The common tern (Sterna hirundo) is a medium-sized seabird found across temperate and subtropical regions worldwide. Terns belong to the family Laridae, which includes gulls, skimmers, and other shorebirds. As their name suggests, terns are most commonly found along coastlines and inland waterways. But is the common tern a carnivore? Let’s take a closer look at the common tern’s diet and hunting strategies to find out.
What Do Common Terns Eat?
The common tern is considered a piscivorous bird, meaning fish make up the bulk of its diet. Common terns feed primarily on small, surface-schooling fish such as herring, anchovies, smelt, and sand lance. During the breeding season, a common tern can consume up to 150 grams of fish per day. This equates to roughly 25-35 fish per day on average.
In addition to fish, common terns will occasionally prey upon crustaceans like shrimp. They also feed on aquatic insects that happen to be at the water’s surface. Some of the insect types eaten include dragonflies, damselflies, water beetles, and caddisflies. However, fish comprise over 80% of the common tern’s total food intake.
Common Tern Hunting Strategies
Common terns are aerial hunters and they utilize several key strategies to catch fish:
– Plunge-diving – Common terns will spot a school of fish from the air, hover briefly, and then plunge directly into the water feet-first to catch their prey. Their streamlined bodies and long, narrow wings make them effective divers.
– Dipping/Contact-dipping – When fish are very close to the surface, common terns will dip down and snatch them while basically still in flight. They may also situate themselves on the water and pick/flutter along the surface contacting fish with their beak.
– Hawking – Common terns will fly and scan for individual prey swimming alone. They will pursue and capture these solitary fish while on the wing.
Food Provisioning for Chicks
During breeding season, common tern parents must capture enough fish not only to feed themselves, but their mate and chicks as well. They carry fish back in their beaks and feed them directly to chicks and mates waiting in the nest colony. Chicks are fed tiny pieces of fish that the parents rip up for them. As chicks grow larger, parents eventually deliver whole fish for the young birds to consume on their own. Both the male and female parent provide food for their offspring.
Are Common Terns Carnivores?
Based on their diet and hunting methods, common terns clearly fit the definition of a carnivorous animal. As mentioned, the vast majority of their diet consists of fish, which are meat. They actively hunt and kill fish as their main food source using specialized aerial techniques. While common terns do occasionally consume insects and crustaceans, their nutritional intake is not substantially derived from these prey items. Therefore, common terns can definitively be classified as carnivorous birds.
Additional Traits of Common Terns as Carnivores
Beyond their piscivorous diet, common terns share other characteristics and adaptations with carnivorous birds and animals:
Sharp, Pointed Beak
Common terns have a sharp, pointed beak which serves as an effective tool for impaling and gripping slippery fish. The beak has a red tip during breeding season. In general, pointed beak structure correlates with a carnivorous diet across avian species. Granivorous and herbivorous birds that consume seeds/plants feature blunter, more rounded beaks.
Aerial Maneuverability
As previously mentioned, common terns are highly maneuverable in flight which aids their fish-hunting strategy. Their long, narrow wings enable agile zig-zagging and diving to snatch prey while airborne. Strong fliers with precise directional control are essential traits for avian raptors and other carnivorous birds that capture food mid-air.
High Metabolism
Carnivores require a high-protein diet to support an energetic metabolism needed for hunting. Fish provide common terns with the protein levels required to fly and dive at fast speeds while foraging. Their metabolism delivers rapid energy turnover during active fishing bouts.
Sharp Claws
While less prominent than raptors, common terns have small, sharp claws on their webbed feet. These claws help them grasp and hold writhing fish caught at the water’s surface. Sharp talons are a hallmark trait among carnivorous bird species.
Trait | Carnivorous Adaptation |
---|---|
Pointed, piercing beak | Spearing and holding slick fish |
Aerial agility | Swift pursuit of prey in flight |
High metabolism | Energy for active hunting |
Sharp claws | Grasping wriggling fish |
Comparison to Other Birds
Looking at the dietary habits and morphology of other types of birds helps illustrate the carnivorous adaptations of the common tern:
Granivorous Birds
Granivorous birds like sparrows and finches primarily eat grains and seeds. To process this plant-based diet, they have wider, blunter beaks more suited for crushing and husking seeds. Their flight abilities tend to be weaker and less acrobatic compared to aerial hunting birds. Sparrows do not actively prey on other animals.
Herbivorous Birds
Herbivorous waterfowl like geese and swans consume aquatic vegetation. They feature broad, flattened bills that strain food from muddy bottoms. Herbivorous birds lack the sharp tools and fast energy required for carnivorous habits.
Raptors
Birds of prey like eagles, hawks, and falcons represent some of the most formidable avian carnivores. They possess large, hooked beaks for tearing flesh and deadly talons for seizing victims. While common terns are carnivorous, their adaptations are not as extreme given their smaller-bodied fish prey. Nonetheless, they share the same carnivorous tendencies.
Conclusion
In summary, while the common tern subsists primarily on small fish, they undoubtedly exhibit all the characteristics of a carnivorous bird species. From their diet to specialized hunting morphology and energy requirements, common terns align with the attributes of avian carnivores. So the verdict on our original question is clear – the common tern is certainly a carnivore. Their reliance on fish and adaptations for catching aquatic prey leave no doubt about their carnivorous status among birds.