Ducks are opportunistic omnivores, and insects and other invertebrates form a significant portion of their nutritional intake. This is true for species like mallards, wood ducks, and many domestic breeds, who actively seek out these protein-rich sources. This diet is crucial for waterfowl thriving in both wetland and terrestrial environments. A single mallard, for instance, can consume upward of 10,000 insects in a single day.
The Essential Invertebrate Menu
The invertebrate menu for ducks is broadly categorized by habitat, encompassing aquatic, terrestrial, and shelled organisms. Aquatic insects are a primary food source, with ducks consuming the larval and nymph stages of creatures like mosquitoes, dragonflies, and diving beetles. These immature forms are easily accessible in shallow water and dense vegetation. Ducks also actively forage for terrestrial invertebrates, especially during the warmer summer months. This part of the diet includes:
- Earthworms
- Slugs
- Spiders
- Various beetles found in the mud or on the ground
Smaller shelled organisms and crustaceans, such as snails and crayfish, are also important components for species that forage more deeply.
How Ducks Forage for Insects
The method a duck uses to acquire its invertebrate meal is linked to its species and environment, generally falling into two categories: dabbling and diving.
Dabbling
Dabbling ducks, such as mallards and northern shovelers, feed primarily on the water’s surface or by “tipping up” to reach food just below the surface. This involves submerging the head and neck while the tail remains visible above the water. This surface feeding is facilitated by a specialized bill structure featuring comb-like projections called lamellae. These lamellae act as a sieve, filtering out small invertebrates and other edible particles from water and mud.
Diving
In contrast, diving ducks, such as canvasbacks, propel themselves fully underwater to pursue prey. They target larger aquatic insect larvae and mollusks that reside in deeper water.
The Nutritional Value of an Insect Diet
Insects provide concentrated nutrients required for growth, maintenance, and reproduction. They are packed with high-quality protein, essential for muscle development in ducklings and for the energy demands of egg production in laying females. During the breeding season, some female ducks may derive over 70% of their diet from animal material to meet this need. The chitinous exoskeleton of insects also provides a natural source of calcium. This calcium is important for female ducks, as it is crucial for forming strong eggshells. Furthermore, the high mineral content, including phosphorus and trace elements, supports overall bone health during periods of rapid development or annual molting.
Toxic and Unsafe Invertebrates
While most invertebrates are safe for ducks to consume, a small number of species can pose a health risk. Certain aquatic snails, for example, can act as intermediate hosts for parasites, such as trematode flukes. These parasites can cause severe intestinal damage in waterfowl. Additionally, some insects contain chemical defenses that make them toxic if ingested. Fireflies, or lightning bugs, contain lucibufagins, a steroid-like toxin that is unpalatable and potentially lethal to birds. Although most wild ducks instinctively avoid such prey, these exceptions highlight the risks associated with chemically defended insects.