HABITAT, NUTRITION, AND MERCURY IN

WATERBIRDS: PTILOCHRONOLOGY AS A

NOVEL BIOINDICATOR TOOL

Charles ClarksonHarbor Herons Meeting

Staten Island, NY13 January, 2011

Photo: Gerald Frost

OBJECTIVES

• Use ptilochronology (feather growth) to predict measures of parental quality, diet, and mercury burden in mixed species waterbird colonies at two locations along the east coast and demonstrate its worth as a universal bioindicator tool in avian studies.

Ptilochronology• Technique of measuring

feather growth– Growth-bars laid down in 24 hr

increments– Correspond directly with

nutritional condition of the individual

– Never used as a tool for bioindication

PREDICTIONS

• 1)Intraspecific variation in feather growth-bar width within a colony site will be indicative of variation in parental investment, as “higher quality” adults will provision nestlings more efficiently.

• 2)Intraspecific variation in feather growth-bar width between multiple colony sites will be indicative of differing habitat qualities (quality/quantity of diet, contaminant load).

Hoffman Island

Canarsie Pol

Chimney Pole

Chincoteague Causeway

Googlemaps.com

METHODS: STUDY SITES

METHODS: STUDY SPECIES• Two species belonging to the same

waterbird guild yet representing two endpoints of foraging habit. – Glossy Ibis (Plegadis falcinellus)

• Tactile forager• Invertebrates and mollusks• Foraging habit delimits spatial exploitation

– Double-crested Cormorant (Phalacrocorax auritus)• Habitat generalist• Free-swimming• Piscivorous

Photos: Gerald Frost

GROWTH-BAR ANALYSIS

FAULT BARS

Future Directions• Model growth-bar width as a

predictor variable: Akaike’s Information Criterion• AICc = N*ln(SS/N)+2K+(2K(K+1))/(N-K-1)

• Captive food supplementation study• National Zoo, Washington D.C

• White-faced Ibis (Plegadis chihi)

• Scarlet Ibis (Eudocimus ruber)

• Colony-wide biomass consumption• How much biomass is

consumed during the breeding season?

• All nesting species (~8 spp)

ACKNOWLEDGEMENTS• Mike Erwin• Susan Elbin• Mark Kopeny• John Porter• Carleton Ray• Matt Reidenbach• UVA; VCR LTER; NYC Audubon; American Littoral

Society; Virginia Society of Ornithology; National Park Service; NYC Parks

• Friends and Family