Ruddy Turnstone foraging. Photo credit Richard DeMay
Louisiana’s barrier islands and headland beaches provide habitats that are extremely important to numerous species of birds. When you see a large group of shorebirds feeding within the same area, you may wonder how do all these birds feed together without competing for the same resources? Each species use different foraging strategies within the various microhabitats.
A Ruddy Turnstone foraging within the wrack line (foreground) while a Dunlin (left) Red Knot (middle) and Sanderling (right) forage in the swash zone. Photo by Richard DeMay.
The intertidal macrobenthic organisms and the wrack-line invertebrate community are the main food sources for foraging shorebirds, including wintering Piping Plover. The morphology of a bird reveals what it eats and how it forages for food. Plovers, with their big eyes and short bill, capture prey on or near the surface of the substrate by sight and by running short distances. Dunlin forage in a few inches of shallow water, using their longer bills to probe the muddy substrate for small clams and aquatic invertebrates. A Ruddy Turnstone uses it squat stature, strong legs and short bill to turn over shells and sift through the wrack line in search for food . Each species pursues its preferred foods by using distinct feeding methods, which helps prevent competition among species. A healthy coastal ecosystem has a diverse and abundant benthic community, providing food for numerous species of shorebirds.
Foraging depth of different shorebirds. Image credit cbbep.org.
Currently in Louisiana, large-scale coastal restoration projects are underway to expand the rapidly shrinking barrier islands and marshes. These projects are essential for migratory birds, increasing habitat availability that would otherwise be lost, but how do these projects affect the benthic community and the numerous shorebird species that depend on the organisms for food?
This spring BTNEP conducted its third year benthic sample survey to analyze the changes within the benthic organism community before and after beach renourishment efforts along the Caminada Headland in Port Fourchon, Louisiana. Collection procedures, sample analysis and data compilation were led by Dr. Jerry McLelland, the sole proprietor of Gulf Benthic Taxonomy Assessment, LLC. Monitoring and understanding the impacts of beach restoration can help inform and assess the ecological impact for future restoration projects.
2015 Benthic Sampling Team (pictured left to right): Natalie Waters, Dr. Jerry McLelland, Jed Pitre, Richard DeMay, Delaina LeBlanc.
Richard DeMay and Natalie Waters elutriating a benthic core sample. Photo by Delaina LeBlanc.
At every sample station, several different types of samples were collected during each year’s benthic surveys. Intertidal samples were collected at each station in the mid-swash zone using a stainless steal box core. Three quantitative core samples were collected per station, approximately one meter apart. Each core sample was treated with weak formalin to anesthetize the benthic organisms and then the sample was repeatedly elutriated through a 0.5mm mesh sieve to separate the organisms from the substrate.
Jed Pitre collecting a wrack line benthic sample. Photo by Delaina LeBlanc
Three wrack line community samples were taken at every station using a 0.25 square meter quadrant. The samples were then treated with weak formalin and elutriated. One qualitative multi-habitat wrack line sample was taken per station to account for large and rare specimens. The qualitative wrack line sample was collected by pushing a kicknet along the 10-meter wrack line section. Physical data such as the air and water temperature, latitude and longitude, salinity, wind speed and cloud cover were also collected at each site.
Dr. Jerry McLelland measuring a 10 meter wrack line section before collecting the qualitative wrack sample. Photo by Delaina LeBlanc.
The samples were analyzed in the laboratory to calculate total biomass, richness, density, diversity, and the various biomass components. The conclusions to be drawn from the data after it is analyzed over time will give us further insight in establishing and implementing best management practices during coastal restoration efforts.
Check out this video to see the various foraging methods of several shorebirds species utilizing one of Louisiana’s barrier islands! Cornell Lab of Ornithology-All About Bird Biology
