THE OREGON DRAGONFLY AND DAMSELFLY SURVEY

To see what a Variegated Meadowhawk looks like, go to:
immature male , photo by Terry Morse
male, teneral male, immature female, scans by Dennis Paulson

What to look for

If you would like to contribute to this effort, watch for small red dragonflies mostly flying in the same general direction. If you see some, make note of the location from which you observed them, the date and time of day, and as much about the weather as you can. Is the sky clear, partly cloudy, or cloudy? Is there a wind blowing? If so, how strongly and from what direction? These can be qualitative descriptions such as still, mildly breezy, a stiff breeze, etc. If you have access to a wind gauge, report the actual wind speed.

(Inexpensive handheld wind gauges are available from Edmund Scientific http://www.edmundscientific.com/Products/DisplayProduct.cfm?productid=1512 ).

In what direction are the dragonflies flying?

Direction of the wind and the flight should be determined with a compass, if at all possible. Reasonably priced compasses can be purchased at most sporting goods or department stores. Local landmarks, such as Highway 101, do not maintain a uniform direction. Judging north and south to be the direction a highway follows can give a very inaccurate impression of flight and wind direction. Similarly, global positoning system (GPS) units do not give accurate direction readings if you are not moving fairly steadily in one direction.

In your report, please state how you determined direction. Let us know whether your compass readings are relative to true north or magnetic north (That is, have you compensated for magnetic declination? True north at Newport, Oregon, is 19.5 degrees west of magnetic north. Therefore, if your compass is not compensated for this, you need to add 19.5 degrees to your compass reading to get the direction relative to true, or map, north. The magnetic declination you should use will be listed on a USGS topographical map for your area.).

(For more information on how to compensate for magnetic declination, see:

http://feature.geography.wisc.edu/sco/maps/m_magnet.html#using)

How can you accurately determine the direction of the flight?

The following is adapted from an article prepared by Monarch Watch http://www.monarchwatch.org/

If at all possible, you should determine flight direction in an open area, such as a field or large parking lot, where the flight will not be affected by obstacles, such as buildings, or redirected and channeled by narrow streets or passages. Select a single dragonfly that is passing near or over you and face the direction it is flying. Follow it with your eyes until it goes completely out of sight. Take a compass reading of the direction you are facing. This is called the vanishing point direction, or vanishing bearing. If there seems to be much variation in the direction individual dragonflies are flying, determine the vanishing bearing for several different dragonflies and average the readings. In my experience, the majority of the dragonflies are flying in the same general direction. In a heavy flight, where many dragonflies are visible at the same time, you can get a reasonably accurate reading by lining yourself up with the overall direction of the flight, rather than by keying on individual dragonflies. In very heavy flights, it may be impossible to keep track of a single dragonfly amongst the masses. Don't worry about it.

Another kind of direction data you can record is body orientation (i.e., what direction is the dragonfly facing as it flies). This may not be the same direction as the vanishing bearing if the dragonfly is trying to maintain a constant direction with respect to the ground but is being pushed off course by an oblique wind. Determine body orientation if you want to and can, but it is more important to record the vanishing bearing of the dragonflies.

If you have a compass, report vanishing bearing and body position in degrees (0º for north, 90º for east, 180º for south, and 270º for west, plus all gradations between 0º and 360º, both of which represent north). Don't forget to correct for magnetic declination (see note above) or tell us that you are measuring relative to magnetic north.

For more detailed information on determining flight direction, see the article "Flight Vector Analysis", by Monarch Watch http://www.monarchwatch.org/class/studproj/vector.htm

Estimating flight rates

It is important to try to estimate the rate at which the dragonflies are passing (number of dragonflies per minute) in a uniform way between observers. The following is adapted from reports by Range Bayer and a book by Hugh Dingle (Dingle 1996):

Note the direction in which the dragonflies are flying, and face perpendicular (at right angles) to that direction. Imagine a line perpendicular to the flight and 50-100 yards long (depending on how far away you can see the dragonflies. Choose your distance somewhat shorter than the limits of your vision, so you don't miss very many dragonflies). Either measure or pace out the distance within which you will count dragonflies. (If you have time and the necessary resources, you could put up two tall poles (say 10' tall) a measured distance apart and count only the dragonflies passing between the poles. That way, you will know the exact distance over which you are counting dragonflies). If you can also estimate the range of heights at which the dragonflies are flying (both the lower and upper limits at which you can see them flying), you will be able to compute the approximate cross-sectional area of the flight you are sampling (length of your line times the height range of the flight [maximum height minus minimum height]). If all observers makes these estimates, it will be easier to make sense of divergent rates reported by different individuals.

If dragonflies are sometimes crossing the line in the main flight direction and sometimes against it, count and report how many cross the line in each direction during your count. If it is too difficult to keep track of both directions at once, do one count in one direction, then a separate count of dragonflies going in the opposite direction.

How much time should you spend counting?

As much as you can. Five minutes should be a minimum, but ten to fifteen minutes would be better. The problem with short counts (five minutes or less) is that there are occasional lulls in the flight. If you do short counts in response to seeing dragonflies flying, you are likely to miss counting during the lulls and will overestimate the overall flight rate. Ideally, you should measure flight rates at times chosen randomly within each hour (with the aid of a random numbers table) so that you will sample lulls and peaks in the flight in proportion to their occurrence. A second best solution is not to start your counting in response to a peak in the flight. Decide that you will start the count at an arbitrary time (say 3 or 5 minutes from now; or at arbitrary times past the hour, say 10, 25, and 45), so that you will not systematically count the peaks and skip the lulls. Try to choose your start time without reference to how many dragonflies are passing at the moment.

If you don't have time for 5 to 15 minute counts, make them as long as you can afford to, but start them at an arbitrary time, as described above. Be sure to report for how long you counted and how many dragonflies you counted, and not just the number per minute. It is important to know the length of time over which you counted. If the flight is a large one, you may want to use a hand counter ("tally whacker") to make counting easier.

Where to submit information

E-mail migration reports to project leader Range Bayer (rbayer@orednet.org), Terry Morse (tmorse@teleport.com), or Steve Valley (svalley@teleport.com).

Submit Your Observations Online

or, If you don't have internet access,

Download a printable observation report form for mailing

Mail your reports to:
Range Bayer
P.O. Box 1467
Newport, OR 97365
USA

Direct telephone alerts of migrations in progress to Range Bayer at 541-265-2965.

All migration reports will be posted on the Pacific Northwest Dragonfly Migration Project webpage.

Where to go for further information

Webpages

Pacific Northwest Dragonfly Migration Project Home Page http://www.ent.orst.edu/ore_dfly/migrate.htm

North American Dragonfly Migration Project http://members.bellatlantic.net/~dbarber/migrant/mig.html

Monarch Watch http://www.monarchwatch.org/class/studproj/vector.htm

Insect Migration website http://www.ph.adfa.oz.au/a-drake/trews/ww_re_im.htm

Dragonfly discussion groups

Dragonflies-L (go to http://dragonflies.listbot.com/ to subscribe)

Dragonfly organizations

Dragonfly Society of the Americas  http://www.afn.org/~iori/dsaintro.html
T. Donnelly
2091 Partridge Lane
Binghamton NY 13903 USA

References

Bayer, R.D. 1993. Dragonfly mass flights along the Oregon Central Coast (unpublished ms.)

Bayer, R.D. 1997. 19-21 September 1997 directed flights of dragonflies: a preliminary report. http://www.ent.orst.edu/ore_dfly/migrate.htm#rep

Dingle, Hugh. 1996. Migration: the biology of life on the move. NY: Oxford University Press.

Recommended Readings

Dunkle, Sidney W. 2000. Dragonflies through Binoculars: A field guide to dragonflies of North America. NY: Oxford University Press. ISBN 0195112687. (Indispensable field guide)

Corbet, Philip S. 1999. Dragonflies: Behavior and ecology of Odonata. NY: Cornell University Press. ISBN 0801425921. (Essential for the real enthusiast!)

Pacific Northwest Dragonfly Migration Project Home Page

Advice for Teachers, Class Project, Monitoring Migratory Dragonflies

Submit Your Observations Online

Download a printable observation report form for mailing.
Mail to: Range Bayer
P.O. Box 1467
Newport, OR 97365
USA

Oregon Dragonfly and Damselfly Survey

For More Information Contact: Terry Morse tmorse@teleport.com , Range Bayer rbayer@orednet.org
or Steve Valley svalley@teleport.com

  Hits since 9/07/2000    Last updated  08/18/2001