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August 2016

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From:
Betsy MacMillan <[log in to unmask]>
Reply To:
Betsy MacMillan <[log in to unmask]>
Date:
Thu, 18 Aug 2016 08:22:46 -0400
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Last evening the marten show was fabulous.  A great sunset was the backdrop and a full sturgeon moon followed it. Amazing!! Thanks for sharing this phenomenon. 

Sent from my iPhone

> On Aug 16, 2016, at 12:37 AM, Coy, Patrick G. <[log in to unmask]> wrote:
> 
> A few hours ago I had the pleasure of sharing the Purple Martin migration staging event at Nimisila Reservoir in southern Summit County with Susan Jones, Clyde Witt and Karin Tanquist. Many thousands of Purple Martins staging for their long migration through Mexico and Central America to their wintering grounds in South America gather each evening in much of August shortly before dusk at Nimisila Reservoir to feed over the water and then roost on some islands of reed beds in the southern reaches of the reservoir. 
> 
> Put simply, the sky was dark and pulsating with massing hordes of purple birds, North America's largest swallow. We had great fun entertaining ourselves with estimates of total number of Purple Martins tonight; we settled on 7,000+. It truly is a wildlife spectacle deserving of the phrase, and one that we bird watchers should enjoy while we can even while we work to mitigate the forces of climate change that are likely to impact it in the future. 
> 
> One of the issues with regard to climate change and bird migration has to do with the differences between short distance migrants that winter in the southern US and Mexico i.e., Eastern Phoebe and Tree Swallow, and long-distance migrants, like the Purple Martin, who winter in South America. Migration is a tricky and risky business; it must be well-timed to maximize food availability, especially if the species is insectivorous, like the Purple Martin.
> 
> What science is beginning to suggest is that, in general, shorter distance migrants seem more able to adjust their migration departure and arrival dates, and/or their migration speed, in response to changing climate patterns, while the latter group of species has been less able to. This may be partly a function of the fact that the warming temperatures associated with climate change are having more impact in temperate zones like much of the US and less impact on the tropics. Thus these shorter distance migrants are starting their northward migration earlier and/or are speeding it up as they encounter abnormally warm temperatures in route. 
> 
> A critical question is whether or not long distance migrants like the Purple Martin, who winter in the tropics, can/will be able to speed up their long and laborious migration while in route as they encounter increasingly warmer temperatures during their migration. This issue has been studied recently and the early news on this particular question (there are others) is not good. An article by Jack Connor in the Cornell Lab's Living Bird magazine in spring 2015 entitled, "Purple Martins and Climate Change," describes a significant study where Purple Martins wintering in Brazil were outfitted with geo-locators in the late winter of 2012. 
> 
> These 52 Purple Martins left Brazil on their "normal" dates and as they hit the southern US that year the region was, in fact, experiencing the hottest spring on record. Nonetheless, they did not accelerate their migration speed, arriving on their breeding grounds in Virginia and Pennsylvania on the dates they historically did. 
> 
> As the article explains, perhaps they recognized the different temperatures suggesting that they were behind schedule but simply couldn't physically fly any faster or any longer each day than they already do. After all, their migration from Brazil to Pennsylvania is already somewhat Herculean, e.g. 4,500 miles in 13 days! Or, perhaps while flying so hard and so fast for two weeks day after day after day they weren't able to also recognize the temperature issue and so couldn't respond to it. 
> 
> In either event, one reasonable conclusion is that Purple  Martin populations, already in decline, are likely to decline even further and faster in response to climate change as the species responds to a warming globe primarily through natural selection, a process taking many, many generations. In this scenario, those individual birds who adjust their migration schedule successfully will pass on their genes whilst those who don't adjust successfully raise fewer and fewer and fewer offspring until those genes are exhausted in the gene pool. As Connor suggests, natural selection is a somewhat slow adjustment process in the face of the accelerating pace of climate change and may result in deleterious effects on overall Purple Martin population numbers. 
> 
> Patrick Coy
> Peninsula, OH
> 
> Here is the link to the Living Bird article: http://digital.livingbird.org/livingbird/spring_2015?__hstc=75100365.88edffd7699d74ffbd5b3ca5d30d7d98.1466442124213.1469031650222.1471315502984.3&__hssc=75100365.1.1471315502984&__hsfp=182416539&pg=38#pg38
> 
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