Iowa State University researchers have determined most bald eagles in Iowa aren’t flying around with high levels of lead in their bodies. Julie Blanchong is one of the researchers who matched lead levels of wild birds to those who have been brought in to wildlife rehabilitation centers for lead exposure treatment.
“The wild birds experienced very low levels of lead exposure in terms of the actual amounts of lead. And the rehabilitation birds had considerable higher average levels of lead,” Blanchong says.
She says they wanted to find out if the birds that were sick enough for treatment indicated problems in the overall population.”There’s been a lot of really good work looking at lead exposure in rehabilitation birds. But what’s going on in the wild was our question,” Blanchong says. “Can we make inferences from rehabilitation birds about what’s going on on average in the wild? And I guess our conclusion would be, no you can’t.”
The researchers took lead levels from the excrement of the birds. Other research has found eagles can ingest lead from the gut piles left over after hunters dress deer in the field. Blanchong, an associate professor of natural resource ecology and management, says they didn’t try to identify lead sources. “All we did was measure lead itself. And so, certainly one source of lead is probably those gut piles and deer that don’t get retrieved by the hunters. There’s probably some sort of environmental residue from the days when lead gas was used as well. We didn’t tease that apart,” Blanchong says.
There’s been some call for banning lead shot to try and reduce the eagle’s exposure. Blanchong isn’t wading into that issue. “This study has got nothing to do with banning lead shot. The purpose was more magnitude of exposure. Are the rehabilitation birds representative of what the average bird flying around in Iowa is likely to experience in terms of lead level,” Blanchong says. “And our answer would be: No.” Blanchong says that doesn’t mean that finding lead in the eagle population is a good thing.
Fellow researcher Stephen Dinsmore, says they did find the levels of lead didn’t interfere with reproduction. He says they monitored more than 100 nests and found 83-percent of the eagles were able to produce young. “And that is among the highest success rates reported in any study of bald eagles in North America,” Dinsmore says. He says that is good news for the continued success of bald eagles in the state.
“Regardless of what may or may not be happening with elevated lead levels — bald eagles are reproducing are very good levels here in Iowa. And again, I think that is something that is a positive to point out in all of this,” Dinsmore says. Bald eagles had disappeared in the state until a comeback that Dinsmore says started in 1977. He says the use of pesticides and loss of habitat were a couple of factors in the disappearance of the birds.