How (and why) to conduct butterfly surveys

Part of my approach to the sport of butterflying is doing butterfly surveys.  Sounds scientific, doesn’t it?  Well, it is.  But that doesn’t make it boring.  And maybe it is just an excuse to get outside more often.

What I do is based on an established method of surveying for butterflies called the “Pollard Transect.”  It is really simple, and here is how you do the survey:

1.  Walk along a path and identify and count all of the butterflies that come within a fixed distance from your vantage point.  Write down the numbers of each and the time it takes you to complete the walk.

2.  Repeat step one.  Record dates and locations.  Repeat as often as is necessary to get the information you want.

That’s it.  Simple, isn’t it?

Here is what the survey tells you:  It gives the numbers of adult butterflies of the different species found in that location which are out where you can see them on that day.  If you keep track of the time you can calculate a rate of butterfly observations.  If you are careful to observe only those found within a fixed distance from your observation point, and know the total distance of the walk, you can calculate the number of butterfly observations in a given area.

Here is what the survey does not tell you:  It does not give you the total number of butterflies in that area—some may be where you don’t see them and some may be present in stages other than the adult stage.  It does not tell you how stable the population is.  You may have counted a number of butterflies that flew in to an area but need some other habitat to survive.

A single survey does not really give much useful information.  However, if information is carefully collected over a long period of time and can be compared on a relative basis it can be very useful.

It does get a little more detailed, depending on what you want to find out.

Butterflies are cold-blooded organisms which rely on the sun to heat up enough to fly.  They are most active on warm, sunny days.  Therefore, you need to restrict surveys to warm sunny days.  Excessive wind can keep butterflies from flying, so you also do not count surveys from windy days.

Then you might want to ask yourself how the information will be used.  Do you want to be able to compare your information with surveys conducted by others?  Do you want to participate in an official butterfly survey organization?  You might want to follow a written protocol that other people are following, so that your results can be compared to theirs.

The Illinois Butterfly Monitoring Network has been coordinating volunteer butterfly surveys for a fairly long time.  They have some wonderful information, including instructions for conducting surveys that can be found here.

Here is a chart I used to compare the numbers of butterflies seen in a rain garden at Camp Dodge with baseline numbers from surveys taken in the Cantonment area, an area with short grass comparable to a typical suburban development.

Next time–more on butterfly surveys…


About the roused bear

Nature photographer from central Iowa.
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