Avian flu decimates the gull colony at Heybridge Gravel Pits!

For several decades now, there has been a sizeable Black-headed Gull colony at Heybridge Gravel Pits, across the river from Maldon Prom. In recent years, there have been around 300-400 nesting pairs, along with around 20 pairs of Common Terns (thanks to Simon Wood for help with these numbers!).

The Heybridge Pits Black-headed Gull colony in a typical prior year,
with plenty of juveniles to be seen (photo June 2012, Simon Wood)

Back in March, I posted some photos showing this year's normal build-up to the nesting season at the pits:

Black-headed Gulls gathering to nest at Heybridge Pits, March 2023

Black-headed Gulls on their traditional nesting area, March 2023

Last year, Avian flu did not have much impact on gulls locally (the only possible casualty I saw was a sick looking BHG by the Sunny Sailor). The main casualties around Maldon then seemed to be a number of Mute Swans.
This year, however, it became apparent by June that our Black-headed Gulls were suffering. Reports included Jo Phillips seeing 9 dead bodies off the Prom and Nic Lindsell seeing multiple dead BHGs, and also Common Terns, at the pits themselves.

Black-headed Gull corpse off the Prom, June 2024

I visited the pits on 3rd July to find the main areas of the colony completely deserted. There were no nesting birds on the spits and just a few adults hanging around. Similarly, while Common Terns were seen, I didn't see any nesting. In total I saw around fifty adult Black-headed Gulls but not a single juvenile.

Area of abandoned gull colony (with two corpses), July 2023

 

Area of abandoned gull colony, July 2023

Black-headed Gull corpse, Heybridge Pits, July 2023

While there were corpses about, there was only a small number compared with the size of the colony, so it seemed that the majority of gulls had consciously abandoned the site because something was going wrong, rather than wait to catch the disease. 

Looking at the southern end of the pits there was a glimmer of hope. There were some adult BHGs on the flat shingly island and amongst them seven or so appeared to be sitting on nests.

A few adult gulls were still present on the flat island at the southern end of the pits

   amongst which a handful or so appeared to be sitting on nests, July 2023

The Heybridge Pits colony has been the only Black-headed Gull colony in the immediate vicinity of Maldon, so is very significant locally. Sadly the losses have been part of a national pattern. It seems that this year there has been a new wave of Avian influenza that has particularly hit these kind of colonies. In June the British Trust for Ornithology were saying that at least 10,000 Black-headed Gulls, 4% of the total UK population, were feared to have died since the end of March. Hundreds of Common Terns also died, with signs of severe losses for this species still to come.

The virus involved, known as a Highly Pathenogenic Avian Influenza (HPAI), is killing birds globally, with big impacts in the UK to sea birds such as Gannets, Great Skuas and Terns. Fingers crossed that it will gradually disappear from populations or else birds might develop some immunity, but who knows?