Nocturnal Bird Migration over Frederick, Maryland, Spring and Fall 2021.

Recording of nocturnal flight calls opens a fascinating window into the largely hidden world of nocturnal bird migration. In 2021, I recorded calls from my backyard on most suitable nights in the spring and fall, for a total of 1,415 hours of recording over 157 nights. To the best of my knowledge, this was the most comprehensive study of nocturnal flight calls conducted in Maryland. I detected more than 164,000 flight calls that were identifiable to at least genus or family, attributed to approximately 86,000 individual birds of 133 species--at least 110 of which were thought to be overflying migrants, with the remainder local residents. Swainson's Thrush was easily the most abundant species, accounting for almost 40% of all calls, but there were 100s or 1,000s of detections for 34 other species. Seasonal patterns show a strong peak of spring migration in early May and a more protracted fall peak in mid-September through mid-October. In addition to the common migrants, I detected several unexpected county or state rarities, including Black Rail, Whimbrel, Bicknell's Thrush, Evening Grosbeak, Clay-colored Sparrow, and Connecticut Warbler. [ABSTRACT FROM AUTHOR]