Cal molecular biology student Edwin Wu was walking along the Virginia Street Extension on October 21 at around 7 pm, after dark, when he found this bird on the ground. He recalls,
I first noticed that there is light reflected by something on the ground and thought it was a piece of trash. As I walked close, I found out it was a bird, and its eyes can reflect light. On October 23rd, I came back and found the bird at the exact same spot but on branches just a little bit above the ground, probably because it was rainy and the ground was wet. The bird just silently sat on the ground or on low branches without any songs or calls.
After October 23rd, I also tried several times at night around 20:00 to find it again, but I did not see it anymore.
The bird he spotted is rare and has very unusual qualities. Actually, bird observers don’t know much about its population numbers. That’s because it’s a nocturnal bird and it’s cryptic in its habits, hard to distinguish from background, and able to hide and remain completely motionless for prolonged periods. Surveys commonly overlook it.
Its metabolism is unique among birds. It can reduce its body temperature to 41 degrees Fahrenheit or less, lower than any other bird. It cuts its oxygen consumption to less than ten percent of normal. In winter, it can remain completely inactive — not moving a muscle — for ten days or longer, up to 25 days. In this it resembles hibernating mammals. During temperate weather, it doesn’t merely sleep, it enters a daily torpor, saving energy. It also handles extreme heat. At an ambient temperature of 116 degrees F, it cools itself more efficiently than any other known bird species.
This bird hunts insects at dusk, dawn, or on moonlit nights. The beak looks unremarkable, but it can open its beak amazingly wide and high, and can swallow big moths and other flying insects. Its red eyes are specially adapted for night foraging. The stiff bristles around its beak, visible in the photo, are thought to help it sense and snag insects in flight. Judging by the brightness of the tip of its tailfeathers, this one is probably a male.
Efforts to study their unique biology in captivity have not gone far because in captivity the birds die. Consequently, bird researchers rate them as “one of the least understood of North American birds.” Key details of their metabolism remain “tantalizingly elusive.” Their breeding habits (other than that they are ground nesters) and their migration patterns are also poorly understood.*
*Woods, C. P., R. D. Csada, and R. M. Brigham (2020). Common Poorwill (Phalaenoptilus nuttallii), version 1.0. In Birds of the World (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.