ALWAYS IN SEASON: Gulls present challenges for birders
Gulls may be the most opportunistic birds.
This struck me forcefully last week, when I encountered a flock of gulls following a tractor. The tractor was pulling a cultivator, and the gulls were picking grubs from the ground overturned by the machine.
This was an old-fashioned tractor, not one of the behemoths that are characteristic of today's agriculture. There was no cab: the tractor driver rode in the open air.
And the gulls flocked behind him.
This is an experience that probably every farmer has had, and for me it was powerfully nostalgic. First there was the machine itself, a throwback to yesteryear; exactly the sort of machine that I drove when I was a teenager.
Then there were the birds.
These were Franklin's gulls, lithe, light and buoyant, aerial and athletic.
And opportunists, too, of course.
The gulls were not performing for me, or for the driver of the tractor. They were taking care of themselves. Agricultural equipment turned the soil, exposed the grubs and presented food for the birds.
And the gulls responded.
We don't know exactly how they knew that a new restaurant had opened, so to speak, but probably there are signals that attract the attention of individual birds, who respond. And as they do, congregations of birds occur.
Bernd Heinrich studied this behavior in ravens, and found that they communicate effectively across great distances. His insights were published in "Ravens in Winter," a modern classic of natural history.
Probably something similar probably occurs with gulls. Somehow, the birds let one another know about a source of food, and a flock forms.
What's not clear, of course, is whether this happens because the birds consciously send a signal or whether individuals simply respond to behavior of other birds.
Of course this might be the same thing.
As a class, gulls are a difficult bunch of birds .
In his "Guide to Birds," now the most widely used bird guide in the country, David Allen Sibley warns:
"Gull identification represents one of the most challenging and subjective puzzles in birding and should be approached only with patient and methodical study. A casual or impatient approach will not be rewarded."
This is true.
The challenge is a little less for those of us in the Red River Valley, however, because we have only a few species to deal with, and they fall easily into categories.
The first of these is black-head gulls. Of these there are two species. Franklin's gull is the usual summer gull here. The other gull with a black head, Bonaparte's gull, is a migrant.
The white-headed gulls present a greater challenge.
There are three of these.
By far the most common is the ring-billed gull, which can be identified definitively by the ring around its bill. Of course, the fact that the bird is named for so subtle a field mark suggests that there are many similar species.
Two of these occur here, California gull and herring gull.
California gull is more frequent here -- that is, in the Red River Valley -- but herring gulls occur regularly in our area, especially on larger lakes, including Red Lake, Lake of the Woods the impoundments at Agassiz National Wildlife Refuge in Minnesota, and at Devils Lake and the Missouri River reservoirs in North Dakota.
Of these five species, Franklin's, ring-billed and California gulls are summer residents, and Bonaparte's and herring gulls are migrants, likely to be seen only in spring and fall.
Winter presents its own challenges, because our area is notorious for attracting vagrant gulls in winter. A glaucous gull showed up in Grand Forks County in a recent December, and several species have been noted at Garrison Dam in the central part of the state. Usually, these are solitary birds , probably wanderers -- or, as ornithologists would have it, "vagrants."
Casual birders should learn the five species that occur here regularly. Two of these have black heads: Franklin's, a common nesting species, and Bonaparte's, a migrant. Three lack the black head and are best distinguished by subtle differences in size and plumage. From most to least likely, these are ring-billed, California and herring gulls.
Mike Jacobs is editor and publisher of the Herald.