DOI: 10.5281/zenodo.18162688
title: The impact of heavy metal pollution on birds' behaviour and cognition: a comprehensive review

description: Description of the data and file structure

Description: This dataset compiles raw data extracted from peer-reviewed studies included in a Biological Reviews synthesis examining the effects of heavy metal exposure on avian behaviour and cognition.

Variables:





Short_citationShort reference for the article, typically including first author and publication year.




APA_citationFull bibliographic reference formatted according to APA guidelines.




TitleTitle of the published article.




Publication_yearYear in which the article was published.




OrderTaxonomic order of the studied species.




SpeciesScientific name of the studied species.




LocationCountry of the research team that conducted the study and published the article.




Metal_exposed_toHeavy metal(s) to which the studied individuals were exposed.




Pop_housing_conditionHousing condition of individuals during the study:captive (born and studied in captivity),wild (studied in situ), orwild-caught (captured from the wild and then studied in captivity).




Lifestage_indivs_when_first_exposedLife stage of individuals (egg, chick, adult) at first exposure to the focal heavy metal(s).




Age_indivs_when_first_exposedAge of individuals at first exposure, when available, reported in days (d), weeks (w), months (m), or years (y).




Exposure_durationDuration of heavy metal exposure, reported in days (d), weeks (w), months (m), or years (y).




Exposure_frequencyFrequency at which heavy metal doses were administered (e.g. daily vs. one or multiple discrete exposure events).




Lifestage_indiv_when_testedLife stage of individuals (egg, chick, immature, adult) at the time of behavioural or cognitive testing.




Age_indivs_when_testedAge of individuals at first testing, reported in days (d), weeks (w), months (m), or years (y).




Sex_individualSex of tested individuals:M = males, F = females, B = both sexes.




Method_briefGeneral methodological approach used to assess effects of heavy metal exposure on behaviour or cognition:comparison between experimental groups,correlation between internal concentrations and behaviour, orcomparison between naturally exposed populations.




Method_nb_groupsNumber of groups or populations compared (e.g. experimental groups, treatment levels, or populations).




Method_detailsAdditional methodological information relevant to the study design.




Total_sample_sizeTotal number of individuals included in the study.




Exposure_dosageDose of heavy metal administered or encountered (experimentally or naturally). Units are reported as in the original publication, with no unit conversion. Multiple values indicate multiple exposure groups. NA indicates natural exposure without administered doses.




Exposure_methodMethod used to administer the heavy metal (e.g. diet, osmotic minipump, injection).




Pollutant_measuredHeavy metal(s) for which internal concentrations were measured. NA indicates no internal measurements.




Concentration_measured_inBiological matrix in which heavy metal concentrations were measured (e.g.: blood, feathers, brain).




Pollutant_measured_mean_concentrationMean measured concentration of the pollutant, reported in original units. Multiple values correspond to multiple groups or sampling times.




Behaviour_endpointBehavioural or cognitive endpoint assessed.




Variable_measuredSpecific variable quantified to assess the behavioural or cognitive endpoint.




Main_resultBrief description of the main finding of the study.




Effect_directionDirection of the observed effect: positive, negative, or none.




Effect_significanceStatistical significance of the observed effect based on a 0.05 threshold:S = significant, NS = non-significant, AS = almost significant.




CommentsAdditional remarks, clarifications, or notes relevant to the study or data extraction.
description: This dataset is the result of a systematic review on the impact of heavy metals on bird behaviour and/or cognition (Gémard et al. submitted). We did not consider studies restricted to apical endpoints such as survival, growth rate, and reproductive success. The term “heavy metal” is itself controversial and inconsistently defined (Duffus et al., 2002), with no universally accepted alternative despite ongoing debate (Ali & Khan, 2018). In line with previous ecotoxicological work, we adopted the broad usage of the term to encompass ten metals and metalloids: arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), cobalt (Co), lead (Pb), mercury (Hg), nickel (Ni), zinc (Zn), and tin (Sn), following the classification of Hübner et al., (2010). Because our focus is on contaminants of concern with established or suspected toxicity, we excluded tin (Sn), which is not included in the ATSDR Substance Priority List (Agency for Toxic Substances and Disease Registry, 2022). Studies on mixtures were also considered, provided that the main constituents were among the metals listed above. We chose to include correlational and experimental studies conducted in captivity or in the field to highlight the diversity of taxa and methodological approaches. Both wild and domestic bird species (e.g., domestic fowl Gallus domesticus, homing pigeons Columba livia) were included.

We followed the standardised Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) method to select the studies to include in our review (Moher et al., 2009). The selection process and eligibility criteria are presented in Fig. S1. We used four large databases as information sources, namely Pubmed (https://pubmed.ncbi.nlm.nih.gov), Web of Science (https://www.webofscience.com), Scopus (https://www.scopus.com), and Dimensions (https://www.dimensions.ai) to systematically review the available literature. We searched for the following keywords in title, abstract, and topic: (bird OR avian OR songbird) AND (cogniti* OR learning OR memory OR behav*) AND (metal OR metalloid OR heavy metal OR trace metal OR arsenic OR cadmium OR chromium OR copper OR lead OR mercury OR methylmercury OR nickel OR cobalt OR zinc) NOT (patient OR children OR child OR adolescent OR astrophysics OR mathematics). Because we obtained studies on human health, astrophysics, or mathematics in previous searches, we excluded related keywords. The final search took place in April 2025.

After merging the results from the four databases, the search returned a total of 13,853 results. Duplicates were removed based on the title, the DOI, or the ISSN (N = 4,837). Documents that were neither written in English nor peer-reviewed were also removed, such as book chapters, books, reviews, proceedings, dissertations, editorials, conference papers, master and PhD thesis (N = 687). We then used exclusionary keywords searched in the titles, abstracts, and keywords to remove articles out of scope (e.g., articles on other taxa than birds, articles not measuring behavioural or cognitive changes; N = 8,329). This automatic filtering was implemented in RStudio 2024.12.0+467 with the R package bibliometrix (Aria & Cuccurullo, 2017).

The abstracts of the 614 articles remaining were manually screened for their relevance to the topic. Again, we manually removed articles that did not fit our scope (N = 508). The 106 articles remaining were entirely read and those that did not fit our scope were excluded (e.g., focusing on survival or reproductive success, or quantifying the lethal toxicity benchmarks or heavy metal concentration in avian tissues, N = 26). During the reading, we performed a forward search (i.e., looking for the sources that cited the original article) and a backward search (i.e., looking at the references cited in the original article), which resulted in 14 additional references. We also added an article in preparation. After the selection process, 94 articles published between 1972 and 2024 were included in the review.