Who's hunting in the wetlands?

Faraaz Abdool writes about the birds that you might see in wetlands all around Tobago. Let’s learn to recognize them and allow them to co-exist in our space. All photos by Faraaz Abdool

 

On an island as small as Tobago, inland bodies of water are not exactly common. It seems like somewhat of a reversal for a land mass wholly surrounded by water to then encase other bodies  of water. Whether there is a connection to the surrounding ocean or not, inland waterways support unique and essential ecosystems. The gentle topography of southwest Tobago allows water rushing down from the central hills to come to a relaxed pace, depositing sediment and widening passages en route to the ocean. While we tend to associate webbed feet with water – ducks, gulls, and terns – there are countless other species that rely heavily on the presence and flow of water through the land. 

 

After spearing a fish, an Anhinga tosses it into the air to position it for swallowing.

The Black-crowned Night-Heron is a secretive resident of several inland waterways within southwest Tobago.

 

Living along these waterways are a selection of predatory birds. Sly, stealthy and patient, herons come in a variety of sizes and forms, but all employ the same sit-and-wait technique. These slender birds lack the powerful feet of aerial predators like hawks; they don’t even have a hooked bill! At first glance herons may seem somewhat benign. Their secret weapon is a spring-loaded neck attached to a razor-sharp bill. Forward-facing eyes ensure that they can lock on to a target. Once prey meanders within reach, the spearfisher pulls the trigger and within a split second, impalement occurs. These voracious predators consume all manner of aquatic life, whether fish or frog. Opportunistic, herons will not pass the chance to snack on a snake or mouse.

 

A Little Blue Heron hunts obsessively at the crack of dawn.

Green Herons are often too preoccupied with hunting to bother about human observers.

The Great Blue Heron is a big bird on Tobago!

The Green Heron is the smallest of these and the most common on Tobago. Though richly colored he can be surprisingly difficult to see as he stands motionless, hiding in plain sight. Green Herons have long, prehensile toes which can grasp firmly onto low-hanging vegetation. Bird-brained they are not! They have been documented using various forms of bait as fishing lures. Tool use has long been considered a phenomenon unique to mammals, but birds like the diminutive Green Heron are helping us to change that.

 

Slightly larger but built in very much the same way is the Little Blue Heron. As its name implies, it is mostly blue with a slight wash of purple on its neck. Young Little Blue Herons have not a speck of blue on them; they are stark white! These youngsters could easily be mistaken for the closely related all-white egrets. However, at all life stages, Little Blue Herons have green legs!

 

Similarly sized and perhaps one of the most sinuous of all herons is the Tricolored Heron. These long-necked and slender-billed herons have an interesting hunting strategy. They open their wings while standing in water to create a large shadow. In a loose arc they daintily walk holding this position, carefully ensuring that their head remains concealed beneath one of the wings. From this near-sideways launchpad, they are almost always successful in an attack.

 

Generally, the dimensions of a bird’s bill are a good indication of its diet. For the large-eyed and somewhat spooky looking night-herons lurking in the dark recesses of overhanging branches, a stout bill confirms a brutal procedure. Crustaceans form a significant portion of their diet, and these powerful bills can be used as hammers. As their name implies, both species of night-heron in southwest Tobago are more active during hours of darkness. The Black-crowned Night-Heron is less encountered than the more widespread Yellow-crowned Night-Heron. As powerful and intimidating as these predators may be, they are dwarfed in the presence of a Great Blue Heron.

 

Great Blue Herons are stately, multicolored birds that stand more than three feet tall. They are also ambush predators, and their preferred method of prey dispatch is impalement. These large herons are well-known for their incredible appetite and penchant for swallowing anything that can fit down their expandable throats.

 

Another impaler with a decidedly different approach is the Anhinga. Unrelated to herons, Anhingas prefer to stalk prey underwater. Equipped with wettable plumage and dense bones, these large birds can easily achieve neutral buoyancy and in water are typically seen cruising with only serpentine neck and head visible. It’s obvious how they came to be called “snakebird.” Anhingas typically inhabit shallow, clear water as they hunt by sight and are unable to spend continuous time submerged. Anhingas are unable to thermoregulate and depend on periodic sunbathing sessions, during which they spread their wings and turn their backs to the sun.

 

The Least Grebe is the smallest member of its family, and may be underwater for half a minute in search of aquatic insects.

A pair of Common Gallinules

Apart from these large, impressive denizens of wetlands, several smaller birds occupy a niche within this ecosystem. Two species of small, plump, colorful and exceptionally long-toed birds are often seen puttering about in shallow water. Purple Gallinules and Common Gallinules resemble and are often found together. Apart from subtle physical differences, they are best distinguished from one another by behavior. Purple Gallinules prefer to climb onto vegetation while Common Gallinules may be seen swimming, like a duck. Both species are mostly herbivorous. Smaller still are species like the Wattled Jacana and the very tiny Least Grebe. The former is also known as the “lily-trotter” for its habit of walking comfortably atop aquatic vegetation, and the latter is one of the smallest wetland birds in the world!

 

The effects of a healthy wetland are far-reaching. Mangroves, one of our defences against climate change, flourish in brackish water. Wetlands like Kilgwyn Swamp serve not only the birds living there, but have connectivity beyond the coast, filtering fresh water before it reaches the sensitive turtle grass and the reef. Wetlands are storehouses of biodiversity, and an island without them is an island doomed.