January1986] ClutchSize in Motmots 13 B., J. J. ReyesR., Wilfrido ContrerasD.) of Direcci(•n KOEt•IC,W. D. 1982. Ecologicaland social factors Generalde la FaunaSilvestre, Secretarla de Agricul- affectinghatchability of eggs.Auk 99: 526-536. tura y RecursosHidr•ulicos (M•xico, D.F.). Officials LACK,D. 1947. The significanceof clutchsize. Ibis of the M•rida office of Divisi6n Hidrom•trica, SARH, 89: 302-352. kindly gave us accessto weather data. George and MARTIN, M. W., & R. F. MARTIN. 1985. Nestling JanetCobb, Joann Andrews, and EdwardKurjack were feeding schedulesof Turquoise-browedMot- generous hosts in Yucatfm. We thank Anne Clark, mots in Yucatan, Mexico. Wilson Bull. 97: 372- Paul Mason, and two anonymousreviewers for use- 374. ful criticismsof a draft of this paper. Partial support OREJUELA,J. E. 1977. Comparativebiology of Tur- for this study was provided by The Explorers Club quoise-browedand Blue-crowned motmots in the and by the TexasMemorial Museum-The University YucatanPeninsula, Mexico. Living Bird 16: 193- of Texasat Austin.The Museumof Zoologyof Lou- 208. isianaState University provided computertime. SCnP•EmER,R. W., & E. A. SC•P•EmER.1983. The world accordingto E1Nifio. Abstr., 101ststated meet- LITERATURE CITED ing of Amer. Ornithol. Union, New York. Scot'r, P.E. 1984. Reproductionof the Turquoise- CLARIC,A. B., & D. S. Wig,SOtS. 1981. Avian breeding browed Motmot in Yucat•n, Mexico. Unpub- adaptations:hatching asynchrony,brood reduc- lished M.A. thesis, Austin, Univ. Texas. tion, and nest failure. Quart. Rev. Biol. 56: 253- --, ,•' R. F. MARTIN. 1983. Reproductionof the 277. Turquoise-browedMotmot at archaeological CONOVER,W.J. 1980. Practical non-parametric sta- ruins in Yucat•n. Biotropica 15: 8-14. tistics.New York, John Wiley & Sons. The Frank M. ChapmanMemorial Fund givesgrants in aid of ornithologicalresearch and alsopostdoctoral fellowships. While there is no restriction on who may apply, the Committee particularly welcomes and favorsapplications from graduatestudents; projects in gamemanagement and the medicalsciences are seldom funded.Applications are reviewed oncea year and should be submittedno later than 15 January-with all supporting material. Applicationforms may be obtainedfrom the Frank M. Chapman Memorial Fund Committee,% JaneConnelly, The AmericanMuseum of Natural History, Central Park Westat 79th Street, New York, NY 10024-5192. Dr. Mary McKitrick was appointedChapman Fellow for the period May 1985 through May 1986. She is studyingthe significanceof individual variation in M. flexor crurislateralis in the Tyrannidae. Dr. Nina Pierpontwas appointedChapman Fellow for the period October1985 through October1986. She is studyingthe evolution of diversity in woodcreepers(Aves: Dendrocolaptidae). Chapmangrants during 1985,totalling $25,482with a mean of $499.65,were awardedto: David J. Ander- son,booby breeding and feedingand marineresources in the Galapagos;John Anderson, tests of cooperative foragingin the White Pelican;Dr. BonnieBowen, genetic structure and paternityin communallybreeding jays;Angelo Capparella,effects of riverine barrierson gene flow in Amazonianforest undergrowth birds; William J. Carmen,social behavior and ecologyof the CaliforniaScrub Jay; Richard Casey, the effectof social interactionduring the criticalperiod of songlearning in White-crownedSparrows; Peng Chai, avianfeeding behaviorand its implicationsfor the evolution of neotropicalbutterfly mimicry; JackClinton-Eitniear, Ca- thartesburrovianus: movement patterns and systematics;Nonie Coulthard,the White-throatedBee-eater (Mer- opsalbicollis): a study of cooperativebreeding in relation to ecologicalfactors; Marilyn England,breeding biologyof the Northern Harrier on Long Island,New York; ChristianErard, systematics of African Musci- capidae;Mark A. Finke, male parental care and the evolution of reproductiveeffort: an experimentaltest; Dr. JonFjeldsa, museum work for a field guide and biogeographicanalysis of the Andeanavifauna; Ronald C. Gaines,nest site tenacity and philopatry of the FerruginousHawk; Steven M. Goodman,museum tour for the birds of Egypt and project;Frederick P. Greene, determinantsof guild structureamong insectivorous birds;Jeffrey G. Groth,systematics of the Red Crossbillin westernNorth America,using vocal, morphological and electrophoreticdata; John M. Hagan, colonialnesting in Ospreys;Dionyssia Hatzilacos, breeding and feeding biology of the White Pelican (Pelecanusonocrotalus) nesting at Lake Mikra Prespa--measuresfor protection;P. Hibbard,John P. Dunning, LaurieM. McKean,and RichardBowers, the efficiencyof foraging behavior:an experimentalapproach; Geoffrey E. Hill, the reproductiveconsequences of sub-adultplumage (continuedon p. 22) MOONLIGHT AVOIDANCE BEHAVIOR IN LEACH'S STORM-PETRELS AS A DEFENSE AGAINST SLATY-BACKED GULLS YUTAKA WATANUKI Instituteof AppliedZoology, Faculty of Agriculture,Hokkaido University, Kitaku kita 9 nishi9, Sapporo060, Japan ABSTRACT.--Diurnalactivity patternsof Leach'sStorm-Petrels (Oceanodroma leucorhoa) and Slaty-backedGulls (Larusschistisagus) were investigated.The petrels reducedactivity in moonlightin May and Junewhen the predationrate by gulls was relativelyhigh. Petrel activitylevels were inverselycorrelated with light intensitiesand the correspondingrisk of predationby the gull. Thissuggests that nocturnalactivity and moonlightavoidance by the petrel in its colonyare an effectivedefense against diurnal predators.Activity synchroni- zationof the petrelwas most marked during the full moon,further supportingthe predator- avoidancehypothesis. Received 15 October1984, accepted 27 April 1985. MANX Shearwater (Puffinuspuffinus; Harris which are coveredwith Calamagrostislangsdorffii, iso- 1966), Leach's Storm-Petrel (Oceanodromaleu- lated rockstacks, and cliff ledges.A few pairsof Black- corhoa;Harris 1974), Fork-tailed Storm-Petrel (O. tailed Gulls (L. crassirostris)nested on these sites. furcata;Harris 1974,Boersma et al. 1980),and The Slaty-backedGull is an important predator of Cassin'sAuklet (Ptychoramphusaleuticus; Tho- adult petrels on the island. Although Jungle Crows (Corvusmacrorhynchos) excavated petrel burrows and resen 1964, Manuwal 1974) are strictly noctur- ate adults, eggs, and chicks,predation by the small nal in their colonies and are less active on crow population (13 pairs) was not significant. moonlit nightsthan on dark nights.Cody (1973) Activitypatterns.--Observations of flying birdswere discussedthe nocturnal activity of alcids as a made from a blind set on top of a headland about 25 defenseagainst diurnal predators.Gross (1935), m abovesea level. For 5 rain every 30 rain, I counted M.P. Harris (1966), and S. W. Harris (1974) also all birds passingan imaginary 20 x 30-m plane ori- suggestedthat nocturnal procellariiformsare ented vertically with reference to the cliff face op- vulnerableto diurnalpredatory gulls on moon- posite the headland. Two 6-volt electric lights, one lit nights. However, the relationship between set horizontally and the other about 45ø upward at daily activities of procellariiformsand preda- the blind, lit the plane facing toward the sea from tion risk has not been studied. the lower corner to the oppositeside. This reduced the effectof the light on landing birds approaching I studied Leach's Storm-Petrels and Slaty- from the sea.If all the landing petrels were attracted backedGulls (Larusschistisagus) on Daikoku Is- instantaneouslyto the lights, the number of petrels land. Their activity patternsare describedand flying through the lights would increaseduring the the nocturnalbehavior of the petrels in the col- observations. However, the number was rather con- ony is discussedas predator avoidance. stant during 5-rain observations(Fig. 1). A few pe- trelsand gullsflew circularlyin the lights;these were excluded from the data. Observations on moonlit STUDY AREA AND METHODS nights showedthat Slaty-backedGulls did not avoid the lights. No differential responseto the lights by Thecolony.--The study was conducted on Daikoku gulls and petrelswas assumed.Observations started Island (42ø52'N, 144ø52'E),Akkeshi, Hokkaido, be- in daylight and lasted24 h (n = 19 days).Data taken tween late April and early October1982. The island during a day with dense fog (13-14 May) were ex- is 6.1 km in circumference and treeless, with the ex- cluded from the analysis becauseof low visibility. ception of birch (Betulaermanii) groves in the ravines. Data of 27-28 April were included in those of May. Leach'sStorm-Petrel (the only petrel breedingon the Light intensitywas measured by a lux-meter(+ 10%) island) nestsin the interior partsof the island, which set horizontally and was divided into four classes: is covered with Artemisamontana and Urtica platy- dark (0 lux), moonlight with no cloud cover(<1 lux), philla. Abe et al. (1972) estimatedthat there were twilight (1-5 x 10ß lux), and daylight (>5 x 10ß lux). 1,070,000breeding pairs of petrels,but a more recent Time of sunrise, sunset, moonrise, and moonset were estimate is 415,000 (Watanuki 1985b). About 3,500 from the astronomical tables for Kushiro, about 40 pairsof Slaty-backedGulls nested on maritimeslopes, km west of Daikoku Island. 14 The Auk 103: •4-22. January 1986 January1986] MoonlightAvoidance in Leach's Petrel 15 TABLEI. Breedingschedule of the petrel and its nest duties shown by egg-daysand chick-daysin the study plots. May June July Aug Sept No. of eggslaid 0 335 16 0 0 No. of chicks hatched 0 0 199 64 0 Egg-days 0 5,785 6,305 390 0 Chick-days 0 0 1,965 7,220 6,935 marked by individually