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Welcome to this installment of BirdCast Traffic Reports, posts describing northeastern US nocturnal bird migration traffic rates, as calculated from a completely automated pipeline of algorithms. The images you see in Traffic Reports present the migration traffic rate (MTR), direction…

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.

IMPORTANT NOTE: Team Birdcast is focusing on preparing for tomorrow’s Global Big Day, and as a result we haven’t been able to write a thorough forecast and analysis by our usual Friday deadline. Here is an abbreviated forecast, with weather…

Migration conditions will be generally more favorable across southern half of the West this week where moderate flights will feature Wilson’s Phalarope, Red-necked Phalarope, Black Tern, Willow Flycatcher, Yellow Warbler, MacGillivray’s Warbler, and Green-tailed Towhee, while midweek in the East will see the most extensive moderate to heavy flights of Black-crowned Night-Heron, Semipalmated Plover, Short-billed Dowitcher, Black Skimmer, Common Nighthawk, Black-billed Cuckoo, Acadian Flycatcher, Eastern Wood-Pewee, Canada Warbler, Blackpoll Warbler, and American Redstart in a pulse of significantly warmer air.

Moderate movements, particularly from California east through the central and southern Rockies, featured Black Tern, Cordilleran Flycatcher, Plumbeous Vireo, Swainson’s Thrush, Black-headed Grosbeak, and Western Tanager and highlighted the period in the West, while moderate to heavy flights, particularly in the central and southern US, featured Common Nighthawk, Yellow-bellied Flycatcher, Least Flycatcher, Philadelphia Vireo, Veery, Magnolia Warbler, and American Redstart and highlighted the period in the East.

When birders in Cape May awoke on Monday morning, an interesting pattern was emerging (interesting is the norm in Cape May!). Numerous observers reported that numbers of migrants had arrived during and after the night and were still coming ashore from the Atlantic Ocean. The first real pulse of arrivals of this spring for a number of species had clearly occurred in Cape May. The combination of on the ground reports from eBird, nightly northeastern US radar data processing with BirdCast algorithms, and the excitement of spring arrivals inspired Team BirdCast to look a bit more closely at the events leading up to this movement.

Welcome to this installment of BirdCast Traffic Reports, posts describing northeastern US nocturnal bird migration traffic rates, as calculated from a completely automated pipeline of algorithms. The images you see in Traffic Reports present the migration traffic rate (MTR), direction of bird movement, and…