Lead in Species of Greatest Conservation Need: Free-flying Bald Eages as Indicators

Project

Principal Investigator:

Julie A. Blanchong

Stephen Dinsmore

Student Investigator:

William Reiter-Marolf (M.S.)

Collaborators:

 

Duration:

January 2012 to June 2015

Funding Source(s):

Iowa Department of Natural Resources (IDNR), State Wildlife Grant

Goals and Objectives:

  • Characterize lead levels in nesting and winterizing Bald Eagles in Iowa State University
  • Compare lead exposure in free-flying eagles with eagles admitted to rehabilitation centers

 

Progress:

The high proportion of Bald Eagles (Haliaeetus leucocephalus) with lead poisoning reported by wildlife rehabilitation centers and wildlife health monitoring programs has raised concern about the magnitude and consequences of lead exposure in this species and other bird Species of Greatest Conservation Need (SGCN).  This study is examining the degree to which avian SGCN are being exposed to lead in their diets by examining lead levels in Bald Eagles admitted to rehabilitation centers and in nesting and wintering Bald Eagles in Iowa.

In 2012 and again in 2013, M.S. student William (Billy) Reiter-Marolf and his technician non-invasively collected excrement samples from wintering Bald Eagle roosts and from up to 110 randomly Bald Eagle nest sites in winter (during egg incubation) and again in spring (when eaglets were 3-9 weeks of age). Half of the nests were in close proximity to the Mississippi River and half were distributed throughout the rest of Iowa.  Blood and excrement samples were also collected from Bald Eagles admitted to 3 rehabilitation centers in Iowa. All samples were sent to the Iowa State Hygienic Lab for lead testing. Testing is complete and we are completing data analysis. In 2014, Billy defended his M.S. thesis and results of this research were presented at the Iowa chapter of the Wildlife Society annual meeting and the national Wildlife Society meeting.

We received approval to use the remaining funds from this project to examine levels of several additional heavy metals in the eagle excrement samples. We will complete statistical analyses of other heavy metal data and prepare manuscripts for publication.

A final report will be submitted in June 2015.

Conclusions and Recommendations:

We did not identify any significant spatial or temporal trends in lead exposure in samples from free-flying Bald Eagles. Lead levels in excrement from free-flying birds ranged from <1.0 mg/kg (our detection limit) to 170 mg/kg while values in rehabilitation birds ranged from <1.0 mg/kg to 520 mg/kg. High lead levels (>5 mg/kg) were documented less frequently in excrement samples from free-flying eagles (2.8%) compared to samples from rehabilitation eagles (29.8%). Our results suggest that free-flying eagles are not experiencing high levels of lead exposure at the same rates as observed in rehabilitation Bald Eagles. However, most samples collected from free-flying and rehabilitation Bald Eagles contained some lead.

Our comparison of lead levels in blood and excrement from Bald Eagles submitted to rehabilitation centers found that excrement lead levels were a significant predictor of blood lead levels. A linear regression model indicated that when excrement lead levels are low, it is likely that blood lead levels will also be low. When excrement lead levels are high, it is likely that blood lead levels will also be high. We concluded that excrement has the potential to be a valuable tool for investigating lead exposure in Bald Eagles. However, additional work is needed to in order to be able to predict clinical outcomes based on excrement lead levels. 

 

Duration: 
01/01/2012 to 06/15/2015