The Auk 116(3):690-701, 1999 BREEDING BIOLOGY OF CRESTED AUKLETS AT BULDIR AND KASATOCHI ISLANDS, ALASKA GAIL FRASER?6 IAN L. JONES,2 JEFFREY C. WILLIAMS,3 FIONA M. HUNTER,4 LISA SCHARF,3 AND G. VERNON BYRD 5 •BiopsychologyProgramme, Memorial University of Newfoundland,St. Johnõ,Newfoundland A1B 3X9, Canada; 2Departmentof Biology,Memorial University of Newfoundland,St. Johnõ,Newfoundland A1B 3X9, Canada; 3AlaskaMaritime National Wildlife Refuge, Aleutian Island Unit, P.O.Box 5251, Adak, Alaska 99546, USA; 4Departmentof Zoology,University of Cambridge,Cambridge CB2 3E J, UnitedKingdom; and 5AlaskaMaritime National Wildlife Refuge, 2355 KachemakBay Drive, Homer, Alaska 99603, USA ABSTRACT.--Wequantified breeding parametersof Crested Auklets (Aethiacristatella) at Buldir and Kasatochiislands in the Aleutian Islands, Alaska, in 1996 and 1997. Crested Auk- lets incubatedtheir eggsfor about36 daysand chicksweighed about 35 g within the first threedays of hatching(14% of adultmass; Buldir, n = 58). Growthrates averaged about 9.9 g per day duringthe linearphase (Buldir, n = 58; Kasatochi,n = 17),and chicks fledged at an averagemass of 248 g (95% of adult mass;Buldir, n = 63) and a wing lengthof 123 mm (88%of adultwing length; Buldir, n = 37) at 34 daysafter hatching. We found no differences in intraislandand intrayear chick growth for Buldir and Kasatochi. Productivity (the product of hatchingsuccess and fledgingsuccess) averaged more than 60% for the two yearsat Ka- satochiand for eightyears (1990 to 1997)at Buldir.Intercolony comparisons of productivity parametersrevealed differences in hatchingdate, age of chicksat fledging,and hatching and fledgingsuccess. Adult massdiffered significantly between the sexes(267 g for males,253 g for females)and amongyears. At Buldir, we observedno effect of variouslevels of inves- tigatordisturbance on hatchingand fledgingsuccess or on otherbreeding parameters. We foundno negativerelationships between hatching date and fledgingage, hatching date and fledgingmass, or fledgingmass and fledgingage, contrary to the predictionsof Ydenberg's (1989)model of intraspecificvariation in timing of fledgingof alcid chicks.Crested Auklet chicks,like thoseof otherdiurnally active species of auklets,grow relatively fast and depart at a youngerage compared with chicksof two nocturnalspecies of auklets.Received 24 April 1998, accepted17 November1998. CRESTEDAUKLETS (Aethia cristatella)are co- (e.g.B•dard 1969,Hipfner andByrd 1993,Jones lonialseabirds that lay a clutchsize of oneand 1993b), and the Whiskered Auklets is the least havesemiprecocial chicks that are provisioned well known (Byrd and Williams1994). Detailed by both parents(Jones 1993b, Gaston and Jones knowledgeof the biologyof theseauklets is re- 1998). This speciesis part of a remarkable quired for an understandingof their life-his- adaptiveradiation of five small planktivorous tory variation,adaptive radiation, and ecolog- auklets(Cassin's [Ptychoramphus aleuticus], Par- ical relationships. akeet [Aethiapsittacula], Least [A. pusilia],and Alcids show considerable inter- and intra- Whiskered[A. pygmaea]auklets) that are en- specificvariation in the age and massof their demicto the North PacificOcean and Bering chicksat the time of departurefrom nesting andOkhotsk seas. These auklets range in mean colonies.For example, the tiny precocialchicks bodymass from the LeastAuklet at 85 g to the of Ancient Murrelets (Synthliboramphusantiq- ParakeetAuklet at 289 g. Adult and chickdiets uus)depart two days after hatching,whereas and chickdevelopment patterns (Gaston 1985, the semiprecocialchicks of RhinocerosAuklets Gastonand Jones1998) alsovary amongspe- (Cerorhincamonocerata) depart close to adult cies.The biologyof Cassin'sand Leastauklets havebeen relatively well studied(see Manuwal size at 38 to 58 daysold (Gaston1985, Gaston and Thoresen1993, Jones1993c), whereas Par- and Jones1998). Ydenberg(1989) and Yden- akeet and Crested auklets are less well known berget al. (1995)provided the first comprehen- sive modelthat explainedvariation in life-his- tory traits in alcidsand offeredtestable predic- E-mail: [email protected] tions. Two main assumptionsof the model 69O July1999] CrestedAuklet Breeding Biology 691 FiG. 1. Map of theNorth Pacific, including St. Lawrence Island and our study sites in theAleutians. were thatjuvenile mortality is lowerat the nest chickgrowth, productivity, and breeding chro- and growthrate is higherat sea.Here, we test nology in Crested Auklets, including eight two of the model'spredictions about intraspe- yearsof data from a singlecolony in the Aleu- cificvariation in life-historytraits using data tians. from CrestedAuklets: (1) fast-growingchicks The objectivesof our studywere to (1) quan- departthe nest younger and heavier (i.e. a neg- tify chickgrowth; (2) examineeight years of ativerelationship exists between fledging age variation in reproductive performance and and fledging mass), and (2) late-hatching breedingchronology from one colonyin the chicksdepart the nest younger and lighter. Al- western Aleutians (1990 to 1997) and make in- though somedata from Cassin'sand Rhinoc- teryearand intercolonycomparisons with an- eros aukletsare consistentwith thesepredic- othersite located in the centralAleutians (1996 tions(Harfenist 1995, Harfenist and Ydenberg to 1997);(3) evaluatethe effectsof investigator 1996,Morbey and Ydenberg 1997), further test- disturbanceon breedingsuccess; and (4) test ing of the model is needed (Gastonand Jones two key predictionsof Ydenberg's(1989) model 1998, Hipfner and Gaston 1999).Crested Auk- to explaintiming of chickdeparture for a semi- let chicksare semiprecocial,depart the nestat precocialspecies of auklet. closeto adult size,fit all of the assumptionsof themodel (Ydenberg et al. 1995),and thus pro- STUDY AREA AND METHODS vide an opportunity to examine the model's predictionsfor the first time within the genus Study areas.--We studied auklets on Buldir Aethia. (52ø21'N, 175ø56'E) and Kasatochi (52ø11'N, Much of the information on Crested Auklet 175ø30'W) islands in the Aleutian chain of Alaska breedingparameters comes from northerncol- (Fig. 1). Buldir, locatedin the westernpart of the onies on St. Lawrence Island (B6dard 1969, chain,contains one of the largestand mostdiverse Piatt et al. 1990;see Fig. 1) wherethe birds nest concentrationsof seabirdsin the Aleutians (Sowlset later than their Aleutian counterparts.The al. 1978,Byrd and Day 1986).Our studyarea on Bul- Aleutian Islandscomprise a substantialpor- dir waslocated at "Main Talus,"a colonywith ap- tion of the CrestedAuklet's breeding range. proximately250,000 Crested and Leastauklets (ratio of 2:1 Crested to Least;Knudtson and Byrd 1982, Nevertheless,Knudtson and Byrd's(1982) and Byrd et al. 1983). Kasatochiis locatedin the central Hipfner and Byrd's(1993) reports on laying Aleutians about 480 km east of Buldir. Our study and hatchingdates, productivity,and nest- areathere was in a colonyon a northeast-facingtalus creviceattributes provide the only published slopewith a minimumof 35,000Least and Crested data from the Aleutians.Here, we presentthe auklets (2:1 Least to Crested; Scharf et al. 1996). first comparisonsacross years and coloniesof Chick growth, productivity,and breedingchro- 692 FRASERET AL. [Auk, Vol. 116 nology were recordedon both islands,whereas in- data from Buldir to a logisticmodel (Ricklefs1967). vestigatordisturbance and effectsof crevicelocation The model'sproducts (asymptotic mass [a] and the were evaluatedonly on Buldir.We selectedcrevices growth constant[k]) were used to calculatethe in- that were configuredso that parentsor chicksin stantaneousgrowth rate at thepoint of inflection(i.e. nestscould not easily hide from view. Becauseour k(a)/4; Hussell1972), which is consideredto be the samplesof creviceswere taken from large areasand maximum growth rate (Hussell 1972, Sealy 1973, were of differentcrevice types (except for very deep Gaston 1985, Piatt et al. 1990). crevices),we believe that the creviceswe monitored Adult mass.--Toquantify variationin adult mass were representativeof the entire coloniesat Buldir within and betweenbreeding seasons and islands, and Kasatochi. For all crevices, chicks were consid- and to compareadult mass with chickmass at fledg- ered fledged (i.e. left the nest) if they were 26 days ing, we caughtbirds at a singlestudy plot centrally or olderupon disappearance(i.e. the crevicefailed if located on Main Talus, Buldir Island, and at a similar chicksdisappeared at lessthan 26 daysof age). plot on KasatochiIsland. We determinedthe sex of Incubationand chick growth.--In 1997, we followed these birds using bill shape (Jones1993a) and eight pairs from laying until hatchingto determine weighedthem to the nearest1 g with a springscale. the duration of incubation on Buldir. We selected Measurementsof adults were taken between May previouslyused crevicesthat were unoccupiedin and August from 1990 to 1997 on Buldir and from mid-Mayand checked them daily until anincubating 1996 to 1997 on Kasatochi. bird was present.To minimize disturbanceearly in Productivityand breeding chronology.--Crested Auk- incubation,we checkedoccupied crevices only once let creviceswere checked approximately every seven a week for the first 29 days. After 29 days, we daysthroughout each breeding season between 1990 checkedcrevices daily to obtain the exact date of and 1996 (1996 to 1997 at Kasatochi).In 1997, we hatching. checkedcrevices every four daysbetween the onset In 1996and 1997,we studiedchick growth on Bul-