Sunday, 30 September 2012

Garden recorders

As I wander around the internet ion search of new hoverfly records, it strikes me that there are lots of potential parataxonomists who take an interest in the insects that visit their gardens. Anybody who regularly keeps a photographic record of what they see can make an important contribution, especially if they do this over a period of several years. There are several people who regularly post photos from their gardens and a few whose garden photographs now form a significant data set in its own right.

Garden recording might just appeal to people whose mobility has declined and yet they want to get involved in biological recording? It might also appeal to a younger generation as a way of getting into insect identification?

It would be great to set up a network of garden recorders but the big question is how to reach them and how to get the message out to people who currently don't use the established mechanisms for posting photographs such as Flickr. I would be grateful for any ideas.

There are some taxa that are better suited to photographic identification than others. For example, shieldbugs, ladybirds and some other beetle families such as longhorns are potentially viable. Hoverflies are not too bad and in my experience about 80% of the species that are regularly encountered in gardens can be identified if the photo captures suitable angles. Some genera are tricky; for example Syrphus, some Eupeodes, Platycheirus, Cheilosia, Eumerus and Pipizines. Even so, progress can be made and I know of one garden where the photographer has recorded well over 40 species of hoverfly. That list would be about 10 species longer if it was possible to ID Eumerus, Pipiza and some Syrphus from photos.

The same approach might be taken with a local wildlife site. We have started to trial the regular monitoring of hovers through our 'Big Hover Watch' - which was largely washed out in 2012! It would be useful to get a feel for levels of interest amongst the non-specialist photographers.

Friday, 28 September 2012

Volucella zonaria records

This summer, Buglife issued a press release that argued that there had been an exceptional influx of Volucella zonaria from the continent.  Prior to this I had a lengthy exchange with Steve Falk in which I argued that there was very little evidence for a migration. In general the traditional migrants such as Episyrphus balteatus, Eupeodes corollae and Scaeva pyrastri have been very scarce compared to previous years, so it is not a year that is obviously suited to major influxes.

The Buglife case was based on the relative scarcity of males amongst records. This I also think is no reason to assume that the records are of migrants. Males tend to emerge earlier in the season, and also tend to be scarcer in samples of all Volucella species apart from V. pellucens. I think the reasons for the imbalance lie in the behaviours of males and females. Males in some Volucella actively seek females and unless they hold territories (e.g. V. pellucens and V. bombylans) they are less likely to be seen. Females, on the other hand, will actively seek nectar and pollen sources and will therefore be seen more frequently.

Using photographic data for this year, a fascinating picture emerges with the emergence of males and females in each Volucella species differing greatly. What is clear, however, is that males emerge earlier than females and are present for a much shorter season.

 Volucella bombylans 2012

 Volucella inflata 2012

Volucella inanis 2012

 Volucella pellucens 2012

 Volucella zonaria 2012

These histograms raise all sorts of interesting questions about adult recruitment that have yet to be answered. Stuart and I looked at population dynamics in several species a few years ago. There is a lot more to be done. A study of the relative numbers of males and females of V. inanis and V. zonaria would be worth undertaking in a locality where both are abundant (maybe a project for an MSc dissertation). A friend of mine looked at V. zonaria a few years ago but has never written it up, so it is time somebody else got in on this question.

Sunday, 23 September 2012

September sunshine!

Today's weather has not been great and so I expect the haul of records from the internet tomorrow will be pretty disappointing. One bad day does not mean that the year is over, and I remain hopeful that there will be lots of new records. Autumn can be very rewarding, especially on nice sunny days when the ivy attracts lots of flies and butterflies.

In northern and western districts Devil's-bit Scabious is often still in flower and this can be very productive. Dipterists Forum held an Autumn field meeting in south-west Scotland in 2009 in mid-September and the Devil's-bit was fantastic. So, maybe there will be a new flush of records.

There has been a noticeable drop-off in species richness on the internet. Most records are of Eristalis species, Myathropa florea, Sericomyia silentis and the occasional Volucella zonaria and V. inanis. But there are occasional surprises and of course a small trickle of photos from earlier in the year. Hopefully poor weather will encourage photographers to post more of their older shots that we have yet to see.

Autumn field meeting

This year Dipterists Forum will go to North Wales in early October. I am hoping for nice weather so we can cover lots of conifer plantations and achieve a similar level of fungus gnat recording to previous years. Last year in Sussex we were exceptionally successful with over 200 species recorded. I doubt we will get close this year, but that remains to be seen.

For me, the Autumn is a much more pleasant trip because the group is small and we are confined to maybe three sites each day. I mainly collect fungus gnats for Peter Chandler and act as a parataxonomist. It is actually very rewarding when one collects a good pile of gnats and makes a real contribution to the sum of knowledge about some of the less well-known families. Without Peter, fungus gnats would not figure in recording but as things stand there is an excellent dataset that provides a great basis for ongoing surveillance.


Saturday, 22 September 2012

WILDGuide: Britain's Hoverflies

Some readers will be aware that Stuart Ball and I have been writing a new book on hoverflies in the 'Britain's' series published by WILDGuides. It has been a much more challenging venture than we had originally anticipated and we are still adding the finishing touches. We have seen page proofs and they look very good. It will be worth the wait and for those lucky few who have pre-ordered via Dipterists Forum it will come at a bargain price. Since we advertised the deal the RRP of the book has risen substantially. We hope that the book will go to the printers in the next month or so, and therefore it should be on the bookshelves before the spring.

Our intention is that this book will be a companion to Stubbs and Falk. It will hopefully help the novice get to grips with the family without the very difficult elements of the opening 'Key to Tribes' that causes so many problems. Over 160 species will be illustrated and we spent many months photographing specific characters that should make identification of some tricky species easier. However, it is no substitute for the comprehensive monograph and anybody wishing to make accurate identifications of trickier species will still need Stubbs and Falk as well as access to a microscope and voucher specimens.

Hoverflies are not easy to identify, and many species can really only be identified under high magnification and by referring to comparative material. We think that perhaps 100 species can be done from photographs or in the field if you are very experienced. I personally reckon to recognise down to species pairs for maybe 200 of the 281 species. But, this is after 30 years of experience and having spent many months poring over difficult specimens. Anybody who has attended our training classes will tell you that even now there are specimens that cause me difficulty. So, the key message for the novice is to keep at it as they do get easier.

We have been extremely clear that this WILDGuide cannot be expected to be comprehensive. Indeed, we have resisted incorporating a broader selection of species and  additional notes on identification of species that have not been illustrated. We have done this for a variety of reasons, but mainly because we think it is important not to suggest that hoverflies can be identified on the basis of a limited description of differences from illustrated species.

Some readers may view this as a mistake but we now have a great deal of experience of the problems that can be encountered. What is more, we too hit problems when using detailed keys and even when we have access to comparative material! So, we think it is best to minimise the opportunities for avoidable mis-identifications.

Our hope is that the WILDGuide will act as a stimulus to interest in hoverflies and that this will lead to a greater use of Stubbs and Falk in due course. We have a revision of this monograph planned for the next five years and will be producing an interim supplement this winter. There are plenty of jobs to get on with and we won't be short of things to do!

Checking that identifications are correct

It is remarkable how often recorders make simple errors in identification. There are numerous permutations and new ones emerge on a regular basis. The commonest mistakes include:
  • Naming females of species that can only be be identified reliably in males.
  • Naming species that can only be identified using microscopic eye hairs or wing hairs that are not visible on photographs.
  • Naming species that clearly do not occur in the area they are recording from - the most obvious mistake being to report coastal species from inland locations and to report northern species from southern locations.
We have developed our introductory guide with these mistakes in mind and have attempted to minimise the potential for new mistakes.  However, doubtless more will emerge and we will eventually have to revise the book in the light of problem identifications. Perhaps the commonest misconception is that each hoverfly is very different from all others. Unfortunately this is not so and there are numerous problem genera: Cheilosia, Eupeodes, Heringia, Pipiza and Platycheirus,to name but a few.

Mistaken identifications can be tricky to spot when one is presented with a simple list, but if a knowledge of the biology of the species and a good feeling for British geography and the distribution of habitats makes it easier spot the problems. Records of certain species are especially telling. For example we frequently get records of Platycheirus immarginatus from inland locations, yet when we map reliable records of males (which are more straightforward) it is clear that this is a strictly coastal species. There is a moral to this story: making a correct identification depends upon use of keys, illustrations and species descriptions. The species descriptions and accounts of geographical range in Stubbs and Falk are especially useful as they highlight additional characters and describe the ecology as best we are able to say.

When lists of species arrive at the Recording Scheme, I immediately look to see what is listed and the relative proportions of difficult and more straightforward species. No list is wholly discounted but if I am uncertain of the reliability I will mark them as uncertain. These records do not appear on maps or in analyses.

Seeking help

I am always happy to help with problem specimens and will do my best to put a name to photographs. However, there will be times when a certain identification is not possible.  Occasionally specimens have to be passed on to other specialists and now and then they have to go to a European specialist for an opinion.

Friday, 21 September 2012

The internet as a source of biological records

For several years, I have been trawling the internet for photographs of hoverflies and other Diptera from the British Isles to improve the data available to recording schemes. So far I have extracted almost 9,500 hoverfly records where it has been possible not only to identify the insect but also to link it to a place name and to at least a ten kilometer grid square. In many instances it is possible to get to a four-figure grid reference and as geotagging becomes more prevalent even more detailed records can be made.

During the mid-summer months, this trawl can take as much as an hour a day to cover the breadth of available data. A great deal is posted on Flickr but there are other sites that also yield regular records. Although a good number of photographers provide some data with their photographs, a remarkable number do not. This seems to me to be a great shame as data for even the commonest insect can be valuable. I would therefore encourage photographers to either geotag their photos or provide a note of the locality name (and county) together with the date the photo was taken.

Over 2700 records of hoverflies have been extracted for 2012. This constitutes around 10% of the data now entering the Hoverfly Recording Scheme each year, and is therefore a not insignificant contribution to the dataset. Trawling the internet allows me to undertake biological recording whilst maintaining my presence in the office (work is rather scarce at the moment!). Regrettably, it does nothing to trim my waistline!

How many other recording schemes trawl for data? I know that Matt Smith and Chris Raper do the same for the Tachinidae, and that Tristan Bantock does for the Hemiptera. There are lots of beetle records (especially longhorns) that would be worth harvesting and some Hymenoptera may be useful although the numbers that can be identified are probably low.

This sort of work might usefully be taken on by field naturalists with modest identification skills who could simply search out the data, create a spreadsheet and let others check the identity. Simple spreadsheets for different Orders would be immensely useful. I do this for the Diptera and farm out data for other schemes. Some scheme organisers are quite dismissive of such data, but others may do well. For example, most of the Bombylidae can be done and Malcolm Smart was able to put names to a large precentage of the Asilidae. Even records of common species can be very useful as most schemes have huge gaps in the data for more remote places.

What can the data be used for?

Modern biological recording has changed a great deal from the days when it focused on the production of simple distribution maps. Records contributed by non-vocational sources (I hate the term amateur as it has inappropriate negative connotations) can be used in many ways. They are now routinely used to investigate changes in species distribution and abundance, to investigate the possible impacts of climate change and to inform policy makers about the ways in which countryside management is affecting our wildlife. Photographers who provide data with their photos are therefore making an important contribution to our understanding of wildlife trends.

In the case of the Hoverfly Recording Scheme the dataset is now sufficiently big that it provides quite reliable indications of the changing fortunes of individual species and the fauna as a whole. These analyses regularly figure in JNCC work that helps to inform policy-makers and decision-makers. They have been used to undertake species status reviews and have made an important contribution to the redefinition of the Red List for Britain's Hoverflies (which awaits publication at JNCC).

It is not infrequent for recorders to question why there is a need for more than a single record of a species, or perhaps the first and last dates for the year? This reflects the historic role of recording schemes where the main interest was on dots on maps. If we have more detailed data we can do so much more. For example, if one wants to monitor changing abundance or distribution, the animals or plants involved need to be sufficiently abundant to generate meaningful and statistically valid trends. Rare species are often less suited to this than commoner ones.

A great example of this is the hoverfly Epistrophe eligans which flies in the spring. Over the past 25 years, its flight period has shifted dramatically earlier so that today it is frequently recorded in March whereas it would normally have appeared in late April 25 years ago! Understanding the change is helped if we can not only look at first and last dates, but are also able to establish the change in dates of peak occurrence. So, all records are helpful, and photographic records are often particularly useful as they reflect the times when the non-specialist observer sees them in sufficient numbers to attract attention. There are several other spring species that are also useful and others such as the 'Heineken Fly' Rhingia campestris tell an important story about the relationship between invertebrate abundance and drought.

Other examples include the big hornet and wasp mimic Volucella species. Data from non-specialists has helped to track their northward progression in response to climate change. Much of the data we used in 2004 to predict possible changes came from occasional notes in journals and even newspapers that helped to create a picture of these species' fortunes. Today, the increase in use of the internet means that there is now an army of recorders that was previously inaccessible.

Over the coming months I will expand on this theme and will explore the ways in which data generated by countryside observers can help raise the profile of the plight of Britain's wildlife.

Opening thoughts

 Stepping into the unknown

This is a new venture for me, especially as friends will tell you I’m an utter technophobe who does not readily adapt to modern technology. My mobile phone is as primitive as possible and I do not own an IPad or any other gizmo.  In fact I find very little use for the plethora of technology that tempts most mortals. So, as usual, I am ten years behind the time! However, I usually have plenty of ideas and opinions, so maybe this is useful a medium to explore? There will be those who will say I'm far too opinionated for my own good!

My intention is to post observations and reflections when they seem to be pertinent. They will be sporadic and will appear as events unfold. My intention is to focus on natural history recording and on conservation issues. Hopefully some will strike a chord with those who choose to read them.