Butterfly distance sampling

[Flora T]

Hi there!

I'm currently writing my proposal for my dissertation project that I will be carrying out this summer. I want to look at 'Butterfly species richness, abundance and diversity in fragmented urban landscapes: implications for conservation and management strategies'.

I am planning to use distance sampling point counts at various grassland sites in and around Bristol. I just had a couple of questions:

Do you know what the recommended time of survey is? I've found some papers regarding bird point counts and they suggest 5 minutes. Is it the same for butterflies?

In terms of the data capture to then use in the distance statistical model, how is this best stored and managed? Does an excel spreadsheet with attributes and results work?

Thank you!

Flora.

[Eric Rexstad]

Flora

You might consider using line transects rather than points; detection function fitting is a bit easier.  Depends upon the size of the fragmented landscapes you intend to sample, but the transects do not need to be terribly long (20-100m).  By using lines, you are moving faster than the butterflies and animal movement causes problems with distance sampling; when using point stations, you are not moving faster than the animals.  When using durations for point transects, the longer the duration the more animals are detected, exactly because of the movement issue.  When using point transects, best to employ what is known as the "snapshot method".

Two references for you related to content above:

Glennie, R., Buckland, S., & Thomas, L. (2015). The effect of animal movement on line transect estimates of abundance. PLOS ONE, 10(3), e0121333. https://doi.org/10.1371/journal.pone.0121333

Buckland, S. T. (2006). Point transect surveys for songbirds: Robust methodologies. The Auk, 123(2), 345–357. https://doi.org/10.1093/auk/123.2.345

Regarding data capture, a spreadsheet will work fine.  Columns will include site, area, transect name, transect length, species, perpendicular distance.  Other columns can be added.

Let us know if you have other questions.

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