Experiments on egg discrimination in two North American corvids: further evidence for retention of egg ejection

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dc.contributor.authorUnderwood, TJ
dc.contributor.authorSealy, SG
dc.contributor.authorMcLaren, CM
dc.date.accessioned2008-03-07T22:29:48Z
dc.date.available2008-03-07T22:29:48Z
dc.date.issued2004-09-30
dc.description.abstractIn the absence of brood parasitism in North America, black-billed magpies, Pica hudsonia (Sabine, 1822), and yellow-billed magpies, Pica nuttalli (Audubon, 1837), may have retained egg-discrimination behaviour that evolved in Eurasian magpies, Pica pica (L., 1758), in response to parasitism by Old World cuckoos. We further examined this hypothesis by testing the egg-discrimination abilities of black-billed magpies and the American crow, Corvus brachyrhynchos Brehm, 1822, which has no history of brood parasitism. In addition, we tested an alternative hypothesis that black-billed magpies evolved or retained egg discrimination to counter conspecific parasitism by testing their ability to eject foreign conspecific eggs and by using a signal detection model to estimate the level of conspecific parasitism required for ejection to be favoured. Black-billed magpies ejected all non-mimetic eggs and 62% of mimetic eggs. Significantly more mimetic eggs were ejected during the incubation stage than during the laying stage. Magpies ejected significantly more non-mimetic eggs than mimetic eggs overall, but there was no difference in ejection frequency during incubation. American crows ejected 21% of non-mimetic eggs and 8% of mimetic eggs. There was no significant difference in ejection frequency of the two egg types. Black-billed magpies ejected 11% of conspecific eggs and a relatively high level of conspecific parasitism (22%-49%) would be required to select for conspecific ejection, which provides little support for conspecific parasitism as a current selection pressure for maintaining egg discrimination. Thus, black-billed magpies appear to have retained egg rejection in the absence of parasitism through speciation from Eurasian magpies.en
dc.format.extent115782 bytes
dc.format.mimetypeapplication/pdf
dc.identifier.citation0008-4301; CAN J ZOOL, SEP 2004, vol. 82, no. 9, p.1399 to 1407.en
dc.identifier.doihttp://dx.doi.org/10.1139/z04-118
dc.identifier.urihttp://hdl.handle.net/1993/3021
dc.language.isoengen_US
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dc.rightsopen accessen_US
dc.statusPeer revieweden
dc.subjectINTRASPECIFIC BROOD PARASITISMen
dc.subjectGREAT SPOTTED CUCKOOen
dc.subjectBLACK-BILLED MAGPIESen
dc.subjectREED WARBLERSen
dc.subjectCOWBIRD PARASITISMen
dc.subjectREJECTION BEHAVIORen
dc.subjectRECOGNITION ERRORSen
dc.subjectSTURNUS-VULGARISen
dc.subjectHOST COEVOLUTIONen
dc.subjectCLIFF SWALLOWSen
dc.titleExperiments on egg discrimination in two North American corvids: further evidence for retention of egg ejectionen
dc.typejournal articleen_US
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