Early breeders - Herons and Ravens

Grey heron (c)Jon Hawkins - Surrey Hills Photography

Despite the cold and wet weather, some birds will be beginning their breeding rituals. Herons and ravens are two of the species mating early. Find out more about them here:

Herons

At this time of year grey herons exchange their usually solitary lives for a bickering ‘tower block’ existence while they raise their families. Notoriously early breeders, the male herons will already be staking their claim to desirable nests in the heronry.

Colonies may comprise over 100 nests, but 20-25 is a respectable size. It isn’t unusual for a single tree to hold as many as ten nests. The birds prefer to use a ready-made nest from previous years, as it can take three or four weeks to construct a new one. There are around a dozen active heronries in Shropshire, scattered across the county. 

Heron

Heron (c) Jon Hawkins - Surrey Hills Photography

Initially, single male herons will be seen standing on their chosen nest, giving ‘advertising’ calls and occasionally looping round the site in display flight.

Heron

A Heron stretch position (after Bauer & Glutz 1966)

Once the females arrive the colony will be alive with posturing, beak-clacking birds – the courtship display has to break down their usual antisocial territorial behaviour patterns.

Ritualised posturing is a key to this. The Stretch Display is performed to attract a mate. Once a female alights near the nest, the male will drive her away using aggressive postures and threat calls. Usually she flies away, but returns several times, with the aggressive display lessening each visit, until she is allowed to alight on the nest itself.

Once the pair has formed they will continue to stretch display regularly through the breeding season.

Grey heron (Ardea cinerea)

Nesting grey heron (Ardea cinerea) (c) Terry Whittaker/2020VISION

Climate change has affected breeding herons in several ways. Cold, wet springs or late snow can lead to loss of eggs or chicks and strong spring gales can destroy nests. Herons are also breeding somewhat earlier, as they need to time the arrival of the chicks to coincide with amphibians coming to the water for their own breeding season, providing plenty of small prey items for the nestlings. This can put them at greater risk of harsh weather conditions.

However, there is evidence that the species is adapting by choosing lower nest sites with more cover than the traditional treetop locations, where the nest will be more protected in high winds. 

Ravens

It’s a great time of year to watch out for courting ravens. These gigantic crows start breeding early, so that when they have chicks to feed there’s plenty of carrion around.

They’ll be on their nests by mid-February in Shropshire, and are now breeding throughout the county – a great increase, having been almost exterminated here by the end of the 19th century.  In 1992, 30-35 pairs were estimated to be breeding here, and by 1999 this had increased to around 175 pairs.

Ravens are easily recognisable by their huge size and deep ‘cronking’ call.

Raven

Raven (c) Margaret Holland

Raven courtship

Raven courtship flight (c) Norman Rich

Watch out for their spectacular courtship flight, when the birds show off with acrobatic swoops and dives.

The male will fly beneath the female and roll in the air, almost flying on his back, sometimes performing a full barrel-roll, or even a double roll, demonstrating his mastery of the air and his fitness as a partner.

Ravens mate for life, but the courtship display is an important reinforcement of the pair-bond. Upland areas are the most likely places to see them, where they nest on cliff or rock ledges, but they also nest in tall trees on parkland, so keep an eye out wherever you are!