Acorns

[Lonsdale73]

Two years ago I went looking for hazelnuts. They were a common sight towards Autumn throughout my childood but it occurred to me I hadn't seen any for a while. Didn't see any then either, not even a hint of one. No half chewed shells, no leafy cups, nothing. It crossed my mind that maybe we have so many grey squirrels now that they're taken as soon as they appear.

Then it occuurred to me that I hadn't seen any acorns in ages either. This afternoon I went for a wander in the bit of woodland behind my home. It contains a number of oak trees but inly two - that I could see - laden with any significant crop of acorns. Most of the others had oak apples and galls where they should have been acorns. Are the number of parasitic wasps now so high that they are posing a risk to our oak trees?

 

[AJB Temple]

Interesting. Good photos. I have recently planted a number of young oaks. They are all about 3m high. Laden with acorns. I know some coppice land that usually has hundreds of hazel trees about 10 miles from our house. I shall have to go and have a look.

 

[Phil Pascoe]

There are two 30' - 40' oaks nearby, about 30 yards apart - one is completely riddled with the wasp, the other has perfect acorns.

 

[Nigel Burden]

I haven't noticed that, but there are a lot of acorns down around her. Admittedly, I usually have my head down looking for mushrooms, or watching what the hound is doing.

Nigel.

 

[marcros]

I noticed this last year but haven't taken much notice this year.

I will have a look at the weekend, because I want to grab some galls for the tannin content.

 

[Woody2Shoes]

I've noticed that an oak which has a lot of galls one year doesn't often have as many, if any at all, the next. I think that to replace itself an oak tree only needs to produce one successful acorn.
You can tell by the marks on a hazelnut what's been eating it. I was in a wood owned by the Hants Wildlife Trust the other day. The woodland floor was littered with hazelnut shells that had been nibbled by dormice. I've been nibbling a few cobnuts myself!

 

[Woody2Shoes]

Knopper galls are fascinating things

 

[marcros]

we have loads of hazelnuts on the tree at my parents place, but 95% will have no nut inside them, and the squirrels can tell the good ones somehow.

 

[Trevanion]

we have loads of hazelnuts on the tree at my parents place, but 95% will have no nut inside them, and the squirrels can tell the good ones somehow.

It was explained in this documentary about a chocolate factory in Britain, very interesting:

 

[MikeG.]

Oaks don't produce the same number of acorns every year. It is part of their reproductive strategy of using squirrels to distribute the acorns into buried caches, and is a delightful example of evolution at work. Here's a really nice little video explaining it:

 

[Suffolkboy]

This year is huge for Acorns around here. I had my daughter collecting some for me the other day I plan to germinate and plant out in a couple of years time.

 

[Sgian Dubh]

Oaks don't produce the same number of acorns every year. It is part of their reproductive strategy of using squirrels to distribute the acorns into buried caches, and is a delightful example of evolution at work. Here's a really nice little video explaining it:

That is a nice wee video, and I suspect the presenter, Steve Mould, intended to concentrate on the role of squirrels in acorn distribution for reasons of concision and punchiness, but a rival and probably equally (more?) important distributor of acorns are jays. Because squirrels are so associated with acorn distribution I suspect most people are either unaware of this, or simply forget the role of jays.

The jays and the oaks evolved at a similar time- about 65 million years ago. It would be fair to say the success of each species depends in large part on the other. To illustrate this there were no sightings of jays in the Scottish Highlands during the 1980s, yet their presence had become quite common in the area in the Bird Atlas 2007- 2011 survey. This change in population numbers was attributed to the marked increase in the number of acorn bearing mature oaks planted thirty or forty years earlier.

In a study of Holm oak (Quercus ilex) acorn dispersal by jays conducted in the Mediterranean area the researcher observed the following characteristics:

• Jays transported and cached acorns to specific locations.
• They avoided moving acorns to shrub and grassland areas.
• Most acorns were buried under the cover of pine stands.
• Acorns were carried at least 250 metres from the source with some carried up to one kilometre.

The jay's beak is adapted to breaking open acorn shells and its throat parts well suited to carrying them. The jay plucks four or five acorns at a time packing all but one of them in its gullet with the last acorn carried in its mouth. The bird travels up to a mile away from the tree to ground near its nest site and buries acorns one at a time in holes it creates. A typical jay probably buries as many as 4,500 acorns each year, yet recovers less than a quarter. From the oak’s point of view jays are an extremely efficient means of spreading and sowing their seed. Not only do jays bury the seed just right, they carry it a long way from the parent.

Another element in the close relationship between oaks and jays is the collection of leaf eating larvae off oak leaves by the adults who then feed them to their new born chicks. Slainte.

 

[MikeG.]

The same factors are at work, though. If jays could eat all of the acorns they cached, the oak tree would fail to reproduce. If the oak tree increased its supply of acorns every year, the jay population would rise to meet the raised level of food supply, and all of the acorns would be consumed.......no new oaks. However, having 4 light years of acorn production (keeping the jay population low) then overwhelming it in the fifth year with a massive crop which the jays could never eat, the oak thus ensures it has a fair percentage of uneaten cached acorns ready to spring into life.

 

[Sgian Dubh]

The same factors are at work, though. If jays could eat all of the acorns they cached, the oak tree would fail to reproduce.

I agree, but I didn't think I needed to emphasise or reiterate the point that the population of jays would be controlled to at least some extent by acorn masting in the same way as squirrels. I do think it's remarkable though, whether it's a masting year or not, just how large a percentage of acorns buried by creatures that feed on them that aren't recovered, 75%+ it's estimated in the case of jays, and I suspect it's a similar amount for squirrels.

I'm not even going to get into the behaviour of North American squirrels and their acorn caching habits and their response to the sprouting characteristics, and the gluts and famines of acorn supply from both the white oaks and the red oaks, ha ha. Slainte.

 

[Woody2Shoes]

There are more jays than squirrels here - the explanation involves ballistics......

Mrs Woody spotted a gall on a rose bush yesterday - a "Robin's pincushion" - different wasp, but similar idea: Diplolepis rosae - Wikipedia

 

[Phil Pascoe]

The same factors are at work, though. If jays could eat all of the acorns they cached, the oak tree would fail to reproduce. If the oak tree increased its supply of acorns every year, the jay population would rise to meet the raised level of food supply, and all of the acorns would be consumed.......no new oaks. However, having 4 light years of acorn production (keeping the jay population low) then overwhelming it in the fifth year with a massive crop which the jays could never eat, the oak thus ensures it has a fair percentage of uneaten cached acorns ready to spring into life.

The oaks probably did well in the years the jays ate my bantams.