Gulls’ dump diet helped them avert extinction

I’ve never been a big fan of gulls. I’m interested to see unusual or uncommon gulls, of course, but the garden-variety gulls, such as the herring gull, are everywhere. I note their presence, but often don’t give them more than a passing glance or thought.

Something happened earlier this summer to change this attitude, however.

I was walking past a small marina when high-pitched, mewing cries drew my attention to the small floating dock that bordered the boats. There, an adult herring gull was being relentlessly pestered by two juvenile gulls, probably its offspring.

The young birds looked to be about the same size of the adult, and perfectly capable of feeding themselves. Yet, they hounded the parent bird ceaselessly. They constantly pecked at its beak, begging for food, all the while emitting what could only be called a squeal.

The parent bird tolerated this nagging for a few minutes, patiently ignoring the young birds’ entreaties. Soon, it seemed to decide that enough was enough, and abruptly lifted off from the dock and headed toward the bay.

I thought the young birds would immediately follow, but they remained there and began to wander about the dock. I watched in amusement as one of them pulled on a mooring rope experimentally, giving up after a few fruitless tugs.

Its sibling, however, soon noticed a pair of eider ducks in the water below the dock. The ducks seemed to be hunting for and finding something to eat there, a fact that was noted by the young gull, which then began directing its begging cries at the ducks. Which was all to no avail, of course, but I had to laugh.

Gulls are nothing if not opportunistic. They forage in widely differing habitats, from human refuse dumps to locations far out at sea. Consequently, they also consume a wide variety of food items, a fact that has earned them a not-quite-sterling reputation, especially around garbage dumps.

Some researchers think this trait had a part in bringing them back from the path of extinction in the 19th century. As were many other birds, gulls were widely decimated by the plumage and egg hunters of the time. Now, ornithologists estimate their numbers are even greater than they were historically, and the gulls have been expanding their ranges southward.

However, there is an interesting twist to this. Although scavenging at human dump sites has been thought to have helped gulls, research shows a disturbing trend in this. Dump refuse fed to chicks has been found to affect their growth and survival rates.

Gull society is an interesting, and sometimes disturbing, mixture of the social and the solitary. Although they often nest in very large colonies, they nest as far apart as space allows. Adult birds will often attack and kill the chicks of other gulls, yet a mated pair – which for the most part remains together for as long as either live – will carefully synchronize their activities to ensure their own eggs or chicks are never left unguarded.

At least some chicks are still fed by their parents months after fledging. I wondered if this would be the case with the pair of youngsters I observed on the dock that day-would the parent be back with food?

Since I couldn’t wait around long enough to find out, I left the young birds to their inquisitive and hungry exploration of the dock. This little glimpse into gull family life had given me a lot to think about.

BDN bird columnist Chris Corio can be reached at bdnsports@bangordailynews.net