Other November events:

• The "Snow Blowing like Spirits in the Sun" moon (Arapaho) was full on Jan. 1.

• Boulder's maximum recorded wind gust was 147 mph at NCAR in January 1971.

• Early Easter-daisies bloom on shale slopes in foothills canyons.

• Courting eastern screech-owls wail and whinny in cottonwood groves and urban parks.

"What was that?" We slammed on the brakes, eased the car backward and gazed at what we guessed was a sharp-shinned hawk or female American kestrel on a cottonwood branch. But the blue feathers on the bird's back, shell-like scales on its breast and short beak gave it away: a merlin, one of the most elusive falcons in North America.

This merlin sighting along a dirt road south of Hygiene was one of only a handful reported during 35 years of Boulder County wintering raptor surveys. But a small merlin population overwinters each year in northeastern Colorado, with individuals seen along country roads east of Longmont, Loveland and Fort Collins.

And what elegant and graceful falcons they are! Capable of exceeding 100 mph during dives, they swoop and dart after small songbirds, separating individuals from flocks before snatching them out of the air.

On their breeding grounds in conifer forests and woodlands from Great Britain, Siberia, Alaska and Labrador south to the northern Great Plains, they lay their eggs in concealed crow nests, on cliff ledges and sometimes on the ground, fighting fiercely to keep other falcons away.


But some have learned to coexist with people. In British "Queen's ringing flights," ladies of the court release trained merlins, which spiral upward after English skylarks. In southern Canada, merlins nest in Saskatoon and other cities, preying on house sparrows, swallows and pigeons.

The name "merlin" derives from the French esmerillon, meaning "small hawk," but this 12-inch tall, half-pound falcon is a true magician when it comes to vanishing into dense cover or tracking down zigzagging songbirds. Also known as "pigeon hawks" for their plump bodies and fluttering flight, merlins mimic the wing beats of their prey so they can sneak up on flocks.

American kestrels are smaller, more colorful, and much more abundant than merlins.
American kestrels are smaller, more colorful, and much more abundant than merlins. (Stephen Jones / Courtesy photo)

"One merlin can dominate an entire flock of frightened birds, directing its fate as a whole," said falconer Matthew Mullenix. "The flock responds like baitfish to a barracuda ... . Merlins demonstrate total mastery of their element."

In an interesting twist, prey species such as skylarks have learned that if they begin singing while being chased by a merlin, the falcon may break off its attack. Biologists believe merlins perceive singing birds as being more fit than silent ones and thus harder to catch.

During the latter half of the 20th century, North American merlin populations plummeted as DDT concentrations in their fatty tissues weakened their eggshells. With the banning of DDT in North America, numbers have rebounded, but merlins that overwinter in Central and South America still show disturbing levels of DDT contamination.

Other threats include cutting of nest trees in woodlots and conversion of grassland hunting areas to farmland. During the last decade, federal incentives for growing corn for ethanol have resulted in more than one million acres of native prairie being plowed under in North Dakota, alone.

In March, our small wintering population of prairie merlins will fly north to woodlands in Wyoming, western Nebraska, the Dakotas, or southern Canada to nest. The two darker North American subspecies, "black merlin" and "boreal merlin," typically breed farther north and winter farther south.

Stephen Jones and Ruth Carol Cushman are authors of "Peterson Field Guide to the North American Prairie" and "Wild Boulder County."