Birds are capable of doing many things that humans cannot do alone (without a machine).
Of cause, flying is the obvious one.
Other than that, some nocturnal birds such as Owls can see in the dark. Oilbirds, on the other hand, have advanced ears from which they locate their prey – the phenomenon called echolocation.
Penguins can swim underwater for more than 10 minutes. Some soaring birds such as Vultures can lock their extended wings and glide for hours. Those are all fascinating. Isn’t it?
But, if you ask, can birds breathe underwater? The answer is “NO”.
Birds cannot breathe underwater since they do not have gills (as in fish) to extract oxygen from the water. Their respiratory system consists of static lungs and several air sacs that facilitate gas exchange – oxygen and carbon dioxide, through inhalation and exhalation.
Yet, we know that Emperor Penguins can dive to a depth of about 500 meters and can stay underwater for about 18 minutes. And Thick-billed Murre possesses the Guinness World Record for the deepest dive by a flying bird with 210 feet dive.
So, how can they do that? Let’s dive deep into the topic.
How does the Respiratory System of a Bird Work?
Birds are very active animals that have high metabolic rates. Some do power flights in high altitudes where oxygen is less. Hence, they demand a high rate of oxygen supply to maintain their physiological needs.
To facilitate that, the respiratory system of birds works very efficiently. Well, it is the most efficient one among animals.
The avian respiratory system consists of small non-inflatable lungs and nine air sacs. It does not include a diaphragm as in mammals. And also, air flows unidirectionally through bird lungs. Hence, the lungs get continuous fresh, oxygenated air flow during both inhalation and exhalation.
When a bird inhales air, it takes two breathing cycles for it to remove the air taken in. The inhalation and exhalation process of birds happen as follows,
- Inhalation 1: When the bird inhales, air enters from the nostrils and passes through the trachea to the bronchus. And half of that air goes to the lungs and the rest is temporarily stored in posterior air sacks.
- Exhalation 1: Deoxygenated air from the lungs and anterior air sacs (which were filled in the previous cycle) goes out through the trachea. At the same time, fresh air stored in posterior air sacks during Inhalation 1 moves into the lungs.
- Inhalation 2: Deoxygenated air in the lungs is pushed to anterior air sacs for temporary storing, while fresh air inhales as explained in Inhalation 1.
- Exhalation 2: Same as Exhalation 1. During this exhalation, the last half of the air entered in Inhalation 1 has also been moved out.
So, birds get the oxygen supply during both inhalation and exhalation. Therefore, a continuous exchange of oxygen and carbon dioxide happens between blood and air capillaries. So, the system is more efficient than other animals.
But it is now clear to us that birds cannot breathe underwater since their respiratory system is not designed to do it.
How do Birds Get the Oxygen Supply When Diving Underwater?
Birds hold their breath when diving underwater. So, they need to store air sufficiently to keep the oxygen supply during dives.
But, mostly, birds dive for foraging, and that activity demands more energy. That means the demand for oxygen is high underwater.
To do effective dives, the bird’s body possesses many physiological adaptations. They have relatively large lungs. Their body has high oxygen storage capacity. In addition to having nine air sacks that support efficient respiration, their blood has a greater oxygen-carrying capacity. And also, oxygen is stored as oxymyoglobin in muscle cells.
During dives, the heart rate of birds slows down, and blood flow is redistributed to the heart.
Further, when a diving bird exceeds the aerobic diving limit (maximum submergence time that a diving bird can stay before it uses anaerobic metabolism), it metabolizes anaerobically underwater while a constant supply of oxygen is maintained to the heart, central nervous system, and oxygen-dependent tissues. That optimizes oxygen consumption.
However, even though all diving birds share most of those mentioned features, oxygen demand during a dive is different from one bird species to another. Some birds forage aquatic vegetation, amphipods, and snails which are relatively nonmoving prey. So, they spend less energy for foraging, thus demanding less oxygen underwater.
On the other hand, piscivorous foragers such as common loons, need to swim and capture fish while holding their breath. Hence, they are very active and need to stay comparatively longer time underwater. So, the demand for oxygen is relatively high for them when diving.
Similarly, flying divers and flightless divers too have many differences. From them, flightless diving birds have relatively more adapted systems for diving than flying birds. Penguins are the most specialized divers that can swim underwater for several minutes.
How Can Penguins Stay Underwater for Several Minutes?
First, let’s look at why penguins are specialized divers among other birds.
Like all other diving birds, mostly, penguins too dive for foraging. However, in terms of depth of dives, swim speed underwater, and duration of dives, penguins are unique.
Some maximum recorded diving depths of different species of sea birds.
These seem to lower the limits of their actual capabilities of them as King Penguin and Emperor Penguins can reach depths low as 500 meters. So, penguins are very impressive deep divers.
In order to achieve such greater depths, they have to be underwater for longer time periods. On average, the dive durations of Emperor Penguins range between 2-8 minutes. However, they are capable of holding their breath even for about 18 minutes when having deep dives. That is unmatched to even some marine mammals.
When it comes to swimming speed, on average, birds’ swim speeds range between 1-3 meters per second. But it is estimated that some Emperor Penguins may swim at 3.5 – 4 meters per second. That is a comparable speed even to Seals and Sea lions.
So, undoubtedly, penguins are impressive diving birds. In order to achieve all those impressive records, their bodies have adapted in many ways.
Since Penguins are smaller in size compared to marine divers such as seals, they have limited storage space for oxygen in the body. Hence, they store oxygen in many ways. From total stored O2 in Penguins, about 29% is stored in lungs and air sacs, about 38% is in blood, and the remainder (33%) is stored in muscles.
Similar to other birds, blood supply is limited to the heart, brain, and other oxygen-dependent organs. And their body is capable of utilizing oxygen in red blood cells the most.
In addition, Penguin bones are solid, and it reduces buoyancy due to air stored in their body. Positive buoyancy is one of the main challenges many diving birds faces and a reduction in that is a greater help for Penguins. And they can propel underwater through their short, flattened wings. Due to the torpedo-shaped body, they can swim with comparatively less friction.
So, as flightless water birds, Penguins live in the water for most of their time even though they can not breathe underwater.
Do Birds Die Due to Drowning?
Yes, birds may drown since they cannot breathe underwater.
One of the related research on the drowning of birds was done by a group of scientists led by the Zoological Society of London. In this study, the team has studied 12 starling drowning incidents. They have concluded that the most likely cause of death of 10 out of 12 birds was drowning.
However, the deaths of birds due to drowning has reported very rarely.
The drowning of birds may cause due to inexperience (especially among young birds) and the inability to identify the water hazard. Or due to an unexpected occurrence of an event that makes birds stay underwater longer than what their system is capable of during a dive that force them to breathe and drown.
Birds are not capable of breathing underwater since their respiratory system does not support that. It does not include gills. But for some birds, water is their habitat and they can dive for longer periods due to their well-adapted body and efficient respiration systems.
The best example of diving birds is penguins. Some species such as emperor penguins are capable of reaching about 500+ meters deep and can stay underwater for 10+ minutes.