Like all of us, I love to gaze upon the beauty of birds, their grace and skill and spectacular colors and textures. I’m also endlessly fascinated by their behavior, and focus in on activity whenever I’m out watching them. I’m just as happy to catch a blurry photo of a bird (or other critter) doing something mysterious as to capture a perfectly composed, lighted, focused avian portrait. There are reasons why creatures do what they do, and without getting down into the weeds of the gigantic field of animal behavior (this website has some good basic articles on aspects of it: www.nature.com/...), the behaviors we see are an expression of what’s going on in their minds. We could be simplistic and say everything they do is for survival, but what interests me more is why? how does this activity contribute to survival? what combination of instinct and learning does it show? What’s going on in their minds, so that they behave as they do?
Sometimes it looks pretty obvious, and we assume birds are doing what we’d do for survival, since we share basic life needs, ie. food/water, shelter from the elements, avoiding predation, and propagating the next generation. Interaction with others is unavoidable, and represents much of the interesting behavior we see, both intraspecific and interspecific.
Here’s an exchange that looks fairly straightforward. We have an adult Glaucous-winged gull esting a crab on the dock, and a juvenile GWGU flies in. Usually when one gull comes in to land, if there’s another already there the perched gull flies away. Incoming gulls, with wings flapping, swooping in at speed, are intimidating.
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Was the adult gull PO’d the juv caused it to lose its crab? Did it decline to fly away because it was a juv incoming, a social inferior? Was it chastizing the juv? That’s how I interpret this, although I know I’m just as likely to be making assumptions about what’s going on in their minds.
Gulls are ubiquitous where I live, and exceedingly diverse in their behavior. I can watch them endlessly, but because their minds seem so alien to me I’m usually at sea trying to interpret what they’re thinking, even after years of observation. I’ve searched out research studies about gull behavior, including those performed by the pioneering animal-behavior biologist Nikolas Tinbergen (www.eebweb.arizona.edu/...). Tinbergen studied insects and fish also, but his main focus was birds, especially Herring gulls, a wide-ranging boreal species. I’ve read his book The Herring Gull’s World (1952) to find out what gulls are thinking with certain postures and behaviors. Why am I reading about Herring gulls and not GWGUs? Well, for one thing, there’s not much work studying GWGU behavior, possibly because Glaucous-winged gulls have a narrow range geographically. Luckily GWGUs are a lot like Herring gulls physically and socially, according to Birds of North America (birdsna.org/...) since many of their references cite Herring gull studies. I gather that there is FAR less information gathered about social behavior of birds in general than about appearance, migration, feeding, nesting and other aspects of birds, which are much more objectively measurable.
If information about social behavior is hard to come by, it’s even more difficult tracking down behavior outside nesting season. Tinbergen’s work is almost exclusively describing interactions at breeding colonies. What about the rest of the year? Perhaps it’s too difficult to perform that kind of work. During nesting season gulls congregate at a site and can be monitored individually (after banding) since they spend most of their time there.
One general principle about gulls (and many other birds) is that males are dominant over females, adults over juveniles, and experienced birds over neophytes (birdsna.org/...). Distinguishing adults vs juvenile is pretty simple — any field guide will show you how... up to age 4. After that it’s impossible to know whether a gull is 5, 8 or 10 — the plumage is the same. Gender, though, is an even bigger problem. Except for an expert examining a gull physically in hand, the average observer on the beach can not tell a male from a female gull. This throws a big monkey wrench into interpreting social interaction.
Two sets of behaviors have been studied fairly thoroughly, from Tinbergen on: postures and calls. The adult in the last panel above is in the “oblique posture” performing the “Long call” (earbirding.com/...) both representing an aggressive signal (although the same behavior is performed by mated pairs on greeting each other, and even a gull greeting a neighbor at a nesting colony).
You see what I mean — there’s not a whole lot to go on to interpret social behavior, especially during the winter season. Nevertheless, I try. Here’s one small incident I watched recently. I’d be very interested to hear your opinions about what was going on. All of you Dawn Chorusters watch birds too!
(I know a video would be nicer but this is what I got. One of these days I’ll figure out video!)
What might these two gulls have been thinking as they did this, and why? Your thoughts?
I’d love to know of any sources that have more information about gull behavior too. Or bird social behavior in general outside the breeding season. Please mention any in the comments.
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Dawn Chorus is now open for your birdy observations of the week.