eBird Purple Martin weekly migration display.

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stan kostka
Posts: 142
Joined: Fri Nov 28, 2003 7:59 pm
Location: Washington, Seattle

eBird Purple Martin weekly migration display.

Postby stan kostka » Thu Dec 06, 2018 1:08 pm

Hi All,

Here's a link to an eBird weekly display of the annual migration. I thought it was pretty cool. You can play it through and/or pause at any particular week. The dates are displayed at the bottom of the map at the control bar.

Stan Kostka

https://ebird.org/science/status-and-tr ... map-weekly

Dave Reynolds
Posts: 1618
Joined: Mon Jan 31, 2011 4:35 pm
Location: Little Hocking, Oh.
Martin Colony History: 2018 Success at Satilite Site.

Re: eBird Purple Martin weekly migration display.

Postby Dave Reynolds » Thu Dec 06, 2018 1:12 pm

Stan... Great Map.. Thanks for sharing... :wink:

Dave
2018 Home Site
Lots of Visitors

2018 Satilite Site “Oxbow Golf Course”
15 Pair, 58 Eggs, 38 Hatched and 36 Fledged :wink:
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Dale D
Posts: 298
Joined: Tue Jan 30, 2018 10:11 am
Location: Orlando, Fl
Martin Colony History: PM Landlord since 2004

Re: eBird Purple Martin weekly migration display.

Postby Dale D » Thu Dec 06, 2018 5:26 pm

Stan, that is an interesting map to follow. I will share it with my FB Group. Thanks for posting!
Orlando, FL Landlord since 2004
Offer 30 Cavities Total
Hosted 21 pairs in 2017

Hanover Bill
Posts: 547
Joined: Thu May 14, 2009 3:10 pm
Location: Pennsylvania/Hanover Township
Martin Colony History: 2009 & 10 - 0
2011 & 12 - Visitors
2013 - 2 pr. fledged 9
2014 - 3 pr. fledged 13
2015 - 7 pr. fledged 27
2016 - 15 pr. fledged 72

Re: eBird Purple Martin weekly migration display.

Postby Hanover Bill » Wed Dec 12, 2018 8:48 am

Great map Stan. Interesting looking at the tract of land comprising the Appalachian mountains and how barren of Purple Martin activity those mountainous areas are. Thanks for posting.

Hanover Bill.
2009 & 10 - 0
2011 & 12 - Visitors
2013 - 2 pr. fledged 9
2014 - 3 pr. fledged 13
2015 - 7 pr. fledged 27
2016 - 15 pr. fledged 72

Dave Reynolds
Posts: 1618
Joined: Mon Jan 31, 2011 4:35 pm
Location: Little Hocking, Oh.
Martin Colony History: 2018 Success at Satilite Site.

Re: eBird Purple Martin weekly migration display.

Postby Dave Reynolds » Wed Dec 12, 2018 9:00 am

Hanover Bill --- That has always got me thinking too. It seems that the Martins fly around the Mountain Change on the East side, to get to PA. and other Northeastern States. And in the same way on the West side of the Mountain Change, to close the gap between Ohio and PA. It can be seen in the delay of the arrival dates, that the Martins must make a right turn and follow the Ohio River east to close the gap around the Mountain Change. Of course I'm no expert, so it is only my opinion

Dave
2018 Home Site
Lots of Visitors

2018 Satilite Site “Oxbow Golf Course”
15 Pair, 58 Eggs, 38 Hatched and 36 Fledged :wink:
PMCA Member

stan kostka
Posts: 142
Joined: Fri Nov 28, 2003 7:59 pm
Location: Washington, Seattle

Re: eBird Purple Martin weekly migration display.

Postby stan kostka » Wed Dec 12, 2018 7:53 pm

Hanover Bill, that’s a great observation. There is clearly a distribution and abundance gap in the Appalachians. (The PMCA Scout Arrival map shows a similar gap.) Of the millions of Eastern birds in the surrounding regions, why are there relatively so few martins in these Eastern mountainous areas ? Is there less martin housing there ? The Western population is very small by comparison, but many western birds breed in tree cavities at these elevations or higher in western Colorado. Speaking of western martins, the map clearly shows just how small the western population is. Thats noteworthy, because we now know that the western birds are on their own, regardless of the millions of martins breeding east of the continental divide. From a conservation perspective they may as well be a different species entirely. Analysis of the birds DNA has shown that Eastern and Western martins became separate breeding populations between 200,000 and 400,000 years ago.

Stan Kostka, Seattle.

For the benefit of Forum readers, Here's a brief analysis of the western map from a friend:

Thanks Stan!... The weekly animation loop is fascinating, and you can easily visualize both the degree of separation (for 200,000-400,000 years, according to Baker's [2008] mtDNA analysis, i.e. since Neanderthal times, long pre-dating modern human evolution!) and the huge disparity in distribution and abundance between the eastern (P. s. subis) and western (P. s. arboricola) PUMA subspecies. Because the information is based on analysis of thousands of birder observations (with any attendant sampling biases therein) throughout northern migration, breeding and (I think for the first time!) post-breeding and southern migration, there is a lot of fine scale regional information to be teased out of this animation by single-stepping through the weekly images. For example, you can see the relatively very small western Rocky Mtn. foothills population begin to arrive in the lowlands around Salt Lake, UT, in May, then disappear as they move to the higher elevation foothills aspen grove breeding sites in CO and UT in June as snow melt progresses, spring green-up begins and the insect food supply starts to show up, for the short June-Aug. breeding season. You can even see the n-s regional difference in nesting timing, as an increase in relative abundance as the young fledge.

Also, given that the Western Desert Martin (P. s. hesperia) has a relatively early lower-latitude nesting season (April-July), similar to California, the increase in abundance you noted later in the season (Aug.-Sept.) in the US south-western desert is presumably due at least in part to the initial migration of Western PUMA from the Pacific Northwest (and CA?) to post-breeding roost sites in (mainly) AZ, w. NM and n. Mexico during their ~1 month pre-migratory roost period, which is concurrent with the late summer southern roost occupancy period east of the Rocky Mts., and entirely consistent with our geolocator tracking results for wPUMA from sw. BC (and several earlier PNW band recoveries). As well, those martins along the east coast of Central America in late Sept. and early Oct., as the sw. desert roosts decline and disappear (and the adjacent Yucatan Peninsula is full of migrating ePUMA), are likely our wPUMA as well, on the way to southern Brazil, where our geolocator-tracked birds arrived in Nov. (also consistent with band recoveries from OR). Again, the difference in distribution and abundance (and to some degree migration routes) is dramatic.

Cheers, ...Bruce
______________________________________________________
Bruce Cousens, B.Sc., M.Sc., R.P.Bio., Senior Biologist,
BC Purple Martin Stewardship & Recovery Program Coordinator,
Georgia Basin Ecological Assessment and Restoration Society
PO Box 41012, RPO Woodgrove Nanaimo, BC, CANADA V9T 6M7
Phone/msg./fax: (250) 758-2922; E-mail: <pmartins@island.net>


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