The breeding numbers of gray herons have been continuously monitored by the British Trust for Ornithology (BTO) since 1928. This makes it the longest record of any British bird. The Covid-19 restrictions imposed in early 2020 meant that many surveyors were unable to visit occupied Heronries across the UK, disrupting this long-term study.
2020 will be remembered for the impact Covid-19 had on all aspects of our lives and, unfortunately, for the much more personal impact the virus had on many families. The BTO’s Heronries census could not escape the effects of Covid-19, although the first lockdown came into effect in late March 2020 at a time when some Heronries census volunteers had already completed one or more visits to the breeding colonies. The first lockdown meant that in 2020, visits could not be made during the main survey period in April.
Gray Heron, Copyright Richard Stonier, from the Surfbirds Galleries
Information was received from 485 locations, the lowest number since 2001, when the survey’s survey was interrupted by the foot-and-mouth disease outbreak. In 2020, a total of 3,224 apparently occupied nests were counted, about half the number in 2019. The historical results of the census show that storms can affect the heron numbers. It will therefore be interesting to see how the cold snap in February 2021 affected them.
Although the Heronries census will be conducted in 2021 (as of today), coverage is likely to be reduced again due to Covid-19 and ongoing lockdown rules across the UK. We may therefore have to wait until the spring of 2022 for our gray herons to be back with their heronries before we can get a full picture of the majority of British heronries.
Ian Woodward, Heronries Census Organizer at the BTO, said, “The 2018 ‘Beast from the East’ showed a relatively small impact on our herons, at least when compared to past winters with much longer storms. If enough survey visits can take place in 2021, we expect the effects of the cold snap in February to be noticeable in our trend data, but also to be relatively minor. It is thanks to the continued commitment of our volunteers that we have such a fantastic long-term data set recording the ups and downs of this enigmatic bird. “
The BTO Heronries Census monitors several other colonial breeding birds, including the recently established little egret and the white heron’s first attempts at heron.