Feather mercury content of grey-faced petrels (Pterodroma gouldi): Relationships with age, breeding success, and foraging behaviour, in known age individuals

• Published in: The Science of the total environment Vol. 951; p. 175778
• Main Authors: Rewi, S.T., Fessardi, M., Landers, T.J., Lyver, P.O’B., Taylor, G.A., Bury, S.J., Dunphy, B.J.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.11.2024
• Subjects: Breeding outcome; Demography; Marine pollution; Mesopelagic; Senescence; Stable isotopes; Senescence; Demography; Marine pollution; Mesopelagic; Breeding outcome; Stable isotopes
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2024.175778

Seabirds have been touted as excellent bioindicators of mercury pollution. We utilised grey-faced petrel (Pterodroma gouldi) feathers to assess interannual differences in total mercury (THg) concentrations in adults (2020−2021) and chicks (2019–2021) breeding in the Auckland region of New Zealand. For adults, we also correlated feather THg with bird age (3–37+ years) and breeding outcome (i.e., Non breeder, Egg failed, Chick reared) recorded for that season i.e., 2020 and 2021. Interannual differences in chick feather THg were matched with bulk stable isotopes (δ13C, δ15N) to map the influence of adult foraging behaviour on chick feather THg values. Adult feather THg levels were similar across the years investigated i.e., mean ± S.D. 38.2 ± 12.8 (2020), and 39.5 ± 14.7 (2021) ug g−1 (some of the highest THg values recorded for seabirds). A slight, but significant decrease in THg accumulation was evident as age increased but feather THg had no significant influence on breeding outcome. Interannual differences in chick feather THg concentrations were 7.78 ± 1.6 (2019), 4.23 ± 1.45 (2020) and 6.97 ± 4.41 (2021) μg g−1, (p < 0.01); and correlated with a significantly lower δ13C value i.e., −17.2 ± 0.4 ‰ (2019), −17.8 ± 0.3 ‰ (2020) and -17.6 ± 0.2 ‰ (2021). This suggests that the lower feather THg values in 2020 chicks resulted from more oceanic, rather than shelf-edge, prey being consumed by chicks that year. Values of δ15N in chick feathers remained consistent among years i.e., 15.2 ± 1.2 ‰ (2019), 15.2 ± 0.2 ‰ (2020) and 15.3 ‰ (± 0.4). Due to these interannual differences, we recommend using grey-faced petrel chicks to monitor Hg pollution over adults. Chicks are also subject to cultural harvests by Māori communities, offering partnership opportunities to generate mutually beneficial information streams for Māori communities and scientists alike. [Display omitted] •We quantified feather Hg in known-age grey-faced petrels.•Adult feather Hg was among the highest recorded for any seabird and did not change among seasons investigated.•High feather Hg had no impact on adult breeding success and showed a slight decline with age for females.•Chick feather Hg differed among seasons and was related to foraging location inferred from δ13C value.•Chicks present a more sensitive indicator of oceanic Hg levels.