When, where, and how far will birds migrate? Our migration forecasts will answer these questions for the first time.
Each night, from local sunset to local sunrise in the Eastern time zone, a BirdCast server downloads radar data from 16 stations in the northeastern US. These data are composed of every scan of the atmosphere made by these radars during this time period, with a particular focus in our case on radar reflectivity products representing the magnitude of targets (whether meteorological, like rain and hail, or biological, like birds, bats, and insects) at a given radar. A pipeline of algorithms extracts information from these radar data about birds, and the resulting bird-specific summary imagery is published daily in early afternoon eastern time (give or take).
Locally favorable migration conditions increase in extent over the course of the work week in the East and feature Common Nighthawk, Ruby-throated Hummingbird, Olive-sided Flycatcher, Eastern Wood-Pewee, Great Crested Flycatcher, Prothonotary Warbler, and Northern Waterthrush, while conditions in the west remain largely marginal for migration, with locally favorable patches featuring movements of Greater Yellowlegs, Western Sandpiper, Red-necked Phalarope, Warbling Vireo, Yellow Warbler, MacGillivray's Warbler, and Western Tanager.
As spring migration winds down, light flights featuring late shorebirds, Eastern Kingbird, Cedar Waxwing, and Grasshopper Sparrow continue in the West early and late in the period primarily in montane areas, while the last vestiges of moderate to locally heavy flights featuring late shorebirds, Yellow-billed Cuckoo, Cedar Waxwing, Sedge Wren, and Henslow's Sparrow grace the East during the second half of the forecast period.
As the peak of migration in most areas recedes with another spring season passing, portions of the West experience light to moderate flights featuring White-throated Swift, Western Wood-Pewee, Warbling Vireo, Swanson's Thrush, Cedar Waxwing, and Gray Catbird primarily mid and late period and patchily distributed moderate to heavy flights featuring Yellow-billed Cuckoo, Eastern Kingbird, Eastern Wood-Pewee, Cedar Waxwing, Orchard Oriole, and Bobolink occur in the East against a backdrop of a dynamic weather scene.
A period of generally favorable migration conditions featuring light to moderate flights of Common Nighthawk, Broad-tailed Hummingbird, Willow Flycatcher, Common Yellowthroat, Grasshopper Sparrow, and Western Tanager is in store for much of the West, particularly in the Rockies, while an unfavorable cool and wet start to the East gives way to later week moderate to heavy flights of White-rumped Sandpiper, Dunlin, Red-necked Phalarope, Black Tern, Black-billed Cuckoo, Red-eyed Vireo, Mourning Warbler, and Scarlet Tanager.
Light to moderate flights graced many areas from California east through the Rockies and featured Black Tern, Willow Flycatcher, Cordilleran Flycatcher, Gray Catbird, and Bobolink, while pulses of moderate and heavy flights featuring White-rumped Sandpiper, Common Nighthawk, Black-billed Cuckoo, Alder Flycatcher, Bay-breasted Warbler, and Canada Warbler were scattered across the East.