December 5, 2019
Green Jays exhibiting agonistic behavior at a food source
Green Jays exhibiting agonistic behavior at a food source
When I referred in a column last year to agonistic behavior in birds, a non-birding friend texted to let me know I needed to proofread better, that I had misspelled “antagonistic.”  But, no, “agonism” is a real word, and it’s a real thing in the world of birds as well as in the realm of physiology, pharmacology, and political thought.  In the birding world agonism refers to aggressive behavior between members of the same species.

It’s complicated because the etymology of the two words is similar, and because agonistic behavior has evolved in common ornithological parlance to refer to intra-specific conflict but not inter-specific conflict.  Agonism and antagonism are both derivatives from ancient Greek, the former from the word for “struggle,” the latter from the word for “opponent.”  The former implied respect and admiration for the opponent, whereas the latter was concerned only with the conflict itself.

Presumably for ornithological purposes these nuances are explained because even though members of the same species may at times come into conflict with one another, in the end they need one another for survival and propagation of the species.  So, if you see two American Coots raking each other with drawn claws, even though very occasionally this results in death for one of the combatants, this is agonistic behavior.  If you see a coot chasing a Common Moorhen, that antagonistic.

Relevant to these nuances of behavior, last month I spent a morning in a photo blind replete with a water hole, a suet feeder, and two seed feeders.  The setting was a cold, rainy day in south Texas, so many of the signature species of the Lower Rio Grande Valley were coming and going, grabbing morsels of protein and quick drinks.  I was trying to photograph, but to say it would have been interesting even without the camera would be an understatement.

Of course with many birds drawn to a small area at the same time for the same reason I saw both agonistic and antagonistic behavior, but the most fascinating thing was that the only actual physical contact I observed was intra-specific, whereas all the inter-specific conflict was resolved by posturing and threats.  Most notable was that, in the eclectic mix of sizes (Plain Chachalaca, Golden-fronted Woodpecker, Olive Sparrow, Black-crested Titmouse) and rainbow mix of colors (Green Jay, Altamira Oriole, Great Kiskadee, Long-billed Thrasher), smaller species always deferred to larger ones and less brightly plumaged species invariably deferred to those more brightly colored if both were the same size.

The most striking examples of agonism involved one Green Jay diving onto another, pecking it, and driving it to the ground on its back, and one Great Kiskadee catching up with another in an aerial chase and bumping it against the blind amidst flashing wings.  The most striking examples of antagonism were seeing the titmice flee the suet whenever a woodpecker approached and watching everything abandon the water when the chachalacas came to drink.

According to the literature, agonistic behavior is most often triggered by competition for food or territory.  Here in the desert within the past year I have seen American Coots, Cactus Wrens, and Curve-billed Thrashers attack one another in brutal looking physical combat that lasted, in all instances, several minutes and covered protracted areas of water and land.  In none of these quarrels, of course, did it appear the combatants had respect or admiration for one another.

It is a slippery slope to ascribe ancient Greek values to our insensate fellow travelers in the animal kingdom.  I found it ironic, though, that I was in Texas parsing the nuances of agonism and antagonism the same week Myles Garrett was beating Mason Rudolph over the head with the latter’s own football helmet.  You’d think we’d have evolved farther than that since ancient Greece.
Curve-billed Thrashers exhibiting agonistic behavior in a territorial dispute
Curve-billed Thrashers exhibiting agonistic behavior in a territorial dispute