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Prey Selection by Urban-Breeding Merlins
Navjot S. Sodhi and Lynn W. Oliphant
Vol. 110, No. 4 (Oct., 1993), pp. 727-735
Published by: American Ornithologists' Union
Stable URL: http://www.jstor.org/stable/4088628
Page Count: 9
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We identified 1,332 items belonging to 36 vertebrate species from prey remains collected near 65 Merlin (Falco columbarius) nests in Saskatoon, Saskatchewan from May to July 1987-1990. Principal prey of breeding Merlins was the House Sparrow (Passer domesticus). They along with the Horned Lark (Eremophilia alpestris) were usually taken more frequently than expected from their relative abundance. Other potential prey species were usually taken in proportion to their relative abundance, or less often than expected. Proportions of adult House Sparrows in the diet decreased while juveniles increased significantly as the Merlin breeding season progressed. During incubation and nestling phases, male and female House Sparrows were taken as expected. In the fledgling phase, Merlins took adult House Sparrows less often and juveniles more often than expected. The relative availability of different species positively correlated with that in the diet during the incubation and nestling phases. Merlins selected prey based on relative availability, independent of prey mass, but not independent of relative abundance. Our data supported the prediction that increase in absolute abundance of selected prey species increased the degree of prey selectivity.
The Auk © 1993 American Ornithologists' Union