Researching Importance of Florida's St. George Island as Trans-Gulf Migrant Stopover

By Alan Kneidel, former Manomet shorebird researcher and landbird bander

 

Nearctic-Neotropical songbird populations are under pressure on their breeding and wintering grounds as well as during migration.

 

Migration stressors are accentuated during the crossing of ecological barriers such as the Gulf of Mexico. Although much research has been performed on the central and western Gulf Coast, little is known about the stopover significance of the barrier islands of Apalachicola Bay, Florida.

 

Barrier islands of the Gulf Coast serve a critical role in the annual cycle of trans-Gulf migrants. The islands serve as the first opportunity for landing, and function as a “fire escape” for physically stressed birds. For these birds on the brink, the islands provide an opportunity to rest and replenish energy stores so that they can continue their northward migration in a timely manner.

 

Crossing the Gulf in a non-stop flight (up to 1,000 miles in 15-20 hours) is a risky endeavor, as migrants are subjected to extreme physical stress as well as unpredictable weather. Most migrants begin their Gulf crossing at night, with optimal conditions featuring clear skies and a tailwind. Once in the air, migrants rely on celestial cues and detection of the Earth’s magnetic field to navigate.

 

I am working with a team to research the importance of St. George Island, Florida, as a spring stopover site for Nearctic-Neotropical trans-Gulf migrants.

 

My field season runs from early-April to mid-May, coinciding with the peak migration period for the Gulf Coast. I have found that St. George Island is especially vital for trans-Gulf migrants during periods of stormy weather that increase the difficulty of northbound migration. During these unfavorable conditions, which include north winds and heavy precipitation, St. George Island becomes covered in glittering migrants. In contrast, during periods of favorable migration conditions, there are relatively few birds on the island.

 

During my two field seasons, I have banded over 600 Nearctic-Neotropical migrants and observed 154 bird species on the island. The vast majority of these birds were banded during a few "fallout" days, where howling north winds forced energy starved migrants onto the island in mind-boggling numbers.

 

Mist-netting provides a random sampling method of migrants on the island and allows us to assess the age class and physical condition of migrants. I use weather data to determine how local and regional weather conditions dictate the temporal variability and physical condition of migrants encountered on St. George Island.

 

Understanding the link between breeding and wintering areas of migratory species has important ecological and conservation implications. To help determine breeding and wintering origin of individuals, stable isotope analysis of feather and claw samples will be performed, the results of which will be examined in light of mist-net and transect data.  I am also determining how arrival date and physical condition of migrants is influenced by breeding and wintering latitude.

 

My colleagues at Delaware State University and I are members of the NOAA Environmental Cooperative Science Center (ECSC). We are working in collaboration with the Apalachicola National Estuarine Research Reserve (ANERR).

 

Our research will provide context for determining the importance of St. George Island as a stopover site for boreal breeding trans-Gulf migrants. The results of our study will be considered in light of a future sea level rise model for the Apalachicola region created by Dr. Lori Lester at DSU.  


Alan has worked at the Manomet bird banding lab, in Alaska with the Arctic Shorebird Demographics Network and as part of the Manomet team assessing shorebird damage from the Deepwater Horizon oil disaster. He is currently pursuing his master’s degree in Natural Resources at Delaware State University.