August 2018

In the June Nature Notes, I mentioned seeing a barn owl flying over the field at the back. 

Not the barn owl mentioned in the text, just the best shot of one that I've got

Well we have seen it several times since then, each time carrying prey and it appears to be nesting in a dead tree at the back of one of the houses on Pett Road, possibly Wetherdene?  A few days ago as we were sat by the pond sipping an aperitif and watching the sunset, we were alerted by a lot of screeching and flapping.  It all happened very quickly but basically, a kestrel was mobbing the barn owl which eventually dropped the prey which the kestrel followed down onto the field.  The barn owl then flew back towards Pannel Valley.  Only a few minutes later, the barn owl was back again with more prey.  I suppose that it is possible that the returning barn owl was the other parent that had already caught another vole while the first was being mobbed as male and female are almost identical.  (The male is slightly paler apparently.)  Another possibility is that the mobbed barn owl deliberately dropped the prey to avoid being followed back to the nest by the kestrel. 

Mobbing of owls by kestrels is well documented on the internet and many people have managed to take photographs or videos.  Sadly the only thing I had to hand at the time was a glass, but even if I’d had my camera with a long lens already switched on I doubt that I would have got even a blurry photo, it all happened so fast.

 ‘Our’ swallows have successfully fledged four chicks this year and it was delightful to watch them sitting on one of the beams in the carport waiting to be fed.  That only happened for a few days as they find their wings and fly increasingly longer distances and eventually come back only to roost.  We’ve not seen the youngsters for a while now, but the parents are busy preparing for the next brood.  The house martins seemed to be late nesting this year.  There is a nest at the front of the house as well as one at the back.  Both nests are from previous years, but that is not really surprising considering the shortage of mud at the moment.  The nesting habits of the martins are a bit mysterious.  Each year we see a lot of activity when the martins arrive back from Africa as they investigate each nest, but then it is often a month or more before they occupy the nest.  The nest at the front has three chicks, but the parents are still sitting on the nest at the back with no sign of hatchlings as I write this.

A while ago, I wrote about flying spiders – the process where freshly hatched spiders eject silk to catch the wind and help them to disperse – a behaviour called ballooning.  Recent research however, has shown that this is not the full story.  Some researchers at Bristol University suspected that naturally occurring electrostatic charges played a part (the sort that build up and cause thunderstorms).  They put spiders in a box inside a Faraday’s cage.  The Faraday’s cage shields the apparatus from natural electrostatic charges and allows the researchers to control the field inside the box precisely.  They found that increasing the electrostatic field encouraged the spiders to balloon and that once airborne they could raise or lower the spiders by changing the field strength.  A biologist also examined tiny hairs on the legs of the spiders that reacted to the field and gave the spiders the means of detecting the field.  Clever stuff indeed!

July 2018

In a recent ‘Nature Notes’ I talked about seed dormancy and rattled on about tough seed cases and scarification.  It turns out that I was completely wrong – or at least that wasn’t the whole story.  Listening to ‘The Life Scientific’ on Radio 4 recently, I heard Professor Caroline Dean explain the genetic and molecular basis of vernalization, the process that tells the seed when it is spring.  It turns out that seeds have a gene that codes for a protein that keeps the seed in a dormant state.  Cold weather turns the expression of that gene off.  However, it turns the gene off only one cell at a time so that it takes several weeks to turn all the genes off and stop the production of the protein.  This explains why seeds don’t suddenly start to sprout when we get a warm spell in mid-December.  Once all the genes are turned off, then the seed has to wait for all the other conditions to be right – temperature, moisture, day length, etc. – before growing into what should then be spring.  Interestingly, plants grown in colder climates take longer for this process than warmer countries with shorter winters.  So if you take seeds from Sweden and plant them in Spain, they will still need  say 10 weeks of cold weather when the native Spanish plants of the same species need only four weeks.

In last month’s Nature Notes I spoke about how interesting it was watching the solitary bees nesting in our solitary bee hotels.  It turns out that we weren’t the only ones interested in them.  One day we went out to find short bamboo tubes all over the patio, emptied of their content, with a corresponding huge hole in the bee hotel above.  We suspected that a woodpecker had learnt that it wasn’t only crevices in trees that contained juicy snacks, but we were open to other possibilities until further evidence presented itself. 

Note that the box on the right is unoccupied, mainly because the tubes are too big.

We didn’t have long to wait.  A few days later we were rudely awakened at 5 in the morning by a loud hammering on the back wall.  Opening the back door scared the great spotted woodpecker away and saved the bees from further carnage.  We still have two more bee hotels that are so far unscathed but we are seriously considering building some sort of woodpecker-proof cage round them.

While I was looking up woodpecker damage on the internet (of course it has happened to others), I found another interesting fact about solitary bee hotels.  The majority of bees in our bee hotels were red mason bees.  These emerge in spring and will have laid their eggs and died long before the end of June.  However, another group of solitary bees – the leaf-cutters, which are summer nesters – have now emerged and are looking for nesting sites.  If a red mason bee has run out of eggs or energy or life before completely filling the nest hole, then the rest of that hole may be used by a leaf-cutter bee.  (If you find almost circular holes in the edges of your lily leaves, it will be leaf-cutter bees that have taken the bits of leaf to seal up their nest cells.)  The problem with this is that the red mason bees will emerge first and will have to eat their way through the leaf-cutter cells thereby killing their occupants.  Life is tough at the bottom of the food chain!