[birding] RE: Black swift puzzle

[David Irons]

Greetings All,

The exceptionally early Black Swift reports that Joel mentions, were, as Joel suggests, almost assuredly Purple Martins. The timing of those three reports was right within the normal arrival window for martins and, by all accounts, 4-6 weeks ahead of the known Oregon/Washington migration window for Black Swifts. Birds of Washington, Wahl et al. (2005) lists no records before early May. Similarly, Birds of Oregon: A General Reference (2003) states (correctly) that the earliest Black Swifts arrive in Oregon around 10-15 May. The 30 March Corvallis report is mentioned in BOGR, but is deemed to be a case of "erroneous" identification by the editors. I think their assessment is spot on. 

The other two early reports from the McGie phenology are not listed in BOGR, for good reason in my opinion. I suspect that the BOGR editors decided that it was necessary to mention the 30 March report because it had been published in American Birds (now North American Birds). It is unfortunate that the American Birds editors chose to lend credibility to that record by publishing it, but in that era much less was known about the status and habits of Black Swifts in the Pacific Northwest. This remains a species about which we have much to learn. As the current Regional editor for North American Birds, I would not publish a pre-May report of a Black Swift without exceptional documentation (photo or specimen).

Dave Irons  




> Subject: Black swift puzzle
> From: joel.geier at peak.org
> To: birding at midvalleybirding.org
> CC: llsdirons at msn.com
> Date: Tue, 20 Apr 2010 08:05:03 -0700
> 
> Hi all,
> 
> Thanks to Dave Irons for a good account of the Black Swift situation in
> spring migration, and suggestions on how & when to look. 
> 
> Now here's an algebra puzzle:
> 
> Alan McGie's phenology for Corvallis shows three local detections in 36+
> years of spring migration records, with a mean of April 9 and an
> earliest date of March 30. 
> 
> Without knowing the other two dates that contribute to the mean, one can
> show (with just a bit of algebra), that at least one of the other two of
> the Corvallis-area Black Swift detections had to be before April 15th,
> and all three had to be by the end of April. 
> 
> It's curious that this should be so out of synch with the statewide
> picture as described by Dave. A couple of ideas:
> 
> 1) Were some or all of those March/April detections really Purple
> Martins? Or
> 
> 2) Is there a northern-nesting population of Black Swifts that might
> pass through the Willamette Valley earlier than the coastal migrants or
> the ones that nest at Salt Creek Falls -- but seldom detected?
> 
> Happy birding,
> Joel
> 
> --
> Joel Geier
> Camp Adair area north of Corvallis
> 
> 
 		 	   		  
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