A few months ago I attended the monthly Atlanta Aubdon Society meeting which was on the role of the Georgia coast and shorebird conservation. The talk was given by Brad Winn from Management center for conservation, Tim Keyes from the GeorgiaDepartment of Natural Resources and Abby Sterling from the University of Georgia.
Abby started the talk by giving a general overview of the habitat on the coast and the life history of shorebirds with a particular focus on Oystercatcher and Wilson’s plovers, the birds she did her doctoral studies on. The beaches on the Georgia coast are dynamic habitats as they do not have engineering typically found on beaches that hinder the natural movement of sand. These beaches are found on a chain of barrier islands that are formed from sediments that drain from the whole state. Shorebirds (at least these two species) lay their eggs in scrapes in the sand or sometimes in a horseshoe crab shells or flowers. The two species did not have an overlap of their nesting habitat which is important for conservation. The nests are typically hard to find and Abby said she had to follow the tracks of birds to find the nets. She monitored nests until they were successful or unsuccessful. This took about 28 days for Wilsons plovers. The chicks get fed by the parents. Abby would catch and band the birds and give the chicks a unique color band combination of ease of field identification.
Both parents protect the eggs and try to keep them cool in the hot Georiga summer. They also will do broken wing displays in which they pretend to have a broken wing in order to draw predators away. Ghost crabs, other birds, coyotes, and raccoons all prey on the young and eggs. The last natural threat the eggs face is washing away.
There are new emergent threats that the birds face as well. These included increased human recreation, driving on the beach, walking on the beach, and climate change which increases sea level and storm surge which can increase the odds that the eggs wash away.
In Georgia, we see high habitat quality but the low success of fledging young compared to other states is of concern. There is a mismatch between selected sites and the most successful sites. This could be due to an ecological trap in which the landscape doesn’t give the birds good clues as to what the best nesting sites are. This could be a result of climate change, more coyotes in Georgia, or the dynamic habitat. However, if you quantify shoreline changes the tidal overwash remains the same. Additionally Wilson’s Plovers, the more rain in a season the poorer the chicks do but high tides, due to the resources they provide, led to healthy chicks.
Tim Keyes then talked about the times of the year in which shorebirds undergo certain activities. He started out by saying that June is the worst month to go breeding on the coast because the arctic birds are in the Arctic and only local breeders are present. The breeding season takes place from March to August, fall migration takes place from July to October, wintering birds can be found from November to February, and spring migration takes place from March to June. Wintering birds can be found in the largest numbers, in some areas the average number of birds on the beach can be 60,000.
The amount of birds is not determined by geographic range because the birds are able to fly incredibly long distances. Rather, the birds look for food resources, remote beaches for nesting (reduced predation of nests), and prefer an area with a large variability between sea level at high tide and low tide (6 -10 feet in the GA barrier islands is the average, while other places average 2 -4 feet). It’s worth noting that most of the salt marshes on the east coast fit this description but Georgia differs in one key aspect, lack of development.
Birds like the Piping Plover (Charadrius melodus), which has large populations decline in the great lakes nesting pairs, down to under 70 nesting pairs, disproportionately nest on the GA barrier islands. Over 60% of these nesting pairs will overwinter on the barrier islands. Over 200 birds from these populations passed through the area. A study found that the body weights and survival of those that overwintered in Georgia was higher than those that overwintered in the Carolinas.
Other species, like the American Oystercatcher (Haematopus palliatus) prefer to nest on the Georiga coast and overwinter in other locations. Though an aerial survey of the area found that 800 to 1200 birds may overwinter. During the nesting season, based on sight surveyrs, there are about 120 nesting pairs. Some biologists state that you can sex these birds based on the size of their eye flecks but that is still up for debate, though it has been shown to have some genetic backing. All Georgia banded Oystercatcher received red bands to help identify them at later dates. The birds have been seen wintering as far away as Central America.