller'sJay (Cyanocittasteller/), generally con- and Sitka spruce (Picea sitchensis). These ex- sideredto be a resident,non-migratory species tensive forests reach the outskirts of urban Victoria (Bent 1946; Guiguet 1954; Godfrey 1986). near Langfordand Metchosin,about 5 kin. to the Wescott(1969) foundthat Steller'sJays invading west. Victoria's native forest was composed of southernArizona were all first-yearbirds. Analy- open standsof Garry oak (Quercusgarryana), ar- sis of band returns lead Morrison and Yoder-Will- butus(Arbutus menziesi/} and Douglas-fir,most of iams (1984) to concludethat the Steller'sJay is which has subsequentlybeen lost to agricultural non-migratoryand characterizedtheir movements and urban development (Stanley-Jones and as wanderingsor dispersals. Benson 1973). Remnants of this original forest are now found only in isolated parks, although mature oak trees have been retained in some resi- Page 90 North American Bird Bander Jul.-Sep. 1994 dential areas. The Steller's Jay is normallyrare isticallyhigh suggestinga migratory movement. within urban Victoriaexcept duringinvasion years Between25 and 29 August,flocks numbering from when it may be abundant (R. W. Campbell, pers. 8 to 23 birdswere seen; and by early September, comm.). countsof over 100 birdswere being reported. The highestcount from a singlelocation was 218 birds This paper describes the spectacular 1992/93 recorded on 5 September at Ten Mile Point, a Steller'sJay invasion,summarizes banding activi- southernland head of Victoria(Siddle 1993). The ties from that period, and reviews historicalinva- highestdaily count was reported on 10 Septem- sions on southern Vancouver Island. ber by localnaturalist R. Sattertield,who observed 250 jays alongan 11 km routebetween Esquimalt METHODS Lagoonand Weir Beach,southwest of the city. Field observationsfrom American Birds' reports Peak movements occurred in the Victoria area for southern Vancouver Island were obtained for between5 and 13 September. Duringthis period the autumn, winter, and spring period from 1977 jaysshowed a similarbehavior and were frequently to 1993. CBC data to 1944 and other historic in- observed in loose, strung out flocks flying at or formationwere obtainedfrom the journalAudubon above tree top level in a commondirection. Typi- Field Notes/American Birds, the local naturalist cally,a processionof birdswould each in turnalight journal Victoria Naturalist, and literature listed in briefly in a tree top before carryingon to follow two bibliographieson BritishColumbia ornithology others, often several hundred metres farther (see Campbellet al. 1979, 1988). CBC data were ahead. One such movementrecorded on 13 Sep- summarized for the south coast region of British tember involvedthe steady passage of 63 birds Columbia and comparedwith Victoria. Because between 1000 and 1130 hrs. Jays were unchar- this highly conspicuousspecies can be detected acteristicallysilent during flight and thus easy to relativelyindependent of survey effort, we chose overlook. Their general behavior was remarkably not to correct CBC data for party hours. similarto that describedfor migratingBlue Jays in easternNorthAmerica (Broun 1941, Gill 1941, Bent Between 2 November1992 and 17 April 1993, 1946). Steller'sJay bandingstations were establishedat 11 sites within residentialVictoria. Bandingsites The last large group of jays was reportedon 27 were located near existing bird feeding stations September;and by the end of the month,jay move- where jays were known to be foraging. Initially ments had ceased and local dispersal occurred. jays were captured by mist net. Later, however,a From this point on, jays were reported in small portablecrow trap (see Bub 1991) proveda more flocks of five to eight birds scattered throughout successfulcapture technique and was usedfor the the city, similar to those described by Wescott remainderof this work. Jays were conditionedto (1969). Much of their initialforaging activity was entering a baited trap several days prior to band- focussedon harvestingand cachingof Garry oak ing. Data on age, sex, wing chord, tarsus, and acorns. Acornproduction during the 1992 autumn culmenwere recordedfollowing Pyle et al. (1987). was reported to be moderate for Victoria (B. Re-trappingwas performedat four sites. Duncan pers. comm.). Followingthe acorn har- vest, foragingactivities switched to residentialbird RESULTS AND DISCUSSION feeders. Jays showed a marked preference for sunflowerseeds and nutsduring this period. Many Chronology of Invasion reportsof jays comingto birdfeeders were received from throughout the city during early October. The invasion of Steller's Jays into southern Seed cachingwas pronouncedduring autumn and VancouverIsland commenced in mid-August.The mid-winter but was observed to decrease by firstbird was notedon 19August1992. Fourdays March. From October to March jays were rela- later,two birdswere observedflying uncharacter- tively sedentary. Jul.-Sep. 1994 North American Bird Bander Page 91 During early April, Steller's Jays began to show and 22 were AHY/ASY (ie. hatchedprior to 1992). signsof restlessnessand on 11April, the firstlarge FollowingPyle et al. (1987), sex could be deter- jay aggregationsince autumnwas reported. The minedfor onlysix birds,these beingfemales. The departurefrom the citywas abruptand notablyless remainder fell within the ranges given for males conspicuousthan the prolonged arrival period. and females. Other measurements taken included Many observersdid not detect this movementbut weight(97-158 g; •'=133 g), wingchord (138-155 noted a decline in the number of jays returningto mm;•'=145 mm),tarsus (38-46 mm;•'=43 mm), their feeders during this period. The last jays re- and culmen(23-32 mm;•':27 mm) All captured cordedfor some cityfeeders was between16 and birdswere representativeof the coastalrace C. s. 20 April(Table 1), and by the end ofApril most had stelleri (Gmelin). vacated urban Victoria. A springbird survey con- ducted on 8 May within the Victoria CBC area Twenty-sevenbirds were recapturedduring 14 re- showed that urban areas had been abandoned capture days at four sites. The longest period by jays althoughthey were still relativelycommon betweeninitial capture and recapturefor one bird in the city outskirts. was 136 days(2 December1992 to 17 April1993) suggestinga winter residency. Two other birds The last large group of jays reportedon southern were recaptured105 days after banding(13 De- VancouverIsland were observed on 23 May, ap- cember 1992 to 28 March 1993). At the location proximately20 km north of Victoria. where most effort was expended, 21 of 34 jays were recapturedon at least one occasion(Table Barriers To Dispersal 1). The initial invasionappeared to be impeded and From November 1992 to March 1993 we detected redirectedby the coastalwaters surrounding south- no movementbetween bandingsites throughre- ern Vancouver Island. Flocks of jays were fre- capturesor band sightings,suggesting individu- quentlyobserved paralleling the coastline,appar- als had establishedwinter territories. During this ently reluctant to cross wide expanses of water. periodwe receivedno reportsof bandedjays far- Thisbehavior likely had the effectof