Mercury contamination in Peregrine Falcons (Falco peregrinus) in coastal Washington, 2001–2016

A Broadscale Assessment of Mercury Contamination in Peregrine Falcons Across the Northern Latitudes of North America

“…As expected, because young birds are provisioned with the same prey regardless of sex, we did not detect significant differences in THg concentrations by sex in either axillary or p4 feathers of HY peregrines. Similarly, an assessment of HY peregrines migrating and wintering along coastal Washington did not detect a significant difference in THg exposure between sexes (Barnes et al 2018), nor did Barnes and Gerstenberger (2015) detect significant differences between siblings of different sexes within peregrine broods in southern Nevada.…”

“…One possible explanation suggests that because female peregrines often begin breeding by their third year (Ratcliffe 1993), the reduced THg concentrations we detected in older females may be due to the additional annual elimination pathway of eggs (Lewis et al 1993); however, we were not able to collect corresponding data on adult males. Similarly, an analysis of HY female peregrines recaptured later in life documented a mean increase of 520% in the THg concentration from HY to SY age classes, but showed more modest increases from the SY to the third-year age class, and no clear trend in exposure after their third year (i.e., four of six individuals experienced declines in THg as they aged; Barnes et al 2018).…”

“…By comparison, a recent assessment at breeding territories of a nonmigratory population of F. p. anatum in southern Nevada in the southwestern USA documented mean THg concentrations of 3.76 lg/g in HY peregrines and 12.19 lg/g in AHY peregrines (Barnes and Gerstenberger 2015). An assessment of migrating and wintering F. p. pealei peregrines along coastal Washington detected mean THg concentrations of 6.05 lg/g and 23.11 lg/g in feathers of HY and AHY individuals, respectively (n ¼ 151; Barnes et al 2018).…”