Photography for site monitoring

I was contacted yesterday by one of the Wildlife Trusts, investigating the possibility of setting up a monitoring project for their sites by encouraging members to visit their sites and then posting the results on the UK Hoverflies Facebook page. It was an interesting proposal that got me thinking. My immediate response was that whilst I am always open to encouraging new participants in the Facebook group, it might not yield the sorts of results that would be useful for the Trust.

I don't want to discourage new initiatives, but I am concerned that such initiatives are heavily reliant upon a very small group of specialists who are willing to engage and provide reliable determinations. Such a system is not really sustainable as the current set-up is in need of significant change if it is to be sustainable in the future. More importantly, I think one has to give serious thought about the concept of monitoring: what are the principle objectives and can they be realised using a particular system?

Site monitoring arguably falls into a number of categories:

1. Development of a simple inventory of what is where and when was it seen.
2. Establishing ongoing surveillance of the continued presence of target organisms.
3. Evaluating responses of target organisms to particular management interventions.

There are doubtless other possibilities that elude me. The big question is, is photographic recording capable of delivering any of these objectives? In the case of hoverflies, I think we are starting to understand the practicalities of what might be delivered:

Site inventory and ongoing surveillance

This is probably achievable to some degree, but it needs to be borne in mind that ad-hoc photographing of what people see on a visit is mainly going to yield the most obvious species that fit the search patterns of the visitor. This is clearly shown by the composition of the photographic dataset generated by the Facebook group. These data show that casual recording reveals a relatively small number of species. Conversely, there is a group of contributors that make a serious effort to photograph everything that they see. This group generates a much broader spread of records and has shown that the FB page has been a valuable teaching tool - many of them have honed skills, developed a knowledge of their targets and now actively seek out species that have eluded them. In other words, they are developing the field skills required to generate comprehensive site lists.

Clearly, photographic recorders can and do provide important site-based data. The big question is therefore the degree to which species lists are comprehensive? I have been looking at this question for a fair while, comparing the composition of photographic lists with those that I generate through my own field work. This analysis shows that although there is considerable overlap, about 50% of the species that I record are either missing from the photographic database, or are represented by far fewer records than might be expected from comprehensive recording. One photographer has crossed over from strict photographic recording to a combination of photography and retaining specimens. His site lists are much more comprehensive and include many of the genera that would otherwise be absent from the photographic database.

Thus, I think that it is possible to develop site inventories if the photographer is experienced and knows what they are looking for. Lists of between 60 and 80 species ought to be possible in more southerly regions but will be harder to achieve further north. If the photographer is assiduous and has the time to sit and record everything they see for several hours on a regular basis, the lists could be even longer.

Species' abundance does vary from year to year, so site lists will grow over time. If the photographers are dedicated and continue to visit sites on a regular basis then the lists will grow and some sort of yearly comparison may be possible, but this will be heavily dependent upon maintaining sufficient active photographers. There is likely to be a long tail of single records and the presence or absence of these species may not be indicative of a change in the ecology of a site.

Responses of target organisms to management

Bearing in mind the natural fluctuation of invertebrate populations and the abundance of the most cosmopolitan species, the big question is whether there are species that can be used as indicators? Hoverflies are pretty good in this respect because they occupy a wide range of niches. Unfortunately, a lot of the specialists that might be useful indicators are difficult (or impossible) to identify from photographs. Genera such as Brachyopa, Cheilosia, Eumerus, Parhelophilus, Platycheirus, Pipiza (and other Pipizini) and Sphaerophoria comprise a significant proportion of the UK fauna but are very tricky to identify. Many require examination of male terminalia, wing microtrichia and characters that are obscured on the animal's underside.  Identifying these animals requires special skills that are built up over a long period of time, so even if a recorder retains specimens it will be several years before they have acquired the skills needed to arrive at reliable identifications. Consequently, photography is unlikely to deliver the sort of data needed to monitor targeted responses unless monitoring focuses on certain niches.

Saproxylic hoverflies are possible contenders as target organisms that may tell a story about woodland management, provided it is accepted that some species will not be reliably identified from photographs (e.g. Brachyopa and some Ferdinandea). Monitoring of single species may also be possible. For example, Microdon devius and Microdon analis have short emergence periods and are highly habitat specific so monitoring my be possible using volunteers who have been trained to recognise the species concerned.

Generating new capacity

The idea of using photographic recorders to gain a better understanding of wildlife presence on nature reserves is a good one because it is a new way of engaging with people and encouraging them to take an interest in the natural environment. The big challenge is doing this without placing greater strains on the existing cohort of specialists who do the bulk of identifications. In the case of hoverflies, we have just three specialists for adults and two specialists for larvae.

I've not kept a record of the actual numbers of photographs posted this year, but can provide a feel for the numbers of records generated in 2016: 27,247 to a firm identification and 7,065 to genus (or occasionally Tribe/Family) - a total of 34,312 records so far. In addition, the recorder who retains specimens as well as takes photographs has generated around 3,400 records and has a large number of specimens in the freezer that I will identify this winter. This phenomenal effort has been achieved by about 1,034 contributors with 65 people contributing 75% of the main photographic data.

This sort of record generation is totally reliant upon the presence of a small cohort of specialists, but there is a growing pool of people who are showing that they have the confidence to identify the more commonly seen species. In time, their skills will grow further. It is this growing skill-base that is essential to the future of hoverfly recording nationally and locally. It might be possible in some parts of the country to develop a partnership between Wildlife Trusts and recording schemes in which local groups of skilled people take on identification, with the Trust extracting records and passing on problem specimens /photographs to the national specialists. What I would not want to do is to generate vast numbers of photographs that have to be validated by national specialists - there is insufficient capacity and there is a danger that overload will lead to the loss of specialists who can no longer cope (I fall into that category if my workload is not significantly reduced).

I therefore think that the next stage is for Wildlife Trusts to consider setting up local systems to encourage recorders but to put in place local specialists to sift out the majority of the readily identified species and only pass on a small body of data for national specialists to determine. Crucially, they need to take on the data management - in the case of hoverflies I cannot cope with any further workload, either on Facebook or on iRecord.