Exaggerated Traits and Breeding Success in Widowbirds by J. Phil Gibson

Part IV—Longer Tails in a Short-Tailed Species

Having conducted the studies described above in two long-tailed species, the researchers conducted a similar tail manipulation experiment in a closely related species, the red-shouldered widowbird (Euplectes axillaris). Although males in this species have distinctive breeding plumage colors, they do not produce a long tail. Data from this experiment are given in Figures 7 and 8.

Figure 7. Number of males with different tail lengths in a population of red-collared widowbirds. Data based on Pryke and Andersson 2002.

Figure 8. Mean number of active nests (± standard error) in a population of red-shouldered widowbirds that had tails shortened (6 cm), elongated (8 cm), or super-elongated (22cm). Groups with different letters above them are significantly different from one another (p < 0.05). Data based on Pryke and Andersson 2002.

Concept Check

12. What hypothesis was being tested in this follow-up study? Why was it necessary?

13. What do the data in Figures 7 and 8 show?

14. Do their results support their hypothesis? What do the results mean? Explain.

Question for further thought …

15. If long tail length is so important to female widowbirds, why don’t male tails continue to get longer and longer?

References

Andersson, M. 1982. Female choice selects for extreme tail length in a widowbird. Nature 299:818–820.
Pryke, S.R., and S. Andersson. 2002. A generalized female bias for long tails in a short-tailed widowbird. Proceedings of the Royal Society of London Series B 269:2141–2146.
Pryke, S.R., S. Andersson, and M.J. Lawes. 2001. Sexual selection of multiple handicaps in the red-collared widowbird: female choice of tail length but not carotenoid display. Evolution 55:1452–1463.

Originally published at http://www.sciencecases.org/widowbirds/widowbirds4.asp