[Tweeters] Re: Question About Site Fidelity in Tropical Kingbirds

B B birder4184 at yahoo.com
Tue Nov 17 09:34:55 PST 2015


I admit that every time I think I am on top of genetics and heredity I find something that confuses and/or proves otherwise.  A hereditary basis for Tropical Kingbirds in Washington November qualifies.
My probably superficial understanding would first require our visiting TRKI's to survive their visits and return to breeding grounds sufficiently healthy to breed.  If this is the case, do we know their path to get there?
Secondly assuming these birds have a genetic makeup that favors (dictates?) a return to the NW by their progeny, this would have to get passed on to them.  Since I expect that our NW TRKI's are a small percentage of all TRKI's on the breeding grounds it would be unlikely that both parents would have this genetic trait.  So per my understanding the trait would disappear quickly unless it is a dominant one. Even so it would seem to me that unless the NW TRKI's somehow are more likely to survive this seemingly aberrant journey compared to "normal" migrants and also more likely to breed successfully than them, the numbers game would still lead this trait (and our visitors) to disappear or at least remain very rare and probably diminish. 
I am sure my "analysis" is at best simplistic and this post is intended to get more info and explanation and not to refute the hereditary basis theory which is fascinating. If it is not heteditary then what is the explanation for these seemingly increasing visits?  Is it simply math ... same percentage of total population is aberrant but the population overall has expanded?  Just more observers so more observations?  
Any Ph.D.'s out there with answers?

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On Mon, Nov 16, 2015 at 9:33 PM, Jeff Kozma<jcr_5105 at charter.net> wrote: To further this thought, migration is hereditary in songbirds, not learned...unlike in geese, cranes and swans where young follow adults on migration paths.  Thus, if a bird survives wintering in an area and returns to its normal breeding grounds and is successful breeding, there is a good chance that migration routes will be passed on genetically to its offspring.  This is believed to be the case with the increasing number of Rufous Hummingbirds now wintering in the southeastern United States instead of making their more traditional fall migrations to Mexico. 

Jeff Kozma

J c r underscore 5105 at charter dot net

Yakima

-----Original Message-----
From: tweeters-bounces at mailman1.u.washington.edu [mailto:tweeters-bounces at mailman1.u.washington.edu] On Behalf Of Mike Patterson
Sent: Monday, November 16, 2015 7:09 AM
To: Tweeters <tweeters at u.washington.edu>
Subject: [Tweeters] Re: Question About Site Fidelity in Tropical Kingbirds

One might postulate that, if all northward ranging Tropical Kingbirds are doomed to death before reproduction, then the behavior would be non-adaptive and should be either remain rare or eventually extinguish itself.  There is, however, pretty convincing trend data that suggests Tropical Kingbird occurrences in the fall are increasing and that individuals are remaining later.  This would be the opposite of rare or eventually extinguished...

I have seen 6 different Tropical Kingbirds this season on the lower Columbia.  Back in the 90's, they were not even annual in this area.

I explored some of the data last season at:
http://www.surfbirds.com/community-blogs/northcoastdiaries/?p=2506

--
Mike Patterson
Astoria, OR
The history of photons
http://www.surfbirds.com/community-blogs/northcoastdiaries/?p=3005
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