Anhingas, also known as darters or snakebirds, are medium-sized water birds that are closely related to cormorants. Anhingas are found across the warmer parts of the Americas as well as Africa, Asia and Australia. They inhabit freshwater lakes, rivers, swamps and estuaries and are known for their slender snake-like necks and pointed beaks.
What do anhingas eat?
Anhingas are piscivorous birds that feed primarily on fish. Their diet consists mainly of freshwater fish such as bass, sunfish, catfish, perch, shad, mullet, minnows and others. The specific species depends on their geographic location and habitat. Anhingas may also occasionally eat amphibians, crustaceans, insects and small reptiles.
Here are some examples of the fish species commonly eaten by anhingas in different parts of their range:
- North America – bass, sunfish, crappie, perch, bullheads
- Central and South America – tetra, oscars, piranhas, catfish
- Africa – tilapia, carp, barbel
- Asia – snakeheads, gouramis, climbing perch
- Australia – rainbow fish, gudgeons, grunters
Anhingas are stealthy hunters that stalk fish from above or while swimming underwater. They spear fish with their sharp beaks and swallow them whole. Anhingas do not have external nostrils, allowing them to fully submerge when fishing.
How do anhingas hunt and catch fish?
Anhingas have a number of physical adaptations that aid their piscivorous lifestyle:
- Long, slender neck – Allows them to dart their heads quickly to catch fish.
- Sharp, pointed beak – Used like a spear to impale slippery prey.
- Webbed feet – Provides powerful propulsion when swimming underwater.
- Hydrodynamic body profile – Reduces drag when diving.
- Keen eyesight – Helps spot fish from above the water.
Here are the typical hunting techniques used by anhingas:
- Perch hunting – Anhingas float quietly along the water’s surface with just their neck exposed. When a fish swims by, they spear it quickly with their beak.
- Dive hunting – From a perch or while swimming, anhingas will fully submerge and chase after fish underwater using their webbed feet for propulsion.
- Stirring – Anhingas will stir up mud and debris with their feet to scare fish out of hiding spots.
Anhingas are successful hunters, catching fish on over 80% of their dives. They can stay submerged for over a minute while chasing prey underwater before returning to the surface to swallow their catch.
What is their daily food consumption?
Anhingas consume approximately 1/4 to 1/3 of their body weight in food per day. Their average food intake is:
- 150-200 grams of fish for a male anhinga (weighing around 600-700g).
- 100-150 grams of fish for a female anhinga (weighing around 450-550g).
However, their food intake can vary considerably based on activity level, life cycle stage, and availability of fish.
Here is an approximation of the daily diet composition of an anhinga:
Fish | Grams |
---|---|
Bass | 50 |
Sunfish | 40 |
Catfish | 30 |
Perch | 20 |
Small fish | 10 |
Total | 150 |
Anhingas need to eat frequently due to their high metabolism and lack of waterproofing on their feathers. They can be found hunting almost continuously during daylight hours.
How do they catch and handle prey?
Here are the key steps in how anhingas catch and eat their prey:
- Stalking – Anhingas stealthily approach fish from above the water or while swimming underwater.
- Spearing – They impale fish on their sharp beaks.
- Surfacing – After spearing a fish underwater, anhingas return to the water’s surface.
- Tossing – They toss the fish up into the air to reposition it headfirst to swallow.
- Swallowing – They catch the fish and swallow it headfirst whole.
- Perching – After eating, anhingas often perch with wings spread to dry their waterlogged feathers.
Some key facts about anhinga prey handling:
- Anhingas do not use their feet to grasp prey – only their beaks.
- They swallow fish whole and head first to aid digestion.
- If the fish is too large, anhingas may repeatedly toss it in the air to reposition it.
- The longest fish recorded eaten by an anhinga is a 29.5 inch pike.
How does their diet vary seasonally?
The diet of anhingas can vary somewhat depending on the season due to changes in food availability and breeding status:
- Breeding season – During courtship and nesting, anhingas focus on hunting in waters near their nesting colonies. Their prey consists more of smaller fish like sunfish, perch, and minnows that are abundant nearby.
- Migration – On migration and in wintering grounds, anhingas expand their diet to take advantage of whatever fish are readily available in the waters they occupy at the time.
- Winter – In colder regions in winter, the diet of anhingas shifts to focus on slower moving fish like catfish and bullheads that stay in deeper, warmer waters.
- Young – Baby anhingas are fed smaller fish that can be more easily swallowed such as minnows and anchovies.
However, the core of the anhinga diet remains medium-sized fish like perch, sunfish, and bass year-round. Their diverse anatomy allows them to exploit a wide array of freshwater fish species in most any aquatic habitat.
How does their diet differ from the closely related cormorant?
Anhingas and cormorants are very closely related water birds that occupy similar ecological niches. However, there are some subtle differences between their diets:
- Habitat – Cormorants focus more on sea coasts, while anhingas primarily inhabit freshwater inland areas. This affects the fish species composition of their diets.
- Fish size – Anhingas tend to eat smaller prey on average than cormorants, which take more large fish like mullet.
- Crustaceans – Cormorants include more crustaceans like crabs, shrimp, and crayfish in their diet compared to the strongly fish-based diet of anhingas.
- Hunting – Cormorants hunt more cooperatively in groups compared to the more solitary hunting habits of anhingas.
However, their diets still overlap significantly, both adapted for swallowing fish whole underwater. The differences reflect their tendencies to hunt in slightly different aquatic habitats and social groups.
Conclusion
In summary, anhingas are specialized aquatic birds that have a strong dependence on freshwater fish as their primary food source. Their diet is dominated by fish like bass, sunfish, perch, and catfish. Anhingas have a number of anatomical adaptations including a sharp, pointed beak and slender neck that allow them to stalk and spear fish underwater. They require frequent feeding and consume about 1/4 to 1/3 of their body weight in fish each day. While their diet varies somewhat seasonally and geographically, anhingas remain strictly piscivorous in all their ranges.