Not Today Ghost Crab!
Least Terns form colonies on bare or sparsely vegetated sand or dried mudflats along coasts and rivers. They typically form nests on sand or shell beaches just above the high-tide level. Colonies can return to the same beach year after year, but this can be influenced by changes in vegetation cover, predators, human activities, floods, and colony size. Due to a shortage of suitable natural habitat, some Least Terns have begun forming nests in agricultural fields, parking lots, bare land associated with airports, and flat, graveled rooftops. Audubon Florida has recorded 26 active rooftops with more than 650 Least Terns across the Tampa Bay region, and we are only half way into this year’s nesting season (1).
Least Terns begin displaying courtship behavior 2-3 weeks in April and May, and a second wave of courtship may occur in June and early July. First eggs appear late April to mid-May. Hatching begins about 20 days later. Once eggs are laid they will incubate 19 - 25 days. Male and females share duties throughout nesting and chick-rearing, with the female doing about 80% of the incubation (2).
After hatching, chicks seek shade or shelter while the adults feed, often taking refuge in vegetation or nearby debris. Chicks leave the nest when they are only 2 days old, and take their first flight at about 20 days.
Eggs, chicks, and adults are vulnerable to a variety of predators. Reported predators include Fish Crow, American Crow, Common Raven, Boat-tailed Grackle, gulls, Great Blue Heron, Black-crowned Night Heron, Ruddy Turnstone, Sanderling, Great Horned Owl, Peregrine Falcon, American Kestrel, Northern Harrier, Loggerhead Shrike, red fox, coyote, raccoon, skunks, opossum, feral hogs, ghost crabs, and human pets such as dogs and cats. There was even a report of a Black Skimmer picking up chicks in Mississippi while skimming through colonies (2,3).
While recently photographing Least Terns in St. Augustine I observed a ghost crab (also called sand crabs) raiding Least Tern nests. The crab went from nest to nest in search of eggs or chicks, but fortunately for the birds it was too early in the season for the crab to have any luck. That will likely change as nesting season progresses.
Least Tern not too happy with a Ghost Crab. Photographed with the Nikon Z9 and Nikkor Z 800mm f/6.3 VR lens on a gimbal head mounted to a Skimmer Ground Pod. ISO 400, f/8.0, 1/2500 sec.
Least Tern defending its territory. Photographed with the Nikon Z9 and Nikkor Z 800mm f/6.3 VR lens on a gimbal head mounted to a Skimmer Ground Pod. ISO 160, f/8.0, 1/1600 sec.
Least Terns vs. Ghost Crab. Another Least Tern has joined the fracas. Photographed with the Nikon Z9 and Nikkor Z 800mm f/6.3 VR lens on a gimbal head mounted to a Skimmer Ground Pod. ISO 200, f/8.0, 1/1600 sec.
Reinforcements arriving! About this time there were about a half dozen terns vs this crab. Photographed with the Nikon Z9 and Nikkor Z 800mm f/6.3 VR lens on a gimbal head mounted to a Skimmer Ground Pod. ISO 400, f/8.0, 1/2500 sec.
Least Tern defending its territory from an invading Ghost Crab. Photographed with the Nikon Z9 and Nikkor Z 800mm f/6.3 VR lens on a gimbal head mounted to a Skimmer Ground Pod. ISO 400, f/8.0, 1/2500 sec.
Standoff. Photographed with the Nikon Z9 and Nikkor Z 800mm f/6.3 VR lens on a gimbal head mounted to a Skimmer Ground Pod. ISO 250, f/8.0, 1/2000 sec.
The crab incursion into Least Tern territory was unsuccessful. With numbers on their side, the Least Terns were able to drive the Ghost Crab back to his burrow where he will certainly regroup and launch another assault. But on this day, the Least Terns won! Not today Ghost Crab!
Sources:
Cook, K. Sea and shorebirds flock to Tampa Bay region roofs. Audubon Florida. https://fl.audubon.org/news/sea-and-shorebirds-flock-tampa-bay-region-roofs?fbclid=IwAR2P3QACJHwghBX6xJyWOTBsJqeECIOzhPkliwJ8tHVXtAC_RYALb-weOxQ, accessed 24 May 23.
Thompson, B. C., J. A. Jackson, J. Burger, L. A. Hill, E. M. Kirsch, and J. L. Atwood (2020). Least Tern (Sternula antillarum), version 1.0. In Birds of the World (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.leater1.01
Jackson, J. A., B. J. Schardien and C. D. Cooley. (1979c). Dispersion, phenology, and population sizes of nesting colonial seabirds on the Mississippi Gulf coast. Colonial Waterbirds 3:145-155.
