I was puzzled. We were anchored at TTSA (Trinidad and Tobago Sailing Association) and almost every night when we returned by dingy to our boat, there would be a low flying group of shorebirds with a very distinctive hoarse barking call. It took a while before we were able to finally catch a view of the birds under a light to see a flock of Black Skimmers.
You do not need to be an ornithologist to recognize a black skimmer; their unusual voice, bill, and feeding behavior make them truly unique. Their most distinctive feature is their long bill which has a lower mandible about one inch longer than the upper. The bill is bright red with a black tip that looks like it has been dipped in black paint. Their bill is laterally (side to side) compressed to cut through water like a knife.
Skimmers have earned their name because of the way they feed. They drop the lower mandible to slice through the surface as they fly inches above the water. When a skimmer encounters food, it will quickly close its mouth, capturing the meal. Black skimmers catch most of their food (small fish, small crustaceans and shrimp) in this manner. Fishing by touch allows skimmers to be crepuscular (dawn and dusk) and nocturnal feeders.
Skimmers forage mainly in waters of bays, estuaries and lagoons but also utilize rivers, and salt marsh pools, creeks, and ditches; such habitats tend to concentrate small fish.
Adults in breeding plumage are black above and white below with a white tail. Non-breeding adults have paler and browner upperparts, and a white collar. Immature birds have brown upperparts with white feather tips and fringes. Tail is short and white with longer central feathers. Their webbed feet are bright orange. Skimmers are the only bird to have a vertical slit in the pupil which assists in gathering light for their crepuscular and nocturnal habits. Their dark eye is within their dark head, giving the skimmers a somewhat eyeless appearance. Adult skimmers are sexually dimorphic (difference between male and female), the male being approximately one-fourth larger than the female.
The other two, rather similar, species besides the Black Skimmer, are the African Skimmer and the Indian Skimmer. All use the same unusual feeding technique. Visitors from North America may be familiar with this bird, the only American Skimmer, because it breeds as far north as Massachusetts to South America on the Atlantic side. On the Pacific side, they breed from the California through central and northern South American coast. They winter in the warmer waters.
In the Caribbean they can be seen as far east as the Virgin Islands and Grenada. In Trinidad we have seen them near Chaguaramas and on the west coast during the summer months.
Black Skimmers are highly social birds, flocking outside the breeding season, and nesting in colonies on beaches and islands, often with aggressive gulls and terns that offer protection from predators. Colony sizes are highly variable, ranging from single pairs to many thousands on the Gulf Coast. The nest is a shallow scrape on an open beach, shell bank, sandbar, and occasionally, a gravel roof. The three to five white, buff, or blue-green eggs are perfectly camouflaged on the beach. During nest building, mates take turns scraping, using exaggerated sand-kicking posture (neck, head, bill, and tail elevated) with alternate foot strokes that throw sand backwards.
Birds rotate in the scrape to create a saucer-shaped depression, similar to resting scrapes used throughout the year.
The chicks are incubated and fed by both parents, and the eggs hatch in about three weeks. They eat regurgitated fish and crustaceans dropped on the ground. Since chicks begin life with mandibles of the same length, they are able to retrieve this food; the lower mandible begins to elongate when chicks are nearly grown. The young birds begin to fly in about 24 days.
Habitat loss from coastal development has reduced the number of suitable nesting spots for black skimmers. Fortunately, the birds have successfully nested on spoil islands and along causeways. On busy beaches, the birds and their nests are extremely vulnerable to human disturbance and to predation by domestic dogs, raccoons and laughing gulls.
Devi Sharp is a retired wildlife biologist and is exploring the birds of the Caribbean with her husband, Hunter on their sailboat Arctic Tern.
Chuck Shipley is a former professor of computer science and an avid amateur photographer. Chuck and his wife Barbara live aboard their trawler Tusen Takk II in the Caribbean.