Investigation of Common Eider Mortality Events at Cape Cod

Julie C. Ellis, PhDJulie C. Ellis, PhDSarah Courchesne, DVMSarah Courchesne, DVM

Seabird Ecological Assessment Network (SEANET)Seabird Ecological Assessment Network (SEANET)Cummings School of Veterinary MedicineCummings School of Veterinary Medicine

at Tufts Universityat Tufts UniversityNorth Grafton, MANorth Grafton, MA

SEANET:Beached Bird Surveys & Necropsies

Volunteers (Citizen Scientists)Volunteers (Citizen Scientists)

Walk same area of a beach 1-2 times per monthWalk same area of a beach 1-2 times per month

RecordRecord::Conditions data Conditions data Beached birds (beached birds/km)Beached birds (beached birds/km)Live birdsLive birds

““Fresh” carcasses collected forFresh” carcasses collected fornecropsynecropsy

SEANET: Goals

Goals• Establish a baseline for temporal and spatial deposition Establish a baseline for temporal and spatial deposition

of seabird carcasses in order to detect unusual events of seabird carcasses in order to detect unusual events (e.g. oil spills, diseases)(e.g. oil spills, diseases)

• Work with the public to research and monitor seabird Work with the public to research and monitor seabird populations, and to contribute to conservation of the populations, and to contribute to conservation of the larger marine ecosystemlarger marine ecosystem

Seabirds are sentinels for the marine environment because they spend some to all or their lives on the ocean

Common Eiders

Common Eider (Common Eider (Somateria mollissimaSomateria mollissima))Largest duck in the Northern Hemisphere!Largest duck in the Northern Hemisphere!

Breeds in eastern North America, on islands along Labrador, Breeds in eastern North America, on islands along Labrador, Newfoundland, Quebec (eastern), Nova Scotia, and Maine (small pops Newfoundland, Quebec (eastern), Nova Scotia, and Maine (small pops in NH, MA)in NH, MA)

Nest in large colonies on islandsNest in large colonies on islands

Populations from Canada and Maine overwinter at Cape Cod in large Populations from Canada and Maine overwinter at Cape Cod in large numbers (especially in the Nantucket Shoals area)numbers (especially in the Nantucket Shoals area)

Location and History of Die-off Events

Great IslandGreat IslandJeremy PointJeremy Point

Nantucket Nantucket Martha’s VineyardMartha’s Vineyard

Since 1980’sSince 1980’s(at least)(at least)

Recent Events: A Timeline

FEB - MARCH 2006: males

OCT 2006: males

JULY - AUGUST 2007 *Mostly Adult Females

OCT 2007: males

More Frequent?

Martha’s Vineyard and Martha’s Vineyard and Nantucket IslandNantucket Island

~300 Common Eiders found ~300 Common Eiders found dead or dying on beachdead or dying on beach

Birds still alive showed non-Birds still alive showed non-specific signs: lethargy, specific signs: lethargy, dehydration, weaknessdehydration, weakness

None survived rehabilitationNone survived rehabilitation

COEI Mortality Events at Cape Cod: Feb – March 2006

COEI Mortality Events at Cape Cod: Feb - March 2006

Necropsy findings (cont):

8 out of 9 emaciated, 1 out of 9 thin

8 out of 9 had varying degrees of acanthocephalan parasites (moderate to severe infestations)

Profilicollis botulus (acanthocephalan)infestations

Thorny head used to Thorny head used to attach to host’s intestinal attach to host’s intestinal wall;wall;nutrients absorbed nutrients absorbed through worm’s body wallthrough worm’s body wall

How P. botulus could kill eiders

• Steal enough nutrients from the host that the host starves

•Plug up the intestine

•Perforate the intestine with the thorny head and allow intestinal contents to escape out into the body (sepsis)

• Leave so many scars in the intestine that there is no longer any surface area for nutrient absorption (malabsorption)

Die-off: Wellfleet Bay, October 2007•14 necropsies performed on birds collected at Jeremy Point

•Demographics: 11 adult males, 1 adult female, 2 immature males (die-off appeared to affect mainly adult males)

•Body Condition: 4 in good body condition, 6 in thin body condition, 4 emaciated

Necropsy Findings

• One bird had died of gunshot wound

• >90% of birds in fair to good body condition showed pectoral muscle atrophy (indicates recent molting)

• 11 of 14 birds had lesions in the digestive system. Most common: Pus and scarring on internal surface of esophagus/stomach (see photo)Hemorrhage in esophagus, stomach, intestine (next slide)

Necropsy Findings

• All but one bird had acanthocephalans (ranged from 4 to 267 worms)

• No apparent relationship between parasite load and degree of intestinal inflammation

• One bird died of intestinal perforation by an acanthocephalan

• One bird died of an intestinal perforation (unknown cause) but had no acanthocephalans

Conclusions From 2007 Die-off

• Scattered liver lesions and hemorrhage in intestinal tract point to a viral cause (NWHS investigating)

• Birds did not starve to death (not universally thin as in previous die-offs)

•Acanthocephalans typically present, but do not appear to be causing big problems

• Most birds had recently been stressed (by molting) and may have been more susceptible to disease

Comparison with eiders shot by hunters• 8 eider (5 adult males, 1 immature male, 2 adult females) shot in November 2007 at Great Island in Wellfleet

• 50% were thin, 50% in good body condition

• 3/8 birds had no lesions (aside from gunshot wounds)

• Remaining 5 birds had varying degrees of lesions in digestive tract (similar to die-off birds)

Acanthocephalans in shot birds•All shot birds had acanthocephalan infestations

•Parasite number ranged from 8 worms to 426 worms (more than in any of the die-off birds!)

•The parasites were NOT associated with any significant lesions or disease

•Higher parasite loads were not associated with decreased body condition

Significance of findings in shot birds

If birds that appear healthy (outwardly) have many of the same lesions as the die-off birds…

…either the lesions are a red herring and have nothing to do with the cause of the die-off…

…or the lesions represent a disease that many eiders may carry but that only sickens and kills birds that are stressed in some way.

Next steps:

Histopathology Contaminants testing

Dietary analysis

Population studies

Beached Bird Surveys

Virology

Cyanotoxins?

Acknowledgements

Jack Renfrew (Ducks Unlimited)Susannah Corona (New England Aquarium)Marc Siegel, KC Horigan, Nadia Stegeman, Emily Christiansen (Tufts vet students)Mark Pokras (Tufts)Michael Moore & Andrea Bogomolni (WHOI)Katie Touhey (CCSN)Becky Harris (Mass Audubon)Mark Jankowski (USGS)Hon Ip (USGS)

Funding:NOAA (Oceans and Human Health Initiative)Bernice Barbour Foundation