AVIS-IBIS

Birds of Indian Subcontinent

Variation in the Appearance of Swallow Eggs and the Detection of Intraspecific Brood Parasitism

Publication Type:Journal Article
Year of Publication:1989
Authors:Brown, CR, Sherman, LC
Journal:The Condor
Volume:91
Issue:3
Date Published:1989
ISBN Number:00105422
Keywords:Hirundinidae, Hirundo, Hirundo pyrrhonota, Hirundo rustica, Petrochelidon pyrrhonota
Abstract:A method sometimes used to study avian intraspecific brood parasitism is to visually examine a clutch of eggs and infer parasitic egg laying if an egg of odd appearance is present in the clutch. Yet the degree to which individual females always lay eggs that look alike has seldom been evaluated quantitatively. We measured variation in egg appearance within and between 33 clutches of Barn Swallows (Hirundo rustica) and 35 clutches of Cliff Swallows (H. pyrrhonota) in southwestern Nebraska. Variables measured were egg length, breadth, shape, total amount of spotting, and degree of spotting in four separate sections of the egg. For both species within-clutch variance was significantly less than between-clutch variance for all variables except upper right and lower right spotting, when a sample size of 26-30 nests was used. Significant differences tended not to occur when small numbers of randomly selected nests (five to seven) were examined. Within-clutch variance for nests known to contain parasitic eggs did not differ from within-clutch variance for nonparasitized nests. Differences in egg appearance probably cannot be used safely to infer brood parasitism in Barn and Cliff swallows. Researchers should quantify within- vs. between-clutch variation in egg appearance before assuming that an individual of a given species always lays eggs that look more alike than do eggs from different individuals.
URL:http://www.jstor.org/stable/1368112
Short Title:The Condor
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith