Does plumage influence winter territory acquisition in American Redstarts?

1. Does plumage influence winter territory acquisition in American Redstarts? Matthew W. Reudink1*, Peter P. Marra3,T. Kurt Kyser2, Colin Studds3, and Laurene M. Ratcliffe1 1Dept. of Biology and 2Dept. of Geological Sciences and Geological Engineering, Queen’s University, Kingston ON 3Smithsonian Migratory Bird Center, National Zoological Park, Washington DC Smithsonian Migratory Bird Center *reudinkm@biology.queenusu.ca Discussion Background and Methods Question Winter Territory Quality In Jamaica, ASY males in high-quality mangrove territories have higher red reflectance 0  Do plumage characteristics vary in relation to winter territory quality? In American Redstarts, winter territory acquisition influences condition and year-to-year survival1 Individuals wintering in low-quality territories arrive later on the breeding grounds, in poorer condition, and suffer reduced reproductive success2,3 ASY males, through dominance, obtain high-quality territories while younger males and females are excluded to low-quality territories4,5  ASY males arriving on the breeding grounds from high-quality winter territories had more red chroma and smaller bibs in 2005, but not 2006  Results  A) Jamaica B) Canada Ontario Red reflectance is also highly correlated with male size (wing length) in Jamaica (r36=0.213, P = 0.004), suggesting that red reflectance may act as a signal of male quality  Bib Size Score  Jamaica Playback experiments will be conducted this fall to determine the relationship between male aggressiveness and plumage during winter territory acquisition  Logwood 2005 Mangrove Wet Mangrove Scrub Wet 13C Dry Mangrove Scrub Figure 1. A) No difference in ASY male bib size between habitat types in Jamaica (t22=-1.21, P = 0.24). B) Bib size increases with 13C in 2005 (r28= 0.149, P < 0.05) in males captured upon arrival in Canada [but not in 2006 (r22= 0.046, P < 0.337)]. Sample Collection -21.5 -24.5 Conclusion 13C (‰) Jamaica - Samples were collected from birds holding territories in mangrove (high-quality) and scrub (low-quality) habitats Male plumage may play an important role in signaling male competitive ability during winter territory acquisition. Evidence from our other studies suggest these male plumage characteristics may be the result of a breeding to winter season carry-over effect. Stable-carbon Isotopes Due to differences in photosynthetic pathways and water stress, plants in different habitats vary in the ratio of 13C/12C (13C). As this signature is transferred up the food chain, redstarts incorporate the stable-carbon isotope signature of their winter territory. This signature is retained through migration. Blood can be sampled upon arrival on the breeding grounds and winter territory quality inferred2,6. ASY Males Canada - Blood samples were collected within 5 days of arrival on the breeding grounds and analyzed for 13C Red Reflectance References 1 Studds, C.E. and P.P. Marra. 2005. Ecology 86: 2380-2385. Mangrove Scrub 2 Marra, P.P., K.A. Hobson, and R.T. Holmes. 1998. Science 282: 1884-1886. Figure 2. ASY males in mangrove have higher red reflectance in the 3rd rectrix (one-tailed t36=-2.02, P = 0.026). 3 Norris, D.R., P.P. Marra, T.K. Kyser, T.W. Sherry, and L.M. Ratcliffe. 2004. Proceedings of the Royal Society of London: B 271: 59-64. Plumage as a Social Signal American Redstarts are sexually dichromatic Bib size and carotenoid-based patches are variable Bib size (negatively correlated with pairing success7) was assessed via observations and photos Reflectance spectrometry determined red chroma and red reflectance in the 3rd rectrix. 4 Sherry, T.W. and R.T. Holmes. 1989. Behavioral Ecology and Sociobiology 25: 327-333.  Color Variables 5 Marra, P.P. and R.T. Holmes. 2001. Auk 118:92-104. 2006 2005 6 Norris, D.R., P.P. Marra, T.K. Kyser, and L.M. Ratcliffe. 2005. Journal of Avian Biology 36: 164-170. Bib Size Scoring7  7 Lemon, R.E., D.M. Weary, and K.J. Norris. 1992. Behavioral Ecology and Sociobiology 29: 399-403. 8 Montgomerie, R. 2006. In: Bird Coloration: Mechanisms and Measurements. Harvard University Press  Red Chroma Red chroma (saturation)8 700 700 Acknowledgements S =  Ri  Ri / 450 450 Funding was provided by the Natural Sciences and Engineering Research Council of Canada (LMR, TKK), the National Science Foundation (PPM), the Canadian Foundation for Innovation (LMR, TKK), Sigma Xi (MWR), American Ornithologists’ Union (MWR), Society for Canadian Ornithologists (MWR), American Museum of Natural History (MWR), Queen’s University, and the Smithsonian Institution. Many thanks to our numerous field assistants, R. Montgomerie for help and guidance with color measurement and to K. Klassen and A. Vuletich for assistance with isotope analysis. 13C Red reflectance (brightness)8 13C 13C 700 Figure 3. Birds arriving in Canada from higher quality habitats had more red chroma in 2005 (r226= 0.152, P = 0.049) but not 2006 (r222= 0.003, P = 0.823). There was no relationship between red reflectance and 13C in either year.  Bred =  Ri 450