SHORT COMMUNICATIONS 439

SERFASS,T L. 1995. Cooperative foraging by North TRIVERS, R. L. 197 1. The evolution of reciprocal altm- American river otters, Lutra canadensis. Can. ism. Q. Rev. Biol. 46:35-57. Field-Nat. 109:4X-459. WHITE, C. M. AND D. A. BOYCE. 1987. Notes on the SULLIVAN, K. A. 1984. Cooperative foraging and court- Mountain Caracara (Phalcoboenus megalopte- ship feeding in the Laughing Gull. Wilson Bull. rus) in the Argentine puna. Wilson Bull. 99: 96:710-711. 283-284.

Wilson Bull., 11 l(3), 1999, pp. 439-440

Predation by on Black-and-Green

Terry L. Master ’

ABSTRACT-I observed a Rufous Motmot (Bar- the black-and-green poison dart frog (Dendro- yphthengus mart@ feeding a black-and-green poison bates auratus) and phantasmal poison dart dart frog (Dendrobates auratus) to another motmot in frog (Dendrobates tricolor). However, these the Caribbean Slope lowland rainforest of northeastern Costa Rica. Neither individual appeared to suffer any frogs were raised in captivity and either do not ill effects from what was probably courtship feeding. produce or have relatively low levels of the Small vertebrates are typical prey for the larger species characteristic skin toxins &richer 1997; C. of motmots. Blue-crowned Motmots (Momotusmom- Rowsom, pers. comm.). ota) have been observed consuming several species of At approximately 9:30 CST on 26 March poison dart frogs raised in captivity but captive reared 1995, an adult Rufous Motmot was observed frogs either do not contain, or have reduced levels of, the toxins that native frogs produce. Relatively little is in secondary lowland tropical forest from a known about the effects of poison dart frog toxins on hiking trail located at Estacion Biologica La predators. Presumably, the digestive system of the Ru- Suerte, near Cariari, Limon Province, north- fous Motmot is capable of neutralizing the potentially eastern Costa Rica (10” 26 ’ N, 83” 46 ’ W). toxic effects of such prey. Received 15 Sept. 1998, The landed 25 m from the trail on an accepted 1.5 Feb. 1998. exposed perch 3 m above the ground and was easily observed for approximately 4 min. Af- ter 4 min another individual landed on the Poison dart frogs have long been known to same branch next to the first individual. The possess toxic skin secretions, and, because of newly arrived motmot was carrying a black- their bright coloration, are thought to be apo- and-green poison dart frog in its beak which sematic to visually hunting predators such as it fed immediately to the first individual. It is Rufous Motmots ( martii) not possible to distinguish between sexes in which presumably have excellent color vision Rufous Motmots; however, this behavior was (Brodie and Tumbarello 1977). Smith (1975) interpreted as a male who was feeding the fe- demonstrated that hand-reared Torquoise- male as a courtship gesture. Both individuals browed Motmots (Eumomota superciliosa) had diagnostic black breast marks and raquet- showed an innate avoidance of snake-shaped tails indicative of adult , suggesting that models with patterns simulating those of coral this was probably not a fledgling being fed. snakes. All other snake models were readily The pair continued sitting on the branch for attacked implying that aposematic coloration is a deterrent to this species. Observations in- approximately 30 min after which they flew dicate that Blue-crowned Motmots ( off together into the forest. Neither individual momota) at the National Aquarium consume appeared to suffer any ill effects from either several species of poison dart frogs including grasping or consuming the poison dart frog. The typical diet of motmots varies somewhat in conjunction with body size. Smaller species I Dept. of Biological Sciences, East Stroudsburg Univ., East Stroudsburg, PA 18301; prefer insects while larger species consume in- E-mail: [email protected] sects along with other invertebrates, small ver- 440 THE WILSON BULLETIN l Vol. 111, No. 3, September 1999

tebrates, and fruit (Orejuela 1980, Remsen et known to be frequented by Rufous Motmots al. 1993). The Rufous Motmot consumes ar- (B. Graves, pers. comm.) One pair was ob- thropods, other invertebrates including crabs, served on the ground rummaging through leaf small vertebrates including fish, lizards and litter where they would undoubtedly encoun- birds, as well as fruit (Remsen et al. 1993). ter D. auratus (B. Graves, pers. comm.). The Frogs have been reported as a dietary compo- level of toxins in the frogs of this area, how nent of the Rufous, Broad-billed ( pla- the motmots physiologically handle the tox- tyrhynchum) and Torquoise-browed motmots ins, and the frequency with which they con- (Remsen et al. 1993), and Blue-crowned Mot- sume D. uuratus remain unknown. mots in captivity (C. Rowsom, pers. comm.). ACKNOWLEDGMENTS The effect of poison dart frog toxins on var- ious potential predators has received relatively I would like to thank Dr. T LaDuke of East Strouds- little attention. Brodie and Tumbarello (1977) burg University, Dr. B. Graves of Northern Michigan University, and C. Rowsom of the National Aquarium tested the response of garter snakes (Thamno- in Baltimore for encouragement and assistance with phis sirtalis) to D. auratus offered as prey. this manuscript. Snakes readily mouthed, or in some cases con- sumed the frogs but all exhibited head shaking, LITERATURE CITED

mouth opening, convulsions, and loss of equi- BRODLE,E. D. AND M. S. TUMBARELLO. 1977. The an- librium. Only one snake actually died and that tipredator functions of Dendrobates aumtus (Am- was after consuming its third frog. These phibia, Anura, Dendrobatidae) skin secretion in regard to a snake predator. J. Herp. 12:264-265. snakes do not possess color vision and might KRICHER, J. 1977. A Neotropical companion. Princeton not be influenced by the aposematic coloration Univ. Press., Princeton, New Jersey. to the extent that an organism with color vision OREJUELA, J. E. 1980. Niche relationships between would be (Brodie and Tumbarello 1977). Torquoise-browed and Blue-crowned motmots. While motmots in general may be warned Wilson Bull. 92:229-244. by aposematic coloration, the Rufous Motmot REMSEN, J. V., M. A. HYDE, AND A. CHAPMAN. 1993. The diets of Neotropical trogons, motmots, bar- at least is capable of handling and consuming bets and toucans. Condor 95: 178-192. this particular species of poison dart frog. SMITH, S. M. 1975. Innate recognition of coral snake Dendrobates auratus reaches densities of 1 in- pattern by a possible avian predator. Nature dividual/180 m* in one locality at La Suerte (Lond.) 187:759-760.

Wilson Bull., 111(3), 1999, pp. 440-442

Evidence Of Egg Ejection In Mountain Bluebirds

Percy N. Hebert ’

ABSTRACT.-When the last two eggs of Mountain Of the approximately 140 biological hosts Bluebird (Sialia currucoides) clutches were replaced of the Brown-headed Cowbird (Molothrus with another bluebird egg and one House Sparrow ater), fewer than 7% have been classified as (Passer domesticus) egg, 20% (3/15) of the sparrow rejectors (Friedmann and Kiff 1985, Ortega eggs were removed within 24 hr. None of the surrogate bluebird eggs was removed. This is the tirst recorded 1998). Rejectors typically remove cowbird instance of interspecific egg ejection in a bluebird spe- eggs from the nest within 24 hr of introduc- cies, and hole-nesters in general. Received 2 Nov. tion (Rothstein 1982). Ejection is accom- 1998, accepted IA ’ Feb. 1999. plished either by grasping the cowbird egg be- tween the mandibles or by puncturing the egg with the beak and then lifting the egg out of the nest (Sealy 1996). Acceptors, by contrast, ’ ’ Dept. of Zoology, Univ. of Manitoba, Winnipeg, do not remove cowbird eggs and in most cases Manitoba, Canada, R3T 2N2; provision the cowbird nestling(s) (see Petit E-mail: [email protected] 1991, Sealy 1996).