At a time when people are encouraged to isolate themselves and remain indoors to slow the spread of the 2019 coronavirus, many of us are feeling antsy or idle. But sitting inactive for long periods of time is the name of the game for the common poorwill. These birds are a member of the nightjar family. Common poorwills (Phalaenoptilus nuttallii) are small, nocturnal, insect-feeding birds that are found in western North America . They live in open, arid environments with patches of shrubbery. With their intricate brown, grey, and black patterned feathers, common poorwills blend in excellently with their environment .
The common poorwill’s main claim to fame is the extended amount of time in which they undergo torpor, a state of decreased physical or mental activity. Many nightjars undergo torpor, but none as long as the poorwill . The use of torpor by the poorwill is known to the indigenous people of southwestern America; the Hopi people called the poorwill hölchoko, or ‘the sleeping one’, due to its prolonged inactive states . The birds can remain in this state for 10 to 25 consecutive days, and the physiological patterns exhibited by poorwills in torpor are similar to those of hibernating animals . But what exactly does it mean to enter torpor? For the poorwill, this means lowering its body temperature by 4–35 Celsius degrees, reducing its body temperature to as low as 5°C (41°F) [2,4]. This also means the poorwill’s metabolic rate declines, decreasing its oxygen intake by over 90% [2,4]. Imagine being that cold and consuming only one tenth of your normal oxygen supply! You may now be wondering, why go through all of this trouble? Well, torpor allows the poorwill to minimize its energy usage and cope with unfavorable conditions, such as food shortages or extreme cold . However, torpor is not solely entered in times of energy emergency. Common poorwills enter torpor regularly throughout the year, except during the breeding season when they must remain active to mate and produce offspring .
In the case of the poorwill, the expression, “what goes up must come down”, is flipped: what goes down must come up. At the end of the poorwill’s torpor, its body must undergo rewarming to increase its temperature back to normal levels . The rewarming phase is the most energetically costly part of the torpor/rewarming cycle; however, when immediate surrounding temperatures are higher, less energy is expended during rewarming . Poorwills take advantage of this by settling on south or southwest facing terrain so they receive the maximum amount of sunlight, which warms up both their body and the surrounding environment . This behavioral strategy allows the poorwills to take advantage of what is termed “passive rewarming”, the use of environmental heat rather than metabolic processes to increase body temperature. Otherwise, rewarming can be achieved actively by shivering or other heat-producing metabolic processes .
As the globe battles against our current health crisis, one of the best defenses we have is to remain at home and suspend our normally social and active lives. But don’t be discouraged; settle in and channel your inner poorwill! Just as these birds decrease their activity level at times of unfavorable conditions, we too must suspend many of our regular activities during this pandemic. Conditions are poor now, but they will improve. And just like the common poorwill, we will come out of this state active, ready to socialize, and ready to resume our normal routines. So, stay safe and think poorwill!
Nicole W. Korzeniecki is a graduate student in the Animal Behavior Graduate Group at UC Davis. She’s interested in the dynamics of social insect colonies, specifically in host-microbiome interactions, collective decision-making, and the self-organization of complex behaviors.
Main featured image by Andy Teucher [Source]
- 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.
- Cornell Lab of Ornithology (2019) Common Poorwill Life History. All About Birds, Cornell Lab of Ornithology, www.allaboutbirds.org/guide/Common_Poorwill/lifehistory#habitat
- Woods, C. P., Zenon J. C., & Brigham, R. M. (2019). The avian ‘hibernation’ enigma: thermoregulatory patterns and roost choice of the common poorwill. Oecologia, 189(1), 47–53.
- Brigham, R. M. (1992). Daily torpor in a free-ranging goatsucker, the common poorwill (Phalaenoptilus nuttallii). Physiological Zoology, 65(2), 457–472.