Avocets are elegant wading birds, instantly recognizable by their long, slender legs and a distinctively thin, black bill that curves upward. These shorebirds are specialized foragers that thrive in various wetland ecosystems across North America and Eurasia. Their survival depends on their ability to locate and consume small organisms within the water and soft sediment. Understanding what avocets eat requires a look at the aquatic life they target, the unique tools they use to capture it, and how their menu shifts with the environment.
Principal Aquatic Invertebrates
The diet of the avocet is almost exclusively composed of small, soft-bodied aquatic invertebrates. A primary food source consists of the larvae of aquatic insects, particularly midges, which are often found in high concentrations within the soft mud of shallow water. Avocets also consume other insect forms, including water boatmen and the larvae of various beetles.
In saline environments, the birds rely heavily on micro-crustaceans, such as fairy shrimp, water fleas, and especially brine shrimp. These small prey items provide a dense source of protein and fat, sustaining the avocet during breeding and migration. Small worms and various mollusks are readily eaten when encountered in the mudflats.
While the diet is dominated by animal matter, incidental consumption of plant material sometimes occurs. This involves the seeds of aquatic plants, like sago pondweed or bulrushes, which are ingested accidentally while the bird filters the water. Plant matter is not a significant component of the avocet’s nutritional intake.
Distinctive Foraging Methods
The avocet employs a specialized feeding technique, often referred to as “scything,” which is suited to its unique bill structure. To capture prey, the bird walks or swims slowly through shallow water, holding its upturned bill slightly open. It then sweeps the bill rapidly from side to side just below the water surface or through the soft, muddy bottom.
This sweeping motion is primarily a form of tactile feeding, where the avocet does not rely on sight to locate its food. The bill tip is supplied with sensory receptors (mechanoreceptors) that detect pressure changes and vibrations caused by hidden prey in the murky water or sediment. This allows the bird to efficiently harvest invertebrates that are invisible to the eye.
Beyond scything, avocets utilize other foraging behaviors depending on the prey’s location and depth. They engage in pecking, lunging their bill to snatch prey visible in the water column or on the substrate surface. In deeper water, they may also perform a plunging motion, submerging their head and neck to grab food items.
Dietary Adaptations to Habitat
The specific composition of the avocet’s diet shows variation based on the water chemistry of its foraging habitat. In highly saline wetlands, the birds rely on specialized organisms that tolerate extreme salt concentrations. Brine shrimp and brine fly larvae become a foundational food source, often available in massive quantities that support large flocks of avocets.
In freshwater or brackish wetlands, the diet shifts away from these salt-tolerant species. The birds instead consume a wider variety of insect larvae, small crustaceans, and other micro-invertebrates found in less saline conditions. This adaptability allows avocets to exploit a range of wetland types across their geographic range.
Osmoregulation is important, particularly in salt-rich environments. By minimizing the amount of water they ingest while feeding and relying on the body fluids of their prey, adult avocets can manage the salt load. However, young chicks raised in hypersaline conditions without access to a freshwater source can suffer from dehydration.