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DIFFERENTIAL COSTS OF A SECONDARY SEXUAL CHARACTER: AN EXPERIMENTAL TEST OF THE HANDICAP PRINCIPLE
Author(s) -
M⊘ller Anders Pape,
Lope Florentino
Publication year - 1994
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.1558-5646.1994.tb02204.x
Subject(s) - biology , hirundo , feather , sexual selection , trait , cheating , barn , zoology , character (mathematics) , ecology , mathematics , civil engineering , computer science , engineering , programming language , geometry
The evolution of reliable signaling can be explained by the handicap principle, which assumes that (1) the cost of a signal guarantees its reliability, and (2) cheating is prevented because the cost of a unit of display is greater for low‐quality than for high‐quality individuals. A test of these two assumptions was performed using manipulations of the length of the outermost tail feathers of male barn swallows Hirundo rustica , a trait currently subject to a directional female mate preference. We found that survival decreased with tail elongation and increased with tail shortening of males, supporting the assumption that the secondary sexual character is costly. Naturally long‐tailed males were better able to survive with an elongated tail, whereas naturally short‐tailed males improved their survival following tail shortening. This observation supports the second assumption of a differential cost of a signal. One mechanism imposing differential costs on sexually signaling barn swallows is foraging. Males with elongated tails captured smaller, less profitable Diptera, whereas males with shortened tails captured large, profitable prey items. The conditions for reliable sexual signaling by the tail ornament of male barn swallows are thus fulfilled.