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Collin Eagles-Smith 1 and Josh Ackerman 2 1 U.S. Fish and Wildlife Service, Sacramento

Monitoring Mercury in Forster’s 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.

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Collin Eagles-Smith 1 and Josh Ackerman 2 1 U.S. Fish and Wildlife Service, Sacramento

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  1. Monitoring Mercury in Forster’s Terns: A Dual Life-Stage Approach to Assessing Effects and Toxic Thresholds Collin Eagles-Smith1 and Josh Ackerman2 1U.S. Fish and Wildlife Service, Sacramento 2U.S. Geological Survey, Davis

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

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

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

  5. Forster’s 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 Abandon (Obj. 1A) Trophic Transfer Fail-to-Hatch (Obj. 1B) Maternal Transfer Incubation Hatch Survive (Obj. 2) Mortality (<10 d)

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

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

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

  15. Forster’s Terns Avocets & Stilts

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

  17. Mercury as Chicks Age: Stilts New Chicago Marsh Eden Landing Ecological Reserve 5 1 Blood [THg] (mg g-1 ww) 0.1 Fledge Hatch 10 20 30 40 50 60 Culmen Length (mm) (age)

  18. Mercury as Chicks Age: Stilts and Terns Stilts Forster’s terns Fledge Hatch

  19. Chick Survival: Stilts & Avocets Newly Hatched

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