Sex, size, and plumage redness predict house finch survival in an epidemic

Abstract

Mycoplasma gallisepticum is a well-known disease of poultry, but until 1994 it had not been observed in passerine birds. From 1994 to 1996, tens of millions of house ¢nches (Carpodacus mexicanus) are believed to have died in an epidemic of mycoplasmal conjunctivitis, similar to`pinkeye' in humans. The outbreak of Mycoplasma gallisepticum a¡ected ¢nches of both sexes, but disproportionately killed males, shifting the sex ratio from male-biased to female-biased. This di¡erential male mortality is consistent with a cost of testosterone, which is a key prediction of the immunocompetence handicap hypothesis. Males and females that survived the epidemic weighed signi¢cantly less and had signi¢cantly shorter wing chords, tarsi, and bills than did individuals before the epidemic. Male survivors also had signi¢cantly redder plumage than males that did not survive, supporting the idea that plumage brightness serves as an indicator of condition, as proposed by the honest advertisement model of sexual selection.

Mycoplasmal Conjunctivitis in Songbirds From New York

“…Interestingly, 81% (13/16) of these cases were limited to the left eye. Our findings also suggest there is no sex bias in diseased house finches or a pattern of susceptibility to disease in larger individuals as suggested by Nolan et al (1998).…”

Susceptibility of a Nai¨ve Population of House Finches to Mycoplasma Gallisepticum

“…Previous published reports of both wild and captive finches indicate a changing relationship between MG and the house finch (Luttrell et al, 1996;Nolan et al, 1998;Roberts et al, 2001a, b). One reason for this change may be an increased resistance in house finches to MG.…”

“…From the point of initial detection the disease spread through the entire eastern population of house finches (Fischer et al, 1997;Dhondt et al, 1998). In early years of the epidemic, prevalence of clinical disease and mortality were high (Sauer et al, 1997;Nolan et al, 1998). In recent years, mortality and prevalence of the disease has declined (Hartup et al, 2000;Roberts et al, 2001b).…”

Brighter yellow blue tits make better parents

“…We do not consider our results are biased by the method used to estimate plumage colour because yellow coloration is largely lacking in emission in the ultraviolet portion of the spectra (Goodwin 1973;Gross 1987;Moss & Weeden 1999). Hue has normally been the parameter of interest when studying the relationship between plumage coloration and sexual selection (Hill et al 1994;Hill 1995;Hill & Brawner 1998;Nolan et al 1998;Wolfenbarger 1999), and hence it was initially the focus of our investigation. However, because colour intensity and lightness have also sometimes been found to have a degree of predictive value (Hill & Brawner 1998;Figuerola et al 1999a), we also explored the relationship of these two variables to parental investment.…”