Unexpected couple

Here’s something notable … a couple of days ago (see an earlier posting) we had a Yellow-bellied Sapsucker on one of the garden feeders, a visitor who should have left for the south some time ago. Turns out that late Sapsuckers are being reported in small and scattered numbers in Quebec this year, but it was unusual enough for eBird to seriously query it. At the same time we have had one of the Carolina Wrens around most of the summer. We remember a very few years ago when Carolina Wrens were very unusual in this region, unusual enough for comment and even for twitchers to travel to see them but now, while still not everywhere by any means they are part of the background bird population.

So this Feederwatch morning, both came to the same feeder at the same time and stayed long enough for a photo.

As the presence of these birds at this time of year (especially together) is undoubtedly associated with our changing climate I am copying a fascinating post after the pictures from the latest ABA blog that I think many readers will find of interest.

 

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Arctic Nesters Migrating Earlier, But Why?

By Nate Swick, on November 23, 2013 (From the ABA blog)

Any amateur phenologist can tell you that migratory birds seem to be returning earlier and earlier every spring. Rising temperatures due to climate change is presumably the culprit, but until recently, the mechanism that selects for that early arrival was unknown. For a long while, it was suggested that individual birds were changing their individual schedules to take advantage of a northern hemisphere that was getting warmer earlier in the year.

But that turns out not to be the case. With the help of thousands of volunteer birders working over two decades, researchers at the University of East Anglia in the UK have found that individual shorebirds – specifically Black-tailed Godwits nesting in Iceland – are still arriving on their breeding grounds at roughly the same date every year regardless of temperature or weather. However, the peak migration of the population of Black-tailed Godwits, was arriving earlier every year. How could this be?

‘The only explanation that’s left, is that new birds are hatching and migrating earlier,’ explains Dr Jenny Gill of the University of East Anglia, who led the research. ‘As the older birds die off, the population fills up with early migrators.’

‘Climate change is likely to be driving this change because godwits nest earlier in warmer years. Birds that hatch earlier are likely to have more time to gain the body condition needed for migration, and to find good places to nest in the winter.’

So entire generations of godwits are slowly pushing the breeding calendar back. Perhaps more fascinating, they’ve been able to actually observe how these generations have adjusted their strategies.

“Because we have been following the same birds for so many years, we know the exact ages of many of them,” said Gill in a press release. “We found that birds hatched in the late 1990s arrived in May, but those hatched in more recent years are tending to arrive in April. So the arrival dates are advancing because the new youngsters are migrating earlier.”

Amazing stuff. It’ll be interesting to see what comes out of this, particularly with regard to longer distance migrants for which the migration window is presumably much narrower. Bird populations can be plastic, but eventually that plasticity has to have limits

 

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