The Calla Lily (Zantedeschia aethiopica) is known for its elegant, vase-like blooms. Hummingbirds are prolific pollinators known for their high-speed metabolism and hovering flight. Their specialized fuel needs drive them to seek flowers offering a high-energy reward. The interaction between these organisms depends on specific floral adaptations. Examining the Calla Lily’s unique structure and pollination strategy reveals whether it provides the necessary resources for hummingbirds.
The Specific Interaction Between Hummingbirds and Calla Lilies
Hummingbirds are poor visitors to Calla Lilies because the plant’s floral design is not adapted for bird pollination. The Calla Lily relies primarily on small crawling insects, such as beetles and bees, for pollination. This insect-focused strategy means the plant does not produce the large volumes of sucrose-rich nectar that hummingbirds require. While a hummingbird might investigate the bloom, the minimal reward quickly shows the energy cost outweighs the benefit. The flower also emits a faint, sweet fragrance, a trait common in insect-pollinated flowers but generally absent in avian-pollinated species.
Structural Reasons for Low Attraction
The Calla Lily is largely ignored by hummingbirds due to its unique floral anatomy, which is structurally incompatible with a long avian bill. What is commonly called the “flower” is technically an inflorescence, consisting of a large, funnel-shaped structure called the spathe, which is a modified leaf. The true flowers are tiny, clustered around a central spike known as the spadix.
This arrangement does not form the narrow, deep, tubular corolla that a hummingbird’s bill and specialized tongue are designed to access. The spathe’s open, broad shape also lacks the protective structure needed to guide a hummingbird to a deep nectary. Instead of nectar, the plant produces sweet-tasting staminodes that reward crawling insects navigating the spadix. Its white color is not the vibrant red or orange that signals a high-calorie meal to a hummingbird.
General Hummingbird Flower Preferences
Hummingbird-pollinated flowers have evolved specific characteristics, known as an ornithophilous syndrome, that align with the bird’s feeding mechanics and visual acuity. These flowers are typically tubular or trumpet-shaped, perfectly accommodating a hummingbird’s long bill and tongue. The narrow opening effectively excludes most large insects, reserving the nectar exclusively for the bird.
The preferred colors are often bright red, orange, and deep pink, which are highly enticing. Hummingbirds are sensitive to these colors, which serve as a long-distance signal for a high-energy source. These flowers produce copious amounts of nectar with a high sugar concentration, often averaging around 25% sucrose.
Preferred flowers often lack a landing platform, requiring the bird to hover while feeding. They are also typically scentless, as hummingbirds rely on sight rather than smell for foraging. These combined traits minimize resource competition from insects and maximize the energetic reward for the avian pollinator.