Publication Type: | Journal Article |
Year of Publication: | 1993 |
Authors: | Mitchell, JS, Robertson, RJ |
Journal: | The Condor |
Volume: | 95 |
Issue: | 3 |
Date Published: | 1993 |
ISBN Number: | 00105422 |
Keywords: | Hirundinidae, Hirundo, Hirundo rustica, Iridoprocne, Iridoprocne bicolor, Tachycineta, Tachycineta bicolor |
Abstract: | We used egg removals, additions, and swaps (controls) to determine whether Tree Swallows (Tachycineta bicolor) are determinate or indeterminate layers. Since Tree Swallows modify their clutch size in response to their environments, and since egg additions and removals occur naturally in this species, we predicted full indeterminacy. Females laid more eggs in response to the removal of their third and fourth laid eggs but did not lay clutches outside the normal range. Females did not lay fewer eggs when an egg was added on each of the second and third days of laying. From this we conclude that Tree Swallows have limited removal indeterminacy but are determinate with respect to egg addition. When daily egg removal was used to keep females at 1 or 0 eggs, which led to abandonment of the nesting attempt followed by relaying, the second clutch was much larger, on average, than the first. This suggests that the first clutch had been terminated early. Thus Tree Swallows, although addition determinate, were capable of early cessation of laying. Although removal indeterminate, they were not capable of laying abnormally large clutches. We therefore argue that determinate and indeterminate laying patterns cannot be used to infer a female's ability to modify clutch size in response to other stimuli, and that strict categorization of Tree Swallows as determinate or indeterminate is not appropriate. |
URL: | http://www.jstor.org/stable/1369598 |
Short Title: | The Condor |
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