Item 2 Mercury in Terns

Monitoring Mercury in Forster’s Terns: A Dual Life-Stage Approach to Assessing Effects and Toxic Thresholds: 

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

Slide2: 

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

Bird Mercury Concentrations: 

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

Slide4: 

Percent of Population at Risk Breeding Birds Only 6% 5% 10% 58% Risk Factor: High + Extra High * Based on breeding adult blood Hg concentrations

Forster’s Tern Habitat Use: 

Forster’s Tern Habitat Use

Developing Monitoring Tools: 

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

Study Objectives: 

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.

Linking Mercury to Effects:A Conceptual Model: 

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

Linking Mercury to Effects:A Conceptual Model: 

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

Project Update: 

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

Slide11: 

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

Slide12: 

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

Linking Mercury to Effects:A Conceptual Model: 

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

Species Studied: 

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

Slide15: 

Avocets andamp; Stilts Forster’s Terns

Slide16: 

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 Forster’s Terns

Slide17: 

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

Slide18: 

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

Slide19: 

Chick Survival: Stilts andamp; Avocets Newly Hatched