Date: Wed, 17 Mar 2004 11:44:35 -0500 Reply-To: Maryland Birds & Birding Sender: Maryland Birds & Birding From: Michael O'Brien Subject: Re: counting scoters Mime-version: 1.0 Content-type: text/plain; charset="US-ASCII" Content-transfer-encoding: 7bit Hi all, I've been reading this thread with interest and saw my name mentioned so I thought I'd chime in. I realize this is somewhat off topic though it does revolve around counting birds in general. The flock of scoters off Cape May Point right now is indeed massive and the numbers, whatever they are, unprecedented. And, in my opinion, counting these birds from shore is virtually impossible. I tried one day about a week ago. The birds are rafting and feeding just offshore with small flocks (of mostly Black Scoters) courting inshore around the jetties. As the tide falls, the birds drift out the bay past the Point and the tail end of the flock picks up and flies back up the bay. So, through the entire falling tide period, you have a conveyor belt of birds, some drifting out the bay, others flying in. The problem is, it's impossible to see where one end of the flock stops and the other begins. Around high tide, before the birds started to fly, I counted about 75,000 birds on the water. I did this in blocks of 100 and it took me an hour. Of course, I only counted what I could see but the flock continued out of site in both directions. Then, as the tide began to fall, the birds started to fly up the bay. I counted these for another hour, again in blocks of 100, and came up with about 110,000 (not including the 1500 or so White-winged Scoters). During the entire period, the flock on the water appeared to be the same size as when I counted them (but were certainly different birds). I stopped counting when there was a lull in the flight but the birds continued to fly. In fact, I'm sure they continued for the entire falling tide period which is at least five hours. The question is, how long should one count in order to count all the birds? I have no idea. What I can say is, the flock I counted on the water was more than 50% Black Scoters but the flock in flight was 95+% Surf so they were mostly or entirely different birds. In the end, I decided to just add the two numbers together, which is where the 185,000 figure came from (actually it should be 186,500 but I didn't want to claim that level of precision). Needless to say, that number should be considered a bare minimum estimate, not a precise count. Based on what I have seen on other days and what others have reported, I believe there are many more than 185,000 birds out there. For one thing, each time I go out there, the apparent volume of birds is different and the ratio of Black to Surf is different. Also, several people have reported birds flying at a pace of 3000-5000/minute for more than two hours, twice the pace and twice the time than when I counted. Others who have been on boats in Delaware Bay report scoters covering a much larger area than can be seen from shore in Cape May. My hunch is that there are between 1/4 and 1/2 million birds out there but I think it would take aerial counts to confirm that. In the mean time, it sure is impressive to watch them! Michael O'Brien West Cape May, NJ ======================================================================= To leave the MDOsprey list, send e-mail to listserv@home.ease.lsoft.com with the following message in line 1: signoff mdosprey ======================================================================= =========================================================================