Great blue herons are large wading birds found throughout much of North America. They are most active during the day when they can be seen standing motionless along shorelines and wetlands waiting to strike at fish with their long bills. But where do these majestic birds go to rest at night?
Quick Answer
Great blue herons generally sleep at night while standing in shallow water or perched in trees close to their feeding grounds. They often reuse the same roosting sites night after night.
Do herons sleep standing up?
Yes, great blue herons have the remarkable ability to sleep while standing. They are able to lock their knees and relax their leg muscles to sleep and rest while remaining upright. This allows them to quickly take flight if startled or threatened during the night. Herons may stand and sleep while wading in shallow wetlands or perched on branches of trees near water.
Do herons roost in trees?
Herons commonly use trees as roosting sites at night, choosing large trees close to water that provide safety from predators. Groups of herons, called “heronries”, will congregate in the same stand of tall trees to roost together in a colony. They may reuse the same roosting trees night after night over many nesting seasons. Favorite roosting trees are often close to feeding areas used by the herons during the day.
What do heron roosts look like?
In trees, roosting herons will sit or stand on large bare branches. They tend to select the highest branches towards the tops of very tall trees. During the day, heron roosts can be identified by the accumulation of white feces splattered on branches and the ground below from the birds overnight presence. Herons daubing white droppings on trees may mark ownership of prime roosting spots.
Why do herons roost communally?
Roosting together in groups is believed to provide safety benefits for herons. Being part of a large colony may help deter predators. And if an attack does occur in the dark, there will be safety in numbers as herons take flight together. Communal roosts also act as information centers, where herons can share knowledge of the best local feeding areas.
Do herons reuse the same roosts?
Yes, herons commonly reuse the same roosting sites over and over again rather than finding new spots each night. Often a successful roost will be used for many years, allowing the birds to return to familiar sites from season to season. This site fidelity saves energy since the herons do not need to find and assess new options every evening.
How do herons choose roost locations?
Herons select roosting areas that provide safety from predators and proximity to feeding areas used during the day. Specific site criteria include:
- Trees or wetlands that are isolated from human disturbance
- Sites that offer easy takeoff for flight
- Locations close to shallow water feeding grounds
- Trees that are extremely tall with many bare branches
Do herons ever roost on the ground?
Herons may occasionally overnight while standing on the ground, but this is relatively unusual. Ground sites leave them more vulnerable to surprise attacks from predators like coyotes, foxes and raccoons. Herons roosting on the ground will seek very secluded spots with dense vegetation that provides protection and early warning of approaching danger.
Do herons roost alone or in groups?
Herons may roost alone or in large groups called heronries or rookeries. Communal roosts are more common during breeding season, when herons nest together in colonies. In winter, herons are more likely to roost alone or in smaller groups. Solitary winter roosting reduces competition for prey when food is scarce.
| Roost Type | Number of Birds | Season |
|---|---|---|
| Solitary | 1 – 2 birds | Most common in winter |
| Small groups | 3 – 20 birds | Year-round |
| Colonies | 20 – 500 birds | Most common in breeding season |
How do herons behave at night in roosts?
Herons remain mostly quiet and stationary through the night while roosting. They may shuffle position on branches or preen feathers, but typically try to conserve energy. Birds will vigilantly scan for predators with sudden head movements. Taking flight at night is risky, so herons will avoid leaving the roost until daylight returns if possible.
What dangers do herons face at night?
Herons are vulnerable to predators while roosting, especially owls and raccoons that are active at night. Colonies with many birds are at greater risk of large-scale attacks. Poor weather like high winds can also endanger roosting herons. The birds may get blown from perches and have difficulty flying in storms. Herons may starve with extreme cold if wetlands freeze over cutting off food access.
Do herons ever switch roost sites?
Herons are loyal to successful roost locations and will use them consistently for many years. But major disturbances like destruction of nesting trees or predator attacks can cause abandonment of traditional communal roosts. Flooding of wetland roosts may also force herons to find alternative sites. Individual herons often use multiple roosts within their home territory and may rotate among them.
When do herons leave roosts in the morning?
Herons typically depart their overnight roosts at first light in the morning. The hunger drive stimulates them to leave and seek breakfast as soon as dim light allows for safe flight and fishing. In heronries, the colony may erupt with activity at dawn as hundreds of large wings stir and birds begin flying out in search of food.
Conclusion
Great blue herons are remarkable for their ability to patiently stand and sleep through the night while remaining alert to danger. By reusing traditional roosting sites in trees and wetlands near feeding areas, herons minimize energy spent on nightly travel. While solitary winter roosting occurs, herons achieve added safety by gathering together in colonies during breeding season. Understanding heron roosting behavior provides insights into the daily survival strategies of these iconic wetland birds.
