R5 PM Avian Sentinels of Environmental Contamination
Thursday, 17 November 2005: 1:50 PM - 5:30 PM in 321-323

(AND-1117-236307) Field assessment of osprey breeding performance through a period of mine-site remediation.

Anderson, D.¹, Suchanek, T.¹, Eagles-Smith, C.¹, ¹ University of California, Davis, CA, USA

ABSTRACT- Osprey (Pandion haliaetus) were studied from 1992 through 2005 at Clear Lake, California, 14 years that spanned a pre-remediation/remediation period (4 years) and a post-remediation period (9 years). The Sulfur Bank Mercury Mine (SBMM) was the major source of Hg contamination. In 1992 and 1993, OSPR productivity (young/nest attempt) increased (P<0.02 and P<0.05) as a function of increasing distance from SBMM. Feather Hg residues in OSPR (and grebe, Aechmophorus sp.) during the earlier period indicated that individuals had high enough Hg residues to expect effects. In 1994 and 1995, the positive relationship between distance from the mine and reproductive success weakened (P<0.10); and from 1996 through 2005, it disappeared entirely (P>0.10). Hg residues in feathers of adult Osprey also declined significantly lake-wide, comparing 1992 and two later years (1999 and 2004) (P<0.01). In 1999 and 2004, Hg in OSPR feathers was comparable to (P>0.10) those from our comparison site, Eagle Lake, where reproduction was normal. Residues in fish decreased in the area nearest the remediated mine-site earlier associated with poor reproduction; and active nests in the highly affected area increased from 2 in 1994 to 6 in 2005. Yet, there were no declining trends in Hg levels of potential prey fish, lake-wide, following the 1992 remediation. The global Clear Lake OSPR population throughout, however, maintained productivity sufficient to maintain numbers, but productivity nonetheless increased (P<0.01) after remediation. The number of OSPR nests at Clear Lake consistently increased from 1992. Hg effects were probably never of population significance throughout the study; but detectable, continuing improvements in various demographic measurements were nonetheless associated with declining Hg levels. Yet, the ecological improvements at Clear Lake could not be attributed singly to the one remediation in 1992, as Hg residues were already declining from the late-1960s. Continuing Hg input from SBMM will probably require further remediation.

Key words: osprey, reproduction, mine-site remediation, mercury