Counting butterflies

[Neil Freeman]

Whilst having a wander around one of my local sites yesterday, I noticed that some of the butterflies I saw were the same individuals repeatedly appearing in different parts of the site. This is something that I have seen on regular occasions before and commented on in my PD when it has appeared that I am seeing the same butterflies of some species e.g. Brimstones repeating circuits around a given area. Also, male vanessids will often move between favoured spots along quite a considerable distance of hedgerow and I have on many occasions identified the same individuals repeatedly as I slowly wander along.
For example, yesterday there was one particular Small Tortoiseshell that was easily identified by the wear and damage to its wings that I saw on at least 5 separate occasions in completely different parts of the site with at least an hour and a half between between the first time I saw it and the last. This site consists of a couple of large meadow/field areas divided by hedgerows around which I wander a circular route and the Small Tortoiseshell had obviously got ahead of me a few times by taking short cuts across the field or behind the hedges.

This all makes me wander how people deal with this kind of thing with regard to counting the butterflies that they see. In the case of the Small Tortoiseshell above, I counted this as just one sighting as I knew that it was the same individual, but without it being so readily identified I could just as easily have counted it 5 times as different butterflies.

I notice that many reports on UKB specify counts of butterflies and am curious as to how people approach this, do people count each and every separate sighting or do people only count the butterflies they are sure are separate individuals? I am aware that some people do transects and I have a basic understanding of how these are done but again, how do you ensure that the same individual butterfly is not counted more than once?

Cheers,

Neil.

[Vince Massimo]

Hi Neil,

There are a set of basic rules for people who walk transects, which aim to strike the right balance between making a correct record and accidental double counting.

This from the guidelines:

Walk each section at a slow, steady pace counting all butterflies seen within 2.5m either side of the survey line,
5m ahead and 5m from ground level up (5x5x5m box). In some habitats e.g. along sea cliffs, it may not be possible to record along both sides of the survey line. In these situations it is acceptable to record at a width of 5m along one side only of the survey line. Similarly, if walking along a narrow lane with hedges either side adjust the position of your recording strip to record in a 5m wide strip as far as possible (i.e. 1m on the left, 4m on the right).
Try to avoid double counting where possible e.g. when an individual butterfly repeatedly flies in and out of your recording box. However, if you lose sight of an individual, and later regain sight of the same species do not assume this is the same individual. Do not count butterflies behind you.

Obviously common sense has to be applied and if it is clear that you have seen that same individual butterfly elsewhere along the route, then it has to be ignored. At the end of the day these things all tend to balance out.

Vince

[Neil Hulme]

Hi Neil

Following on from Vince's succinct summary of how counting is performed via UKBMS transects, I'd like to add some broader comments, which apply to all methods of recording, including the compilation of 'casual records'.

In the great scheme of things a double-count here or there really doesn't matter. It is the larger scale fluctuations in populations over the medium and longer term (not e.g. shorter term weather-related changes) which gives value to the data, and in some cases will inform habitat management decisions, or allow important scientific research on issues such as climate change. Smaller scale inaccuracies will all come out in the wash, and observers (particularly non-transect method) will often miss more than they'll double-count.

The most important issue when discussing butterfly counts is that they're submitted to local or national recording schemes. If records just sit in a notebook or blog, they're not of much value anyway.

BWs, Neil

[bugboy]

I do 2 transects at work and I also record casually over the whole site. My own personal rule is to not record casually on the day I do my transects unless it's a species I hadn't seen. I also use a bit of common sense based of the natural habits of each species. For example if I record 20 Gatekeeper in their usual patch of grassland habitat on my transect I wouldn't then record another 10 casually a few days later. But for species that habitually wander further afield such as whites and nymphalids I would.

I do an end of year report for my bosses st work (partly to show I'm not just wandering looking at butterflies and avoiding work) and it's interesting how my local tally always broadly follow wider local and national results showing how these recording schemes really do work.

[David M]

I personally follow prescribed rules if and when I do an official transect. However, if I'm out on my own I tend to try to follow a linear path and if I do return in the reverse direction I only count butterflies that weren't counted on my way in (e.g. if I've seen 2 Small Tortoiseshells inward but then 4 outward then I'll record an additional two).

Of course, this practice gets shot to pieces when in France, given the phenomenal numbers of butterflies generally. Here, I will resort to estimates.

[Paul Harfield]

Hi All

I don't do a transect, but I do casually count most of the time. I count what I see in one direction leaving out anything which I suspect to be duplication. I often visit the same sites regularly at which I count and submit results for each visit. Undoubtedly, I will be counting some of the same individuals here. If I visit a particular site twice or three times in a month for instance, is submitting these regular sightings from the same place a mistake

I use Living Record to submit my sightings which I use as per the guidelines. It has the facility for recording absence and presence (without a count) of a particular species. It also has the facility for disitinguishing between male, female and egglaying female together with a total adult count. I have noticed on more than one occasion that when reading our Hants & IOW annual report that I have been attributed with sightings (in the written species reports) that are not accurate to those I have submitted. These have only been minor discrepancies and I have not made my branch aware of them. Should I be concerned about this Do the submitted records enter the database by an automated system and manually extracted for the purposes of the report or are they all inputted manually

[NickMorgan]

Hi All

I don't do a transect, but I do casually count most of the time. I count what I see in one direction leaving out anything which I suspect to be duplication. I often visit the same sites regularly at which I count and submit results for each visit. Undoubtedly, I will be counting some of the same individuals here. If I visit a particular site twice or three times in a month for instance, is submitting these regular sightings from the same place a mistake

Paul,
I don't see a problem at all about recording two or three times a month from the same site. After all, transects are done every week, so up to five times a month.
I used to work in a country park where I kept a daily tally of all the butterflies I saw. Undoubtedly, I was recording the same butterflies on occasions, but I was able to put together graphs which nicely illustrated different broods, etc.

[Neil Freeman]

Many thanks all for the replies.

Some interesting comments and good points, especially on things balancing out overall and the fact that as many butterflies are probably missed as double counted.

In my case, I am very much a casual observer and often follow a circular route or wander back and forth around sites depending on pathways. My local sightings are submitted to Warwickshire BC via their website and my garden records on the online Garden Butterfly Survey.
When I am out and about around the country I will submit my sightings wherever possible on the area BC website but find that some areas have a better ways of doing this than others. I have also emailed county recorders directly if I am in doubt how to submit any sightings.
When I visit popular sites I will often check to see if any sightings have already been submitted for that day and if they have I will usually only submit any additional sightings so as to prevent duplication.

Cheers,

Neil.