MP17 Endangered Species and Environmental Contaminants: Status of Science
Monday, 14 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(RAU-1117-829786) Contaminants and egg quality of snowy egrets (Egretta thula) from Florida estuarine and freshwater habitats.

Rauschenberger, Heath¹, Hemming, Jon², Boughner, Emily³, Peterson, Jim⁴, Benjamin, Karen¹, ¹ US FWS, Jacksonville, FL, USA² US FWS, Panama City, FL, USA³ US FWS, Vero Beach, FL, USA⁴ St. Johns River Water Management District, Apopka, FL, USA

ABSTRACT- In Florida, urban development and wetland restoration activities have increased dramatically in recent years. Both activities may attract birds to contaminated areas and expose migratory wading birds, such as the endangered wood stork ( Mycteria americana), to pollutants through contamination of aquatic habitats. Therefore, assessing contaminant exposure and effects are important in developing conservation plans for these species. Our study examined the relationship between egg quality, nest productivity, and organochlorine pesticide (OCP) and heavy metal burdens in eggs of snowy egrets (Egretta thula , a representative wading bird). During 2004 and 2005, snowy egret nests were monitored at St. Marks National Wildlife Refuge (SM), an estuarine habitat, and along Lake Apopka′s north shore (AP), which is proximal to a 1,214 ha wetland restoration area (reclaimed agricultural property). Over the two-year period, AP nests (n = 51) had larger clutch sizes (p>0.0001), and thinner eggshells (p>0.0001) compared to SM nests (n = 31). Hatch rates, egg mass, and dry eggshell mass did not differ between the sites, although higher variability was observed for AP hatch rates. Analytical data for 2004, indicated AP eggs contained higher organochlorine pesticide burdens (p>0.0001 to 0.0016), higher Ba (p>0.0002) and Mn (p>0.0036) concentrations, but lower Hg, Se, Cu, Zn and Sr (p>0.0001 to 0.0238) burdens. No differences were detected between sites with respect to total PCBs or other heavy metals. Our results suggest that OCP exposure may be associated with eggshell thinning in AP eggs, but a connection to reduced hatch success or clutch size has not been demonstrated. Future studies should examine variability in hatch success between sites, within clutch variability of studied parameters, and the relationship among bird foraging habits, contaminant burdens and egg quality. Additionally, heavy metal exposure routes and effects warrant further investigation at SM. Support provided by a US FWS Environmental Contaminants Program grant and in-kind service by St. Johns River Water Management District.

Key words: organochlorines, metals, avian reproduction, endocrine disruption