The goshawk, a powerful predatory bird that can take down prey like pheasants, rabbits and crows, is having a literary moment with “H Is for Hawk,” an award-winning memoir by Helen Macdonald that mixes a tale of personal loss with the struggle to train a goshawk to hunt.
The bird is also attracting scientific attention. Suzanne Amador Kane, a physicist at Haverford College, collaborated with falconers to record and analyze the way goshawks pursue prey.
Ms. Macdonald’s memoir gives the reader “an indelible impression of a raptor’s fierce essence,” as the author Vicki Constantine Croke put it in her review for The Times. Dr. Kane has more limited goals, but she does have video, from a camera mounted on a goshawk’s head.
She was interested in seeing which of several different pursuit strategies the goshawk would use. These strategies, named and described in work on missile guidance, Dr. Kane said, are very useful in studying raptors.
One is a classical pursuit, or flying right after the prey. Another, which betrays its military engineering origins in its name, is constant absolute target direction, or C.A.T.D. In plain language, Dr. Kane said, that means the missile or hawk angles its flight toward the prey so the two paths will intersect.
What surprised her, and what she reported Jan. 15 in The Journal of Experimental Biology, is that the goshawk, named Shinta, used both of these strategies. Shinta’s flights and other video show that a goshawk starts off with a classical pursuit when it sees its target.
Once the prey starts moving, however, the goshawk may switch. “If the prey goes straight away, they just use classical,” Dr. Kane said. “But if it goes off at an angle, they use C.A.T.D. to cut if off at the pass.”
In the last moments before the kill, goshawks change back to straight pursuit, an adjustment they can make in a wingbeat or two. Goshawks don’t kill by force of impact, as peregrine falcons do. Goshawks must catch their prey and kill it, so they come up from behind rather than risk a glancing blow.
“A goshawk kills by grabbing the prey and kneading its talons into it,” Dr. Kane said. “It needs time.”
The surprise for a viewer of Shinta’s head-cam video is that the hawk’s flight through a thicket is so fast, with so many twists and turns, that it would be likely to give a fighter pilot motion sickness.
Dr. Kane said other work had shown that birds, in effect, see four times faster than people. In other words, at 25 frames per second, humans are tricked into seeing continuous motion, as in a movie. Birds would see the individual frames. For them, a movie would have to be shown at 100 frames per second to be convincing. That is worth remembering when seeing what a chase looks like from Shinta’s point of view.
Having produced a video glimpse of one part of a goshawk’s life, Dr. Kane said she was looking forward to a literary study of the bird. Ms. Macdonald’s book was at the top of her reading list.
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