Volunteer Phil has been admiring the hornets and has shared his musings, research and photos...
There has been much talk on the reserve by visitors, staff and volunteers about how many hornets can be seen this autumn. This has prompted to me to wonder why I rarely see hornets anywhere else. Here are my musings on the subject although please be aware that I am no expert. Everything here represents my own observations and some internet research.
The hornets we see at Pulborough are European Hornets (Vespa crabro) – the only species native to the UK. They are spectacularly large insects of the bee and wasp type which show a particularly bright yellow abdomen. The bands across the abdomen, instead of being the typical black stripes to show danger, are a more attractive chestnut brown colour.
Hornets seem to have an unfortunate fearsome reputation in the press as giant scary insects. It is of course wise to follow the old saying and not “stir up a hornets nest” as they do have a painful sting and could attack in numbers if they feel threatened just like common wasps. However, unlike wasps which have an extremely annoying habit of investigating humans and the food and drink we consume, hornets are generally happy to leave us alone. This means that it is easy enough to observe them in action without feeling worried.
One type of hornet that we do we need to be concerned about is the Asian hornet which has been become a serious problem in France and increasingly other Western European countries in recent years. It arrived most likely on imported food or plants. This is an invasive species that preys voraciously on European honeybees and other types of bee acting as important pollinators in our ecosystem. It has not yet become a major problem yet in the UK, but a few nests have been found and eradicated in recent years. You can read more about Asian hornets in this article from the RSPB website.
https://www.rspb.org.uk/our-work/our-positions-and-casework/our-positions/species/invasive-non-native-species/asian-hornets/
It seems reasonable to assume that hornets just like other animals will be attracted to places where there are good food sources and undisturbed nesting sites. So my first observation is that the reserve does have many good food sources.
Like the Asian hornets the European variety does feed mainly on insects, including honeybees, but it has evolved to be in balance with our native ecosystem and doesn’t pose an undue threat here. Indeed, just like the common wasp, it will eat other insects that are generally regarded as pests and thus provides a useful service. There is an abundance of insect life at Pulborough Brooks precisely because of the way it is managed as with most nature reserves.
Hornets will however supplement their diet with other food sources and these are most often where we observe them. This happens particularly in the Autumn when mated queens stoke up on other types of food prior to going into hibernation. Male hornets die prior to winter, so it is the hibernating queens that ensure the survival of the species during this most difficult time of year.
Ivy bushes, flowering in September and early October are a good example of a supplementary food source as they provide a wonderful supply of nectar for all sorts of insects including hoverflies, ivy bees and hornets. I have written before about my favourite ivy bush at the end of Fattengates Courtyard which often catches the sun but this photo was taken on another good one behind West Mead hide.
Just like the common wasp hornets are attracted to rotting fruit. This photo shows a hornet feeding on rotting apples put out in the Visitor Centre courtyard to attract butterflies.
Hornets also like to feed on tree sap and here a pair of hornets appear to have been attracted to a sapling near Winpenny Hide. Notice how the bark has been stripped.
So we have an abundance of food sources and yet these can be found in many other parts of the British countryside so this does not in itself answer the question of why there appears to be such a good population of hornets on the reserve. My hypothesis is based on the idea that there are excellent sites for nest building.
Hornet nests are like wasp nests and built of a papery substance produced when the insect chews up dead wood or other plant material. They will doubtless be built in a place sheltered from wind and rain and, just like wasp nests, can appear in buildings.
However more often nests are built in tree cavities or holes in rotting stumps. Pulborough Brooks has wonderful old trees in many parts of the reserve which have had plenty of time to develop such cavities. And our wardens are well aware of the benefits to wildlife of leaving dead wood to rot instead of tidying it up. This means that there will be many good sites on the reserve for hornets to build nests, so completing the jigsaw of habitat requirements for them to thrive.
Whatever the truth is I would urge readers to treat these impressive insects with respect but enjoy their presence.