Rufous hummingbirds and late spring flowers

The serviceberry bushes at Discovery Park hold their white flowers open to the morning light. Five petals each, clustered along branches that two weeks ago were bare. The Saskatoon serviceberry blooms now in late spring, and the timing matters more than you might expect. Listen for the high whir of wings, a sound like a tiny motor running at impossible speed.

The rufous hummingbird arrives in the Pacific Northwest when the flowers do. This threatened migrant, no bigger than your thumb, travels two thousand miles from Mexico to reach these coastal meadows and forest edges. The male rufous hummingbird burns orange across his throat and back, a color that catches the light as he hovers at each serviceberry cluster. His heart beats twelve hundred times per minute. His wings stroke eighty times per second. He weighs less than a nickel, but his flight muscles make up thirty percent of his body mass. Every flower he visits must pay for this extravagant machinery of flight.

The serviceberry provides what he needs. Each small white bloom holds a drop of nectar, sugar water concentrated enough to fuel those racing wing beats. The rufous hummingbird feeds every ten to fifteen minutes throughout the day, visiting up to two thousand flowers between dawn and dusk. He cannot store much energy in his tiny frame, so the flowers must be there when he needs them. The serviceberry obliges, opening its blooms just as the hummingbirds push north through the region. This is not coincidence but consequence, the result of countless springs when the birds that arrived too early or too late found fewer flowers, less fuel, smaller chances of reaching the northern breeding grounds. The lilac bushes nearby are finishing their purple sprays, their peak nectar flow already past. But the serviceberry holds steady through late spring, its white clusters lasting long enough to see the hummingbirds through their journey. The rufous hummingbird gives something back to the serviceberry as he feeds. Pollen grains stick to the feathers around his bill and throat as he probes each flower. When he moves to the next bloom, some of those grains brush off, fertilizing the plant that feeds him. The serviceberry depends on this exchange. Its flowers need cross-pollination to set the dark berries that will ripen in summer, feeding thrushes and waxwings and bears. Without the hummingbirds and other pollinators, the serviceberry would bloom but not fruit, spending its energy on flowers that lead nowhere.

The relationship runs deeper than a simple trade of nectar for pollination. The rufous hummingbird's spring migration is timed to follow the wave of flowering that moves north with the warming season. Desert wildflowers in Arizona bloom first, then mountain meadows in Oregon, then coastal shrubs here in Washington. The hummingbird rides this floral wave northward, each stop providing the fuel for the next leg of the journey. Break the chain anywhere and the whole migration falters. Climate change pushes some flowers to bloom earlier, before the hummingbirds arrive. Development removes others entirely. The rufous hummingbird population has declined by sixty percent in the last fifty years, partly because the flowers it depends on no longer bloom when and where they should.

Step closer to the serviceberry bush and you might see the tiny scratches on the bark where a rufous hummingbird has perched between feeding bouts. The males are territorial, defending their flower patches with dives and chases that seem impossibly aggressive for something so small. But the aggression makes sense when you understand the mathematics of migration. Every flower counts. Every calorie matters. The white petals around you are not just decoration but fuel stations, precisely timed to appear when a tiny traveler needs them most.