The Contradiction of Robins

In woods in mid-winter, living trees, shorn of leaves, join their dead companions in extending naked branches to the sky.  What was hidden in summer behind a green curtain is revealed.  The track along the edge of the pond near my home takes me to a point where, across the frozen surface, I now can see through the trees to where I started.  As a result, though the horizon has expanded in this season, this pond today seems much smaller.

In the mid-Atlantic region of the United States, this February has been bitterly cold and battleship gray with little hint that we are heading to spring.  Yet, the days are inexorably growing longer.  A full hour of sunlight will be gained between now and mid-March, though it won't feel that way amid the rain, the snow, the gray.

One of the contradictory phenomenon of winter throughout much of the central and eastern U.S., particularly at lower latitudes, is the bird we salute as the herald of spring, the American robin (Turdus migratotius).  Although it is actually with us through much, if not all, of this bleak season.  On my winter walks, robins have been my frequent companions, sometimes signaling their presence just by calling, and, sometimes, by swooping in large numbers onto the trees and bushes that still bear fruit (or, at least did, until the marauding robins descend).

I recently read Margaret Renkl's inspiring and graceful The Comfort of Crows:  A Backyard Year (2023).  Its essays track the passage of a year in the events and changes in the natural world, largely in Renkl's Nashville backyard.  The life and death, losses and gains, the comings and goings in that world move and educate her as she deals with changes in her own life, and responds to the chaos that has overtaken the country.  Ultimately, the persistence and resilience of the natural world offers her hope.  In nature, she remarks, "so much life springs from all this death that to spend time in the woods is also to contemplate immortality."  (p. 259)

What prompted me to write this post is a passage early in the book.  In a chapter set in winter, she cites a tradition among birders that the first bird seen in a new year will characterize the kind of year you will have.  One year, she spots a passing woodpecker but cannot determine if it is a downy or a hairy, so she goes with the second bird sighted, a robin.

I love robins. . . .  I love the way they flock up in winter, with the locals and their new offspring welcoming the migrators to a season-long family reunion.  (p. 5-6)

Renkl's portrayal of the local robins sharing their winter home with those migrating through pleased me, prompting research on the bird's migration patterns, including the relative balance between robin homebodies and travelers, and how far the latter actually migrate.

I admit that I've always found the robin's scientific genus name a bit off putting, in part because it evokes South Park.  But the Latin root for Turdus means "thrush" which the robin is, being a member of the thrush family Turdidae.  It's the species name that I think revealing because its dual meanings capture the bird's contradiction I just cited.  The Latin root of migratorius means both "migratory" and  "wandering."  Robins are restless creatures, they all wander, even those who seldom travel far from home.  Their search is constant for a supply of soft-bodied invertebrates in some months and fruit in others.

Populations of robins may be comprised of both migrants and year-round residents.  Indeed, this is possibly true of the majority of bird species.  For robins, this phenomenon has been explored by biologists David Brown and Gail Miller, using data on bird banding and recovery from 80 years of Federally supported bird banding.  They looked at robins in these data for which there were observations in both the breeding season (May to August) and the wintering season (November to February).  They defined individual, local/non-migrant robins as those for which the distance between locations of observations in breeding and wintering months was less than 100 km; all others were considered migrants.  (Band Recoveries Reveal Alternative Migration Strategies in American Robins, Animal Migration, Volume 3, 2016.)

Their findings document the overall complexity of the migratory behavior of T. migratorius.  Overall, they find 80 percent of recoveries to be migrants.  The distance traveled by migrants is stunning.  Of migrants, some 96 percent (nearly 77 percent of all robins) traveled 500 to 2,100 km from their breeding sites.  Curiously, the further south a migrant robin wintered, the further it had migrated.

A fifth or 20 percent of robins covered by their data stayed locally across breeding and wintering seasons, a phenomenon that has been increasing since 1980.  Overall, non-migrants moved on average slightly less than 21 km between these seasons.

A more detailed study of the movements of a small number of robins over a year suggests just how complicated migration can be for these birds, and how generalizations may fail to capture the reality.  Alex E. Jahn, et al. tagged 31 robins in the 2017 breeding season with devices that recorded their movements.  (First Tracking of Individual American Robins (Turdus migratorius) Across Seasons, The Wilson Journal of Ornithology, Volume 131, Number 2, 2019.)  Although only 7 of the birds were recaptured in the 2018 breeding season, the journeys of these birds over the course of the year were fascinating, almost idiosyncratic.

Of the 11 tagged in Alaska, 4 were recaptured.  By the middle of September, these robins had left Alaska, flying into western Canada.  A month later, some had reached Montana and North Dakota.  One ultimately reached Texas, 4,480 km from where it originated; another migrated 4,508 km to Oklahoma.  Only one of the 14 birds tagged in Massachusetts was recaptured a year later.  That bird first lingered during the fall near its breeding grounds, only leaving Massachusetts in November.  Then, over the course of 20 days in early November, it winged its way to South Carolina, a distance of 1,210 km, where it overwintered.  Finally, of the five robins tagged in the District of Columbia, only two were recaptured and both stuck around their home territory for the entire year, migrating not at all.

The routes migrating robins follow during any particular journey south may not be fixed, possibly varying from year to year (bird to bird?).  The Cornell Lab's entry for the American Robin in Birds of the World, posits:

The term 'routes' does not really apply to robin migrations and there does not appear to be strong connectivity between overwintering and breeding grounds.  Indeed, evidence from banding records shows that robins in a particular area originate from widely scattered areas to the north.  (E. Natasha Vanderhoff, et al., American Robin, Birds of the World, Cornell Lab of Ornithology, 2020.)

Indeed, migrant status from year to year may not be immutable for individual robins.  Though Brown and Miller concede that their data do not allow them to determine whether any specific bird migrated one year but not the next, they add:  "It is possible, especially given the typically vagrant nature of robins during the non-breeding season."  (p. 43)  I am really taken with the idea that the impulse to migrate at all might be up for grabs for individual birds from year to year.

Ultimately, I believe that the robin's migratory behavior, bridging the seasons, offers some solace in this world where life inevitably leads to death.  Robins are heralds of restorative spring, the season when life is new and renewed, and, in the dark days of winter, they show that, even then, life persists.