This is one of the best reader photos I’ve ever posted, and it comes from photographer John Chardine. He described the scene in his first email (all posted with permission):
I’ve been photographing a pair of Peregrine Falcons at a nest not far from home.Right now there is a single chick in the nest. The (much smaller) male is hunting for birds—mainly American Robins—and is bringing them back plucked and usually without the head (which he eats). The interesting part of the story is that rather than bring them back to the nest, the male transfers the prey to the female in mid-air, and the female then takes the prey item back to the nest and feeds the chick. All this happens in 5 seconds ± so you have to be quick on the the camera trigger!In the image the smaller male is above with the food item in its beak. The female is reaching up with her talons to grab the food item.
There is pronounced (reverse) sexual dimorphism in the Peregrine with the male much smaller than the female. When the chicks are young the parents only need to bring in small prey like robins and the male is supremely built to kill small birds. Peregrines capture their prey by diving on them at incredible speeds—the fastest in the bird world. Later on when the chicks get older, they need more food delivered per unit time and sometimes the larger female will step in taking larger prey like for example ducks and gulls. A big problem for flying predators like Peregrines is “payload mass”. They have to be able to carry back the prey (payload) and if it’s too heavy they can’t do it. Larger females can fly with bigger prey than the smaller males.
But why doesn’t the male just feed the small birds he catches directly to the chicks? Why does he hand them over to the female?
That’s a good question and I don’t know the answer. There are many options for what the male could do. The simplest might be to do what you suggest- bring back the prey and feed the chick. The next obvious option might be for the male to deliver the prey to the female at the nest and then she feeds the chick. This is known to occur in some pairs. What I can say is that immediately after the food exchange in mid-air we see the male fly away and we assume he is traveling to his “kill” location. There is no lost time in doing this, which may explain why he does not stick around and feed the chick. If he stayed, the most efficient system would be for the female to fly out to hunt, and that is indeed an option that probably occurs when the chick is old and requires bigger meals. To have both birds attending the nest- one feeding and one hanging around- is inefficient and indeed may not allow sufficient power delivery (energy per unit time) to the nest. It should be mentioned that feeding takes time as the parent has to tear apart the prey in appropriately small morsels for the chick. Currently, with a chick about 12 days old, a complete feeding may take 20-30 minutes.