US Geological Survey


Date of this Version



Arch Environ Contam Toxicol (2012) 62:145–153


U.S. Government Work


To evaluate the potential toxicity of copper

(Cu) in raptors that may consume Cu bullets, shotgun

pellets containing Cu, or Cu fragments as they feed on

wildlife carcasses, we studied the effects of metallic Cu

exposure in a surrogate, the American kestrel (Falco

sparverius). Sixteen kestrels were orally administered

5 mg Cu/g body mass in the form of Cu pellets

(1.18–2.00 mm in diameter) nine times during 38 days and

10 controls were sham gavaged on the same schedule. With

one exception, all birds retained the pellets for at least 1 h,

but most (69%) regurgitated pellets during a 12-h monitoring

period. Hepatic Cu concentrations were greater in

kestrels administered Cu than in controls, but there was no

difference in Cu concentrations in the blood between

treated and control birds. Concentration of the metalbinding

protein metallothionein was greater in male birds

that received Cu than in controls, whereas concentrations in

female birds that received Cu were similar to control

female birds. Hepatic Cu and metallothionein concentrations

in kestrels were significantly correlated. Histopathologic

alterations were noted in the pancreas of four treated

kestrels and two controls, but these changes were not

associated with hepatic or renal Cu concentrations, and no

lesions were seen in other tissues. No clinical signs were

observed, and there was no treatment effect on body mass;

concentrations of Cu, hemoglobin, or methemoglobin in

the blood; or Cu concentrations in kidney, plasma biochemistries, or hematocrit. Based on the parameters we

measured, ingested Cu pellets pose little threat to American

kestrels (and presumably phylogenetically related species),

although the retention time of pellets in the stomach was of

relatively short duration. Birds expected to regurgitate Cu

fragments with a frequency similar to kestrels are not likely

to be adversely affected by Cu ingestion, but the results of

our study do not completely rule out the potential for

toxicity in species that might retain Cu fragments for a

longer time.