Sea Birds on Louisiana Barrier Islands

           Field of dreams? We’ve built Barrier Islands, so where are the birds?

 After Katrina, most people in Louisiana know the value of barrier islands and coastal wetlands for storm protection.  However, few people are aware of the importance of barrier islands to Louisiana’s nesting seabirds.  Brown Pelicans are just one example of birds dependent on barrier islands for nesting.  Pelicans were driven to extinction in Louisiana about five decades ago due to pesticide, but reintroduced birds from Florida made a rapid recovery.  Unfortunately, today the biggest threat to pelicans is not man-made poisons but the loss of the coastal islands that are essential nesting habitat.  Pelicans and other seabirds like Black Skimmers, several terns, several species of gull, and a host of other birds benefit from the restoration of barrier islands. 

Barrier island restoration is shockingly expensive because it involves pumping dredged sand to recreate islands.  Several restored islands look like great seabird habitat, yet they don’t have nesting colonies.  This isn’t a field of dreams; we built it yet the birds didn’t come.  Cecilia Leumas, an RNR graduate student, is working with me to understand why the birds have not responded.  Our work is focused on one of the bigger restorations projects, namely Trinity Island.  This island was split into two islands by storms that washed a mile wide hole in the center.  This middle segment of the island was recreated in a major coastal project, but the seabirds are not nesting on the island. 

We have three explanations for why seabirds have not come back.  The first idea is no-new-tricks hypothesis.  The idea is that the birds are just not good at trying new things, so while Trinity Island may provide good habitat but the birds are simply slow to get around to testing the island as a potential nesting area.  Cecilia and I are focused on two species of seabirds – Royal Terns and Black Skimmers.  There is some concern about the population status of both species, though they are not in any immediate treat of local extinction.  The basic idea for the no-new-tricks hypothesis is that seabirds return to prior nesting sites, start nesting there first, then the later nesters are attracted to those sites and unlikely to pioneer to new areas.  In such cases, biologists have borrowed an age old idea from duck hunters – they try and attract birds with decoys and calls.  No, we are not talking about a spread of greenhead decoys, we are talking about a spread of tern and skimmer decoys on a nice plot of beachside sand.  The idea is to use decoys that appear to be a new nesting colony so that seabirds looking for a nest site are enticed to nest in a new area.  Sounds wild, but it has worked for Puffins in main and Terns in the both the Midwest and on the Pacific Coast. 

Cabellas doesn’t sell skimmer or tern decoys, so Cecilia learned the art of decoy making.  She cast and hand painted over 300 decoys, which she then put out on 8 potential colony sites on the island in the spring.  Cecilia spent the summer doing observations on those decoy plots to see if the decoys attracted the real thing.  Plenty of passing birds appeared very interested, but we did not attract any skimmers or Royal terns to nest on the plots. 

A second hypothesis to explain the lack of nesting seabirds on Trinity is nest predation.  Perhaps seabirds attempt to nest on the island but predators destroy the nests or cause so much disturbance that the parents abandon the new colony quite rapidly.  We know that raccoons are all over the island.  They are brazen raccoons, regularly venturing into our field camp looking for dinner even when we are sitting right by the campfire.  To test the predation hypothesis we took half of the 8 potential colony sites described above and enclosed them in 300 feet of wire fence to exclude mammalian predators.  Yes, it was a ton of fun to dig the 2,400 feet of trench to partially burry the 4 foot fence so that the coons wouldn’t dig under the fence.  We hoped the fence would exclude the abundant raccoons and allow birds nesting inside the fence to hatch their eggs. 

Unfortunately, no skimmers or Royal Terns nested on fences or unfenced plots, but we think the fences will be successful at excluding predators.  We did lots of track surveys and never found evidence of predators inside the fenced sites.  In contrast, predator tracks cris-crossed the non-fenced sites that were paired with each fenced plot.  We had Least Terns, another rare seabird, nest inside some of our predator fences and ¾ of those nests hatched.  In contrast, we found almost 50 Least Tern nest outside of our fenced plots, but not one of those nests hatched; predators destroyed the vast majority of the eggs. 

A third explanation for the lack of nesting seabirds on the restored islands is that the islands provide poor habitat.  This idea is being tested by collaborators at Nicholls State University.  Dr. Aaron Pierce and his students are quantifying habitat on islands that have seabird nesting colonies as well as the islands with no nests.  Likewise, they are monitoring nest success to find what makes for good habitat. 

The goal of this unorthodox research program is to be able to guide restoration projects so we can increase wildlife benefits while we protect the fragile Louisiana coastline.  Louisiana accounts for up to 75 % of the totals US population of some breeding seabirds, such as Sandwich Terns.  So the breeding numbers in this state represent the majority of the birds in the country.