Heron and Egret Survey

Sunday, 18th April 2010

What a pleasure to be in the open air, ambling gently along the Calamansack road with the blackthorn bushes in full flower and listening to bird song. The sun shone warmly from a cloudless blue sky and a goldfinch popped on to a nearby hedge to greet the 21-strong party with a cheerful tune. Chaffinch and blue tits added to the chorus, a couple of linnets flew over, twittering, and an unseen dunnock gave forth a beautiful melody. As if in contrast, a green woodpecker ‘yaffled’ in the distance. Turning off the road and across pastured fields we had an uncommon view along Polwheveral Creek, with white houses at its head and above them the village of Constantine, dominated by the church, whose bells were ringing out clearly across the valley. A short distance further down the field we stopped at a position which gave an excellent view of Merthen Woods on the opposite side of the creek. Binoculars and telescopes were quickly brought to focus on clusters of birds high in the trees. What had appeared from a distance as white specks were now readily seen as Little Egrets, a dozen or so, generally standing on the branches but occasionally flapping into the air and then alighting in another place. It did not seem that any were actually nesting yet. By contrast the Grey Herons were well advanced. Our high vantage point gave views into the nests. Some birds remained sitting, but when the parent stood up it was possible to see one or two large youngsters, approaching adult size, feathered and perhaps several weeks old. Martin Rule, who was leading the party and has surveyed this heronry for a number of years, said that national heron counts are among the oldest of bird surveys. One figure to obtain is the number of nests ‘apparently occupied’. It’s not easy. Large platforms of sticks occupied by youngsters and/or parent are obvious, but is the motionless heron, farther into the wood and half-hidden by branches, sitting on a nest or just resting? My own guess was about 10 nests.
The breeze on the hillside was a touch chilly, but a swallow flew overhead and then a sand martin to announce that summer was coming. Down in the creek, three oyster catchers were searching the sand banks exposed by the receding tide, a couple of shelduck drifted along and a sandpiper was actively probing the shoreline. It was time to leave and a group of very contented bird watchers thanked Martin sincerely for what had been a most enjoyable excursion. The HMCG would also like to thank Mr Collins for allowing access to his land to view the heronry.

Footnote from Martin

Yes it was indeed a fabulous morning – we were really blessed! It’s always a lottery, setting dates for our events over a year in advance; for this event we certainly hit the jackpot!

I visited the Polwheveral heronry three times this year to contribute my findings towards the national British Trust for Ornithology’s Heronry Census. Started in 1928, it’s the longest running single species survey in the world. Regarding Helford counts, only 27 years out of 83 since 1928 are missing data, so that’s a great contribution.

As I told people on our walk, there used to be several smaller heronries on the Helford – in Gillan Creek, for example. From around 1985, for some reason, they all joined together at Polwheveral where they’ve stayed ever since. The average number of nests here since 1985 is 11.3, while on the Helford overall, since 1928 it is 8.5.

As Paul has said, it can be surprisingly difficult to count the nests, despite the size of the birds, but we estimated about 11 on this visit. During my final count on 30th April, I was pretty confident I’d seen 12. We can feel reassured then that breeding numbers are very stable on the Helford. BTO had been concerned following the cold winter that herons would be scarcer. As a wetland species, they tend to suffer when feeding areas freeze up for long periods. My theory is that because birds in the south west use the coast, they are less prone to this hardship – plus it wasn’t really THAT cold here was it?! The same cannot be said of some of our smaller birds. I have noticed much reduced numbers of species such as goldcrest, song thrush and chiffchaff this spring in areas I count or visit regularly. All we can hope is that they will build their populations again if we provide suitable habitats for them.

However, we could always learn more about our herons. One of our members has observed far less feeding activity recently in and around Port Navas creek. While breeding numbers may be stable, we actually know very little about precisely which parts of Helford they use to feed and what is their main prey. A research project for someone?

Regarding the Little Egrets, as we saw, they nest seemingly randomly in amongst the herons. Nesting slightly later than the herons, they were far more obvious on 30th April. I counted 22 adults in and around the heronry, with an estimated 7 pairs on nests. This also is very stable for the last 8 years – perhaps they have reached a peak? Let’s see what next year brings – that’s the joy of an annual survey.

I would like to echo Paul’s thanks to Mr Collins of Calamansack, and to thank the attendees for their company and enthusiasm. We hope to organise a repeat trip next year, as long as the weather gods are still smiling on us…….