Every three years (give or take over the decades) since 1972, biologists and volunteers up and down the coast have counted waterbird nests as part of the North Carolina colonial waterbird census. The census includes egrets, herons, ibis, pelicans, terns and other coastal waterbirds, and it encompasses hundreds of sites. Coordinated by the North Carolina Wildlife Resources Commission (WRC) and assisted by Audubon North Carolina, it is a large undertaking that provides valuable information for wildlife managers and other decision-makers.
The census began in the early 1970s when Dr. James Parnell and Dr. Robert Soots, both biology professors, began to study the development of plant communities on man-made dredge material islands. Through this work, they quickly realized that the islands were important to nesting waterbirds, and that many man-made changes were likely to impact coastal birds. But, without information about statewide populations of these species, they could not evaluate these impacts. So, they began work to locate and census all nesting waterbirds in the state through aerial surveys to find nesting sites, and on-the-ground counts to record exact numbers of nests. That work continues today.
The numbers collected by tiptoeing around nests, peering through thickets of brambles, and braving the cries, swoops and poops of angry birds illuminate the ups and downs of our state's waterbird populations through more than 40 years. The census depicts a low of only 30 Brown Pelican nests in 1972, the year the EPA banned DDT, to over 5,150 pairs in 2011, as the species recovered from the pesticide, which weakened its eggshells and prevented parent birds from successfully incubating. It shows declines in Common Tern and Black Skimmer numbers today, allowing biologists to look more closely at what may be affecting their populations.
This year, the census is on again. The timing of a census that aims to count every colonial waterbird in the state is a delicate task. Colonial species--those that nest in groups--tend to be synchronous, meaning members of a colony tend to begin nesting at the same time. However, with multiple colonies and multiple species within many colonies, it's important to count at the right time: when the greatest number of nests are active and before most of the eggs start to hatch, so the chicks are not disturbed by counting humans.
Early May saw the counting of heron and egrets. With the exception of Cattle Egrets, which stubbornly start later than other wading birds, these are the first waterbirds birds to nest in North Carolina. Though some always have chicks when counting time comes, they are young enough that they won't leap out of their nests during the census. Wading bird chicks need to be in their nests where their parents can feed them, and they won't be flooded out by a high tide.
Battery Island usually hosts the largest wading bird colony in the state, and this year was no disappointment. After a hiatus from the island, White Ibis returned in 2012, and this was the first census year since their return. The count found 8,049 nests, with some 500 or more latecomers still constructing nests (only nests with eggs count for the census records). More than 400 pairs of other wading birds--Great Egret, Tricolored Heron, Little Blue Heron, Black-crowned Night Heron--were also nesting on Battery Island. All counts aren't in yet, but it's likely that Battery Island will account for 60-70% of the state's White Ibis.
Later in May, colonies of Royal and Sandwich Terns have formed, and these are counted next, along with Least Terns and, a little later, Black Skimmers. On Audubon's islands on the Cape Fear River, over 2,800 Royal Terns and over 1,000 Sandwich Terns are nesting this year. In a good year, Audubon sanctuaries will hold over 20% of the state's Royal and Sandwich Terns.
The census continues into June, as remaining tern colonies will be counted in the coming weeks. In all, more than 70,000 nests are expected to be counted. By summer's end, the final tallies will be summarized in the WRC's database, and we will know a little more about how coastal birds are faring in North Carolina.