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Common Tern Egg Predation by Ruddy Turnstones’ SHORT COMMUNICATIONS 521 Beach, fall and winter 1938 and 1939. Bird Lore 41: TAYLOR,L. R. 1963. Analysis ofthe effectoftemperature 11-16. of insectsin flight. J. Anim. Ecol. 32:99-l 17. ERSKINE,A. J. 1964. Nest site competition between Buf- TYLER,W. M. 1942. Tree Swallow, p. 384400. In A. flehead, Mountain Bluebird, and Tree Swallows.Can. C. Bent. Life historiesof North American flycatchers, Field-Nat. 93:202-203. larks, swallows,and their allies. U.S. Natl. Mus. Bull. HERSEY,F. S. 1933. Notes on Tree Swallows and blue- No. 179. birds. Auk 50: 109-l 10. WEATHERHEAD,P. J., S. G. SEALY,AND R.M.R. BARCLAY. HUSSELL,D. T. 1983. Age and plumage color in female 1985. Risks of clusteringin thermally-stressedswal- Tree Swallows. J. Field Omithol. 54:3 12-3 18. lows. Condor 87:443-444. KUERZI, R. G. 1941. Life history studies of the Tree WEBER,J. A. 1940. Destruction of Tree Swallows. Auk Swallow. Proc. Linn. Sot. N. Y. 52-53:1-52. 57:405. LEFFELAAR,D. AND R. J. ROBERTSON.1984. Do male WHITMORE,R. C., J. A. MOSHER,AND H. H. FROST. 1977. Tree Swallows guard their mates? Behav. Ecol. So- Springmigrant mortality during unseasonableweath- ciobiol. 16:73-79. er. Auk 941778-781. SCHAEFFER,F. S. 1972. Tree Swallow breeding biology ZELENY,L. 1976. The bluebird. Indiana Univ. Press, at a coastaland inland area. EBBA News 34:216-222. Bloomington. The Condor 88521-522 0 The Cooper Ornithological Society 1986 COMMON TERN EGG PREDATION BY RUDDY TURNSTONES’ ANNEFARRAWAY 540 Merton Street, Toronto, ON M4S IB3, Canada KATIETHOMAS 74 ChestnutPark Road, Toronto, ON M4 W 1 W9, Canada HANSBLOKPOEL Canadian Wildlife Service,1725 WoodwardDrive, Ottawa, ON KlA 0E7, Canada Key words: Ruddy Turnstones:Arenaria interpres;terns; as a tumstone devoured the contentsof its nest. The Com- eggpredation. mon Tern removed the broken egg shells from the nest site and then returned to the empty nest. At no time did Ruddy Turnstones (Arenaria interpres)are opportunistic the tern attempt to chase the tumstone. In the second feederswith a varied diet (Beven and England 1977). Pre- instance,about 5 m from the vehicle, a tumstone pecked dation on eggsby Ruddy Turnstones has been reported vigorouslyat the eggs,devoured the contents,and ate any for Grey-backed Terns (Sterna lunata, Bent 1929), Sooty ground spillage before moving to the next nest. This be- Terns (S. fuscata, Crossin and Huber 1970), Royal Terns havior continued for a minimum of 13 min. Then there (S. maxima, Loftin and Sutton 1979), and Common Terns was a panic flight by the terns and an attempt to harass (S. hirundo,Parkes et al. 1971). The observationsof Parkes an intruding Ring-billed Gull (Larus delawarensis).The et al. (1971) in 1970 on Great Gull Island (Long Island tumstone was subsequentlychased by a tern upon its re- Sound, New York) involving a singletumstone, were the turn to the nest area. In the third incident, the incubating first reported cases of Common Tern egg predation by Common Tern walked away from the nest without any turnstones in North America. The authors wondered attempt of nest defence. A second tumstone then joined whether this, presumably new, behavior might spread in the first and a conflict of “ownership” developed. The following years. dominant tumstone then ate contents of all eggs at the In this note, we report several cases involving many undefended nest. Incubation at six Common Tern nests turnstonesdepredating Common Tern eggsat the Eastern nearby continued undisturbed throughout this incident. Headland of the Toronto Outer Harbour. This landfill site On 3 1 May, we found 20 depredated nests with a total extends ca. 5 km into Lake Ontario. At the time of our of 33 eggsin Colony A. The numbers of Ruddy Tumstone observationsthere were seven Common Tern colonies (A peaked on 6 June, when a flock of 200 landed in Colony through G) on the Headland. B. Numbers of them were observed depredating eggsin this colony. Although 40 Red Knots (Calidris cam&s) 1983 and 10 Dunlins (C. alpina) were also part of that shorebird During 24 May to 3 June, we saw 11 separateincidents flock, they did not participate in egg predation. of egg predation by Ruddy Turnstones. Although each 1984 incident will not be detailed here, behavioral character- istics common to all are highlighted. On six separate occasionsduring the first two weeks of On 28 May, we observedfrom a vehicle parked outside July, eggpredation was noted in Colony D. On 6 July, 10 the colony, three casesof egg predation in Colony B. In Ruddy Turnstones landed in Colony D and depredated the first case, approximately 12 m from the vehicle, a about 25 of the 30 nests. During 1 to 14 July destroyed Common Tern watched from a distance of less than 1 m eggs were noted in more than 20 nests in Colo- ny B. DISCUSSION LReceived 17 September 1985. Final acceptance3 Feb- Our experience on the Eastern Headland agreed with the ruary 1986. findings of Bent (1929), Parkes et al. (197 1) and Loftin 522 SHORT COMMUNICATIONS and Sutton (1979) in that the incubating terns failed to or just a hitherto unnoticedbehavior. Further effortsshould recognize the tumstone as a predator in most cases, no be made in other tern coloniesbeing studied to document matter how closely they were approached by the tum- the frequency of occurrenceand the impact of egg pre- stones.Mobbing behavior was elicited only when Canada dation by Ruddy Turnstones. Geese (Branta can&ens@ and Ring-billed Gulls were We thank the Toronto Harbour Commissionersand the passing.Turnstones in the area at this time would also be Metropolitan Toronto and Region Conservation Author- mobbed. ity for-allowing us to work at-the Eastern Headland. G. Contrary to Parkes et al. (197 I), our observationswere D. Tessier heloed in the field. C. T. Collins. S. G. Curtis. not confined to a singletumstone, rather they concurwith J. R. Walters, and D. A. Welsh commented’on the manu: Bent (1929) in that many were involved. The impact of script. turnstoneswas higher at the Headland than at the Com- mon Tern colony on Great Gull Island (Parkeset al. 197l), LITERATURE CITED yet it did not result in total destruction of the colony, as was reported for Royal Terns near Florida in 1978 (Loftin BENT. A. C. 1929. Life Histories of North American and Sutton 1979). Shorebirds(Part II). U.S. Natl. Mus. Bull. 146. There have been no further reports of egg-eating by BEVEN.G.. AND M. D. ENGLAND. 1977. Studies of less turnstonesin well-studied Common Tern colonies since familiar birds, 181, Turnstone. Br. Birds 70:23-32. that of Parkes et al. (197 1). Neither have there been any CROWN, R. S., AND L. N. HUBER. 1970. Sooty Tern egg previous observationsrecorded at our study site since re- predationby Ruddy Turnstones.Condor 721372-373. search began here in 1976. Similarly, at the Royal Tern LOFTIN,R. W., ANDS. SUTTON. 1979. Ruddy Turnstones colony studied by Loftin and Sutton (1979), the investi- destroy Royal Tern colony. Wilson Bull. 9 1:133-l 35. gatorsdid not notice eggpredation by turnstonesuntil the PARKES,K. C., A. POOLE,AND H. LAPHAM. 1971. The fourth year of their study. However, it is difficult to say Ruddy Tumstone as an eggpredator. Wilson Bull. 83: whether this form of egg predation is a new, expanding, 306-308. The Condor88522-524 0 The Cooper Ornithological Society 1986 VARIATION IN SIZE SPECIFIC COMPOSITION OF BLACK-BILLED MAGPIE EGGS WITHIN AND AMONG CLUTCHES WESLEYM. HOCHACHKA~ Department of Zoology, Universityof Alberta, Edmonton, Alberta, Canada T6G 2E9 Key words: Black-billed Magpie; Pica pica; egg com- set of eggswas analyzedfor intraclutchvariation in Brown- position. headed Cowbirds (Molothrus ater). Thus, it is unclear whether size-dependentvariation in eggcomposition fol- In recent years, descriptive data on egg composition of a lows the same pattern within a clutch as among clutches. number of altricial specieshave been published,e.g., Great The purpose of this note is to examine whether size-de- Tit, Parus major and Pied Flycatcher, Ficedula hypoleuca pendent variation in egg composition within a clutch can (Ojanen 1983), EuropeanStarling, Sturnusvulgaris (Rick- be predicted on the basis of patterns observed among lefs 1984), and Boat-tailed Grackle, Quisculusmajor (Ban- clutches. croft 1985). One possible application of these data is to METHODS relate egg composition to life history characteristicsof a species.For example, one could examine Howe’s (1978) As part of a study of Black-billed Magpie (Pica pica) re- suggestionthat variation in egg composition could influ- productive ecology, eight complete clutches of eggswere ence brood reduction. As brood reduction is proximately collected in the city of Edmonton, Alberta, Canada, in the result of events within a single nest and appearsto be 1984. Clutcheswere collectedon the day on which the last relatedto intraclutchvariation in eggsize (e.g.,Howe 1976), egg was laid, or on the following day. Within 2 hr of one needs to know how egg composition varies with egg collection, eggswere brought into the laboratory, weighed, size within nests. However, most detailed descriptionsof and measured (length and breadth at largest diameter to variation in eggcomposition with eggsize are comparisons 0.1 mm with dial calipers). Eggswere then separatedinto among clutches (e.g., Bancroft 1985), or combine inter- albumen, yolk, and shell plus membrane, and wet masses clutch and intraclutch variation (e.g., Ricklefs 1984). Only of all componentsdetermined. All componentswere dried Ankney and Johnson (1985) presented separateanalyses to constantweight at 60°C in a drying oven, and dry masses of variation within and among clutches,although only one were measured, water content was calculated as the dif- ferencebetween total wet and dry massof eggs.Yolks were ground up and placed in Soxhlet apparatus, and neutral lipids were extractedfor a 2-hr period with petroleum ether I Received 14 October 1985.
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