72 Microseasons of the Pacific Northwest

By mid-April the Pacific Northwest sky is alive with swallows. Violet-green swallows (Tachycineta thalassina) — one of the first migrants back — pour in from late March onward, their iridescent green-and-purple backs flashing in low light as they quarter over ponds and streambanks. Tree swallows (Tachycineta bicolor), barn swallows (Hirundo rustica), and cliff swallows (Petrochelidon pyrrhonota) follow in successive waves through April, each species identifiable by its flight silhouette: the forked tail of the barn swallow, the squared tail of the tree swallow, the stumpy tail of the cliff swallow. Watch for violet-green swallows investigating woodpecker holes, rock crevices, and nest boxes — they are cavity nesters and begin claiming sites almost immediately on arrival. Tree swallows compete for the same holes and nest boxes, and aerial disputes are common, with birds hovering and dive-bombing each other above wetland snags. Barn and cliff swallows, which build mud nests on bridges and rock faces, can be seen gathering mud at streamside puddles and creek banks through April and into May. The diversity is highest in the Interior Valleys, where five or six species may hawk insects simultaneously over Willamette Valley wetlands, Fern Ridge Reservoir, and the Columbia River bottoms. Puget Sound observers should check Nisqually National Wildlife Refuge and the Snohomish River delta. The cliffs at Cape Flattery and the river bridges of the Olympic Peninsula host nesting cliff swallows, with work beginning as soon as warm weather stabilizes insect abundance. By late April, the combined chatter of hundreds of swallows feeding over water is one of the defining sounds of spring in the Pacific Northwest.