Spatial and sex differences in mercury contamination of skuas in the Southern Ocean

Variation in blood mercury concentrations in brown skuas (Stercorarius antarcticus) is related to trophic ecology but not breeding success or adult body condition

“…We also tested whether body condition and breeding success were related to levels of Hg contamination. Although the mean RBC THg concentrations of brown skuas were lower than reported at more northerly breeding colonies in the Southern Ocean (Goutte et al 2014;Mills et al 2022), our data are comparable to adults of other Arctic and Antarctic seabirds, including little auks (Alle alle) (Albert et al 2019;Fort et al 2014), snow petrels (Pagodroma nivea) (Tartu et al 2015), and Antarctic petrels (Thalassoica antarctica) (Carravieri et al 2021).…”

“…Although sex was not included in the most parsimonious GLMMs (Table 2), THg concentrations were slightly higher in males than females in both seasons (Table 1, Mills et al 2022). One possible explanation is that egg production provides a route through which females are able to eliminate Hg (Robinson et al 2012;Ackerman et al 2020).…”

Spatial variations in winter Hg contamination affect egg volume in an Arctic seabird, the great skua (Stercorarius skua)

“…Mercury concentrations measured in female feathers were higher (estimates ± SE = 1.71 ± 0.08 µg g -1 dwmean value ± SD = 8.30 ± 3.61 µg g -1 dw) than in males (estimates ± SE = 1.15 ± 0.13 µg g -1 dwmean value ± SD = 5.23 ± 2.78 µg g -1 dw). This influence of sex on Hg concentrations found in great skuas has been shown in other seabird species, but males were generally found to have higher concentrations than females (but see Mills et al, 2022;Provencher et al, 2016). Similarly, Leat and colleagues (2013) studied contamination with POPs for the same population of great skuas, and also found that males had higher concentrations of POPs (i.e., organochlorines, PBDEs) than females.…”

“…In the present study, Hg was measured in feathers (i.e., representing an integrated annual contamination), while Hg and POPs in previous studies were assessed in blood during the breeding time (i.e., indicating shorter-term contamination) only. Such contrasting sexual patterns in different periods thus suggest that female are more contaminated during winter, but then partly excrete Hg into their eggs at the onset of the breeding period (Leat et al, 2013;Mills et al, 2022;Robinson et al, 2012), decreasing their body loads below the ones of males in summer as reflected by blood. Higher contamination during the non-breeding period found in female great skuas could also partly result from a trophic segregation (Carravieri et al, 2014a) with females feeding at higher trophic level or in different feeding habitats.…”

Higher mercury contamination is associated with shorter telomeres in a long-lived seabird – A direct effect or a consequence of among-individual variation in phenotypic quality?

“…Feather (S8) mercury concentrations reflect mercury exposure in the nonbreeding areas, where feathers are moulted, and a higher variation in mercury exposure in males is in agreement with their greater diversity of non-breeding destinations as compared to females (Gatt et al, 2020). The higher mercury concentrations in males may be explained by their larger body size and associated higher bioaccumulation potential or higher trophic levels (De Felipe et al, 2019;Mills et al, 2022). We have shown previously, that in Cory's shearwater telomeres shortened more in males compared to females (Bauch et al, 2020).…”