Turnstones are small shorebirds that are found on coastlines worldwide. They get their name from their interesting feeding behavior – they use their short bills to flip over rocks, shells, seaweed and other objects to find food underneath. Turnstones are omnivores and eat a wide variety of small invertebrates and plant material.
Invertebrates
Turnstones feed on a wide variety of invertebrates including insects, crustaceans, mollusks and marine worms. Some of the main invertebrate prey items in their diet include:
- Insects – flies, beetles, dragonflies, damselflies
- Crustaceans – amphipods, isopods, shrimp, crabs
- Mollusks – snails, limpets, mussels
- Worms – polychaetes, nematodes, flatworms
Insects make up a large portion of the invertebrates that turnstones eat. They often feed on insect larva, pupae and adults that they find under seaweed and debris on beaches and intertidal zones. Beetles, flies, dragonflies, ants and bees are commonly consumed insects.
Crustaceans are another significant food source for turnstones. They use their short bills to pry small crabs, shrimp and amphipods from under rocks and shells. Larger crabs are flipped onto their backs and their undersides are consumed. Sand fleas, beach hoppers and other small crustaceans living in the sand are rapidly picked off the surface.
Mollusks such as snails, limpets and mussels are hammered open with the turnstone’s bill and the soft meat inside is eaten. Worms are plucked from the sand or extracted from tubes and consumed. Turnstones will scavenge on dead fish and squid washed up on shore.
Plant material
In addition to animal prey, turnstones also consume a variety of plant material including:
- Algae
- Aquatic plants
- Seeds
- Fruits/berries
- Shoots/sprouts
Turnstones often supplement their diet with algae, aquatic plants and organic plant debris found along shorelines. They may graze on microscopic algae coating rocks or eat pieces of macroalgae like kelp or sea lettuce. Seeds and sprouts of beach plants like sedges and grasses are consumed. Turnstones pluck berries and fruits from coastal bushes and trees.
Food availability
Turnstones are very opportunistic feeders. Their diet varies depending on the local availability of prey items in the habitat. At any given location, they will concentrate on consuming whatever prey is most abundant and easy to find. For example:
- On rocky shorelines, they primarily feed on mollusks attached to rocks as well as crabs, isopods and other crustaceans hiding in crevices.
- On sandy beaches, they target burrowing invertebrates like sand fleas, mole crabs and worms.
- On mudflats, they probe for crabs, worms and mollusks buried in the mud.
- At estuaries and lakes, they feed heavily on small fish like fry.
Turnstones will adjust their diet and foraging behavior to capitalize on seasonal changes in food availability. In spring and summer when invertebrate populations are higher, they feed more heavily on insects, crustaceans and worms. In fall and winter when fewer invertebrates are active, they shift to eating more plant material like seeds and fruits.
Foraging behavior
Turnstones exhibit a unique foraging behavior as they search for food along the coastline. They methodically pick up and turn over objects with their short straight bills looking for prey items. Some key aspects of their foraging strategy include:
- Flipping over seaweed, rocks, shells, debris
- Probing into sandy and muddy substrates
- Prying open crevices
- Hammering to open hard-shelled mollusks
- Rapidly picking up insects and small invertebrates
- Plucking fruits/seeds
- Excavating burrows and tubes
- Pecking at algae coatings
Their bills are perfectly adapted for quickly manipulating and flipping over objects. The undersides of rocks, shells and debris are hotspots for many of the crustaceans, worms and mollusks that turnstones prey on. They will probe deep into mud and sand in search of buried invertebrates. Tiny insects and crustaceans on the substrate surface are rapidly picked off. This constant probing, flipping and pecking behavior gives turnstones their characteristic active foraging style.
Feeding locations
Turnstones forage in a variety of intertidal and shoreline habitats searching for food including:
- Rocky coasts – feed among tidepools and rocky outcroppings
- Sand beaches – probe into sandy substrate
- Mudflats – use their bills to probe deep into mud
- Estuaries – pick insects and small fish from shallow water
- Lakeshores
- Rock jetties and breakwaters
- Piers and docks
- Wetlands and salt marshes
Rocky shorelines with abundant tidepools offer a diversity of prey options like mussels, limpets, crabs and shrimp. On sandy beaches, turnstones drill into the sand searching for burrowing worms, crustaceans and mollusks. Mudflats are a prime feeding ground for finding worms, crabs and buried bivalves. Estuaries and lakes provide small fish, insect larvae and submerged aquatic plants. Jetties, piers and docks provide attachment sites for mussels and barnacles.
Hunting techniques
Turnstones use a variety of hunting techniques and behaviors to capture prey including:
- Rapid pecking at the substrate surface to pick up insects and crustaceans
- Probing bills into sand or mud to feel for buried prey items
- Flipping over seaweed, rocks, shells to expose hiding prey
- Prying open closed bivalve shells like mussels and clams
- Excavating burrows and tubes in search of worms and crustaceans
- Plucking fish and insect larva from shallow water surfaces
- Creeping through vegetation to startle and pick up insects
Their feeding repertoire allows them to take advantage of a wide range of food sources. Turnstones will flick their bills from side to side to disturb insects and crustaceans that are then snatched up. They can hammer through mollusk shells or dig deep into the substrate probing for buried prey. By flipping rocks and shells, they expose numerous crustaceans, worms and insects. Their agile bills are adapted for prying, pecking, probing and digging.
Where do they forage when the tide is in?
When the tides come in and cover up their typical intertidal feeding grounds, turnstones must seek out alternative foraging areas. Some places they go to feed when the tide is high include:
- Upper beaches and dunes beyond the high tide line
- Rocky cliffs and sloped shorelines above the water
- Coastal marshes and wetlands
- Bays, estuaries and protected coves
- Piers, docks, jetties
- Nearby grasslands and fields
- Offshore rocks and islands
They forage among debris and dry seaweed deposited along upper beach areas away from the rising tides. Coastal wetlands provide rich feeding grounds when tides are high. Protected bay waters allow them to wade and probe for prey. Floating piers and docks give them a place to pick insects and small fish from the water surface. Offshore rocks remain exposed at high tide providing refuge. Turnstones may also fly inland to feed in fields and grasslands while waiting for the tide to recede.
What adaptations help turnstones find food?
Turnstones have several key adaptations that help them locate and capture food along the seashore including:
- Short, stout bills – Ideal for prying, pecking, flipping objects
- Excellent camouflage plumage – Lets them blend in and stealthily approach prey
- Distinctive black and white wing stripes – Startle small fish and insects so they can snatch them
- Sensitive bill tips – Can feel for vibrations signaling buried prey
- Quick reflexes – Grab insects and worms before they can retreat
Their short, wedge-shaped bills are perfect for probing and manipulating objects to expose food underneath. Cryptic black, brown and orange plumage allows them to go unnoticed as they forage. Bold black and white stripes on their wings may induce small fish and insects to dart away and reveal their location. Sensitive bill tips can feel subtle vibrations indicating buried prey. Lightning fast reflexes enable them to instantly grab foods like worms before they disappear into the substrate.
Do they ever feed in large groups or flocks?
Turnstones may feed in loose flocks, particularly at rich food sources, but they primarily forage individually or in very small groups. Some situations where larger foraging flocks may form include:
- Large concentrations of easily caught prey like swarming insects or fish fry
- Expansive feeding grounds like extensive mudflats and sandbars during low tide
- Abundant food availability following events that strand marine organisms like storms or extremely high tides
- High quality food patches with dense populations of prey
Flocks allow turnstones to take advantage of and collectively exploit temporary conditions of superabundant food. This might occur along mudflats teeming with worms and crustaceans or beaches littered with shellfish and marine invertebrates deposited by storm waves. Some level of competition can occur in dense foraging flocks, but the benefits of shared vigilance against predators seem to outweigh any disadvantage.
Do they ever steal food or fight over food resources?
Thievery and competition for food resources is fairly uncommon among turnstones. Their foraging style and habitat preferences make stealing food and fighting over food sources rare. Reasons include:
- Their prey is usually small, quick and scattered making theft impractical
- There is little advantage to chasing down competitors for tiny items like individual insects or worms
- Their habitat tends to have an abundant and renewable supply of prey
- They spread out and keep distance even when foraging in groups
- Each bird can find adequate food by overturning their own objects
The difficulty and minimal payoff of stealing tiny prey typically prevent turnstones from engaging in this behavior. Likewise, the advantage of aggressively competing for small prey is negligible when their habitat provides a constant renewal of similar food items. Resources are rarely scarce enough to warrant thievery or antagonism. By spreading out, each bird can access sufficient food beneath the objects they overturn.
How do they catch and handle prey?
Turnstones use their specialized bills in several different ways to catch and handle prey including:
- Pecking – Make quick repeated strikes into the substrate or water to grab insects, worms, fish
- Probing – Insert bill into mud, sand or cracks in search of buried or hiding animals
- Hammering – Break open hard shells of mollusks by pounding bill repeatedly against them
- Prying – Wedge bill into bivalve shells and twist to force them open
- Flipping – Use bill to turn over rocks, debris, seaweed and expose prey
- Excavating – Dig into sand or mud to excavate prey burrows
The wedge-shaped tip of their bill allows them to be highly dexterous when capturing and handling different prey. They can swiftly stab downward to pick up food from the surface or flick their bills sideways to catch darting insects. Hard shelled organisms like mussels and limpets are wedged open with their bill or hammered repeatedly into submission. Any food that tries to retreat into the sand or mud is promptly excavated.
What kind of habitat do they prefer to forage in?
Turnstones strongly prefer foraging in coastal habitats with the following characteristics:
- Intertidal areas exposed at low tide
- Gently sloping or flat terrain
- Substrate of sand, pebbles, mud, or scattered rocks
- Presence of tidepools, rocks, seaweed
- Abundance of detritus like shells, driftwood
Foraging is closely tied to the intertidal zone and associated tide cycles. Gently sloping beaches, sandbars and mudflats that are left extensively exposed during low tides offer prime habitat. These areas provide an abundance of crevices, objects to overturn, and access to burrows. The mixture of rocks, shells, seaweed and other debris provides shelter and attachment sites for prey. Exposed mud and sand substrate is also ideal for probing and digging.
Do they ever forage in human habitats like landfills?
Although turnstones are loyal to marine coastlines, they will occasionally venture into human-impacted areas or terrestrial habitats to find food, including:
- Garbage dumps and landfills
- Sewage ponds
- Agricultural fields
- Roadsides and parking lots
- Urban areas
Landfills provide easy access to discarded human food scraps. Fields offer grains, seeds and rodents. Ponds and flooded fields provide ample small fish and aquatic invertebrates. Pavement areas may collect bits of dropped food or insects. However, the availability of adequate natural food sources means turnstones only occasionally take advantage of these marginal, human-linked habitats.
Do the adults feed their chicks?
Yes, adult turnstones provide extensive parental care and provisioning for their chicks. They use a couple strategies to feed chicks:
- Direct feeding – Adults regurgitate food directly into the chick’s mouth
- Leading chicks to food patches – Adults lead mobile chicks to foraging sites with abundant prey
Very young chicks are directly fed by regurgitation. As chicks grow older but are still flightless, the adults will lead them to rich food patches where the chicks can forage for their own food while under watchful supervision. Adults continue supplementing the independent feeding by regurgitating additional food items.
What kinds of prey are fed to chicks?
Adult turnstones feed chicks a wide variety pre-digested food including:
- Insects – flies, beetles, moths, spiders
- Crustaceans – amphipods, isopods, shrimp
- Mollusks – small snails
- Worms – polychaetes, nematodes
- Eggs – fish, frog
- Fish – small fishes, fish fry
- Plant material – seeds, sprouts, fruits
Chicks are fed soft-bodied prey like worms, insects and crustaceans early on. As they grow, adults provide larger and harder items like snails, shrimp, and small fish. However, food is always pre-digested either by soaking in water or partial digestion before feeding chicks. Turnstones may bring plant foods like sprouts, seeds and berries to chicks as well. A varied diet ensures chicks get all necessary nutrients for growth and development.
How often do the adults feed the chicks?
Adult turnstones feed young chicks very frequently, sometimes up to every 20-30 minutes during the day. Feeding frequency depends on factors like:
- Chick’s age – younger chicks fed more often
- Brood size – chicks in larger broods fed less frequently
- Food availability – feed less often when food is scarce
- Weather – may feed more often during cold periods
Newly hatched chicks require almost constant provisioning from dawn to dusk. As chicks grow, feeding becomes less frequent but remains regular throughout the day. Parents adjust feeding rates based on the abundance of available food, averaging 5-15 feedings per day under normal conditions. Frequent feedings ensure a constant supply of nutrition for developing chicks.
Do they drink water or just eat food from their environment?
Turnstones get most of their necessary water requirements directly from the food they consume. Some ways they acquire water include:
- Prey like insects, worms, mollusks contain high water content
- Drink drops of water accumulated on rocks and leaves
- Drink freshwater from small streams, ponds, puddles
- Filter droplets of water from cracks and pores while probing
- Ingest ocean water while feeding and bathing
Their prey items like worms, crabs and mussels have high water composition, meeting much of their needs. Additionally, they opportunistically drink droplets and pools of fresh water accumulated in their coastal habitat. The capability to filter and ingest seawater helps maintain fluid balance.
Conclusion
In summary, turnstones are remarkably adaptable shorebirds that employ a diversity of foraging techniques to take advantage of the assortment of small prey items found along coastlines. Their short but pointed bills allow them to capture insects, worms, mollusks, crustaceans and other invertebrates. They probe and dig through sand and mud, overturn objects, and hammer open shells. Chicks are carefully provisioned by regurgitation and led to ideal feeding patches. Turnstones are capable of shifting their diet and foraging strategy to take advantage of any readily available food sources in their immediate environment.
