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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.

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Presentation on theme: "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."— Presentation transcript:

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 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 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 Culmen Length (mm) (age) Blood [THg] ( g g -1 ww) Hatch Fledge

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

19 Chick Survival: Stilts & Avocets Newly Hatched


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