Migration update: the top 5 flights in spring 2021

Andrew Farnsworth and Adriaan Dokter The Cornell Lab Jun 01, 2021

The spring of 2021 offered many migration highlights (fact: every migration season has an enormous highlight reel!), and here we showcase the mega-flights of this soon-to-be-in-the-books season. Below is an animation of our top 5 migration nights, a by-the-numbers ranking of the biggest flight nights for nocturnally migrating birds over the contiguous US during peak of spring movements.

The list for 2021, with a little discussion of each movement, follows:

Number 5. 2-3 May. Just over 552 million birds were aloft at the peak of this night’s movement, with literally white hot intensity over central and northern Texas. Movements in these areas of the Lone Star State surpassed 50,000 birds per kilometer per hour, amazing! Note, however, that this intensity was not widespread across the contiguous US, and the magnitude of movement in Texas dominated the country’s migration. There are several areas with less intense but still significant flights, including portions of the southeastern US, the mid Atlantic region, and the Upper Midwest. With so much migration traffic occurring on this night in the southern and eastern US, it is no surprise that much of the movement is in a generally northerly direction in the center of the US and in a northeasterly direction in East.

Number 4. 15-16 May. Coming in at almost 576 million birds is this night, on which we saw a very different, much more uniform distribution of intense movements in the northern and central Plains, the central Mississippi River valley, and portions of northern New England. The directions of travel are noticeably different, as well, with a broader diversity particularly apparent in the center of the US where birds were moving toward the northwest, the north, and the northeast. In the eastern US note the similarities to 2-3 May, with birds moving generally in the northeasterly direction in many areas.

Number 3. 1-2 May. The very beginning of the month saw nearly 579 million birds aloft, with heavy traffic over Texas and the central Mississippi River valley as well as portions of the coastal southeastern US. Travel directions in the areas experiencing the most intense flights were similar to those on 2-3 May.

Number 2. 13-14 May. We blew past the 600 million bird mark to 645.5 million birds on this night, with the central US experiencing the bulk of the flight. Northerly movements were the dominant direction of travel.

and, drum roll, please ….

Number 1. 14-15 May. With a whopping ~700 million bird night, the movements occurring on this night in the central and southern US as well as those in the northern Plains, Upper Midwest, and portions of the Northeast represented the largest single night of movement we have visualized since the start of BirdCast migration mapping. Although there were no white hot intensities here, the magnitude of very high intensity flights was widespread, begetting an epic movement eclipsing all others though with a similar diversity of flight directions as our number 4 and number 2 nights.