Dj. Delehanty et al., CIRCULATING PROLACTIN OF INCUBATING MALE WILSONS-PHALAROPES CORRESPONDS TO CLUTCH SIZE AND ENVIRONMENTAL-STRESS, The Condor, 99(2), 1997, pp. 397-405
We measured the effect of clutch-size changes on levels of circulating
prolactin (prl) among incubating male Wilson's Phalaropes in order to
identify the influence of clutch-size as an exogenous determinant of
circulating prl, and to better understand the endocrinology of clutch
abandonment. One year of the study was characterized by unusually high
temperatures and drought, and incubating males appeared to be heavily
stressed based on ambient temperatures and rates of weight loss. We u
sed the contrasting environmental conditions between years to compare
levels of circulating prl among males experiencing different levels of
environmental stress. We found a strong inter-year effect, with signi
ficantly lower prl during the high stress year. We also found a clear
effect of clutch-size on level of circulating prl during the low stres
s year of the study. Males with increased or decreased clutch-size had
lower levels of circulating prl than did control males. Because prl l
evels were so variable, we sought alternative explanations to year and
clutch-size effects. We examined nine environmental and physiological
factors a posteriori for a relationship with circulating prl. Althoug
h we identified weak correlates, none of the additional factors could
account for the variation in prl explained by year and clutch-size. in
cubating male Wilson's Phalaropes appear to experience an adaptive end
ocrine change when the potential fitness of their clutch is compromise
d.