Last summer one of my pleasures was watching flocks of Chimney Swifts, with their swallowlike appearance and behavior, and their slender, scythelike wings cavorting in the sky above the Loblolly Field along Sandy Creek, in Mississippi. Chimney Swifts are migratory so by the time I left Natchez in November they had already departed for their overwintering grounds in the upper Amazon basin of Peru in South America.
When I got here I was glad that the skies above Komchen were just as busy with swifts swooping and darting for insects as they'd been all summer in Mississippi.
However, though Komchen's swifts looked almost exactly like Chimney Swifts, which are the only swifts in eastern North America, with my first glance I could see that Komchen's swifts weren't Mississippi's swifts. Komchen's swifts darted and fluttered with more quickness and agility than what I was used to seeing. That's because the swifts we have here are Vaux's Swifts, and Vaux's Swifts, which are 4-1/4 inches long, are smaller than Chimney Swifts, which are 5 inches long, and small birds are simply more agile than big ones.
Chimney Swifts do occur in the Yucatan, but only during spring and fall migration, as they pass between eastern North America and Amazonian Peru. In parts of western North America Vaux's Swifts are common during the summer, but migrate south during the winter. Here Vaux's Swifts are permanent residents, and I'm glad for that.
You can see details about the Vaux's Swift at www.mbr-pwrc.usgs.gov/id/framlst/i4240id.html.