Swallow on an Odd Night Roost

Explanation: As I stepped outside a rental house here in central coastal California, with the porch light on, I happened to glance up and was quite surprised to see a nighttime visitor perched on the porch light lamppost, sitting in the bright light.

This is a Barn Swallow, a very common and widespread landbird and migrant found throughout the world.

Barn Swallows are well-named, as they have long adapted to using human-made structures for nest sites, including bridges, buildings, towers, and more.

But there is little information on their use of artificial structures and sites for nighttime roosts. Some studies refer to use of reedbeds, grasslands, marshes, and other natural sites.

Further, Barn Swallows tend to roost in pairs or in small colony groups.
This one, however, was solitary, perhaps temporarily stopping here on a migration northward, as this was mid-May.
This bird is an adult, as the tail is deeply forked, whereas the tail in juveniles has only a shallow fork.
The species is indeed a classic human commensal, an organism that tolerates or even depends on humans for food, shelter, or other needs.

EPOW - Ecology Picture of the Week