Grey Heron

Description

Grey Herons are distinctive birds with grey, black, and white plumage. They are often spotted standing beside rivers, lake margins, or flooded fields.

The juveniles are more uniformly grey, without the black plumage highlights and ornamental plumes.

In flight, they present an unmistakable silhouette with their neck folded, an impressive 6ft wingspan and their long legs trailing behind them.

Grey Heron chicks are browny-grey, with a fluffy head crest and white underparts.

Calls

They are vocal birds with a variety of calls and sounds. The most distinctive is the Fraarnk flight call, which is loud and far-carrying; they also have a go-go-go alarm call.

Variations of oooo are used as an aggressive warning and during courtship. Males use a rwo call to attract a female. Both males and females clap their bills at each other in greeting and during mating displays.

Grey Herons are abundant throughout the UK and commonly found around still or slow-moving, shallow water with trees for roosting nearby. They can also be spotted in damp grassland areas, where they can be seen standing stock-still while they digest their morning meal.

The Suffolk Bird Atlas 2007-11 has maps showing their historical abundance, breeding data and population trends for that time.

According to the BTO, the population across the country has been increasing. However, it peaked in 2003, and recent years have seen a decline in their numbers.

Population trends

Lifecycle

Grey Herons live to around five years old and begin breeding from two years old.

In the Spring, male herons look for a good perch or an old nest to advertise themselves to passing females with a loud yelping call.

Their courtship display includes neck stretching, bowing, mutual preening, and bill clapping.

Once they have found a mate, they set about creating a platform nest about 25m above ground. The males forage for the perfect branches and twigs and bring them back for the females to build with.

They lay three to four pale green-blue eggs at intervals of two or more days. Both birds share the incubation, which lasts 26-27 days.

Chicks hatch in the same order the eggs were laid, with a gap between hatchings. This leads to a substantial variation in chick sizes in the nest, and the last chicks to hatch rarely survive the 50 days to fledging.

Newly hatched chicks are fed predigested prey that the parents regurgitate. As the chicks grow, the parents begin to feed them whole prey.

Diet

They eat newts, frogs, small reptiles, small mammals, waterbirds and, unsurprisingly, a wide range of fish, from minnows to adult eels. 

According to Dominic Couzens: A study of a daytime roost of Grey Herons in a Yorkshire field found that many individual herons spent almost all the daylight hours doing nothing. They slept for 6% of the day. However, nearly 77% of the day was spent just standing still, perfectly awake. 

So when do they hunt? Although there was some variation, they mainly foraged at dawn and dusk. A few will have hunted by night, but most herons roost at night, which leaves remarkably little time to find food.

However, fish are highly nutritious. If they catch their ideal-sized prey, which is around 15-20cm long, they are perfectly satiated for hours afterwards. 

Created by: Suffolk Biodiversity Information Service
With thanks to:

Dominic Couzens fascinating article on how Herons spend their day, BirdWatching

British Trust for Ornithology

Jess Brooks, Game and Wildlife Conservation Trust

Heron Conservation