Edinburgh Napier University

  Current non-invasive biomonitoring techniques to measure heavy metal exposure in free ranging birds using eggs, feathers and guano are problematic because essential metals copper (Cu) and zinc (Zn) deposited in eggs and feathers are under physiological control, feathers accumulate metals from surface contamination and guano may contain faecal metals of mixed bioavailability. This paper reports a new technique of measuring lead (Pb), Cu and Zn in avian urate spheres (AUS), the solid component of avian urine. These metal levels in AUS (theoretically representing the level of metal taken into the bloodstream, i.e. bioavailable to birds) were compared with levels in eggs (yolk and shell), feathers and whole guano from chickens (Gallus gallus domesticus) exposed to a heavy metal-contaminated soil (an allotment soil containing Pb 555 mg kg−1 dry mass (dm), Cu 273 mg kg−1 dm and Zn 827 mg kg−1 dm). The median metal levels (n{þinspace}={þinspace}2) in AUS from chickens exposed to this contaminated soil were Pb 208 $μ$g g−1 uric acid, Cu 66 $μ$g g−1 uric acid and Zn: 526 $μ$g g−1 uric acid. Lead concentrations in egg yolk and shell samples (n{þinspace}={þinspace}3) were below the limit of detection (