August 2026

The drought and heat hardly went away in August. There was a heatwave on the 13th and 14th and higher than average mean temperatures afterwards, even if nothing above 25C. After no rain since June 27th, just 2mm of rain fell around the 19th August and 7.7mm between the 27th and the end of the month, barely enough to moisten the ground surface and then evaporate away within a day or so. Lake levels were affected. They dropped below the outfall weir crest at the beginning of May and, despite 100mm of rain in June, remained below. The minimum in this drought year occurred at the end of August, just before the return of rain in early September. This was 135mm below the dam crest.

Aphanizominon 

can be seen with the naked eye

I sampled the lake water more often than usual, as the heat waves and drought might have resulted in interesting changes. On the 10th there was a big change, as the cyanobacterium that had been blooming since the end of May (Aphanizomenon) had greatly declined. Before concluding that the ultrasonic device installed to control cyanobacteria had been effective, I took a closer look at the data. First, one of my sampling points  was within a few metres of the ultrasonic kit and the two others distant. Yet, the decline was evident at all three. Second, I had observed large numbers of a predator of filamentous cyanobacteria in my sample of 29th July. This doubtless had risen to such large numbers on a diet of Aphanizomenon, so was an alternative explanation for the decline the latter. 

Third, and crucially, I found a bloom of a non-filamentous cyanobacterium on the 10th. This was Mrcrocistis, notorious from often being toxic and much more difficult to detect with the naked eye. It bloomed right to the end of the month. So, the ultrasonic device had been tested first against a species that probably succumbed to a predator and then with another that survived for weeks without any apparent decline. I'd like to see better information before believing ultrasound to be effective in our context. What a pity, the ultrasound kit is based upon a nice bit of science and it would be delightful to think it effective.

It was good to see the distinctive hip of the Burnet Rose in Admiral's hedge just north of the athletics gate. 

 

 

 

My bird count was on the 6th. As in July, numbers of Canada Geese were lower than normal, suggesting a possible adverse effect of heat waves. The waterweed-feeder, the Coot was also in reduced numbers. Unusually, there were no Tufted Ducks to be seen, perhaps an effect of the cyanobacteria, although this species is not a waterweed specialist like the Coot. Perhaps most of these birds went off to greener pastures. Again, as in July, the other two species of goose were as abundant as in previous years. The geese continued to feed on the Great Field in the early morning, only to retreat to the lake as dog walkers arrived, so the geese were finding some food there, perhaps a spindly crop of Perennial Ryegrass seeds.  No other species seemed affected, there being 1 Common Tern, 16 Mallards, 8 Moorhens, 2 Mute Swans, 7 Great Crested Grebes and three Grey Herons. So, there was no strong indication that any bird species was affected by whatever caused the mass death of large Carp. The number and variety of fish-feeding birds showed that fish populations were doing well, despite the death of large Carp and Eels.

Burnet Rose

Someone is campaigning on bird feeding at the lake and notices have been posted with a familiar story. Over a year ago the Friends of Wimbledon Park were approached by an organisation that provides machines to vend "healthy" bird food for people who come to feed the birds. Perhaps they are planning to approach LB Merton for permission to install their machines.

Stories abound on the internet that bread is not suitable nutritionally, pollutes the water and causes the deformity "angel wing". I have often sought expert views on this subject and found nothing but rejection of the, all too popular view on bird nutrition. Nor is there anything going for the story about angel wing. 

Bird feeding, nevertheless, is popular.There is a great social benefit to people feeding birds, attracting them in for viewing, so giving youngsters contact with nature and allowing the disadvantaged and those holding social or religious traditions for feeding to follow their tradition. Many people believe that the birds need our help, and I saw someone in the recent droughts who came with several loafs of bread, claiming that the parched Great Field provided no food. In fact, the geese were out on the Great Field eating the seeds of Perennial Ryegrass in the early mornings right through the drought. As in other, non-drought, years the geese resorted to the lake to feed once dog walkers arrived at around 6am, and it was clear that more food was being provided than the birds could eat. 

At least the pollution caused by uneaten food seemed correct, but this applies equally to the alternatives to bread. The seeds sink out of reach of most birds faster than does bread, so are even more likely to remain uneaten and decay. As the lake and its surrounds provide wild food for the birds, the birds don't need our help. This is especially so in summer when wild foods are growing, but most feeding occurs on fine, weekend days in the summer, just when the birds don't lack food.

The ideal would be not to feed the waterbirds, or to restrict feeding to small amounts, but persuasion is unlikely to be effective and enforcement would be both discriminatory and disproportionate. We have not seen an effective solution to this conundrum.