Photo: narcah / Flickr / CC BY 2.0
Hummingbirds comprise around 320 species of birds in the Trochilidae family – a family native to the Americas. Hummingbirds are some of the smallest bird species in the world, with the highest animal metabolic rates.
The Trochilidae family contains the world’s smallest bird – the Bee Hummingbird (Mellisuga helenae) which grows to a maximum of six centimeters in length and weighs approximately two grams.
The largest hummingbird, called the Giant Hummingbird (Patagonia gigas), is still very small – weighing approximately twenty grams and measuring twenty centimeters in length.
Hummingbird feathers have splendid glittering colors that capture the eyes of birders and non-birders alike. Many people put out feeders to attract hummingbirds to their yards and enjoy watching their antics around flowers.
Those that have watched hummingbirds may have noticed that they sometimes stop their activity and sit motionless on a branch or hang upside down from a perch.
That has caused concern for many and has led to people asking if hummingbirds play dead, or if is there another phenomenon at play.
The answer is not straightforward, and we will take a deeper look into the information surrounding the question in the following article.
The Life Of A Hummingbird
Hummingbirds have an extremely high metabolism leading them to live an extremely energy-consuming lifestyle that requires them to eat one and a half to three times their body weight in food every day.
To do this, they have a unique feeding strategy that involves hovering next to a flower and using their long thin tongue to feed on nectar.
To hover successfully, the wings move at a rate of up to 70 wingbeats per second and that is why such a vast amount of energy is needed.
The Phenomenon Of Playing Dead
Feigning death or playing dead is a well-known phenomenon in the animal kingdom which is known scientifically as tonic immobility or thanatosis.
The most common reason for an animal to feign death is to avoid predation. It has been noted in many animal taxa, including mammals, fish, sharks, reptiles, insects, and birds.
There is, however, no scientific evidence of hummingbirds playing dead and therefore, hummingbirds do not play dead.
What Do Hummingbirds Do To Conserve Energy?
Hummingbirds, like many other smaller birds, can enter a state of torpor. Torpor is similar to hibernation, but it is a short-term change in physiological state, rather than a state of long-term dormancy.
What Happens In A Hummingbird’s Torpor?
When hummingbirds enter torpor, they decrease their body temperature, heart rate, and breathing rate to conserve energy.
During torpor, a hummingbird’s metabolic rate can drop to as much as 95% of the normal rate and their heart rate can decrease from between 1,000 and 1,200 beats per minute to a mere 50 beats per minute. Their energy usage drops to approximately 50% of the energy it would use while being active.
A hummingbird in torpor may look dead, as they often hang upside down, with their claws grasping onto a perch.
Why Do Hummingbirds Enter Torpor?
Cooling Themselves Down
There are multiple reasons why a hummingbird may enter the state of torpor, but the main reason is to conserve energy at night to survive when the temperatures cool down.
Hummingbirds maintain a body temperature of between 40 and 42 degrees Celsius during the height of activity, but their body temperature may drop as low as 5 degrees Celsius. That is the minimum temperature required to keep essential bodily functions active while at the same time, conserving the energy that is needed to survive the night.
In very cold temperatures, hummingbirds may not be able to conserve enough energy while maintaining bodily functions to survive one night.
They’re Hungry Or Hurt
Hummingbirds may also enter a torpid state during the day when they cannot obtain the required amount of food and energy.
Entering a torpid state is particularly useful for injured or sick hummingbirds because they don’t have the required amount of energy to feed.
Hummingbirds can die from starvation if they do not eat for more than two hours, so entering the state of torpor provides the hummingbird with a safe way to rest and recover.
The reason can also simply be because the hummingbird needs to rest during the constant feeding activity.
When & How Does Their Torpor End?
When the hummingbird is ready to exit the state of torpor, the wings start quivering, which aids the circulation of blood around the body. This increases the body temperature until it reaches the normal level of functioning.
The process of emerging from torpor can take up to one hour.
Dangers Of Torpor
While in torpor, hummingbirds are unresponsive and they are incapable of reacting and flying away when a predator approaches.
There is also a risk of hummingbirds becoming more susceptible to diseases because the processes used to restore overall health, remove waste material and repair cells do not take place while in the state of torpor.
Misconceptions Surrounding Motionless Hummingbirds
If a hummingbird appears to stop moving when it sees a predator, it is not playing dead or entering torpor. In this case, it is simply staying motionless while in the predatory field of vision, hoping that the predator will be unaware of its presence.
It is different from entering torpor because it does not involve a decrease in physiological activity and the bird could still fly away if the opportunity presented itself.
Hummingbirds may appear to play dead, but this is not what really happens. Instead, hummingbirds enter a state of torpor to conserve energy while resting during the day and being inactive at night.
Hummingbirds use torpor to survive. They may be seen hanging upside down on a branch or feeder when they are in a torpid state. It is best to leave the bird alone in this state because touching the bird to see if it is alive may cause a disturbance, leading to the bird using unnecessary energy that it cannot afford to lose in extreme cases.
It may appear as though hummingbirds sleep when in a torpid state, but it is still unknown whether this is true. That is because the body temperature is substantially lower than the temperature required to sleep under normal conditions.
Read More About Hummingbirds:
- Where & How Do Hummingbirds Sleep?
- Can Hummingbirds See In The Dark?
- Can Hummingbirds Fly In The Rain?
- Can Hummingbirds Fly Backwards?
- Can Hummingbirds Open Their Beaks?