It started with a question from a reader: "Do birds mourn?" He described a scene at the family cabin, where a pair of barn swallows had been nesting under the deck. Unfortunately, one of the pair was killed in a collision with a cabin window. The other swallow then seemed to be holding a vigil, sitting halfway between its dead partner and its nest for some time.

The question of whether birds feel emotions — and grief is surely a major emotion — is a contentious area in avian research. Some say it is likely that birds experience feelings, while others hold out for some kind of proof. The problem is that emotions are a tough thing to pin down, even in humans. We're a very expressive species, easily able to read facial expressions to assess how others are feeling, but birds are a pretty expressionless bunch, at least to us.

So, we tend to look at bird behavior to try to gauge what might lie behind it.

Many people seem to have observed what is often called a crow funeral, with crows flying in to gather near a dead crow, usually on a roadside, calling and standing in a semicircle. Is this truly a funeral, or is something else going on?

An adult osprey returns to its nest to find it empty, both young osprey having been snatched by a great horned owl. The osprey stands on the edge of the nest and makes soft calls for a half-hour or more. Is the adult osprey lamenting the loss of its family, or is there something else at work?

And how about the barn swallow seeming to mourn the loss of its partner after a collision with a window?

Fifty years ago, experts would only say that the birds in all three cases were reacting to stress or change. They'd label as anthropomorphism any suggestion that anything more was at work in these scenes.

But since the 1970s, those who study birds, either in the lab or in the field, have found more and more instances where bird behavior often seems similar to our own. Birds have been shown to be having fun, getting angry, expressing pleasure.

"We have made a lot of progress," says animal behaviorist Tim Birkhead (in his excellent book, "Bird Sense: What It's Like to Be a Bird"). "The more we find out, the more it seems that birds do have feelings."

But as Laura Erickson (renowned author and birder in Duluth) points out, "The complexities of how our own species feels grief are hard enough to tease out. It must be very complicated for scientists to break down grief into its components for any other species."

Let's look again at that gathering of crows around a dead crow. Is that a funeral, or are the birds assembling to warn each other that roads present perils? Might they be assessing how the crow's death affects the local hierarchy, territorial claims or the sudden availability of a possible mate?

The osprey parent could very well be lamenting the loss of its healthy chicks or she may primarily be shocked and stressed by the empty nest, unsure what to do next.

That could explain the barn swallow's behavior, as well: It might be saddened by the loss of its partner and the now-reduced chances for raising their brood alone. Or the swallow might be stunned by the dead swallow's lifeless body, its normal equilibrium destroyed in a moment.

Humans have come a long way from the days when the operative theory was that birds were stimulus/response machines. We now grant them the ability to learn from their experiences, to vary their behavior to fit a situation and even, in some cases, to speculate about future events.

But do they grieve? The jury is still out on this question. Let's let John Marzluff, noted corvid researcher at the University of Washington, have the last word: "Birds certainly possess the capacity to mourn — they have the same brain areas, hormones and neurotransmitters as we do, they can feel what we feel"— but that doesn't mean we know when it's happening.

St. Paul resident Val Cunningham, who volunteers with the St. Paul Audubon Society and writes about nature for a number of newspapers and magazines, can be reached at