Another entry in Abby’s Birdbrained Summer. Abby, the summer communication intern for the Coast Office of Audubon North Carolina, is visiting sites with Audubon’s field staff and our community of volunteers. After she goes into the field, she’ll post blogs detailing her experiences.
My most recent field work with Audubon was checking oystercatcher nests on Masonboro Island. I walked the island with Zach, one of the coastal office’s biological technicians. Since the barrier island is eight miles long, we were dropped off via boat at the north end and picked up at the south end six hours later. This is the first year that American Oystercatcher breeding has been monitored so closely on Masonboro Island.
The island was desolate and vacant when we arrived. Masonboro Island has an interesting topography; according to the North Carolina Coastal Reserve, “the habitats found within this site include subtidal soft bottoms, tidal flats, hard surfaces, salt marshes, shrub thicket, maritime forest, dredge spoil areas, grasslands, ocean beach, and sand dunes.” There are also three dead trees near the shore, which is unusual for a barrier island. Walking along the beach, Zach showed me evidence that Masonboro Island is actually moving towards the mainland. The Atlantic shoreline has retreated to an area that was formerly marsh. Sand had washed over Spartina and other marsh vegetation.
Masonboro Island has an interesting variety of challenges for nesting shorebirds. Although the undeveloped island is only accessible by boat, it is used heavily by surfers, campers, and party-goers during summer months. Human disturbances such as lighting fireworks on the beach can cause birds to abandon their nests, and people can unintentionally trample a nest if they are not careful, or flush birds off their nests. That's why it's so important to obey posted signs. Additionally, Masonboro Island has natural predators including raccoons and foxes that eat eggs and chicks. Since the island is so narrow, it is particularly susceptible to overwash when there are storms or unusually high high tides.
Zach had programmed coordinates of previous nests and scrapes in his GPS, which considerably expedited our job. When we came into a territory where there was no nest marked, it was much harder. A pair started piping at us and behaving protectively as soon as we entered their territory, so Zach suspected that they had re-nested (the pair had a previous nest that failed). The oystercatchers' nests are almost indistinguishable from the surrounding sand and shells unless you know what you are looking for. We looked for a long time before finding oystercatcher footprints leading to a nest with three eggs. Zach marked it with his GPS unit so it could be checked again next time.
In addition to the oystercatchers, we saw two colonies of nesting Least Terns and a number of Wilson’s Plover nests. Zach likes the Wilson’s Plovers because they run along the beach; he said sometimes it seems like they follow him around the island. I noticed that they are great architects. Their nests always had pretty shells and were near vegetation that looked like miniature palm trees.
By the time we rounded the south end of the island, I was exhausted. We found six nests; many former nests had failed. The next time Zach went, he said that weather from Tropical Storm Andrea wiped out many of the nests we found, but there was a hatchling in one of the nests. It is growing late in the season, so the oystercatchers will either re-nest soon, or spend the rest of the summer moping on the beach. It is remarkable how the birds grieve the loss of a nest, but continue to try to produce offspring.