Dan's Feathursday Feature: Herring Gull, or If Biologists Write Limericks

Precocials are usually nidifugous
A label that sounds most ridiculous
   I’m precocial too
    said the gull to the goose.
But I prefer that you call me nidicolous.

Translation: Some birds hatch from the egg hardy and covered in dense down, able to stay warm and get about on their own almost immediately. Such precocial chicks usually leave the nest as soon as they stop wobbling enough to pass a breathalyzer test. Birds that can and do leave the nest right after birth are called nidifugous.

But some that could leave the nest, don’t. Most gulls, for example, hatch well clothed and quite hardy. But unlike goslings and ducklings that jump in the water and paddle along with their parents almost immediately, gulls remain in the nest and in the care of their parents for five to six weeks. Precocial birds that choose to stay in the nest are called nidicolous.

Of course, there are many bird species that hatch naked as a J-bird, weak and barely able even to hold their large heads aloft enough to be fed. Biologists call these species altricial, roughly translated as “needing to be nursed.” These chicks couldn’t leave the nest right after hatching even if they wanted to. They are completely dependent on the parent birds for warmth and sustenance until they sprout enough feathers to maintain a steady body temperature and eventually leave the nest.

Precocial, altricial, nidifugous, nidicolous. Fancy words like these can make scientists sound downright pedantic. But you have to admit, the right four-syllable word can save many syllables elsewhere. It was impossible to shoehorn “chicks that leave the nest right away after hatching” into the first line of my limerick, but “nidifugous” was a shoo-in.

Sometimes, though, biologists just can’t leave well enough alone. Let a big word sit long enough on a biologist’s desk, and it will be coddled and fed until it sprouts feathers and flies off on its own. It’s not enough to call a bird just precocial or nidifugous. Biologists have identified different levels of precociality and nidifugosity, depending on the condition of the chicks when they hatch. It’s all neatly summarized in this table:

Long hours are spent on the beach arguing over whether gulls and terns are semi-precocial or semi-altricial 1.

Which is where the Herring Gull comes in. As researchers sit down over lunch to argue semantics, it swoops in, nabs a sandwich from the picnic table and flies off, shrieking, “I’ve got three semi-precocial chicks that are eating me out of house and home!”

The gull is not exaggerating. Since his mate laid three eggs in their rooftop nest two months ago, the two birds have been foraging practically non-stop to keep the family fed. During the month-long incubation period, they took turns tending the nest—one bird sitting on the eggs while the other procured food for the two of them. When the chicks emerged from the shell, they were covered in a speckled coat of dense down (they’re precocial, remember) and able to amble around in the nest within hours of hatching. But they stayed put in the nest (they’re nidicolous) doing what all babies do—eat, poop and grow. The parents, instead, lost weight as they focused on keeping the chicks well fed. That researcher’s tuna sandwich is not as good for the chicks as protein rich crustaceans or small fish, but for a desperate papa gull, it will do in a pinch.

A month after hatching, the chicks are large and very active, but their wings are not developed enough to fly. They remain in or near the nest, and it may be as much as another month before they finally spread their wings and leave. And even then, they’ll follow their parents for as much as another month, begging for food and taking nidicolous to a ridiculous extreme. All told, by the time their chicks are fully on their own, the Herring Gull pair will have spent about a third of their year on the important task of procreation.

With the nest finally empty, and only themselves to feed now, the parent gulls have more time to do what we most often see gulls doing—nothing. Except for intermittent foraging visits to the local dump, or a recently plowed field, or the wake of a fishing boat, Herring Gulls spend a vast majority of their day not doing much of anything, lined up on rocks and wharfs and breakwaters in Zen-like contemplation. Of course, biologists have a name for this behavior. They call it “loafing.” I’m serious.

And on that note, I think it’s time to wrap up this essay, jump out of my nest and join the gulls loafing at a local park, content in the knowledge that there is a scientific name for what we are not doing.

Dan's Feathursday Feature is a regular contribution to the COS blog featuring the thoughts, insights and photography of Chicago birder, Dan Lory on birds of the Chicago region.