Reader Bruce Lyon has graced these pages with wonderful photos of peregrine falcons (Falco peregrinus) nesting in California (see here, here and here), and now he adds a third batch to the set. His notes are indented:.

More photos of the nesting peregrine falcons (Falco peregrinus) I have been following on the California coast between Santa Cruz and San Francisco. Today’s offerings focus on the birds in flight, where they really shine (sometimes gobsmackingly so).

Peregrines are famously the world’s fastest birds. A National Geographic video claims an astonishing 240 mph dive, determined with a falconry bird equipped with a transmitter and skydivers enticing it to chase a plunging lure. As the video shows, the birds reach their exceptional speeds by going into a stoop, i.e. diving with wings tucked close against the body to produce an aerodynamic teardrop shape. I often see my falcons stooping, mostly during hunts but also on windy days. The birds become feisty on windy days and they sometimes seem to stoop and fly loops just for the sheer fun of it—an avian airshow.

Below: the female stooping on a windy day.

The birds are also remarkably maneuverable, even at high speeds. I have seen full tight loops during hunts. Below: The female suddenly flips upside down in flight.

Below: the male partially tucks his wings to give me a speedy flyby.

On windy days the falcons also become more feisty about chasing gulls, pelicans and other large birds. It seems like play to me because they never appear serious about trying to kill their victims. Below: A couple of photos of the peregrines chasing Western gulls.

A pair of black oystercatchers tried to nest around the corner from the falcon nest, just out of sight of the nest. The falcons soon began chasing the oystercatchers, first by trying to sneak around the corner and ambush them. The oystercatchers got wise to this strategy and one oystercatcher then stood sentry at the corner where it could watch the falcons. This did not stop the falcons who then began chasing the oystercatchers out over the water. It looked like the falcon might be trying to herd the oystercatchers, perhaps to get them off balance and then grab them.

Below. Male falcon herding the oystercatchers.

Below. The oystercatchers were not amused. After a couple of days of this harassment they deserted their nest and moved to a different part of their territory.

The open coastal landscape around falcon nest lets me observe the birds going off to hunt, and I have been lucky to see several successful hunts. The birds often watch for birds from the nest cliffs and then suddenly take off when they see a hunting opportunity. I can tell when the leave to chase something because they are clearly flying with a purpose—fast and direct. They must have remarkable eyesight because some of the birds they have gone out after have been more than a mile away, according to my Google Earth estimates. I have seen two hunting methods: climbing up very high, nearly out of sight, and then diving in a stoop, or simply chasing a bird down and grabbing it out of the air.

Below: The male launches from the cliff, perhaps to go after some prey.

I suspected that the birds might hunt cooperatively as a team because they often leave the cliffs at the same time and then fly off together rapidly. Below: the team heading off to chase something together. The size difference is apparent, with the smaller male above.

I eventually watching a successful cooperative hunt. The pair flew off north but then quickly circled around to the south, behind a bluff. Their U turn made suspicious so I scanned southward with my binoculars and saw a lone dove flying inland, half a mile away. The peregrines suddenly appeared, streaking like meteorites. The male, in the lead, swooped at the dove but missed because the dove swerved. A split second later, an explosion of feathers—the female had done her job. She followed the tumbling dove to the ground and then brought it to her favorite plucking site near the nest. Since then I have seen several tag team chases and kills. The photo below is pretty crappy but it shows a different cooperative chase—that time the dove (bird in center) got away:

Below. The male returns from a successful hunt with a freshly killed collared-dove:

The falcons also have aerial prey transfers. The male sometimes transfers prey to the female, who then takes it to the nest. After the chicks fledge, both parents transfer prey to the chicks. In transfers, the prey is dropped into the air and the recipient has to snatch it while it is falling.

Below: The female has just grabbed a dove the male dropped.

Below: Sometimes the fledgling falcons are kind of klutzy. Twice, the parent had to fetch a gull chick that the fledgling failed to grab after the drop. The parent gave up and brought the gull chick to the cliff, where the fledgling picked it up. It then dropped it in the sea. Doh!