[Tweeters] Peregrines carrying ducks

Jeff Kozma jkozma at charter.net
Fri Jan 12 21:46:28 PST 2007

I think most raptors are capable of carrying at least, or slightly more than, their own body weight. Look at Great-horned Owls...average weight is 3 lbs. Yet, they kill and carry striped skunks to their nest to feed young...striped skunks weigh from 6-14 lbs. Figure the owl decapitates the skunk and guts it, the most common feeding strategy, you are still probably looking at 8-10 lbs for a large skunk. Similarly, they frequently prey on mallard duck hens when they are nesting...mallards weigh between 3 and 3.5 lbs...

And here is a blurb on Ospreys I found on the net...

Ospreys are often rated as the most powerful birds of prey based on a ratio comparing their body weight to the size of the prey they are capable of flying with. For the American Bald Eagle, the ratio is 1:1. For Osprey, it is 1:2 meaning they can carry twice their body weight or the same size fish that is the maximum load for the much larger bald eagle.

I would imagine that how the prey was taken greatly influences how far birds of prey can take their prey. If caught in the air, they probably have the momentum needed to carry prey much farther than if they kill the prey on the ground or recover prey on the ground and have to lift off with it. Most likely, they consume some of the prey before taking off with it. Does consuming a portion of the prey make it easier to lift it if it is lighter, or does the added weight in the bird of the part consumed hinder it? I watched a Sharp-shinned Hawk take a domestic pigeon similar in size to a Rock Dove in mid air but was only able to carry it about 50 yards before landing on the ground. It was obviously too heavy to carry a great distance.

Does shape of wing effect how much they can carry? Are broad-winged raptors such as eagles, buteos and owls capable of carrying larger prey due to more wing surface area for lift? Perhaps falcons, because they take almost all their prey in the air, have a greater capability to carry larger prey greater distances? Does muscle mass of the breast muscle differ between raptors to effect carry capacity? So many questions....

Jeff Kozma

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