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

Dennis Paulson dennispaulson at comcast.net
Tue Nov 17 10:45:41 PST 2015


Blair, you raised good questions.

One thing seems clear from TRKI movements is that individuals, perhaps from populations in the northwestern part of the range of the species but perhaps from elsewhere, routinely move in a northwesterly direction in the fall. Are they programmed to move all the way up here, or are they not programmed to stop somewhere farther south? We know a lot of birds go the wrong way in the fall in the mirror-image migration that Dave DeSante described so long ago in California, but this is another phenomenon, reversed-direction migration, assuming those kingbirds would normally have migrated south-southeast, along the axis of Mexico and Central America. That seems to be less common, but I wonder if the kingbirds aren’t the poster child for it just because they are conspicuous. Perhaps a lot of other sw US/nw Mexico birds are also coming up here but remain undetected. Well, we know this happens in Lucy’s Warblers as well, probably Vermilion Flycatchers, surely other examples.

Farther south, the coasts of CA and OR are saturated with TRKI records. There are also a lot of them in the interior of CA and AZ. But an interesting thing about many of the southern and interior records is that they can be at any time of year, so they probably aren’t part of the movement, which really seems to end up along the coast. As you go north along the coast from southern California, all of a sudden pretty much all the records are in the fall, and there are a huge number of them (plus, as Bob Boekelheide wrote, not all bird records are on eBird, and I hope everyone always keeps that in mind).

So there is a major movement up the Pacific coast in fall. If you set the eBird date range to Dec-Feb, the number of records diminishes greatly, with only a single record from WA and five from OR, all in December, at the early part of the winter. But there are quite a few from about Eureka south, some of them in Jan/Feb, although nothing like the number in fall. Do these winter records all represent birds that migrated to that point and were still present in winter, or could some of them represent birds moving back to the south? Obviously we have no idea, without marked birds. I didn’t pursue the records enough to see whether some of those in the Eureka area were the same birds reported in Oct/Nov. That would indicate survival, but that’s a lot farther south than WA, and other flycatchers survive winters at that latitude.

Set the date range to Mar-May, and there are still a few birds from northern CA south, but again a lot fewer. The majority from around Eureka were in March and then presumably left. That seems more likely than that they died in March. Lots of birds in AZ at this time, perhaps overshoots of birds already in northbound migration from the tropics.

It’s a lot of work sifting through these records, and I often wish that eBird would post just one record for one bird rather than all the records from everyone who saw the bird. You open a record and see a long list, and your impression is of lots of occurrences, and then you realize that this long list was from one bird seen by many, many observers. I don’t know what the solution is to this, but it will presumably only get worse in the future.

I can’t conclude as glibly as Wayne did that all the birds are doomed when they come up this far. I don’t strongly disagree with him, as I’ve had the same thoughts myself, but we still don’t have any evidence that they don’t turn around and head back south. Even if they disappeared with the first bad weather, either alternative could have occurred. Tree Swallows move south en masse along the Atlantic Coast when bad weather comes in, and kingbirds seem to be strong fliers. The lack of records of them in southbound movement could be because they are moving pretty fast, not hanging around in one place where birders come upon them. Too bad it’s not easy to capture kingbirds for banding!

I agree that selection should be working against individuals that fly so far northward if in fact they are dying, and that should reduce the tendency to do that in populations. But as has been asked, then why are there more and more such records? I think we need to consider the fact that there are more, and more savvy, observers all the time, so are there really more birds? If there are, I don’t know if climate change can explain it, as western Washington in winter is still not kingbird-friendly. An increase in the populations of the species could explain it, and we should look at that perhaps to determine if it is the case.

One interesting thing is how they pile up at Neah Bay, as if they would be going still farther north if it weren’t for the water barrier. There is at least one record from the southern Alaskan islands in fall.

I’d say we really don't what is going on—sorry it took me that long to say it.

Dennis Paulson
Seattle


On Nov 17, 2015, at 9:34 AM, B B <birder4184 at yahoo.com> wrote:


> 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?

>

>

> Sent from Yahoo Mail on Android

>

> 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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-----
Dennis Paulson
1724 NE 98 St.
Seattle, WA 98115
206-528-1382
dennispaulson at comcast.net






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