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11513Fwd: [SanDiegoRegionBirding] Hornblower trips; some comments on recent booby sightings; Nazca i.d.

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  • Stan Walens
    Aug 24, 2014
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      On August 17, a masked/Nazca-type booby was photographed 6 miles south of the U.S. border, in Mexican waters. It was a third-year/subadult bird, with a bill that was orange at the base but yellow for the distal half. Photographs are linked to in the bottom part of this message.

      There has been much offlist discussion of this bird, but we are looking for sulid experts who might have developed/discovered/studied any diagnostic characteristics for Nazca vs. masked booby in. See Sue Smith’s clarification to my post. 

      The question: Can masked boobies be told from Nazca boobies at ages less than full adult? And what features can be used to separate either from masked/Nazca hybrids in subadult stages?

      Sue and my email addresses are embedded in the email headings. Thanks in advance for your help.

      Stan Walens
      San Diego

      Begin forwarded message:

      From: Susan Smith <seiurus ataoldotcom>
      Subject: Re: [SanDiegoRegionBirding] Hornblower trips; some comments on recent booby sightings; Nazca i.d.
      Date: August 24, 2014 at 5:45:03 PM PDT
      To: stan.walens atgmaildotcom, sandiegoregionbirding@yahoogroups.com

      To Stan and SDRBirders, 
      To perhaps clarify a bit more about the Nazca or Nazca-Masked Booby thing,  I'll try to paraphrase some recent comments I got from by Bob Pitman (NOAA,Southwest Fisheries Science Center, La Jolla), who wrote the original paper with Jehl on separating out these two species.  What Bob said was that he could only rule out a "pure"  Masked Booby based on the photographs, but he could not rule out a Nazca- Masked Booby hybrid based on his experience.  He hadn't worked on the large Nazca colonies much (only those colonies where both species overlap, e.g Clipperton) to have had enough experience with the  3rd year plumage of Nazca Boobies to tell definitively whether last Sunday's bird was a pure Nazca rather than a hybrid. So its still possible it could be a third year Nazca.  He also added that  sub-adults tend to be rare on the breeding  colonies, where most people study these birds, so maybe we will never know unless this same bird is seen and photographed again next year (at presumed full adulthood).  Nonetheless, he suggested that someone might want to contact people working with the Nazcas  on the Galapagos.  They may have more experience with this particular plumage, and might have some useful photos.  Or maybe they could comment on Christopher's photos.   I looked up some Nazca Booby research and there is a Dr. David Anderson of Wake Forest University, N.C. (behavioral studies on Nazcas at Galapagos)who might have some comments on this.   Some of you out there who are more familiar with the sulid  literature and may know of researchers at the Galapagos who might also be of help.   
           Happy Sulid-ing...Sue

      Susan Smith
      Seiurus Biological  Consulting
      Del Mar, CA 

      -----Original Message-----
      From: Stan Walens stan.walens atgmaildotcom [SanDiegoRegionBirding] <SanDiegoRegionBirding-noreply@yahoogroups.com>
      To: SDBirding <sandiegoregionbirding@yahoogroups.com>
      Sent: Sat, Aug 23, 2014 7:35 pm
      Subject: [SanDiegoRegionBirding] Hornblower trips; some comments on recent booby sightings; Nazca i.d.


       …..3. Now as for the possible Nazca booby seen on August 17 a few miles off the Coronados Islands, in Mexican waters. It was a third-year/subadult bird, nearly in adult plumage but with remnants of black on the lower back, with a partially yellow bill with orange coming in quite strongly at the base [many photos available on the sandiegoregionbirding listserv]. There was much offlist discussion of this bird, but an important comment was made by Bob Pittman. If I am summarizing correctly, hybrid Masked/Nazca boobies are known from the colonies closest to California, and are more common than one might suspect. A non-adult bird with a partially yellow/partially orange bill could be a young Nazca whose bill has not achieved adult coloration, or it could be a hybrid. Even a third-year bird cannot be called a Nazca just because there is some orange in the bill. All we know is that it has some Nazca in its parentage. If I interpret Bob’s comments correctly, only birds with entirely orange bills can be considered to be Nazca boobies, and all those with partially orange bills have to be left as masked/Nazca.

      Stan Walens
      San Diego

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