Guidelines for evaluation and treatment of lead poisoning of wild raptors

Abstract

Lead poisoning is a threat to birds, particularly scavenging birds of prey. With the availability of portable lead-testing kits, an increasing number of field researchers are testing wild-caught birds, in situ, for lead poisoning. We describe guidelines for evaluation of lead toxicity in wild raptors by outlining field testing of blood-lead concentrations, presenting criteria for removing a lead-poisoned bird from the wild for treatment, and suggesting strategies for effective treatment of lead intoxicated raptors. Field testing of birds is most commonly accomplished via portable electrochemical analysis of blood; visual observation of condition alone may provide insufficient evidence upon which to make a decision about lead poisoning. Our intended audience is not only the avian research community, but also rehabilitation facilities that may receive apparently uninjured birds. Best practices suggest that birds whose blood-lead levels are <40 mg/dL be released back to the wild as soon as possible after capture. The decision to release or treat birds with bloodlead levels between 40 mg/dL and 60 mg/dL should be made based on the presence of clinical signs of poisoning and relevant biological characteristics (e.g., breeding status). Finally, birds with blood-lead levels >60 mg/dL are potentially lethally poisoned and best served if removed from the wild for appropriate treatment at a licensed rehabilitation facility and later released. We present guidelines for decision-making when treating lead poisoning of wild raptors. Future work based on experimental studies will clarify the role of lead poisoning for specific species and be important to refine these guidelines to improve effectiveness.

Suitability of anodic stripping voltammetry for routine analysis of venous blood from raptors

“…Using the threshold of 10 mg/dL described for background BLLs in raptors (Redig and Arent 2008;Langner et al 2015;Fallon et al 2017), we found that the LCII measurements correlate better with those of the ICP-MS in the series of animals with BLLs >10 mg/dL (which includes all of the griffon vultures examined in the present study) than in those with background BLLs (Figure 4). Using the threshold of 10 mg/dL described for background BLLs in raptors (Redig and Arent 2008;Langner et al 2015;Fallon et al 2017), we found that the LCII measurements correlate better with those of the ICP-MS in the series of animals with BLLs >10 mg/dL (which includes all of the griffon vultures examined in the present study) than in those with background BLLs (Figure 4).…”

“…On the other hand, we considered the threshold of 10 mg/dL, which has been proposed as a limit at which a raptor can be considered to have high levels of Pb, probably with pathological consequences (Redig and Arent 2008;Fallon et al 2017). We considered 2 different thresholds for this.…”

“…On the one hand, we considered the threshold value of 3.4 mg/dL for both the overrated and the underrated values by the LCII, which would correspond with that of the LOD of the LCII, as measured by ICP-MS, plus the maximum RSD of the whole series (13%). On the other hand, we considered the threshold of 10 mg/dL, which has been proposed as a limit at which a raptor can be considered to have high levels of Pb, probably with pathological consequences (Redig and Arent 2008;Fallon et al 2017). Otherwise, if we considered all the overrated or underrated values, we would be introducing a bias in the interpretation of the ability of the technique to correctly identify the animals with low BLLs ("negative to Pb" or without clinical relevance).…”

Lead in piscivorous raptors during breeding season in the Chesapeake Bay region of Maryland and Virginia, USA

“…A total of 44% (n ¼ 31) of the sample concentrations were <LOD (Table 1), 15% (n ¼ 10) of the bald eagle blood samples were above the threshold for background blood lead concentrations (10 mg/dL), and 2 of the bald eagles had blood lead concentrations above the threshold for clinical poisoning (40 mg/dL; Pokras and Kneeland 2008;Fallon et al 2017). A total of 44% (n ¼ 31) of the sample concentrations were <LOD (Table 1), 15% (n ¼ 10) of the bald eagle blood samples were above the threshold for background blood lead concentrations (10 mg/dL), and 2 of the bald eagles had blood lead concentrations above the threshold for clinical poisoning (40 mg/dL; Pokras and Kneeland 2008;Fallon et al 2017).…”

“…We tested blood lead concentrations of 244 osprey including 47 breeding adults ( (n ¼ 92) of the osprey blood samples fell below the LODs (Table 1), 3% (n ¼ 7) of the osprey blood samples were above the threshold for background blood lead concentrations (10 mg/dL), and none of the osprey had blood lead concentrations above the threshold for clinical poisoning (40 mg/dL; Pokras and Kneeland 2008;Fallon et al 2017). There was no statistical difference in the detection frequency (p ¼ 0.84, x 2 ¼ 0.04, df ¼ 1) or lead concentrations (p ¼ 0.92, x 2 ¼ 0.01, df ¼1, note that both the chisquare test for detection frequency and the modified Wilcoxon test for concentrations produce a x 2 statistic) between adult and nestling osprey.…”