A pollinator is any animal that moves pollen from the male part of a flower to the female part, enabling the plant to produce seeds and fruit. Bees are the most familiar example, but the full list includes butterflies, moths, flies, beetles, birds, bats, and even some small mammals. Roughly 75% of flowering plants and dozens of major food crops depend on these animals to reproduce.
How Pollination Works
Flowers produce pollen in their anthers, the male reproductive structures. For a plant to make seeds, that pollen needs to reach the stigma, the sticky receptive surface of the female part of the same or a different flower. Most flowering plants can’t do this on their own because their male and female organs are physically separated, sometimes on entirely different plants. Their flower structures actually prevent self-pollination during the period when the stigma is receptive.
This is where pollinators come in. When a bee lands on a flower to drink nectar, pollen grains stick to its body. When that bee visits the next flower, some of those grains rub off onto the stigma. The pollen grain then grows a tiny tube down into the flower, delivering genetic material to the ovule. Fertilization happens, and the plant begins developing seeds and fruit. It’s a transaction: the pollinator gets food (nectar, pollen, or both), and the plant gets to reproduce.
Not all pollination requires animals. Wind carries pollen for grasses and cereal crops like wheat, rice, and corn. A small number of aquatic plants use water currents instead. But the vast majority of flowering plant species rely on living pollinators.
Insects: The Largest Group of Pollinators
Bees do the heaviest lifting. Honeybees and carpenter bees are generalists, visiting a wide range of flowering plants rather than sticking to one species. This flexibility makes them enormously effective. In field studies across both disturbed and intact landscapes, bees in the order Hymenoptera consistently show the strongest and most frequent interactions with flowering plants, visiting everything from beans to sunflowers to wildflowers.
Flies are the second most important group, and they rarely get credit for it. Hoverflies, blowflies, and tachinid flies all visit flowers and transfer pollen. When researchers statistically removed honeybees from pollination data, flies interacted with the greatest number of flowering plant species. They’re especially active in cooler conditions and at higher elevations where bees are less common.
Butterflies and moths contribute too, though differently. Butterflies tend to visit flat, open flowers during the day, while moths pollinate pale, fragrant flowers that open at night. Beetles round out the insect pollinator roster. They’re less precise than bees, often chewing on flower parts, but they still move pollen around, particularly in tropical ecosystems.
Birds, Bats, and Other Vertebrate Pollinators
Bird pollination occurs in nearly 500 genera of plants worldwide. At least six families of tropical and subtropical birds are strongly adapted for nectar feeding, with hummingbirds being the most recognized in the Americas. These birds have long, slender bills and tongues that reach deep into tubular flowers, picking up and depositing pollen along the way.
Bats pollinate roughly 250 plant genera. Two major families handle most of this work: Old World fruit bats across Africa, Asia, and Australia, and leaf-nosed bats in the Americas. A single nectar-feeding bat can deposit thousands to over 20,000 pollen grains per night on the stigmas of columnar cacti. Bat pollination has evolved independently many times from insect-pollinated, bird-pollinated, and even mammal-pollinated ancestors, suggesting it’s a highly successful strategy for plants.
Why Pollinators Matter for Food
Animal pollination adds an estimated $235 to $577 billion to global crop production each year. In the United States, crops like almonds, apples, blueberries, cherries, tomatoes, pumpkins, and alfalfa all need insect or bird pollination to produce food. Without pollinators, these crops would yield little to nothing.
The economic value is staggering in context. One widely cited assessment valued global pollination services at about 9.5% of the world’s total agricultural food production. The Mediterranean, Southern and Eastern Asia, and Europe see the greatest economic benefits. This figure only captures direct crop value. It doesn’t account for the role pollinators play in maintaining wild plant populations that support entire ecosystems.
How Plants and Pollinators Shape Each Other
Over millions of years, plants and their pollinators have evolved in response to one another, developing physical features that fit together with remarkable precision. One striking example involves a short-tongued bee species, Andrena lonicerae, and a Japanese honeysuckle, Lonicera gracilipes. The flower has an unusually long, narrow tube measuring 10 to 12 millimeters, far longer than related species. Most short-tongued insects can’t reach the nectar inside.
But this particular bee has evolved an extremely elongated tongue, head, and mouthparts that match the tube length almost exactly. Detailed measurements show a precise correspondence between the bee’s anatomy and the flower’s dimensions. The flower essentially produces nectar almost exclusively for this one bee. Even the cleaning structures on the bee’s mouthparts have been reduced to just one to three bristles, a streamlining that reflects generations of specialization. This kind of tight fit between a single plant and a single pollinator species illustrates how deeply these relationships can run.
Threats to Pollinator Populations
Pollinator declines are well documented and accelerating. In Europe, at least 10% of wild bee species (172 out of 1,928 assessed) face extinction risk. Fifteen percent of European butterfly species are threatened, with 65 out of 442 assessed species at risk. Hoverflies are in even worse shape: 37% of all hoverfly species in Europe are threatened with extinction, according to a continent-wide assessment published in 2022.
The drivers are overlapping. Habitat loss removes the wildflowers pollinators depend on for food and the undisturbed ground or dead wood they need for nesting. Pesticide exposure weakens immune systems and disrupts navigation. Climate change shifts bloom times out of sync with pollinator activity, so flowers open before their pollinators emerge, or pollinators arrive after peak nectar production has passed.
How to Support Pollinators at Home
Creating pollinator habitat doesn’t require acres of land. A few targeted choices in a yard or balcony garden make a measurable difference. Plant a wide variety of species that bloom from early spring into late fall so there’s always something flowering. Choose plants native to your region, and plant them in clumps rather than scattering single plants, which makes it easier for pollinators to find them. Avoid modern hybrid flowers, especially those with “doubled” blooms, because the extra petals often replace the pollen-producing structures that pollinators actually need.
Night-blooming flowers support moths and bats, so don’t limit your garden to daytime bloomers. If you want butterflies, include host plants for their caterpillars, not just nectar sources for adults. Monarchs need milkweed. Swallowtails need parsley, dill, or fennel.
Nesting sites matter as much as food. Leave dead trees standing when safe, or at least spare dead limbs. Many native bee species nest in hollow stems and old wood, not hives. You can build a simple bee house by drilling holes of varying width about 3 to 5 inches deep into a piece of scrap lumber and mounting it under eaves or on a post. For butterflies and bees that need minerals, create a damp salt lick by letting a hose drip onto bare soil and mixing in a pinch of sea salt or wood ash. Even setting out slices of overripe banana or orange can attract butterflies looking for nutrients beyond what flowers provide.