Volume 151, Number 1, 241-245, DOI: 10.1007/s10336-009-0449-4

Tail-racket removal increases hematocrit in male Turquoise-browed Motmots (Eumomota superciliosa)

Troy G. Murphy

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Abstract

Graduated avian tails with short outer tail feathers and longer central tail feathers are thought to handicap aerodynamic function. The Turquoise-browed Motmot (Eumomota superciliosa) has a highly graduated tail with a long racket-tip that may impose a substantial aerodynamic cost. Previous research on this species has demonstrated a moderate sexual dimorphism in the tail, and has provided evidence that the racketed tail functions as a sexually selected trait only in males. To explore whether costs are associated with the maintenance of the ornamental male tail, I tested whether tail-racket removal affected hematocrit, a measure of condition and metabolic activity. I removed tail rackets from a manipulated group of males and left the rackets intact among a control group. I then compared change in hematocrit between the two groups over the breeding season. Males with rackets removed experienced a greater increase in hematocrit than did control males. This result suggests that males either experienced an increase in condition after being emancipated from bearing a costly sexually selected ornament, or that a social cost was associated with the loss of an ornament used in communication. This work supports previous research showing that the male tail functions as a sexual signal.

Keywords  Aerodynamic costs - Hematocrit - Tail-plumage - Sexual selection -  Eumomota superciliosa

Communicated by C. G. Guglielmo.

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