Abstract

Lead (Pb) and mercury (Hg) are heavy metals known to be major pollutants in the environment and to have negative effects on wildlife ecosystems. Many studies have been completed analyzing how Pb and Hg affect birds and how widespread these heavy metals are within wild populations. However, much of this research focuses on Pb in waterfowl. The extent of Pb in other species and of Hg in all wild birds has not been as widely studied or documented. This study provides a retrospective analysis of the Pb and Hg test results of wild bird patients from the mid-Atlantic region by reviewing and evaluating species tested, entry dates, outcomes, and threshold levels. These test results were generated at the New Bolton Center Toxicology Laboratory (NBC) from whole blood samples from patients at Tri-State Bird Rescue and Research, Inc. (TSBRR) in Delaware using atomic absorption spectrometry. The records analyzed date from January, 1997 through December, 2007. During that time period 562 different patients were tested for Pb, and 218 of these birds were also tested for Hg. This encompasses 41 different species from 12 orders. The most common species tested included Canada Geese (Branta canadensis) at 100 and Bald Eagles (Haliaeetus leucocephalus) at 119. These birds came from locations within six states: Maryland, Pennsylvania, New Jersey, Delaware, Virginia, and New York. ArcGIS® version ArcView 9.2 was used to analyze data geographically and to look for potential locations of high heavy metal environmental contamination. Specific regions were noted as having high Pb contamination, however similar areas were not noted with Hg as this is due to a more widespread environmental contamination. Of the birds tested (most tested based on clinical signs), 23.5% had > 0.20 ppm Pb blood wet weight levels (requires treatment) indicating a high contamination problem.1 The Hg positive value used was > 0.30 ppm blood wet weight, 56% of the birds tested had levels greater than this.2 One main finding of this study showed that 69% of birds with > 0.20 ppm Pb blood wet weight concentration, considered clinically significant, entered the clinic from November through March. These dates are significant as they denote the beginning of a harsher living environment and the start of hunting season where more Pb shot is available for consumption in the environment. Date correlations with Hg were not as significant as they mainly denoted a higher number of birds in the summer months which correlates with the higher case-load of TSBRR and matches the migration patterns of many of these cases. General conclusions show that Pb and Hg contamination remains a big problem in the mid-Atlantic area in wild bird populations and should continue to be monitored as it continues to move up the food chain.

References

1.  Pain D.J. 1996. Lead in waterfowl. In: W.N. Beyer, G.H. Heinz, and A.W. Redmond-Norwood (eds). Environmental Contaminants in Wildlife. SETAC Special Publication Series. CRC Press Inc., Boca Raton, Florida; Pp. 251-264.

2.  Thompson D.R. 1996. Mercury in birds and terrestrial mammals. In: W.N. Beyer, G.H. Heinz, and A.W. Redmond-Norwood (eds). Environmental Contaminants in Wildlife. SETAC Special Publication Series. CRC Press Inc., Boca Raton, Florida; Pp. 341-356.