Royal Tern chick diet and growth as indicators of the forage fish stocks in the Chesapeake Bay, Virginia

Study species:

The life history traits of seabirds make them suitable candidates as marine bioindicators because they are long lived, forage at multiple trophic levels, often a top level predator and consume a divers array of forage fishes. In addition to these characteristics, Royal Terns, in particular, are an excellent candidate as a bioindicator species on the Atlantic seaboard because they: are a colonial-nesting waterbird found mainly along the east coast from Florida to Maryland, long-lived, have a delayed sexual maturity, nest in dense breeding colonies, lay a single-egg clutch (usually), plunge dive, and are near-shore feeders.

Background:

Diet composition and the availability of quality prey are important factors that play a major role in the health and survival of animals. A number of studies have detailed seabirds as monitors of the marine environment by quantifying the sensitivity of these birds to reductions in prey availability and abundance. As potential monitors of fish stocks, the sensitivity to fish population fluctuations have an effect on the reproductive, breeding, and chick-rearing success of seabirds.

Near the top of the marine food web, seabirds are more susceptible to short-term changes in their diet and by effectively monitoring piscivorous seabirds, a better understanding of the local marine environment might be gained.

Study site:

The barrier islands of Virginia provide a unique opportunity to study Royal Terns as an indicator species. The islands support one of the most northern breeding populations on the Atlantic seaboard with Fisherman Island National Wildlife Refuge hosting the largest colony. Fisherman Island is located at the mouth of the Chesapeake Bay, where estuarine and marine forage species are abundant.  This study site was chosen because during most years the colony is relatively large (between 1000-2000 nests) and little is known about the population, breeding success, and feeding habits of the terns on the island. This distinctive location offers critical habitat and access to abundant prey for terns during the breeding cycle.

The Chesapeake Bay is heavily exploited by commercial fisheries and has produced a total average of over 42 million pounds of finfish in the last five years, mainly in flounder, herring, and drum species landings--generating at least $130 million annually. The effects of these activities have been recorded by the Virginia Institute of Marine Sciences (VIMS) and fisheries landing and stock abundance data are readily available.  

Royal Terns may rely on these harvested forage species for their survival and reproductive success. Demographic data are important from both Virginia and North Carolina as they represent different environments where seabird productivity is high along the Atlantic Seaboard.  These areas provide critical habitat for Royal Terns and effective conservation and management of fisheries stocks and coastal habitat is of key importance.

My research:

Past research has demonstrated that seabirds can serve effectively as indicator species for the health and productivity of coastal and marine environments.  The dietary composition of seabirds can be used to monitor prey stocks and past studies have shown a positive correlation between seabird chick diet and fish recruitment. For my study, I will investigate Royal Tern chick diet and growth as indicators of forage fish stocks in the Chesapeake Bay. Specifically, I will determine chick diet by observation of parental foraging and relate growth rates of chicks (gr day-1) with the quantity of forage fish species in the diet. These objectives also may contribute to coastal and fishery management issues in the Chesapeake Bay and Virginia coastal region.