1. Monitoring Mercury in Forsters Terns: A Dual Life-Stage Approach to Assessing Effects and Toxic Thresholds Collin Eagles-Smith 1 and Josh Ackerman 2 1 U.S. Fish and Wildlife Service, Sacramento 2 U.S. Geological Survey, Davis

2. Central nervous system effects Altered behavior Impaired vision, hearing, and motor skills Endocrine effects Embryo death Embryo deformities Chick death Waterbirds Represent a Sensitive Endpoint for Mercury Toxicity

3. Bird Mercury Concentrations Blood [THg] (ppm ww) Forsters tern Caspian tern Avocet Stilt 0.01 0.1 1 10 Surf scoter Avian LOAEL

4. Avocet Stilt Caspian tern Forsters tern Percent of Population at Risk Breeding Birds Only Low RiskModerate RiskHigh RiskExtra High Risk 6% 5% 10% 58% Risk Factor: High + Extra High * Based on breeding adult blood Hg concentrations

5. Forsters Tern Habitat Use

6. Developing Monitoring Tools Need to be: Indicative of local exposure. Reflective of recent exposure. Linked to population-level effects. Logistically feasible. Insert photo egg/chick in nest

7. Study Objectives Obj. 1: Determine egg toxicity thresholds for: –1a. Abandonment –1b. Hatchability Obj. 2: Determine effects threshold of egg-derived mercury on chick mortality. Obj. 3: Link mercury concentrations in eggs to those in down feathers.

8. Linking Mercury to Effects: A Conceptual Model Trophic Transfer Maternal Transfer Fail-to-Hatch Hatch Mortality (<10 d) Survive Incubation Abandon (Obj. 1A) (Obj. 1B) (Obj. 2)

9. Linking Mercury to Effects: A Conceptual Model Maternal Transfer Fail-to-Hatch Hatch Mortality (<10 d) Survive Abandon

10. Project Update Terns have arrived and began initiating nests at South Bay breeding grounds. Nest monitoring underway at 5 separate colonies. Chicks will begin hatching in ~4 weeks

11. Egg Micro-Sampling Pilot Study Drill tiny hole in shell. Sub-sample albumin. Seal shell hole. Analyze albumin Link Hg to individual egg hatchability.

12. Mercury in Micro-Sample versus Whole Egg (mallard eggs)

13. Linking Mercury to Effects: A Conceptual Model Trophic Transfer Maternal Transfer Fail-to-Hatch Hatch Mortality (<10 d) Survive Incubation Abandon (Obj. 1A) (Obj. 1B) (Obj. 2) (Obj. 3) Egg Hg Abandonment Egg Hg Hatchability Egg Hg Chick Survival Egg Hg Effects

14. Littoral Foragers – eat insects & crustaceans American avocets Black-necked stilts Obligate Piscivores – eat fish Forsters terns Caspian terns Species Studied Benthic Foragers – eat bivalves Surf scoters

15. Avocets & Stilts Forsters Terns

16. Mercury in Eggs Extra High High Risk Category Low 0.1 1 10 North Bay Central Bay South Bay Egg [THg] (ppm dw) Moderate Avocets Stilts Forsters Terns

17. New Chicago Marsh Eden Landing Ecological Reserve Mercury as Chicks Age: Stilts 102030405060 Culmen Length (mm) (age) Blood [THg] ( g g -1 ww) 5 1 0.1 Hatch Fledge

18. Mercury as Chicks Age: Stilts and Terns Forsters terns Hatch Fledge Stilts

19. Chick Survival: Stilts & Avocets Newly Hatched