Jacob Loyacano
I received an email from a graduate student at FSU to go on a trip to Caladesi Island State park to collect samples for their PhD work on Eastern Diamondback Rattlesnakes (Crotalus adamanteus). We would be camping on an island looking for Rattlesnakes. What could be more fun!? In order to get to Caladesi Island State Park we first needed to drive to Honeymoon Island State Park and then take a boat from there to get to Caladesi Island State Park. Upon our arrival at Honeymoon Island State Park I noticed a flock of Black Skimmers all standing on the shore, all facing the same direction. I asked if I could stop to photograph them and was quickly reminded that this was a trip for snakes not birds. We then boarded the ferry to take us to Caladesi Island State Park. On the boat ride over an Osprey flew by with a freshly caught fish. There were Double –crested Cormorants paddling around in the water. Another student even spotted a Roseate Spoonbill wading in the shallows near the mangroves. And I could still see the Black Skimmers all lined up on the distant shore. We arrived on Caladesi, set up camp and then the hunt for Eastern Diamondback Rattlesnakes began. Within an hour I had checked a small area on the interior of the Island and found a baby ratttlesnake. We bagged it up and continued hunting. We hunted for a couple more hours with no luck so I decided to take a break when I saw a wooden bench located conveniently on the beach facing the ocean. As soon as I sat down I noticed two dark colored birds with bright orange bills right in front of me. The Skimmers! I was overjoyed that another opportunity to photograph them had presented itself to me. However, I looked closer at the birds. Dark on top, white below, orange bill, but they were taller than Black Skimmers, with longer legs, and walking down the beach shoving their bills into the sand. American Oystercatcher! My excitement rose even more.
I had only ever seen or heard of American Oystercatchers (Haematopus palliatus) (Image 1) in our Ornithology Lab session on order Charadriiformes. From the moment I saw the specimen in lab I had wondered why a boy who grew up living on the beaches of South Florida had never seen this attractive and interesting shorebird. Well my question did not go unanswered long. Upon consulting National Geographic’s Field Guide to the Birds of North America, the range of the American Oystercatcher extends, on the east coast, all the way north to Cape Sable Island, Nova Scotia south to about St. Lucie County Florida; two counties north of where I grew up. However, Caladesi Island State Park was on the West Coast of Florida and I was well within the American Oystercatcher’s known range.
As oystercatchers are among the most attractive looking shorebirds, I quickly threw down my backpack, whipped out my camera, attached my telephoto lens and began snapping photos. First, I began from the bench, close to the sand dunes and far from the shoreline where the birds were. Then I slowly approached the birds trying the get as close as possible without scaring them. I noticed that there was a pattern to their hunt. They would shove their bills into the sand quickly and then continue walking southward down the beach. When I picked up on this I decided the best way to get a good picture was to go about 25 yards south of the birds and lay down on my stomach and let the birds come to me. They slowly continued south toward me, being followed by a Willet. After many investigatory pecks into the sand, one of the American Oystercatchers finally pulled out a small bivalve and quickly ran to higher ground out of the tidal zone and away from the other oystercatcher and Willet. The American Oystercatcher poked and prodded with its strong thick bill and eventually opened the shell, ate its catch and continued hunting down the shoreline. Other people walking the beach noticed me lying there on my stomach, camera in hand and said, “Well that is a pretty bird.” I don’t think they would have even noticed the oystercatchers had I not been there. The American Oystercatchers came closer and closer. I kept taking more and more pictures. When they were within about 15 feet of me I noticed their behaviors change. They still continued to hunt, however after every few prods into the sand they would freeze and stare at me, not quite sure what I was or if I was a threat or not. Once one of the oystercatchers was well within 10 feet of me the hunt stopped. No more prodding the sand. Its entire focus was on watching me. Slowly it approached even closer and then all of a sudden one took off in a full on sprint past me and into deeper water. Once it was well past me the American Oystercatcher came back on shore and continued hunting. After this, the other oystercatcher didn’t seem to mind me as much. It continued hunting right by my side although it was much more wary than it was when it was further away from me. Soon they were both well past me so I stood up and just watched them from a distance again. They continued hunting showing no new behavior for about ten minutes. Then I could see further down the beach an overweight Homo sapien running right down the shoreline. As far as he was concerned it was his beach, no regard for other creatures that inhabit it. He ran right through the path of the American Oystercatchers when he could have quite easily gone around them. While his ignorance and lack of respect deeply bothered me, this act did give way to new behavior to observe. When the man got close enough the oystercatchers took to the air, flying over the water and began calling a high pitched wheep-wheep-wheep call. I thought it was a little strange because the man ran by relatively quickly and they could have easily landed back in the same spot in less than thirty seconds. Instead they continued flying up and down the coast, but over the water, and calling repeatedly for about five minutes. They were only flying up and down about a fifty yard stretch of coastline. Their flight allowed me to see the whites of their secondaries and tail coverts making this bird seem more and more attractive. Eventually they landed to continue their hunt for food (Image 2) and I left and continue my hunt for rattlesnakes.
After returning home from Caladesi Island I was curious about the American Oystercatcher so I researched more about them. One of the most common words in the titles of literature I was reviewing was “kleptoparasitism.” I had no idea what this word meant but eventually ending up clicking on an article written by Joanne Tuckwell and Erica Nol that clarified things for me. I found that kleptoparasitism is a form of feeding where an animal takes the food that another animal has caught. Immediately I realized that I had witnessed an effort to avoid kleptoparasitism when I watched the American Oystercatcher take its catch away from the other birds. Tuckwell and Nol’s article states that other species of bird as well as other American Oystercatchers will try to take food that an American Oystercatcher has caught (See figure 2).
Another study that I found related to my observation of the American Oystercatchers was by Kimberly A. Peters and David L. Otis. In this study they observed the vigilance of American Oystercatchers when certain predators or human disturbances are around. Peters and Otis found that American Oystercatcher spent more time watching for predators when there was an increase in boat activity, or when more Northern Harriers and Osprey were around. This relates back to my observation of when the birds came close to me lying in the sand. They spent less time hunting and more time making sure that I was not going to attack them. Also, I think their seemingly excessive caution after the runner scared them and could have also been due to Ospreys and Northern Harriers in the area. I saw both of these predators on Caladesi during my trip.
I began to wonder if these American Oystercatchers were only out on Caladesi Island for food or if maybe they used the Island as a nesting area. This brought me to a study done in North Carolina by Conor P. McGowan and colleagues. These authors report that barrier islands are traditional breeding areas of American Oystercatchers. Caladesi is a barrier Island off the west coast of Florida near Clearwater. It is very possible that the oystercatchers do use Caladesi as a site for reproduction. What I found interesting about McGowan’s paper was that there has been a change in reproduction sites used by American Oystercatcher, at least in North Carolina. McGowan found that more and more American Oystercatchers have started using river islands instead of barrier island nest sites and that the American Oystercatchers were having more success raising their chicks on these river islands (Figure 1). He thinks that this is because of an increase in mammalian predation on nests on barrier islands. Continuing my research on American Oystercatcher reproductive success led me to another study; this time from Cumberland Island National Seashore in Georgia. John Sabine and colleagues’ paper provided much insight to the hardships American Oystercatchers have been having in their reproductive success. First of all Cumberland Island is unique in that it has a wild population of horses. Horses were found to be one of the causes of nest failure for shorebirds because they can trample the eggs. Other, more significant, causes of nest failure were predation by bobcats, raccoons and even people! During this study the nest were monitored by video throughout the nesting season and a young boy was caught on tape picking up an egg of an American Oystercatcher. From this study the main cause of reproductive failure was due to mammals although abiotic factors such as tidal over wash also played a role as well as predation by American Crows and Ghost Crabs. Another study done by McGowan and colleagues found that increased human recreation may affect American Oystercatcher reproductive success negatively. For example, in their study they found that ATVs had run had run over chicks in nest sites.
Works Cited
Dunn, J. L., and J. K. Alderfer. National Geographic Field Guide to the Birds of North America. Washington, D.C.: National Geographic (2006): 160. Print.
Mcgowan, C. P., and Simons T. R. “Effects Of Human Recreation On The Incubation Behavior Of American Oystercatchers.” The Wilson Journal of Ornithology 118.4 (2006): 485-93. Print. DOI: 10.1676/05-084.1
This article shows how American Oystercatchers and their reproductive success can be affected by human recreation.
Mcgowan, C. P., Simons T. R., Golder W., and Cordes J. “A Comparison of American Oystercatcher Reproductive Success on Barrier Beach and River Island Habitats in Coastal North Carolina.” Waterbirds 28.2 (2005): 150-55. Print. DOI: 10.1675/1524-4695(2005)028[0150:ACOAOR]2.0.CO;2
This article shows a change in nest site from traditional barrier island nest sites to river island nest sites.
Peters, K. A., and Otis D. L. “Using the Risk-Disturbance Hypothesis To Assess The Relative Effects Of Human Disturbance And Predation Risk On Foraging American Oystercatchers.” The Condor 107.3 (2005): 716. Print. DOI: 10.1650/0010-5422(2005)107[0716:UTRHTA]2.0.CO;2
This article displays an increase in vigilance when predators or human disturbances are present.
Sabine, J. B., Schweitzer, S. H., and Meyers J. M. “Nest Fate and Productivity of American Oystercatchers, Cumberland Island National Seashore, Georgia.” Waterbirds 29.3 (2006): 308-14. Print. DOI: 10.1675/1524-4695(2006)29[308:NFAPOA]2.0.CO;2
This article shows factors that affect reproductive success of American Oystercatcher on Cumberland Island National Seashore.
Tuckwell, J., and Nol, E. “Intra- and Inter-specific Interactions of Foraging American Oystercatchers on an Oyster Bed.” Canadian Journal of Zoology 75.2 (1997): 182-87. Print. DOI: 10.1139/z97-025
This article shows the interactions that American Oystercatchers have with other species as well as other American Oystercatchers when feeding.
Image 1. American Oystercatcher
Image 2. American Oystercatchers foraging.
Figure 1. The figure above, from McGowan’s et al. (2005) shows a higher daily nest content survival for river islands than for traditional nest sites on barrier islands.
Figure 2. This figure from Tuckwell and Nol (1997) shows observations of intra-specific kleptoparasitism between adults and immature American Oystercatchers.
FSU ornithology 
