Date: 8/25/18 8:18 am
From: <phawk254...>
Subject: [MASSBIRD] Plum: Raptors, Baird's and Whiterumps: A Shorebird Learning Experience
Yesterday Julie and I birded Plum, looking primarily to shorebird. We were surprised by excellent views of several raptors. An immature female Sharp-shinned hunting near lot 2. Farther down the island we had a juvenile Cooper's Hawk who was being duetted by a crow, which flew in sync with the young hawk. If it had been another Cooper's Hawk, you might have sworn it was courtship flight. They alighted together. The crow then harassed the Coop standing next to it, so the Coop took off, flushing a female juvenile Sharp-shinned Hawk from a nearby bush. Earlier we had had a Redtail on the pink house. Now we found a very faded pinkish one eating prey in the marsh south of the Old Pines.


At Sandy Point we had two Killdeer in the parking lot, but on the beach our first shorebird was a lone juvenile Baird's Sandpiper, working one high wrack line for insects. It spent the next 20-30 minutes working that wrack line by itself. No other shorebirds or beachgoers. It was awesome. Best views we've ever had of a young Baird's, as it walked to us and turned around only feet away. It walked back about half the length of the wrack line, and then flew off to the northwest.


I then studied Sanderlings and their molt for quite a while, as more birds came up to roost on the upper beach about 150 minutes before high tide. My clear impression was that the cold front of Thursday had taken away large numbers of birds I had been seeing earlier in the week and brought in very limited numbers to Sandy Point. Semipal Plovers still dominated overwhelmingly, but there were noticeably fewer and far fewer Semipal Sandpipers than earlier in the week. Had about two dozen Sanderlings but did not see two adult Ruddy Turnstones that apparently had been around for several weeks. Had two juvenile Peregrines, apparently one female and one male, rocket over the beach, followed by the female chasing the much smaller apparent male across Stage Island pool.


It was then we ran into Carol Decker carefully studying what she thought might be a Western Sandpiper. I think it likely was, but I was quickly distracted by the sight of bunches of White-rumped Sandpipers clustered on wrack in several dozen bunches. Almost every cluster of shorebirds had numbers of White-rumps, but these Whiterumps had apricot colored feathers around the base of the bill and extending out on somewhat more on some of the birds. (I had first called them orangish buff or ochre-colored, somewhat like a Killdeer's rump but finally settled on "apricot.") Everywhere there were Whiterumps with apricot "moustaches" or even much more of their face colored. I couldn't recall seeing this before. I photographed many of the clusters, which extracted a price. I use a Nikon P500 megazoom (to 2000m or 82X) which has a very low res electronic view finder (EVF) that can make it difficult if not impossible to find individual birds in a cluster of birds or in much vegetation. !
I can rarely identify ANY bird as seen through the viewfinder, but have to look at the 82X photos, usually offsite in a shaded room, to ID the birds.


Some of the birds were clearly juveniles, but some were questionable. Suddenly, a number of shorebirds lofted quickly and spun out of the area. As I looked at the flock wheeling, it seemed homogeneous. When I looked back on the ground, the clusters were still there, but of alert Semipal Plovers, and small numbers of Sanderlings and Semipal Sands. The Whiterumps were all gone. All gone.


Carol, Julie and I walked back to the parking lot where I pulled out Richard Chandler's excellent "Shorebirds of North America, Europe and Asia." Not a photo of a bird in the plumage we had seen, and no discussion of Whiterumps with apricot moustaches (like a milk moustache, but probably more accurately like a full beard.) I pulled out O'Brien', et. al., "The Shorebird Guide." No photos of such birds, and no discussion of such plumage. At home I checked the Birds of North America account, written in 1992. Also no mention of color around the base of the bill.


Intriguingly, in the text of "The Shorebird Guide" O'Brien. et al., say that peak numbers of adults pass through the mid-Atlantic states in late August and the first half of September. Juveniles depart the breeding grounds "by about mid- to late September...Peak numbers of juveniles pass through e Canada from mid-October to mid-November...." Was this an usually large and unusually early flock of juveniles that had just arrived?


However, then I examined Hayman, Marchant and Prater's Shorebirds: An Identification Guide (1986), my favorite shorebird guide and in my opinion one of the two best family (or broader) guides ever done. Hayman specifically says under White-rumped Juvenile "Bill shows yellowish-brown patch at base." Intriguingly, he also says "...juveniles are late migrants, with first arrivals in New York not until late Sept."


Now I had some secondary source explanation for/confirmation of what we had seen. I had roughly estimated the flock we saw flying was a minimum of 100 to possibly as many as 200 birds. Certainly the cluster after cluster I had looked at with my scope was consonant with that, but I don't recall ever seeing that number of Whiterumps together before. Checking Veit and Petersen's "Birds of Massachusetts," they say, "In fall, the maximum counts...average 200 birds. Juveniles are rare before mid-September but regularly occur until late November."


August 24 was apparently a very early date for an apparently unusually large flock of juvenile White-rumped Sandpipers. Now I could research Whiterumps on ebird to see what been happening in Mass. and elsewhere with regard to juveniles in recent years, but I do not have that much time available. I hope that someone else has, or has already done it and is just about to publish it somewhere.


The Baird's experience has also generated renewed curiosity. Reading the "Birds of North America" account, I was amazed that it had been published in 1992, 26 years ago, and based fairly heavily on research I had first read almost 40 years ago! Baird's really are pretty incredible according to that research. When I have time I'll have to google Baird's and carefully check S.O.R.A. to learn more about this species, which we rarely see well in Massachusetts. I'm also intrigued that Veit & Petersen say Baird juveniles (we see few adults in the East) are seen primarily late August to late September. Many sources tie Baird's and white-rumps together, in part because of their very similar appearance and likely because of breeding range and general behavior. I'm intrigued that juvenile Baird's migrate so much earlier than juvenile Whiterumps. Both are very long distance migrants but have different fall migration patterns and apparently calendars.


Meanwhile, I'm still researching Bristle-thighed Curlew! I'd never read much about the species, but this summer I saw three on the Seward Peninsula. It was a much more moving experience than I had ever expected. I subsequently began researching them (and other curlews), and was amazed at how unusual THEY are. I've read the standard accounts and have gone through S.O.R.A. reading the very limited number of articles on the species, but I want to know more.


Seeing accipiters and falcons was exciting, but seeing the Baird's and the juvenile Whiterumps were unexpected thrills and reignited my curiosity about and renewed my love of shorebirds. The day was the beginning of a new learning experience about some of my favorite birds.


Best,


Paul



Paul M. Roberts
Medford, MA
<phawk254...>
 
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