We examined circulating plasma prolactin (PRL) levels in incubating Mountain Plovers, a shorebird of conservation concern with an uncommon parental care system where males and females tend to separate nests. We modeled PRL related to the sex of the incubating bird and examined how it varied throughout incubation and the nesting season. PRL levels were similar for incubating male and female Mountain Plovers. The mean circulating plasma PRL concentration for incubating female plovers was 32.40 ng/ml (n = 33) and ranged from 7.33 to 78.04 ng/ml. The mean for males was 29.36 ng/ml (n = 36) and there was greater variation in the samples with the lowest measured at 5.18 ng/ml and highest at 140.86 ng/ml. There was no relationship between day of incubation and the concentration of circulating PRL for either incubating female plovers or male plovers and day of incubation did not explain a significant proportion of the variance in PRL concentration for either sex (R2 = 0.002 and 0.034 respectively). There was no relationship between the Julian day of nesting season and concentration of circulating PRL for either sex and day of season did not explain a significant proportion of the variance for either females (R2 = 0.047) or males (R2 = 0.001). This study provides further information about the relationship between parental care and circulating PRL and the breeding biology of a shorebird of conservation concern.
Available at: http://works.bepress.com/stephen_dinsmore/12/