Piscivorous birds have several unique adaptations that help them catch their aquatic prey. Most fish-eating birds are equipped with specialized bills to capture fish either by spearing them with a sharp tip or catching them with ridged edges, and their bills are often very sensitive to detect the brush of prey even if the birds can't see the fish directly. More than just their bills are essential for catching prey, however, and most piscivorous birds also have one or more of the following adaptations:
- Sharp, strong talons with a powerful grip for slippery prey
- Heavily ridged or scaled feet to hold wet prey securely in flight
- Long, thin legs for wading into mud and water in search of prey
- Larger, more productive preen glands for superior plumage waterproofing
- Countershaded plumage to provide camouflage when hunting in the water
- More tapered, flipper-like wings that can aid when pursuing prey underwater
- Feet that are set further back on the body for stronger swimming
- Gular sac or throat pouch below the bill to dip into water when fishing
The exact adaptations any bird may have will vary depending on its exact species, the types of fish and other aquatic life it eats, and how the bird hunts.
What Is a Piscivorous Diet?
Piscivorous describes a carnivorous diet that consists largely of fish, though a piscivorous diet may also include similar aquatic foods such as aquatic insects, jellyfish, mollusks, and crustaceans. Fish, however, is the majority of the diet, though a piscivore may eat many different kinds of fish. Both freshwater and saltwater fish diets are piscivorous.
How Piscivorous Birds Are Different
Piscivorous Bird Species
Many different birds have at least some fish in their diet, but some species are more well known as superb fishermen, and generally eat only fish. Examples of familiar piscivorous fish include:
Many other types of birds, including herons, egrets, and some eagles, such as the Steller's sea-eagle, also eat a lot of fish. These birds, however, are less discerning in their diets and will consume a variety of other foods as well, so they are more general carnivores rather than specialized piscivores.
How Birds Hunt Fish
Many piscivorous birds, such as ospreys, pelicans, and kingfishers, hover, soar, or perch above the water to spot accessible fish, then plunge-dive from the air to capture their prey. Wading birds stalk their prey carefully before spearing it, even using "bait" such as a piece of bread or a leaf to attract curious fish into striking range. Some birds will drape their bills into the water and wait for prey to brush against it, while exceptionally aquatic birds, such as puffins and penguins, swim after fish to capture their prey. Depending on the bird species and the size of the prey, the fish may be swallowed whole or ripped into pieces for easier eating.
When these birds are nesting, they carry fish back to their brooding mate and hungry chicks. Ospreys will align a fish in their talons to point headfirst so it is more aerodynamic in flight, while puffins will line up a dozen or more small fish in their bills before heading back to the nest.
Threats to Piscivorous Birds
Because they depend on the water for food, piscivorous birds are highly susceptible to water pollution, including oil spills. Discarded fishing line and litter can also be dangerous hazards for these fish-eating birds. At sea, birds will often become tangled in commercial fishing lines or nets along with other marine life such as sea turtles and dolphins. Many of these birds may mistake colorful bits of plastic such as floating bags, deflated balloons, bottle caps, or other broken shards as fish, and can eventually starve when their digestive tracts become filled with indigestible debris.
Climate change is another grave threat to piscovorous birds. Changing water temperatures shift where schools of fish congregate, which means these birds must travel further from nesting grounds to hunt successfully. This can lower breeding success as many chicks may starve if their parents cannot catch adequate amounts of fish.
Because several types of piscivorous birds, such as cormorants, are colonial nesting birds, they can cause problems with local fishing communities as hundreds of birds may deplete the fish available for sport. To manage the bird populations, wildlife officials may cull large colonies to help balance wildlife needs with recreational needs, a practice that can be controversial among birders and other conservationists.
Also Known As
Fish-Eating, Piscivore (noun), Fish-Eater