Sometimes it is the subtle details that reveal the truth – or essence – of a thing. This was driven home to me some weeks ago as I observed two birds of prey passing through the neighborhood.

The first was a red-tailed hawk that I would never have known was there were it not for the mobbing calls of several crows. Looking up into the distance, I saw the ebony birds harassing the hawk. As the raptor circled in the air, trying to attain altitude, the crows took turns diving at it in kamikaze fashion – or so I thought. The red-tail, as far as I could tell, never made a move to attack its tormentors. It just kept climbing, followed by its angry escorts. In minutes all of them had disappeared beyond the distant tree line.

I didn’t think much more of the incident until a day later. Again, I heard the frenzied cawing of crows. They were coming closer and I was sure that they would pass overhead any second. Something did appear – a lone bird flying swiftly with powerful wing strokes. The dark cap on its head and its beautiful, finely streaked gray chest identified it unmistakably as an adult northern goshawk.

Strangely enough, there was no crowd of mobbing crows around this raptor. They seemed content to yell from a distance, apparently reluctant to be overt in their objections. The goshawk was left to fly along in solitary splendor, untouchable.

From what I know about the red-tail and the goshawk, I thought I knew why the crows acted differently toward the two raptors.

The red-tailed hawk belongs to a group of raptors called buteos. These birds have long, broad wings and short tails -features that make them adept at soaring. However, these characteristics cost them in maneuverability. They are known as “sit-and-wait” predators: a red-tailed hawk may perch for hours on a fence post, waiting to catch its prey of small mammals, reptiles, or amphibians out in the open. It may do the same by slowly gliding a short distance above the ground, hoping to surprise its prey with a quick plunge earthward.

The goshawk takes hunting to a whole new level. It belongs to a group of raptors known as accipiters, which are primarily bird-catching hawks. Their short, rounded wings and long tails give them speed and maneuverability, enabling them to pursue their feathered prey through the thickest tangle of trees.

Goshawks are also well known for their tenacity and ferocity. “In Hawks in Flight,” author Pete Dunne writes, “Goshawks exhibit a legendary singe-mindedness with regard to prey – in the north, in winter, prey is scarce. Something that moves lives. Something that lives may escape but not from a goshawk.”

No wonder the crows employed different tactics between the red-tailed hawk and the goshawk. It took this small, simple detail to illustrate the fundamental difference between these two raptors – the crows really would have been kamikazes if they had approached the goshawk!

Chris Corio, a volunteer at Fields Pond Nature Center in Holden, can be reached at fieldspond@juno.com