Use of a Florida Gulf Coast Barrier Island by Spring Trans-Gulf Migrants and the Projected Effects of Sea Level Rise on Habitat Availability.

Barrier islands on the north coast of the Gulf of Mexico are an internationally important coastal resource. Each spring hundreds of thousands of Nearctic-Neotropical songbirds crossing the Gulf of Mexico during spring migration use these islands because they provide the first landfall for individuals following a trans-Gulf migratory route. The effects of climate change, particularly sea level rise, may negatively impact habitat availability for migrants on barrier islands. Our objectives were (1) to confirm the use of St. George Island, Florida by trans-Gulf migrants and (2) to determine whether forested stopover habitat will be available for migrants on St. George Island following sea level rise. We used avian transect data, geographic information systems, remote sensing, and simulation modelling to investigate the potential effects of three different sea level rise scenarios (0.28 m, 0.82 m, and 2 m) on habitat availability for trans-Gulf migrants. We found considerable use of the island by spring trans-Gulf migrants. Migrants were most abundant in areas with low elevation, high canopy height, and high coverage of forests and scrub/shrub. A substantial percentage of forest (44%) will be lost by 2100 assuming moderate sea level rise (0.82 m). Thus, as sea level rise progresses, less forests will be available for migrants during stopover. Many migratory bird species' populations are declining, and degradation of barrier island stopover habitat may further increase the cost of migration for many individuals. To preserve this coastal resource, conservation and wise management of migratory stopover areas, especially near ecological barriers like the Gulf of Mexico, will be essential as sea levels rise

Transects on St. George Island, Florida, USA.

<p>Transects were conducted at two study sites: (A) Nick’s Hole and (B) Unit 4. Observers detected migrants by sight and/or sound while walking nine transects: one in Nick’s Hole and eight in Unit 4. Avian abundance was calculated as number of migrants observed divided by transect length in each cell.</p

Environmental Parameters for Sea Level Affecting Marshes Model.

<p>Environmental Parameters for Sea Level Affecting Marshes Model.</p

Most Common Nearctic-Neotropical Migrant Species Detected Visually or Audibly by Observers during Transects.

<p>Most Common Nearctic-Neotropical Migrant Species Detected Visually or Audibly by Observers during Transects.</p

Sea Level Affecting Marshes Model (SLAMM 6.0).

<p>Sea Level Affecting Marshes Model (SLAMM 6.0).</p

Results of Sea Level Affecting Marshes Model (SLAMM 6).

<p>The SLAMM simulation modeling results for 2 m sea level rise scenario predict that 98% of palustrine forested area will be lost between 2009 and 2100.</p

Best Fit Model Selection.

<p>Best Fit Model Selection.</p

Comparison of Habitat Characteristics among Sites.

<p>Comparison of Habitat Characteristics among Sites.</p

Habitat Maps.

<p>Habitat maps of sites were created using the supervised classification method on WorldView-2 satellite imagery. Percent habitat type coverage was calculated for each cell and compared to avian abundance.</p