Quick Answer
Yes, terns do eat worms. Terns are seabirds that feed primarily on small fish, but they will also eat other small marine creatures like worms, shrimp, and aquatic insects. Worms provide a good source of protein and nutrients for terns. The main types of worms terns eat include marine worms like ragworms, lugworms, and sandworms. Terns use their sharp beaks to catch worms near the water’s surface or along the shoreline. Though not their primary food source, eating worms can be an important part of the tern’s diet.
Do All Species of Terns Eat Worms?
Most species of terns have been observed eating worms, including:
Common Tern
The common tern feeds on small fish, but will also consume worms, shrimp, and insects. Worms can make up a larger part of the diet for nesting common terns who need extra nutrition when feeding chicks.
Arctic Tern
The Arctic tern migrates long distances and has a varied diet including sand lance, herring, worms, and crustaceans. On their breeding grounds in the northern hemisphere, Arctic terns will hunt for worms in intertidal areas.
Forster’s Tern
Forster’s terns mostly eat small fish, but also prey on shrimp, marine worms, and insects like dragonflies. Worms are an especially important seasonal food source for nesting terns feeding young chicks.
Royal Tern
Royal terns consume a mixed diet of fish, squid, shrimp, crabs, and worms. Worms can make up a substantial portion of the diet in some populations of royal terns.
Sandwich Tern
Small fish are the preferred prey of sandwich terns, though they also eat shrimp, marine worms, mollusks, and insects. Worms provide a nutritious supplementary food.
So in summary, the major tern species found worldwide exhibit a degree of dietary flexibility and frequently eat worms to supplement their consumption of small fish and other marine creatures.
Why Do Terns Eat Worms?
There are several key reasons why worms are an important part of the tern diet:
High Nutritional Value
Worms provide essential protein, fats, vitamins, and minerals that are vital to tern health and breeding success. Just a few worms can provide a nourishing meal.
Readily Available
Marine worms are abundant in many of the coastal habitats where terns feed. Terns can easily find worms in tidal flats, beaches, salt marshes, and estuaries.
Easy to Catch and Swallow
The slender bodies of worms make them easy for terns to catch and swallow whole. Terns don’t have to expend as much energy capturing and eating worms versus larger prey like fish.
Feed Chicks
Parent terns need to deliver plenty of small, nutrient-dense food items when feeding chicks in the nest. Worms are the ideal size and nutrition level for growing tern chicks.
Seasonal Availability
Some types of worms have peak availability at different times of year. Terns can take advantage of abundant seasonal worm hatches.
So for terns, worms can serve as a convenient, reliable, and nutritious food source to complement their fish diet and provision hungry chicks. The ease of catching worms likely gives terns an evolutionary incentive to include them as prey.
What Types of Worms do Terns Eat?
Terns feed on a variety of marine worm species, including:
Ragworms
Ragworms belong to the Nereididae family and live in burrows in intertidal sediments. Different ragworm species are common prey for terns in coastal areas worldwide.
Lugworms
Lugworms or sandworms (Arenicola genus) live in U-shaped burrows below the sand on beaches. Terns will catch them when they emerge to feed.
Sandworms
Sandworms are any worm species that inhabits sandy marine sediments. They are abundant in shoreline areas where terns hunt.
Bloodworms
Bloodworms (Glycera and Glycinde genera) are prized as fishing bait. Terns will eat them where they occur in intertidal mudflats.
Clam Worms
Clam worms (Alitta virens) are common insoft sediments in bays and estuaries. Terns feed heavily on them during seasonal population booms.
So in coastal regions worldwide, various worm genera and species make up an important proportion of tern diets. Terns are able to adapt and take advantage of whatever worm prey is locally and seasonally available.
How do Terns Catch and Eat Worms?
Terns have several hunting strategies and adaptations that help them effectively catch and consume worms:
Vision
A tern’s vision is adapted to spotting small prey while flying over water. Their sharp eyes can pinpoint worms moving in exposed mud or sand.
Diving
Terns will hover and then plunge dive headfirst to grab worms below the water’s surface before they can retreat into sediments.
Aerial Hawking
In a swift aerial attack, terns grab worms exposed on the surface then carry them away in their beak.
Beak Shape
The tern’s long, pointed beak is ideally shaped for spearing worms and holding onto slippery prey.
Swallowing
To quickly swallow worms before they can wriggle free, terns tilt their head back and let prey slide down their throat.
So terns are well-adapted hunters that use their speed, precision, and specialized beak to effectively catch and consume wiggly worm prey. This allows worms to be a productive part of their diet.
When and Where are Worms Most Important in the Tern Diet?
Worms tend to feature more prominently in the tern diet during certain times and places:
Breeding Season
Worms are especially important when terns are feeding chicks. The high nutrition and small size of worms make them ideal for delivering to developing chicks.
Wintering Grounds
Some tern species switch to eating more worms in wintering areas when fish are not as readily available.
Intertidal Habitats
Terns catch lots of worms in mudflats, beaches, salt marshes, and estuaries where marine worms congregate.
Sand Eel Shortages
When populations of preferred sand eel prey crash, terns will rely more on supplementary foods like worms.
Worm Blooms
Spectacular worm hatches or seasonal population booms attract intensive tern feeding.
So worms generally grow in importance for terns during breeding times, seasons of low fish availability, and areas/events with abundant worm presence.
Do Tern Chicks Eat Worms?
Yes, parent terns frequently deliver worms to feed growing chicks:
– Chicks need lots of small meals, which worms are perfect for
– High fat content of worms provides energy for fast growth
– Chicks can easily swallow worms whole
– Worms contain nutrients like protein, zinc, iron, and Vitamin A vital for development
– Parents can efficiently carry worms back to nests to provision chicks
Studies of tern chick diets consistently find substantial percentages of worms and other invertebrate prey in addition to small fish. The proportion of worms in the diet increases in the first few weeks after hatching, as chicks require easily digestible nutrients. So worms are an integral food source for healthy, thriving tern chicks.
What Percentage of the Tern Diet is Worms?
The proportion of worms in the diet varies:
Tern Species | Worms in Diet |
Common Tern | 5-20% |
Arctic Tern | 10-25% |
Forster’s Tern | 15-40% |
Royal Tern | 5-30% |
Sandwich Tern | 10-20% |
The percentage reflects availability, time of year, prey abundance, and breeding status. On average, studies show worms composing 15-25% of the diet across tern species, though the proportion can be higher or lower. While small fish are the primary food, worms provide a nutritious and reliable supplementary prey item.
How do Terns Help Control Worm Populations?
Terns may help regulate worm numbers and prevent overpopulation through:
Direct Predation
Terns directly reduce local worm numbers by consuming them as prey. Just one tern can eat dozens of worms per day.
Disrupt Lifecycles
Heavy tern feeding on worms can interfere with worm mating, egg-laying, and juvenile recruitment. This helps control population growth.
Shift Behavior
Predation pressure from terns may force worms to stay buried more, limiting their feeding and reproduction opportunities.
Enhance Diversity
Selective feeding by terns on the most abundant worm species helps prevent any one species from dominating.
So through direct consumption and altering worm behavior and lifecycles, tern feeding helps regulate worm population size and diversity. This can have positive ecosystem impacts like enhancing nutrients cycling in sediment and reducing the risk of harmful algal blooms from excess organic waste.
Do Other Seabirds Eat Worms?
Many seabird species consume worms in addition to fish and other marine prey:
Gulls
Gulls of many species are opportunistic feeders that will readily eat worms in intertidal areas, especially to feed chicks.
Auks
Auks like guillemots and puffins dive and swim underwater to catch worms and other bottom-dwelling prey.
Sandpipers
Sandpipers probe wet sand for hidden worms, which provide an important food source during migration.
Shearwaters
Shearwaters snap up worms congregating in rafts at the ocean surface after mass spawning events.
Phalaropes
Phalaropes pick worms and other small prey items while spinning in tight circles on the sea surface.
So many coastal and pelagic seabird species supplement their primary food sources by taking advantage of readily available worm prey. The dietary flexibility helps support thriving seabird populations.
Conclusion
In conclusion, worms form a frequent secondary food item in the diets of terns. Worms like ragworms, lugworms, and sandworms provide an abundant, nutritious, and easily caught prey source for terns. Eating worms supplies essential nutrients for self-feeding adults and fast-growing chicks. Terns use their specialized hunting adaptations to effectively catch worms in intertidal areas and surface waters. Though small fish make up the bulk of their diet, supplementing with worms helps support tern health and breeding success. Terns likely also influence worm populations through direct predation and altering behavior and lifecycles. Many other seabirds also regularly consume worm prey, taking advantage of the abundant nutrition source that worms provide.