Blood lead levels in an endangered vulture decline following changes in hunting activity

Lead ammunition stands out as one of the most pervasive pollutants
affecting wildlife. Its impact on bird populations has spurred efforts for
the phase-out of leaded gunshots in several countries, although with
varying scopes and applications. Ongoing and future policy changes require
data to assess the effectiveness of adopted measures, particularly in the
current context of biodiversity loss. Here, we assessed the long-term
changes in blood lead (Pb) levels of Egyptian vultures from the Canary
Islands, Spain, which have been severely affected by Pb poisoning over the
past two decades. During this period, the reduction in hunting pressure
and changes in legislation regarding firearms usage for small game hunting
likely contributed to a decrease in environmental Pb availability. As
anticipated, our results show a reduction in Pb levels, especially after
the ban on wild rabbit hunting with shotguns since 2010. This effect was
stronger in the preadult fraction of the vulture population. However, we
still observed elevated blood Pb levels above the background and clinical
thresholds in 5.6% and 1.5% of individuals, respectively. Our results
highlight the positive impact of reducing the availability of Pb from
ammunition sources on individual health. Nonetheless, the continued use of
Pb gunshot remains an important source of poisoning, even lethal, mainly
affecting adult individuals. This poses particular concerns for long-lived
birds, compounding by potential chronic effects associated with Pb
bioaccumulation. Our findings align with recent studies indicating
insufficient reductions in Pb levels among European birds of prey,
attributed to limited policy changes and their uneven implementation. We
anticipated further reductions in Pb levels among Egyptian vultures with
expanded restrictions on hunting practices, including a blanket ban on Pb
shot usage across all small game species.