Quick Answer
Grey herons are opportunistic predators that will eat a variety of prey, including small mammals, amphibians, reptiles, insects, fish, crustaceans, mollusks, and even small birds on occasion. However, fish make up the majority of a grey heron’s diet.
Do Grey Herons Eat Other Birds?
Grey herons are most well known for being patient hunters, standing motionless in shallow water or wetlands waiting to spear fish and other aquatic prey. However, they are opportunistic and will eat whatever prey is readily available. This does sometimes include smaller birds.
Grey herons have been observed preying on ducklings, goslings, moorhen chicks, coots, songbirds, and other smaller bird species, though these only make up a very small percentage of their total diet. When hunting terrestrial prey like small birds, grey herons will walk slowly through wetlands or grasslands and strike quickly to grab an unsuspecting victim.
Some key points about grey herons occasionally preying on smaller birds:
They Mostly Eat Fish and Aquatic Prey
– Fish make up around 70-90% of a grey heron’s diet. They are exceptionally well adapted to hunting fish and aquatic prey.
– Crustaceans, mollusks, amphibians, and aquatic insects are also common prey.
– Small mammals, reptiles, terrestrial insects, and birds are a much smaller component of their diet.
They are Opportunistic Hunters
– Grey herons are adaptable predators and will eat whatever prey is most readily available. This includes vulnerable young birds.
– They do not solely target other bird species but will eat them if the opportunity arises.
– Their diet varies based on habitat and what prey is easiest to catch.
They Mostly Eat Injured, Sick, or Young Birds
– Healthy, adult birds are challenging prey for grey herons. They typically only target vulnerable juvenile birds or injured/sick adults.
– Ducklings, goslings, and flightless baby birds are easier to catch as they cannot escape.
– Songbird fledglings are also targeted when they are just learning to fly and can be caught more easily.
Birds Form a Very Small Part of Their Diet
– Best estimates suggest birds only make up around 1-5% of a grey heron’s annual diet.
– Even in breeding colonies where young waterbirds are abundant, most of their prey remains fish, frogs, rodents, and insects.
– They do not rely on other bird species as a primary food source.
Hunting Techniques Used Against Birds
When grey herons do prey on birds, they use a variety of hunting techniques:
Standing Motionless and Ambushing
Grey herons often take birds by remaining completely still in shallow water near vegetation and ambushing unsuspecting prey that gets too close. They stab quickly to grab the bird with their sharp bill. This technique works well for taking ducklings and other young waterbirds.
Actively Pursuing Prey
Rather than standing still, grey herons may actively walk through an area looking for vulnerable fledglings or injured birds to target. They often hunt along marshy edges and in wetlands.
Aerial Pursuit
On rare occasions, grey herons have been observed pursuing flying birds that venture too close. With a six foot wingspan, they can take fleeing prey on the wing.
Stealing Pirated Food
Grey herons may steal birds from other predators. They may grab birds pirated or caught by raptors like ospreys. This allows them to eat birds without expending much energy hunting.
Examples of Birds Grey Herons Eat
Some specific types of birds grey herons are known to prey upon include:
Ducks and Geese
– Ducklings and goslings are commonly eaten. Adults are rarely taken.
– These waterbirds are easy prey during breeding season when young cannot fly.
Coots and Moorhens
– Their chicks are vulnerable to grey herons and are eaten in wetlands.
– Adults coots may occasionally be taken if injured or ill.
Seabirds
– Young gulls, terns, and other seabirds are eaten, especially where colonies border wetlands.
– Injured adults resting on the water may be ambushed.
Songbirds
– Fledgling songbirds are taken in forested wetlands and edge habitats.
– Sparrows, warblers, finches are often eaten when young and inexperienced.
Wading Birds
– The young of herons, egrets, rails, and other wetland species may sometimes get eaten.
– These juvenile waders fall prey when feeding in the open.
Impacts on Bird Populations
Grey herons predation on other bird species has minimal impact on most bird populations. A few reasons why:
Predation is Opportunistic and Variable
– They do not selectively hunt birds and each individual heron may rarely eat them.
– Predation rates vary locally and by season based on availability.
– Their diet is inconsistently composed of birds year to year.
Healthy Adults are Rarely Targeted
– It is almost always vulnerable juveniles or injured/sick adults that get predated.
– Removal of adults would have much larger population impacts.
– They do not usually limit reproductive success by taking eggs or chicks.
Many Birds are Too Large to be Prey
– Larger waterbirds like swans, cranes, albatrosses etc. are not impacted.
– Maximum prey size is limited by a heron’s bill size and hunting ability.
– Small passerines and juvenile waterbirds are the only suitable bird prey.
Waterbird Colonies are Rarely Hunted
– Dense concentrations of breeding waterbirds are dangerous places to hunt.
– There is minimal evidence herons hunt colonial nesting sites.
– Foraging takes place primarily in wetland feeding habitats away from dense colonies.
Benefits of Grey Herons Eating Birds
While any predation pressure has impacts, there are some potential benefits to grey herons occasionally preying on other bird species:
Controls Overabundant Species
– When waterbird, gull, or songbird populations get very high, predation can help regulate numbers.
– Grey herons may help limit massive increases and imbalance.
Keeps Prey Populations Vigilant
– Predation risk encourages prey to be alert and aware in wetland habitats.
– This pressure enhances survival adaptations and skills.
Supports a Native Predator
– As a natural wetland predator, herons may need supplementary bird prey at times.
– Preying on common species may help sustain healthy heron numbers.
Scavenging Removes Sick Birds
– Scavenging dead or weakened prey removes ill individuals.
– This may limit spread of disease like avian botulism and avian cholera.
Conclusion
In summary, while grey herons are primarily fish-eating birds, they are opportunistic predators and will occasionally prey on ducklings, goslings, coot chicks, juvenile songbirds, and other smaller bird species typically found in wetland habitats. However this predation on other birds forms a very small percentage of their overall diet and tends to have minimal impact on prey populations. They target vulnerable juveniles and take relatively few healthy adult birds of any species. Grey heron predation can help regulate overabundant prey populations and remove sick or weak individuals. Though they certainly eat some birds, they cannot be considered a significant threat to other bird species overall. Their ecological role as a native wetland predator likely necessitates occasional bird predation when fish and other aquatic prey availability is low.
Grey Heron Diet Composition
| Prey Type | Estimated % of Diet |
|---|---|
| Fish | 70-90% |
| Amphibians | 5-10% |
| Crustaceans | 5-10% |
| Mollusks | 1-5% |
| Insects | 1-5% |
| Small Mammals | 1-5% |
| Reptiles | 1-5% |
| Birds | 1-5% |
