Birds swallowing fish is not a common occurrence, but it does happen from time to time. Generally, only large bird species are capable of swallowing small fish whole. The ability to swallow fish depends on the size and characteristics of a bird’s throat and digestive system.
Some key questions around birds swallowing fish include:
What types of birds swallow fish?
The bird species most likely to swallow fish are seabirds, wading birds, birds of prey, and other large bird species. Examples include pelicans, herons, egrets, gulls, ospreys, eagles, owls, storks, and cormorants. These birds have large throats and digestive systems capable of accommodating fish in their diet.
How do birds swallow fish whole?
Birds that swallow fish whole use their muscular throats and elastic esophagi to ingest fish. They are able to open their mouths very wide and relax their throats to temporarily expand their swallowing capacity. Their digestive acids also help break down the fish once swallowed.
What size fish can birds swallow?
The size of fish a bird can swallow depends on the size and species of the bird. Large seabirds like pelicans and cormorants can swallow fish up to 1-2 feet long. Smaller bird species can only manage swallowing smaller fish, typically under 8 inches long.
Do all birds that eat fish swallow them whole?
No. Many birds that eat fish do not swallow them whole. For example, kingfishers catch fish but beat them against a perch before swallowing smaller pieces. Likewise, herons, egrets and some raptors may tear fish into chunks before eating them. Only the largest birds swallow fish whole.
Why do some birds swallow fish whole?
Birds evolved the ability to swallow fish whole as an adaptation for hunting and feeding efficiency. Swallowing fish whole allows birds to quickly capture and consume prey. It also minimizes handling time and energy spent eating. For seabirds, the ability lets them efficiently feed on schools of small fish.
Bird Species Known to Swallow Fish
The following birds are known to be capable of swallowing whole fish:
Pelicans
| Species | Fish Size Swallowed |
| Brown Pelican | up to 30 cm (1 ft) length |
| American White Pelican | 20-30 cm (8-12 in) length |
Pelicans are large waterbirds with very expandable throat pouches that let them swallow large fish. Brown pelicans plunge dive for fish and are able to swallow them whole. American white pelicans scoop up fish into their bills and swallow them.
Herons and Egrets
| Species | Fish Size Swallowed |
| Great Blue Heron | 15-20 cm (6-8 in) length |
| Grey Heron | 15-20 cm (6-8 in) length |
| Great Egret | 10-15 cm (4-6 in) length |
These long-legged wading birds all regularly swallow smaller fish whole after catching them with their sharp bills. They retract their sinuous necks to align fish for swallowing.
Cormorants
| Species | Fish Size Swallowed |
| Double-crested Cormorant | up to 60 cm (2 ft) length |
| Great Cormorant | 25-35 cm (10-14 in) length |
Cormorants are highly adapted for catching and swallowing fish. They have expandable throat pouches and are able to swallow large fish whole. Great cormorants are known to occasionally drown from getting large fish stuck in their throats.
Other Seabirds
| Species | Fish Size Swallowed |
| Northern Gannet | up to 30 cm (1 ft) length |
| Brown Booby | up to 25 cm (10 in) length |
| Laughing Gull | 5-10 cm (2-4 in) length |
Seabirds like gannets, boobies, and gulls use plunge diving to catch fish and are adapted for swallowing them. Gulls take smaller fish than the larger gannet and boobies.
Birds of Prey
| Species | Fish Size Swallowed |
| Bald Eagle | 50-60 cm (1.5-2 ft) length |
| Osprey | 25-40 cm (10-16 in) length |
| Snowy Owl | 15-25 cm (6-10 in) length |
Large raptors like eagles, ospreys and owls use their formidable talons to snatch fish from the water and swallow them head first. Their digestive systems adapt them for whole fish ingestion.
Other Large Species
A variety of other large bird species are capable of swallowing fish depending on their size, including:
– Storks – up to 25 cm (10 in) length fish
– Cranes – 15-20 cm (6-8 in) length fish
– Geese/Swans – 10-15 cm (4-6 in) length fish
– Hornbills – 5-10 cm (2-4 in) length fish
How Birds Physically Swallow Fish
The physical process by which birds swallow whole fish relies on the expandable characteristics of a bird’s throat and esophagus. Here are some of the ways birds are able to pass large fish down their throats:
- Extensible throat skin – Allows throat expansion
- Stretchable esophagus – Can elongate to accommodate fish
- Relaxation of muscles – Throat muscles relax to open up passage
- Lowered larynx – Larynx moves down to open up room
- Raising tongue backward – Tongue gets flattened and lifted
- Wide opening of mouth and jaw – Unhinges mouth widely
In addition, seabirds have expandable throat pouches that provide even more room for swallowing large objects like fish. Raptors are able to swallow fish head first, which provides a more streamlined shape for ingestion.
Step-by-Step Swallowing Process
The swallowing process occurs in the following general sequence:
1. Bird spots and grabs fish, usually with bill
2.manipulates fish into head/bill first position
3. Opens mouth and throat as wide as possible
4. Relaxes throat and begins passing fish inside
5. Esophagus expands to make room for fish
6. Peristaltic contractions push fish down throat
7. Esophageal sphincter opens to pass fish into stomach
8. Stomach acids and muscles break fish down
Unique Adaptations for Swallowing Fish
Specific adaptations give some bird groups an enhanced ability to ingest fish, including:
Pelican Throat Pouch
Pelicans have an extremely large expandable throat pouch that provides room for fish to be contained before swallowing. This allows them to scoop up many fish at once.
Cormorant Mouth Position
A cormorant’s mouth is positioned such that it can more easily swallow large objects. The mouth positioning enables easier alignment of fish down the throat.
Seabird Saline Glands
Seabirds have special glands that excrete excess salt, allowing them to swallow fish from salty ocean waters. The glands eliminate the excess salt they ingest.
Oil Secretion
Some seabirds secrete oil from a stomach gland which coats swallowed fish. This helps seabirds digest fish bones and exoskeletons by making them easier to regurgitate.
Raptor Talons
Sharp raptor talons enable catching fish firmly so they can be more easily maneuvered into swallowing position. The talons give raptors a strong grip on fish.
Role of Swallowed Fish in Birds’ Diets
For many bird species, the ability to swallow fish plays an integral role in their dietary habits and survival:
Key Calorie and Nutrient Source
Fish provide a vital source of protein, calories, vitamins, minerals and healthy fats for birds. Swallowed fish aid birds’ growth and development.
Access to Aquatic Food Source
Swallowing fish allows birds to take advantage of an abundant food niche. Fish are a plentiful prey source birds can access.
Alternative to Warm-Blooded Prey
Fish provide a cold-blooded alternative to birds and mammals, which some species rely on. Fish do not require energy-intensive warm-blooded hunting.
Abundant and Renewable
As a prey source, fish are plentiful, easily found, and rapidly renewing, providing a reliable nutrition source for sustained feeding by bird groups.
Coastal and Freshwater Habitat Food
Swallowing fish enables coastal and inland waterway bird species to feed on locally available food sources suited to their environments.
Challenges and Risks of Swallowing Fish
While important for feeding, swallowing whole fish does pose some risks and challenges to birds:
Choking Hazard
Large fish or those swallowed at the wrong angle can get lodged in a bird’s throat, blocking airflow and causing death by choking. Cormorants in particular suffer choking on large fish.
Difficulty Breaking Down Bones
Bird stomachs and digestive acids are not designed to efficiently break down larger fish bones, making them difficult to pass and metabolize.
Energy Cost
Expanding the throat and passing large fish requires extra energy expenditure and effort compared to smaller prey. It costs birds more calories.
Increased Vulnerability
Birds are more exposed to predators and threats when focused on handling and swallowing larger fish that require more effort and time to ingest.
Dangers of Marine Toxins
In marine habitats, swallowing fish exposes birds to higher levels of mercury, PCBs, and other aquatic toxins that accumulate in fish over time. This can poison birds.
Unusual Cases of Birds Swallowing Fish
While most fish-swallowing birds are large waterbirds or raptors, some unusual cases have been documented of smaller landbirds ingesting fish:
Seagulls Swallowing Live Goldfish
Cases have been reported of pet goldfish being snatched up and swallowed by opportunistic seagulls. These very small fish provide miniature meals.
Kingfishers Swallowing Small Aquarium Fish
In household ponds and aquaria, relatively small kingfishers have been observed swooping down to grab and swallow small pet fish like guppies and tetras. Their agility allows them to catch even fast-moving indoor fish.
Songbirds Accidentally Ingesting Fry
There are rare incidents of songbirds unintentionally ingesting baby fish or fish eggs when feeding on algae, insect larvae or other aquatic items around freshwater habitats. The tiny fish fry are accidentally swallowed.
Herons Impaling Larger Fish
While limited in how large a fish they can swallow whole, herons have been witnessed impaling bigger fish on their bills – breaking them into more manageable chunks that can be piecemeal ingested.
Eagles Dropping Fish to Break Apart
Bald eagles sometimes snatch fish exceeding their maximum swallowing size. They then fly upward and drop the fish repeatedly to break it into smaller, more swallow-able bits.
Conclusion
The ability to swallow fish is an important adaptation seen in various large waterbirds and raptors. Their expandable throats and digestive systems allow them to take advantage of fish as an abundant food source. Carefully swallowing fish helps sustain these bird species in their respective habitats and ecological niches. However, ingesting whole fish does pose some risks and challenges as well. Overall, observing how different birds swallow fish provides fascinating insight into their anatomy, behavior and feeding strategies.
