A new open access research paper reviews 114 studies on lead contamination in European raptors. Lead exposure in birds has been studied extensively for more than 50 years, so it is no surprise that this latest study found evidence for the high occurrence of contamination, especially in scavengers.
Monclús, L., Shore, R.F. & Krone, O. (2020). Lead contamination in raptors in Europe: A systematic review and meta-analysis. Science of the Total Environment. https://doi.org/10.1016/j.scitotenv.2020.141437
The abstract is reproduced here in full:
Lead contamination is a widely recognised conservation problem for raptors worldwide. There are a number of studies in individual raptor species but those data have not been systematically evaluated to understand raptor-wide lead exposure and effects at a pan-European scale. To critically assess the extent of this problem, we performed a systematic review compiling all published data on lead in raptors (1983–2019) and, through a meta-analysis, determined if there was evidence for differences in exposure across feeding traits, geographical regions, between hunting and non-hunting periods, and changes over time. We also reviewed the impact of lead on raptors and the likely main source of exposure. We examined 114 studies that were unevenly distributed in terms of time of publication and the countries in which studies were performed. Peer-reviewed articles reported data for 39 raptor species but very few species were widely monitored across Europe. Obligate (vultures) and facultative scavengers (golden eagle, common buzzard and white-tailed sea eagle) accumulated the highest lead concentrations in tissues and generally were the species most at risk of lead poisoning. We found no evidence of a spatial or decadal trend in lead residues, but we demonstrated that high lead blood levels relate to hunting season. Exposure at levels associated with both subclinical and lethal effects is common and lead from rifle bullets and shot is often the likely source of exposure. Overall, our review illustrates the high incidence and ubiquity of lead contamination in raptors in Europe. However, we did not find studies that related exposure to quantitative impacts on European raptor populations nor detailed studies on the impact of mitigation measures. Such information is urgently needed and requires a more harmonised approach to quantifying lead contamination and effects in raptors across Europe.
Some points that I found particularly interesting:-
- Book chapters, reports and conference proceedings were excluded from the analysis, leaving 293 published papers which were filtered to exclude non-European and non-raptor species. Leaving a total of 114 published papers to be included in the review. That sounds like a substantial amount of research on the impacts of lead contamination.
- Only 3 papers covering the UK were included in the final analysis.
- The Common Buzzard (23 papers) and White-tailed Eagle (20 papers) were the most commonly studied species (in Europe as a whole)
- As maybe expected the Griffon Vulture (an obligate scavenger) had the highest mean lead concentrations (in liver & kidney). Followed by Common Buzzard, Golden and White-tailed Eagles (facultative scavengers – that is, they don’t rely wholly on carrion but take other food too). Of course, all three species occur in the UK.
- In total, there were 226 species-specific datasets in the 114 papers reviewed. Just over half (52%) reported lead concentrations that exceeded subclinical threshold values.
- Three species that occur in the UK (Red Kite, Common Buzzard and White-tailed Eagle) were amongst those that showed the highest prevalence of exceedances.
- Ten of the studies reviewed found embedded shot in muscles of birds, suggesting a non-ingestion source of contamination but one that was still associated with hunting – (this seems like a very diplomatic way of saying that some birds had been illegally shot!).
- The review showed a seasonal trend towards higher blood levels during the hunting season, although most of the studies were from Spain (and non in the UK). Given the large number, and recent increases, of gamebirds released for shooting (in the UK), the vast majority of which will be shot using toxic lead ammunition, I wonder what the impact may be on widespread raptors such as Common Buzzard and Red Kite?
This is an excellent study, it’s open access and can be found here: https://www.sciencedirect.com/science/article/pii/S0048969720349664?via%3Dihub#s0035
It is yet another study that highlights the effect of lead exposure in birds. Lead has been banned in petrol, paint, water-pipes and fishing weights – at some point it will be banned in ammunition used for hunting/gamebird shooting. The shooting industry will continue to resist but a ban is inevitable.
Photo credits: Header image of a Red Kite in Lincolnshire (courtesy of Steve Nesbitt)
Graphical abstract from Monclús, L., Shore, R.F. & Krone, O. (2020) used under a Creative Commons license