THE TRUE REASON WHY AMERICAN ROBINS MIGRATE EARLIER!

A bunch of researchers from a bunch of US universities finds out that the timing of American robins' (Turdus migratorius) "spring migration to [their] Arctic-boreal breeding grounds" (P) got 12 days earlier in the last 20 years (about 5 days per decade in the 1998-2018 time period).

Moreover, the brains analyze data collected between 2016-2018 from GPS tracking devices stuck on the backs of 55 American robins. And these data indicate that "the [American robins'] arrival timing and likelihood of stopovers, and timing of arrival to breeding grounds" (P) are highly impacted by the environmental conditions the birds find along their migratory paths. Among the factors, the "dynamics in snow conditions" (P) appear to be a key one. 

The researchers' study (P) is published on the journal Environmental Research Letters and can contribute in creating predicting models of birds' responses to climate change.

The findings are coherent with what scientists already know, which is that one of the strongest effects of "global climate change has been the advancement of spring at high northern latitudes [...] where temperatures are rising nearly two to three times faster than the global average" (P), and that migratory birds adjust their trips' schedule to their breeding territories in response to the changes in local climate. 

But, dear reader, this dumb blog has an alternative explanation for the earlier migration's timing of American robins. And a cartoon to explain it.

American robins discuss about smart early departures (by @sciencemug)

[American robin pic by Mark Nenadov is under Creative Commons Attribution 2.0 Generic license (source: Wikimedia Commons); adapted by @sciencemug]

Now, the following ones hare just for fun...

Batman and Robin meme 1 about American robins' earlier migration's timing (by @sciencemug)

[Batman and Robin meme pic by ap. is under Attribution-NonCommercial 2.0 Generic (CC BY-NC 2.0) license (source: flickr); adapted by @sciencemug]

Batman and Robin meme 2 about American robins' earlier migration's timing (by @sciencemug)

[Batman and Robin meme pic by ap. is under Attribution-NonCommercial 2.0 Generic (CC BY-NC 2.0) license (source: flickr); adapted by @sciencemug]

Paper (P)

Oliver, R.Y., Mahoney, P.J., Gurarie, E., Krikun, N., Weeks, B.C., Hebblewhite, M., Liston, G., and Boelman, N. (2020). Behavioral responses to spring snow conditions contribute to long-term shift in migration phenology in American robins. Environ. Res. Lett. 15, 045003.