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

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 emanci-pated from bearing a costly sexually selected ornament, or that a social cost was associated with the loss of an orna-ment used in communication. This work supports previous research showing that the male tail functions as a sexual signal