Birds of Indian Subcontinent

Extra-pair fertilizations in Tree Sparrows Passer montanus

Publication Type:Journal Article
Year of Publication:2002
Date Published:2002
ISBN Number:1474-919X
Keywords:Passer, Passer domesticus, Passer montanus, Passeridae, Salicipasser, Salicipasser montanus, Spain, Switzerland
Abstract:Females of socially monogamous bird species frequently accept or solicit copulations from males other than their social mates. At the interspecific level, it has been proposed that species with few or no sexual plumage differences have lower levels of extra-pair fertilizations (EPFs) than more dichromatic species. This is because it is easier for females to assess the quality of extra-pair mates in dichromatic than monochromatic species. To test this, by using genetic profiling, we compared the occurrence of extra-pair young in nests of Tree Sparrows Passer montanus, a monochromatic species, in Switzerland and Spain, with published estimates for the House Sparrow Passer domesticus, a closely related dichromatic species. We found that 25% (10/40) of Tree Sparrow broods in Spain and 23% (8/35) in Switzerland had at least one extra-pair offspring, and that 8% (12/151) of nestlings in Spain and 10% (12/114) in Switzerland were sired by extra-pair mates. These proportions did not differ significantly between the two populations. Tree Sparrow EPF rates did not differ significantly from available data for the House Sparrow, either in the proportion of broods with EPF young (24%, 18/75 in Tree vs. 26%, 92/359 in House Sparrows) or the overall proportion of extra-pair young (9%, 24/265 in Tree vs. 11%, 142/1110 in House Sparrows). Our results suggest that a close taxonomic relationship and similarities in behaviour and ecology may be more important in determining levels of EPF in these species than sexual phenotypic differences.
Short Title:Ibis
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith