We have special treat today: some lovely photos and videos of peregrine falcons taken by reader Bruce Lyon. His notes are indented:
Jerry previously posted some of my peregrine falcon (Falco peregrinus) photos. This new batch illustrates the photographic fruits from a lucky discovery last year—the peregrines almost always take their prey back to one of two favorite plucking/eating sites near their nest. Finding the plucking sites allowed me to see what species they eat as well as how they eat their prey. I also initially imagined unlimited wonderful photography opportunities, but it turns out the birds are shy when they have prey and would not let me approach them while eating. J. A. Baker also noted in his book The Peregrine that his peregrines became shyer when they had food. Maybe it is general peregrine thing—perhaps a carcass is a valuable commodity worth stealing so the birds become warier. To get photos I initially I had to resort to a camouflaged camera connected by long cable to my laptop; this setup allowed me to hide from sight and take photos remotely. I also set up small video cameras to run continuously and record whatever prey items the birds bring in, and below I include a couple of segments from these videos. The birds continue to get tamer over time and, finally, this year they will now let me watch them while they dine.
Below: The female on the pairs’ current favorite plucking station, a tiny pinnacle jutting up from the cliff very close to the nest. The feathers build up over time, like a fossil record of the victims—looks like the result of a macabre pillow fight.
Below: I had hoped to get photos of the falcons with a nice variety of prey species but the falcons had other ideas. They are dove specialists and, in particular, they really love introduced Eurasian Collared-Doves [Streptopelia decaocto]. As a result, the menu at the plucking station has been disappointingly boring—doves, doves and more doves. Here is the female with a freshly killed collared-dove.
Below: The female flies by the cliffs with a collared-dove in her talons.
Below: The male with a collared dove. I include this blurry photo for a couple of reasons. First, it is a nice still life of predator and prey (literally still life for the dove). Second, about half of the days my camera will not simply not focus on the bird on the plucking stack. It is not a problem with the camera’s auto focus mechanism because manual focus will not work. On these days is almost a mirage-like quality to the air. I have wondered if the problem is the salty air or a swirling mixture of warm and cold air? If any readers know what might be going on I would love to hear some ideas. Whatever the explanation it is bloody frustrating to have an amazing opportunity to photograph the falcons and their prey and then not be able to get a single remotely sharp image on a given day.
Below: Finally, something other than a dove! The male with an embarrassment of riches: a male Black-headed Grosbeak and what I believe is a Tennessee Warbler (but possibly an Orange-crowned Warbler since Tennessee warblers are not very common here).
Below: The male’s beak has ‘tomial’ notches. Falcons generally use these notches to sever the spinal chord of their victims. The upper beak has a projecting “tooth”, and the lower beak has a corresponding notch, and these fit together to make a devastating cutting implement. According the online Birds of North America species description for peregrines, this biting the prey neck action is instinctive—captive raised young birds do it when presented with their first intact bird carcass. The tomial notches are also used to cut bones; I assume this is how they snip away at the breastbone, which my birds always eat. In fact, the birds eat everything and at the end of the meal all that remains are the plucked feathers.
Below: The video [JAC: videos also taken by Bruce] shows the female biting the neck of a collared-dove as soon as she arrives at the plucking spot. I watched her chase this dove and comparing her departure time with the time stamp on the video camera for her arrival revealed that the entire chase and return to the plucking site took 2 minutes! Note that the female starts by eating the head—they always do this.
The birds always pluck the all of the flight feathers on the wings and tail at some point during the meal, and they typically pluck many of the body feathers too. They pluck body feathers by yanking beakfuls of feathers and then spitting them out, as this photo shows for the female:
Below: The wing feathers are so aerodynamic that after the falcons spit them out they sometimes spin upwards in the wind currents like a wind dispersed seed (e.g. maple keys), sometimes spinning for several minutes. The video below, taken a couple of days ago, shows the male plucking wing feathers from a dove and some of the primary feathers twirl away in the wind:
The pair sometimes share a prey item (the first bird to eat leaves some of the prey for the other bird). In the two photos below, the female has just eaten her share of a dove while the male sat impatiently on the nearby cliff, whining frequently about wanting his share. Once the female was done and no longer holding the dove down to eat, the wind blew the half eaten dove to the edge of the stack where it threatened to topple over and disappear into the ocean below. The female watched teetering carcass inch towards the precipice but did nothing. At this point, the male couldn’t stand it any more and had to come in an rescue his meal:
Below: The birds really do eat everything. Often the prey’s feet are the last thing to go down the hatch. Kind of fitting—head first, feet last. Here a fledgling savors a dove foot.