Perfect Time for Moonwatching

Friday night May 4th (2012), between 10:00 and 10:30 p.m.

Read this article by Kimball Garrett posted on Facebook, May 3, 2012 ...



This weekend we'll have a full moon, and since it coincides with the peak of spring migration for many passerines in our area this means it's a perfect time for moonwatching. Basically, this means watching the face of the full moon with a spotting scope and observing silhouettes of birds passing by. It's surprisingly easy to see birds, though of course it's harder (close to impossible, really) to identify them. Nocturnal flight calls can give a hint of what is passing over, and it's not hard to tell small "warblery things" from larger "thrushy things."

We have a great chance to compare the volume of nocturnal migration in widely scattered parts of the Los Angeles Region. Do more migrants pass along the foothills than over the flat L. A. Basin? Are many birds moving right along the coast? What about the deserts and the higher mountains? By having observers scattered over the region we might be able to get some idea of the medium-scale differences in nocturnal movement.

Radar (particularly newer "NexRad" technology) is the method of choice for studying nocturnal bird migration, but it's a bit removed from the sensory experience of birders. In short, it's more fun to moonwatch. Nocturnal flight call counts are also an important technique, but (a) apart from distinctive species like Swainson's Thrushes most calls are hard for most birders to identify,and (b) some birds don't call, while moonwatching records silent and calling birds equally well.

So, SAVE THE DATE AND TIME! On Friday night May 4th, 2012, between 10:00 and 10:30 p.m., try moonwatching and counting all birds passing in front of the face of the moon. We can then get rates (birds per hour -- that's half an hour times two) and compare the rates in different geographical areas.

Why Friday? It's actually the night before the true full moon, but the moon will be higher in the sky at 10:00 p.m., and it will be very close to full. The weather is predicted to be clear (though conditions along the immediate coast are less certain right now), and it gives us the opportunity to postpone until Saturday if unexpected cloudiness develops.

I urge everybody to PRACTICE moonwatching Thursday evening (the moon will, of course, be higher earlier, so you can try before 10:00).

How to moonwatch? Just set up your spotting scope on the moon and zoom in (to about 30-40X, though 20X will do if that's your fixed objective lens). BE SURE TO WEAR SUNGLASSES! The full moon is quite bright, and good dark sunglasses are essential. You might even experiment with a tinted filter for your scope.

What to record? We're looking for two main things. First, the total number of birds crossing the face of the moon during the observation period (10:00 to 10:30 p.m.). If you observe for less than those 30 minutes, indicate how many minutes you observed. Second, the general direction of travel of the birds. You can express this by considering the moon a clock face and indicating "9:00 to 3:00" (i.e., left to right), "7:00 to 1:00" (i.e. lower left to upper right), etc. Obviously there will be a fair bit of scatter, but in general most birds seem to move in generally the same direction, so just give a general "average" and an indication of the degree of scatter.

How to report? If you have good coverage, feel free to post your results to the listserve. If you prefer, just e-mail me with your results and I'll post a summary a day or two later.

[Note: folks in other counties are free to pass this along to other listserves for a more region-wide moonwatching snapshot.]


Kimball L. Garrett
Section of Ornithology
Natural History Museum of Los Angeles County


Once again, a reminder that this Friday evening, 4 May, 2012, we'll try a
simultaneous county-wide Moonwatch beginning at 10:00 p.m. Below are
links to a couple of instructional references that might be of interest,
but what we propose to do Friday is much simpler.

There is one important CHANGE in the instructions I posted earlier.
Instead of counting continuously from 10:00 to 10:30 p.m., I propose
that we start at 10:00, count for ten minutes, then rest our eyes for
five minutes, counting for an additional ten minutes from 10:15 to
10:25. You can vary this by resting at different times, but everybody
should count for a TOTAL OF TWENTY (20) MINUTES beginning at 10:00 and
ending no later than 10:30. If you've tried moonwatching, you can
appreciate that a resting period after ten minutes is important.
Twenty minutes total isn't much, but it should be enough of a "snapshot"
to indicate whether more ambitious efforts would be worthwhile in the

20-40X will be fine (and yes, thank you Don S. - obviously I meant the
eyepiece, not the objective lens in my previous post) - 30X is what is
most often suggested. A binocular will not be sufficient. Remember to

Previously, I didn't mention before WHERE to conduct your moonwatch.
Your backyard/frontyard would be ideal (or a site as close to your home
as possible where you can get a clear view of the moon). If a few of
you are more ambitious, you can get out to mountain, foothill, desert,
or coastal point areas to increase our geographical spread. You just
have to be able to get an unobstructed view of the moon.

Check out these sites:

I look forward to having you share your results - number of birds total,
exact times of observation, your exact location, and some indication of
general/average direction of flight (using the moon face as a clock).


Kimball L. Garrett
Ornithology Collections Manager
Natural History Museum of Los Angeles County