As I've wandered the trails around The Lodge recently, I've noticed something strange. Where there should be smooth, shiny, ripening acorns dangling from the oak twigs, there are distorted, crinkly growths which - to my eyes, anyway - look a bit like Ferrero Rocher chocolates...

It turns out that this is the work of a small wasp which goes by the snappy name of Andricus quercuscalicis. The weird growths themselves are known as 'knopper galls' - the word knopper being derived from a word for a knob, stud, tassel or hat.

The 'gall' is the growing acorn's response to the wasp grubs developing inside after eggs were laid there earlier in the year. In a similar way, you might have seen the robin's pincushion gall before - it's a common sight on wild rose bushes, with a tangled mass growing from the stem eventually turning red.

At The Lodge, at least, there are not many acorns to be found this autumn. The galls are turning brown and falling off the trees, and the newly-hatched wasps making their escape.

Jays are famous for their love of acorns, able to store away as many as 5,000 for a rainy (or cold) day. What will they do here this year?

As members of the crow family - clever, bold, adaptable and omnivorous - I doubt jays will go hungry. They just might need to look for some different foods in different places, so I wonder if that could mean an influx of jays to garden bird tables? In the same way, might we see squirrels launching a hunger-fuelled assault on our feeders?

Let us know what you see!

Have you spotted knopper galls on your local oak trees? Leave a comment and let me know.

Knopper gall by Katie Fuller

  • I have tried adding chilli powder to bird see; the birds were fine with it - it lessened the squirrel depredations for a while, but not for long!

  • Is it true that squirrels don't like chilli but birds don't mind it? Thinking in terms of adding some to fat balls.

  • I fully agree with Doug, Compass and Dee - and add pigeons to the list of undesirables - they are very greedy feeders and grab food before other birds have much of a chance - when the squirrels don't get there first.  I trap the squirrels and shoot them as the most humane way of dealing with them and put them on the common for the crows.  Occasionally pigeons are silly enough to go into the squrrel trap and they end up in the freezer.  A welcome addition to a pensioner's diet.  These two things give the other, smaller birds a fighting chance - such a bad summer that we have had they need all the help they can get.

  • I noticed recently that the oaks near us were growing these strange-looking deformed acorns, and their leaves were whitish and shrivelled.

    We have a pair of jays along with one of their youngsters that visit our garden most days, and I was worried as to what they were going to eat, (other than the monkey nuts which they frantically have been gathering the past week or so!)

    Yesterday we went on a walk in a country park near where we live in North London, and we found some oaks producing acorns... only they don't seem to be English oaks, because the caps are frilly. We gathered as many as we could, and to keep them from going mouldy I dried them a bit in the oven on low heat.  The jays have been collecting them as quickly as I can put them out today!  

    The squirrels have also been in the garden all day, of course.  :-(   I have greased the pole of the bird table with olive oil and then dusted it with cayenne pepper, and that seems to be deterring them for the time being.   Hateful things!  I wouldn't begrudge them a few nuts, except for the fact that out of all the ones we tried to gather yesterday, MOST of them had bite marks in them- spoiled by the squirrels.  

    I don't feel sorry for them- they waste far more than they actually eat!

  • Looking forward to possibly seeing some elusive Jay's on my feeders and bird table!