NOTES
UNUSUAL FORAGING STRATEGY BY THE GREATER ROADRUNNER
JAMES W. CORNETT, Palm Springs Desert Museum, 101 Museum Drive, Palm Springs,California 92262
The Greater Roadrunner(Geococcyx californianus) feeds on a remarkablediver- sityof animalsincluding rodents, birds, reptiles, and arthropods (Hughes 1996). Often the speciesdemonstrates surprising adaptability in acquiringprey: individualroadru- nnershave been observedcapturing insects by turningover surfaceobjects (Jaeger 1947), hiding near artificialfeeders to take hummingbirds(Spofford 1975), and removingpasserines from mistnets (Barclay 1977). At approximately0800 on 4 August1998, whilehiking near the mouthof Sabino Canyon, Tucson, Arizona, ! witnessedan adult roadrunnerchasing band-winged grasshoppers(Trirnerotropi$ sp.) on a rarelyused paved access road. Though ! have witnessedroadrunners foraging on numerousoccasions, I have never seen a roadru- nneractive for solong a time. Over a periodof approximately1 hour,the birdserially rushedupon grasshoppers resting on the pavement.Hunting bouts lasted between 5 and 10 minuteswith the roadrunnerstanding and restingon the pavementfor 1 or 2 minutesbetween bouts. Its huntingpath followedthe east-westdirection of the road, and the bird movedcontinually away from my positionin a zigzagmanner. In most instancesthe roadrunnerrushed several meters toward a resting grasshopper, attempting to capture it on the ground. If unsuccessful,it sometimesmade an additionalcapture attempt after the grasshoppertook flight. Of the 150 capture attemptsthat I counted,the roadrunnerwas successful 22 times,for a successrate of about 15%. On mostcapture attempts the roadrunnerlowered its head and ran directlytoward each grasshopper,then snappedat the insectwith its mandibles.If it missed,the roadrunnerwould visually follow the insectfor 1 or 2 secondsand occasionallylunge a final time while the prey was airborne.Captured grasshoppers were bitten 3 to 6 times, then tosseda few centimetersin the air, caught in the mandibles,and swallowed. The band-wingedgrasshoppers in this observationpossessed a mottled and speckledpattern consisting of the colorstan, rufous,white, and graythat madethem next to impossibleto seewhen they were restingon the desertsoils of the region.On the darkgray paved roadway, however, the grasshopperswere quite conspicuous and couldbe easilycensused. They were unusuallyabundant with aboutone grasshopper per 2 mz of road surface.I assumedthat the grasshopperswere attractedto the pavementin the relativelycool earlymorning hours because of its warmth. On naturalterrain the roadrunnertypically captures a band-wingedgrasshopper afterit hasaccidentally startled the insect(pers. obs.). The grasshopperimmediately takesflight, whereupon the roadrunnerlunges for the insectin midairor capturesit on the groundafter it haslanded. The roadrunnerdoes not appearto seea grasshopper untilit moves--assuggested by roadrunnersoften makingmisdirected initial capture motions. The presenceof this,and perhapsother, paved roadways can allow roadrunners to developa novel, more direct, foragingstrategy for hunting grasshoppers.This is significantsince grasshoppersare one of the roadrunner'smost important food resources(Bryant 1916, Parmley 1982).
Western Birds 31:61-62, 2000 61 NOTES
LITERATURE CITED
Barclay,J. S. 1977. Roadrunnertakes birds from mist net. Bird-banding48:280. Bent,A. C. 1940. Lifehistories of NorthAmerican cuckoos, goatsuckers, humming- birds and their allies. U.S. Natl. Mus. Bull. 176. Bryant,H. C. 1916. Habitsand food of the roadrunnerin California.Univ. Calif. Publ. Zool. 17:21-50. Hughes,J. M. 1996. GreaterRoadrunner (Geococcyx californianus), in The Birdsof North America (A. Poole and E B. Gill, eds.), no. 244. Acad. Nat. Sci., Philadelphia. Jaeger,E. C. 1947. Stone-turninghabits of somedesert birds. Condor 49:171. Parmley,D. 1982. Fooditems of roadrunnersfrom Palo PintoCounty, north-central Texas. Tex. J. Sci. 34:94-95. Spofford,S. H. 1976. Roadrunnercatches hummingbird in flight.Condor 78:142. Accepted 28 January 2000
62