Reproduction

Breeding occurs in January or May in the northern areas of their range. In temperate areas they will breed during spring and summer while in Africa and the tropics breeding can occur year round with this event concentrated during the rains.

To breed successfully they require four months of warm weather.

Males will call call to advertise their presence to females. They will also point their bill upwards and stretch their wings to initiate preening.

Nesting colonies may include thousands of pairs though some choose to nest singly.

Their nest is formed from sticks and used for multiple years. Often it is located high in a tree though it may be on the ground or a cliff edge.

In to the nest they will deposit between 1 and 10 eggs. Only 1 brood is raised each year. These eggs are incubated for between 25 and 26 days. If this brood is unsuccessful they may lay a second.

These chicks are fledged within 45 and 55 days of hatching. Hatchlings may cannibalize their nest mates. The fledglings do not become independent till 9 or 10 weeks old.

Both the male and female are involved in providing care to the young. Parents begin by feeding the chicks directly but eventually regurgitate food in to the nest and all the chicks compete for this.

Juveniles can be distinguished from adults as they have a tatty looking appearance to their plumage.

Sexual maturity is reached between 2 and 3 years old.

Behavior

Populations in the palearctic region will migrate after the breeding season in September or October and return in February. In the south of their range the populations remain in one place year round.

Feeding tends to be undertaken singly. Where food is abundant groups of them may congregate. It may occur anytime of the day or night.

In flight they tuck the head against the body and take slow wing beats.

During cold weather these birds will sleep longer each day.

A range of vocalizations are produced by the grey heron. They will also clap their bills together during mating or to greet another.

Predators and Threats

Foxes are the main threat to adult grey herons while the eggs are hunted by birds such as crows.

Previously the species has faced heavy persecution as they feed on fish which were viewed as important to local fisherman. This would lead to persecution through shooting, drowning or poisoning. They may also be hunted for the bushmeat trade.

Habitat alteration is an emerging threat across their range with timber hunting removing their nesting sites.

Virus outbreaks such as avian influenza and botulism have reduced their populations and future outbreaks pose an ongoing risk.

Quick facts

Previously roast heron was considered a delicacy in parts of their range though this is now uncommon.