When it comes to birds, body temperature can vary greatly between different species. The average body temperature for birds tends to be around 105°F. However, some birds can have much lower body temperatures than this. So which bird has the lowest body temperature of all?
The Common Poorwill
The bird with the lowest recorded body temperature is the Common Poorwill (Phalaenoptilus nuttallii). This medium-sized bird is found across western North America. During winter months, the Common Poorwill enters a state of torpor in order to conserve energy. Its body temperature can drop to as low as 84°F during this time. This is the lowest body temperature of any bird recorded to date.
The Common Poorwill is able to survive these remarkably low body temperatures through specialized physiological adaptations. When torpid, the bird’s heart rate and breathing slow down dramatically. Its metabolism decreases to just 1-2% of normal levels. Body fat reserves provide energy during this prolonged dormant state. Torpor enables the Common Poorwill to survive colder winter periods when insects and other food sources are scarce.
Torpor in Birds
Torpor is a state of decreased physiological activity used by some species to save energy. It involves a regulated drop in body temperature and metabolic rate. Torpor is not the same as hypothermia, which is an unintentional and dangerous drop in body temperature. Birds use torpor strategically to maximize their chances of survival when conditions are harsh.
A number of other bird species are known to utilize torpor. These include:
- Poorwills
- Nightjars
- Swifts
- Hummingbirds
However, the Common Poorwill has the lowest recorded body temperature during torpor at 84°F. Other birds only drop their body temperatures to around 88-95°F while torpid.
How Low Body Temperatures Help Birds Survive
There are a number of benefits that torpor and lower body temperatures provide birds:
- Conserves energy – Their metabolic rate is dramatically slowed, requiring less energy.
- Requires less food – Foraging needs are reduced at a time when food is scarce.
- Avoids starvation – Birds can potentially survive for weeks in a torpid state.
- Provides thermal protection – Lower temperatures help prevent heat loss.
For small birds especially, torpor is an essential survival strategy during cold periods when food sources are limited. The Common Poorwill maximizes these benefits by lowering its body temperature further than any other bird.
Adaptations for Torpor
Birds have evolved a number of adaptations that enable them to use torpor effectively:
- Slowed metabolism – Their metabolic rate slows down dramatically, requiring much less energy.
- Fat deposits – Birds store body fat to provide energy during torpor.
- Reduced heart rate – Heart rate decreases significantly but circulation continues at very low levels.
- Minimized water loss – Their respiration rate drops during torpor.
These adaptations allow birds to overcome the physiological challenges of lowering their body temperature for extended periods. The Common Poorwill in particular has fine-tuned these adaptations to reach body temperatures as low as 84°F.
Other Cold-Tolerant Birds
While the Common Poorwill has the lowest recorded body temperature, other birds have adaptations that allow them to withstand extremely cold conditions:
- Emperor Penguins – Can survive temperatures as low as -76°F by huddling together.
- Snowy Owls – Have thick plumage insulation to retain body heat.
- Ptarmigans – Grow dense winter feathers and have feathered feet for warmth.
- Gyrfalcons – Reduce blood flow to extremities to avoid frostbite.
These behavioral and physiological adaptations allow various bird species to inhabit the harshest polar and alpine environments on Earth.
Measuring Bird Body Temperatures
Determining the body temperatures of wild birds requires specialized techniques. Some methods used by researchers include:
- Cloacal thermometers – Measure internal temperature by briefly inserting a small probe into the cloaca.
- Temperature dataloggers – Miniature sensors attached externally to record body temperature over time.
- Thermal imaging – Infrared cameras can detect surface temperatures of birds remotely.
These methods allow scientists to gather temperature data on birds with minimal disturbance. The lowest body temperature ever reliably recorded – 84°F in the Common Poorwill – was measured using cloacal thermometers.
Importance of Studying Torpor
Understanding bird torpor has implications beyond basic biology. Potential applications include:
- Wildlife conservation – How birds use torpor can inform habitat management efforts.
- Climate change impacts – Effects of changing winters on bird energy use and survival.
- Space travel – Inducing torpor could help preserve resources on long spaceflights.
- Human medicine – Mimicking natural torpor mechanisms could preserve organs for transplants.
The Common Poorwill’s remarkably low body temperature provides insights into the extremes of avian torpor. Continued study of this unique species will reveal more about the potential of torpor across fields.
Conclusion
The Common Poorwill holds the record for the lowest body temperature recorded in birds at 84°F. This moderate-sized bird uses exceptional torpor abilities to survive harsh winters across western North America. By dramatically lowering its metabolic rate and body temperature, the Common Poorwill conserves energy when food is scarce. Other birds can enter torpor, but none have been documented with body temperatures as low as the Common Poorwill. Understanding the extremes of torpor in this species can provide wider insights into bird biology, evolution, and much more.
