mercury contamination and body condition in birds

Overview

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Key numbers

The worker extracted the full PDF text with layout preservation twice and compared extraction hashes before commit. The following lines are copied from numeric/table-bearing regions of the PDF and retain the source units and wording where legible:

• 67 experimental investigations (90%) showed a significant relationship between mercury
• 71 associations, of which only 14% were statistically significant. Therefore, the overall effect of
• 191 the stress response (Wada et al., 2009; Franceschini et al., 2017), which can have a range of
• 214 statistical information and a lack of a response by contacted authors meant that some relevant
• 215 studies had to be discarded (see online Supporting Information, Table S1). The literature
• 216 search resulted in the selection of 47 studies spanning publication years 2000 to 2020 (Table
• 218 (Table 1). In addition, we included nine studies from the authors’ unpublished work in order
• 231 (Table S1), preventing an accurate estimation of their potential influence on the Hg–body
• 234 (Peig & Green, 2009) as body condition index (see Table S2 for the frequency of all condition
• 245 arithmetic mean of the body length variable chosen for each study. As different measures of
• 266 contamination was inferred from concentrations (in parts per million (ppm) or g per unit wet
• 269 number (Table S1). In experimental studies all Hg concentrations were reported on a wet
• 273 calculation was based on a moisture content of 65% in red blood cells (P. Bustamante, O.
• 274 Chastel unpublished data), and 77% in whole blood (mean of moisture values measured in
• 292 individuals (Table S1), where body condition could be biased. Effect sizes obtained from less
• 309 Table 2. Dietary guild was assigned based on results in the sampled population of each study
• 323 values, F-values, P-values, means and standard deviations, or correlation coefficients,
• 325 the comparison of experimental groups, we calculated standardised mean differences
• 380 (parsimony criteria) (Table S3). Using the random structure of the best selected model, we
• 386 Thompson, 2002; Higgins et al., 2003). I2 was moderate to high (defined as I2 > 50%; Higgins
• 410 The experimental data set was too small for multifactorial statistical analysis (N = 20
• 412 multilevel meta-analytic model (fitted by REML) with the selected random structure (Table
• 422 (Egger’s test N = 91, z = 2.148, P = 0.032; see Table S6 for funnel plots). By contrast, we
• 425 publication status had no effect on the Hg–body condition association (Table S6). Therefore,
• 429 experimental studies (Fig. 2; Egger’s test: N = 20, z = –1.894, P = 0.058), but this bias was
• 437 individuals inspected per effect size was 16 (range: 4–1051). Comparison of intercept-only
• 439 individual effect size ID and species ID (Table S3), which were retained in the random
• 444 heterogeneity was moderate (I2 = 55%; Cochran’s Q test = 668, df = 314, P < 0.0001),
• 447 model, Table S4): wintering birds were more likely to show a negative effect of Hg on body
• 449 association (Table S4).
• 453 Falco sparverius, Gavia immer, Setophaga coronata, Taeniopygia guttata). The median
• 454 number of individuals inspected per effect size was 24 (range: 5–49). Only individual effect
• 456 (Table S3). Hg contamination was not related to body condition (0.262 ± 0.309, (–0.344;
• 458 high (I2 = 99%; Cochran’s Q test = 887, df = 19, P < 0.0001). In the experimental data set, no
• 459 moderator predicted the Hg–body condition relationship (Table S5, Fig. 4, P > 0.100 in all
• 470 significant effect of Hg concentrations on body condition, with 90% of estimated effect sizes
• 471 being significantly positive or negative. Conversely, only 14% of correlative effect sizes for
• 474 these were often in the upper range of levels encountered in the wild (Kobiela, Cristol &
• 481 perceived risk or unpredictable access to food can cause birds to store energy as a buffer
• 482 against unpredictable environmental changes (Schultner et al. (2013) and references therein).
• 497 may be weak, and thus become (statistically) detectable only at high exposure levels, and/or
• 514 Hg on body condition, while positive effects were more likely to remain unpublished (Table

Methods (brief)

• 285 as a moderator. Body feathers are preferentially sampled for ethical and practical reasons,
• 301 (7) geographical zone (polar/subpolar, temperate, tropical/subtropical); whether the sampled
• 309 Table 2. Dietary guild was assigned based on results in the sampled population of each study
• 318 each study, we extracted the moderators, as well as sample and effect sizes as detailed below.
• 406 AIC corrected for small sample size (AICc) by at least 2. Data on BMR were available only
• 500 cannot exclude that further experimental work in a larger sample of individuals and species
• 614 sample of individuals and species.
• 639 were measured on subsamples of blood collected within the SPILE program (Camille
• 907 JACOBS, S.R., ELLIOTT, K., GUIGUENO, M.F., GASTON, A.J., REDMAN, P., SPEAKMAN, J.R. &
• Moderators not included in meta-analytic models of experimental studies given the limited sample size.

Implications

This page makes the source discoverable for category-level evidence routing. Values remain source-native and should be used only with the stated matrix, species, basis, geography, and censoring context from the paper. The page does not convert total mercury to methylmercury or use total arsenic as inorganic arsenic.

Wiki pages this source may touch

• Fish — marine, non-predatory (sardines, anchovies, salmon, cod)
• Shellfish (shrimp, crab, lobster, clams, oysters, mussels)
• Seaweed/kelp foods (nori, wakame, kombu, dulse — as food products)
• Mercury
• Mercury
• Cadmium
• Lead
• Arsenic
• Tin

Verification notes

• Identity check: DOI, raw handle, candidate cite-key, and SHA-256 were compared against existing wiki/sources/ pages before creation.
• Full-PDF read: pdftotext -layout was run on the full PDF twice; extracted text hashes matched before the page was written.
• Numeric verification: numeric/table-bearing lines were selected mechanically from the verified extraction and preserved without unit conversion or rounding.
• Brand firewall: the worker skips PDFs when extracted numeric lines appear brand/manufacturer-sensitive; this page contains category-level or species-level evidence only.
• HMTc firewall: no threshold, percentile, pass/fail, clean/dirty, or certification math is stated.

Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.