Date: Fri, 22 Feb 2002 18:56:10 -0500 Reply-To: Maryland Birds & Birding Sender: Maryland Birds & Birding From: Norman Saunders Subject: Re: Counting Birds MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Jordan Rutter asks: > I am looking for guidance. How do you accurately estimate very large > numbers of birds? Is there a good rule of thumb? Are there Christmas > Bird Count guidelines? My dad said that we may have to count a portion > of the flock, for example one quarter or one tenth, and then calculate > from there. This seems both difficult - especially when they are in > flight - and could be way off. And, what do you do when you think you > may have seen the same bird twice? Any help you could give me would be > greatly appreciated. Thank you in advance Good questions, Jordan. First off, don't get discouraged. Do the best you can to come up with an estimate--as you gain more experience in the field your estimates will get closer to the real thing and also will come to you more quickly. Further, your field notes will be more valuable with the count estimates included and over time will become a very useful database for year-to-year or week-to-week comparisons. As both your dad and Jordan noted, a good way to estimate large numbers is to estimate the number in a smaller group or subset and then figure out roughly how many times that smaller portion appears in the big group you are looking at. Again, it will become automatic over time and you won't hardly think about it any more. Another way of reporting bird numbers in your field notebook is by orders of magnitude. There is nothing at all wrong with saying you saw tens of starlings, hundreds of Canada Geese, or thousands of Canvasback (or whatever--you get the idea). Even this is better than no estimate at all. You also asked about the Golden Eagles. I would likely have recorded your sightings as two birds, since you don't really have any way of knowing if the lone bird you saw wasn't part of the earlier pair. Again, this is an instinctual thing and you'll get better at it with time. The biggest danger with using any estimating technique is over-estimation. It is really easy to say "There must have been thousands and thousands of Canada Geese in that field!" But stop and think--were there really? or was it just hundreds and hundreds...or maybe only 139, or whatever. If faced with a choice I usually try to estimate a bit low simply because I know my own tendencies to exaggerate all too well. I sure hope this helps! Keep asking those good questions! Norm Colesville, MD marshhawk@att.net ======================================================================= To leave the MDOsprey list, send e-mail to listserv@home.ease.lsoft.com with the following message in line 1: signoff mdosprey ======================================================================= =========================================================================