Convergent migration strategies in birds (an excuse to show a cool bird gif)

There’s a new paper in the Proceedings of the Royal Society (B) by Frank La Sorte et al. about migration routes surveyed in 118 species of birds. I’ve only scanned it, as this is an excuse to show you a lovely new gif of bird migrations. But first the paper (reference at bottom; free download) and its abstract, which should be understandable by the non-scientist:

Abstract:

Migration is a common strategy used by birds that breed in seasonal environments. Selection for greater migration efficiency is likely to be stronger for terrestrial species whose migration strategies require non-stop transoceanic crossings. If multiple species use the same transoceanic flyway, then we expect the migration strategies of these species to converge geographically towards the most optimal solution. We test this by examining population-level migration trajectories within the Western Hemisphere for 118 migratory species using occurrence information from eBird. Geographical convergence of migration strategies was evident within specific terrestrial regions where geomorphological features such as mountains or isthmuses constrained overland migration. Convergence was also evident for transoceanic migrants that crossed the Gulf of Mexico or Atlantic Ocean. Here, annual population-level movements were characterized by clockwise looped trajectories, which resulted in faster but more circuitous journeys in the spring and more direct journeys in the autumn. These findings suggest that the unique constraints and requirements associated with transoceanic migration have promoted the spatial convergence of migration strategies. The combination of seasonal atmospheric and environmental conditions that has facilitated the use of similar broad-scale migration strategies may be especially prone to disruption under climate and land-use change.

That’s not an earth-shattering finding, I think, but still useful.

Here’s a figure showing similarity of migration routes, with most over land, but when it’s over the ocean they tend to go in the same direction (i.e. clockwise or counterclockwise). I won’t report further on the paper as I’m struggling with a new PNAS paper on the “readiness potential” for physical events (i.e., stuff relevant to free will), but have a look at this:

F1.large

From paper: Figure 1. (a) Population-level migration trajectories within the Western Hemisphere at a daily temporal resolution for 118 migratory bird species for the combined period 2002– 2014. (b) Migration trajectory classification within 18 latitudinal bands for the 118 species with each point defining species’ annual centroid within that band (note the use of transparent points). From the 118 species, 53 were classified as clockwise, 14 as anticlockwise, and 51 as repeated.

There’s a nice summary of the article at the Cornell eBird site, but this is all prelude so I can show you this lovely gif, an animation of the diagrams above. As the legend says, “Each dot represents a single bird species; the location represents the average of the population for each day of the year (see paper for a more precise explanation of the “average location”). Here’s a key to which species is which.” The concordant movement of the dots, each a single species, shows the convergent migration that’s the subject of the paper:

Voilà:

la-sorte-map-118-spp-64-725

h/t: Lauren

_______

LaSorte, F. A., D. Finke, W. Hochachka, and S. Kelling. Convergence of broad-scale migration strategies in terrestrial birds. Proc. Roy. Soc. B: vol 283: DOI: 10.1098/rspb.2015.2588

18 Comments

  1. GBJames
    Posted January 22, 2016 at 1:01 pm | Permalink

    These are all New World birds so I guess we shouldn’t expect any new info on the airspeed of an unladen swallow.

  2. Ben L
    Posted January 22, 2016 at 1:09 pm | Permalink

    The gif is nice but I really like those maps. I would have made the axes show the standard N/S degrees but otherwise I think they are very informative and do a good job showing broad trends.

    • gravelinspector-Aidan
      Posted January 22, 2016 at 9:59 pm | Permalink

      I would have made the axes show the standard N/S degrees

      Huh? Looks like about normal axes to me. Equator is about right.

  3. LG
    Posted January 22, 2016 at 1:38 pm | Permalink

    Bird migrations are to me one of the most beautiful things in nature. Just another reason to look forward to spring.

    • Paul S
      Posted January 22, 2016 at 4:58 pm | Permalink

      We’re in a migration path for mallards, southwest Chicago bubrs. Every spring we get a pair in our yard for about a week. They paddle around in the pool cover and no one disturbs them. It usually has about 6 inches of water with lots of leaves and twigs.

  4. Posted January 22, 2016 at 2:21 pm | Permalink

    That was indeed a lovely gif.

  5. Posted January 22, 2016 at 2:36 pm | Permalink

    Great gif and an interesting post.

  6. Torbjörn Larsson
    Posted January 22, 2016 at 3:54 pm | Permalink

    OOOooo…
    …oooOOO
    OOOooo…

    …I’m so going to use this!

  7. Paul S
    Posted January 22, 2016 at 4:53 pm | Permalink

    Speaking as a non-scientist, yes, the abstract was easy to understand, the gif is cool too.
    Also as a non-scientist visitor to your web site, I appreciate that most of your posts are easy to understand.

  8. Marilee Lovit
    Posted January 22, 2016 at 6:09 pm | Permalink

    Very nice! I saw #78 barely coming down from the arctic to the Canadian Maritimes, and yes it is the purple sandpiper. But this bird does winter off the coast of Maine, and I think even a little farther south but not much.

  9. gravelinspector-Aidan
    Posted January 22, 2016 at 10:09 pm | Permalink

    #106 White-rumped Sandpiper seems to spend about 2.5 months heading south over the western Atlantic, from late August to early November. I don’t know the bird in particular, but with such an extended period at sea, I rather suspect it’s a bird that can rest on the water.

  10. Diane G.
    Posted January 23, 2016 at 3:51 am | Permalink

    And see that Pacific Flyway going right over Malheur…


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