Notes from the Field - A Nighttime Trill…
Common poorwill observed on Mariano Rancho Preserve, Photo by Katie Daniels
On a brisk, overcast morning in January, armed with a shovel, I ventured into Mariano Rancho Preserve to tackle my day's mission: the manual removal of invasive crimson fountain grass (Pennisetum setaceum). This rapidly spreading fire-prone perennial grass has a penchant for sprouting from rock crevices, demanding careful scrutiny of the substrate to avoid missing smaller sized individuals. Kneeling down to inspect the green carpet of winter plant growth, I happened upon a seemingly lifeless large-ish bird, perfectly disguised as a rock or shed branch, allowing it to blend seamlessly with its surroundings.
The common poorwill (Phalaenoptilus nuttallii) is an understudied and enigmatic nocturnal bird. Found across western North America as residents in the American southwest and northern Mexico, and as migrants breeding in British Columbia to Mexico, this small member of the nightjar family possesses several distinctive features that set it apart from its avian counterparts. One of the most remarkable traits of the common poorwill is its ability to enter into a state of torpor, a hibernation-like condition, during periods when food is scarce. The Hopi word for this species is Hölchoko, “the sleeping one”. This is the only bird known to be completely inactive for long periods of time through the colder months.
Common poorwills are most active at night when they forage for insects, with flight patterns reminiscent of flying bats or moths. Their large eyes, wide mouth, and specialized rictal bristles (feathers around their mouth that help to both sense and funnel insects captured in flight) make them efficient nighttime predators, capable of catching moths, beetles, and other flying insects with precision. The common poorwill is also known for its distinct vocalizations. Its call and song are identical, a soft, repetitive “poor-willip”, most intensely heard at dawn, dusk, and on moonlit nights during breeding season. This unique sound contributes to the bird’s mystique, often heard in the quietude of the wilderness during the warmer months.
Because the behavior, distribution, and abundance of this unusual bird is not well understood, neither are the needs for its conservation, particularly considering the increasing threats of climate change and habitat loss. Protecting and stewarding diverse and intact natural areas like Mariano Rancho Preserve from development and degradation from invasive species may serve as crucial support for this remarkable animal as we learn more about it. The common poorwill stands as a testament to the wonders of nature, showcasing unique adaptations that enable it to thrive in its nocturnal niche. As we delve into the mysteries of this extraordinary bird, we gain a deeper appreciation for the intricacies of the natural world that continue to captivate and inspire.
Sedate common poorwill discovered on Mariano Rancho Preserve while removing invasive crimson fountain grass (Pennisetum setaceum)
Photo by Katie Daniels
Mariano Rancho Preserve slope with coastal sage scrub invaded by crimson fountain grass (Pennisetum setaceum)
Photo by Katie Daniels
References
Brauner, J. (1953). Observations on the Behavior of a Captive Poor-Will. The Condor, 55(2), 68–74. https://doi.org/10.2307/1365027
Cornell Lab of Ornithology. 2020. Birds of the World website. Common Poorwill (Phalaenoptilus nuttallii) [Accessed 28 March 2024]
Woods, C. P. & Brigham, R. M. (2004). The avian enigma: ‘hibernation’ by common poorwills (Phalaenoptilus nuttallii). Life in the cold: evolution, mechanisms, adaptation, and application. Twelfth International Hibernation Symposium. Institute of Arctic Biology, University of Alaska Fairbanks, USA.