Tonight I’m presenting the second part of the encounter that I witnessed between two juvenile Caracaras.
Having attained sole possession of the lamb carcass, the second juvenile Caracara did something I had never previously seen. It stood erect, raised its head to its highest possible elevation — to the point where the bird’s head actually tilted backwards, and emitted a victory cry. It was a sort of coarse rattling noise, a kind of “uk-uk-uk” lasting for just a few seconds.
The bird slowly lowered its head, still standing as erect as possible.
It stood that way, defiantly, for a few seconds more, as if to say to the other Caracaras in the field: “challenge me at your peril!”
Notice that in this third photo the bird’s crest is erect, apparently, another sign of aggressiveness. Having completed its display, the Caracara then began eagerly tearing chunks of flesh from the lamb’s carcass.
Caracaras congregate in flocks in the agricultural flatlands of southern Arizona only during the fall and winter months. Where they go in the summer is an open question, but I suspect that their summer home is on the Tohono O’odham Indian Reservation, about 40 miles to the south. Interestingly, one can find Caracaras on the reservation all year ’round, but never in flocks. Observers note that on the reservation they generally show up as single birds or in pairs. Another interesting fact about the flatlands’ flocks is that juvenile birds seem to make up a very high percentage of the population. What explains the flocking behavior and the seemingly high percentage of juveniles in the flocks?
I haven’t found any literature that discusses the phenomenon. I’ll offer a guess, but it’s just a guess on my part. I’m speculating that the breeding grounds for Caracaras in southern Arizona lie on the Tohono O’odham Reservation. Caracaras nest in Saguaro cacti and there are very few Saguaros on the flatlands. There are many of these cacti on the reservation, however. Adult Caracaras also mate for life. My guess is that during the fall and winter months juvenile birds — bachelors — migrate to the flatlands where they hang out in the winter. As the weather warms the younger birds return to the reservation. Perhaps after a couple of years of this activity, they are mature, they find mates, and they become reservation homebodies. Just a guess on my part and I wish that someone could provide a more definitive explanation for the flatlands’ flocks.
Images made with a Canon 5Diii, 400 DO+1.4X Extender, aperture priority setting, ISO 640, f6.3 @ 1/1250.
Sonoran Images 
This is one very challenging Caracara!