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Please use this identifier to cite or link to this item: http://hdl.handle.net/1993/3021

Title: Experiments on egg discrimination in two North American corvids: further evidence for retention of egg ejection
Authors: Underwood, TJ
Sealy, SG
McLaren, CM
Keywords: INTRASPECIFIC BROOD PARASITISM
GREAT SPOTTED CUCKOO
BLACK-BILLED MAGPIES
REED WARBLERS
COWBIRD PARASITISM
REJECTION BEHAVIOR
RECOGNITION ERRORS
STURNUS-VULGARIS
HOST COEVOLUTION
CLIFF SWALLOWS
Issue Date: 30-Sep-2004
Citation: 0008-4301; CAN J ZOOL, SEP 2004, vol. 82, no. 9, p.1399 to 1407.
Abstract: In 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.
URI: http://hdl.handle.net/1993/3021
DOI: http://dx.doi.org/10.1139/z04-118
Appears in Collection(s):Research Publications (UofM Student, Faculty and Staff only access)

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