July 30, 2005
The Fishing Expert
Nest Update: Each day the oldest chick is getting closer to its first flight, as we're seeing more photos of the oldest getting some air under its wings. At this point, the chick has to be careful that a strong wind doesn't take it off the platform prematurely. Sometimes a powerful breeze can send a practicing chick into its first flight whether it wants to go or not.
Also, the father osprey is back to his erratic food deliveries. The other evening, one of the chicks made it known to mom that it was hungry and tired of waiting on dad. The mother osprey left the nest and within fifteen minutes returned with dinner.
And yesterday we saw the oldest chick commandeering a fish piece for itself, after which the mother osprey retrieved a smaller fish and fed the youngest with it. Seems the mother osprey is still doing a fine job of making sure the youngest gets fed.
And speaking of fishing for dinner, the post below takes a good look at what makes an osprey such a fishing expert...
Ospreys are admired by many people who love birds, and one of the things birdwatchers find most compelling about the osprey is its fishing ability. Ospreys are considered to be one of the greatest fishermen nature has ever witnessed.
Everything about the osprey is geared towards making it an efficient predator of fish. The osprey's feathers are oily to reduce water absorption. Their legs have few feathers so they can dry quickly after a hunt. They have the distinction of being the only raptor with a reversible toe that lets them hold a slippery fish with two toes in back and two toes in front. Their feet are covered with small barbs -- or spicules -- that help them hold onto a thrashing fish. They have long slitted nostrils that can close when entering the water. And their vision is typical of a hawk in that it's sharp and powerful, but with the added advantage of being able to judge the location of fish as they move under the surface of water, which refracts light and distorts the fish's exact location.
Ospreys are, in fact, our only bird of prey that dives into the water for fish. On occasion ospreys will scoop fish from the surface like eagles, but the majority of time they will fly and hover above the water, and then when a fish is spotted, plummet from as high as 200 feet, extending their feet in front of them right before they penetrate the water and drive their talons into the slippery prey. Once airborne again, ospreys will often position the fish headfirst in their talons to reduce aerodynamic drag.
Ospreys can reach a speed of almost 40 mph during their dives, and the average adult is successful about one out of every four attempts, although some have recorded success rates as high as 70-80%. Ospreys weigh less than four pounds and can catch a fish of almost equal size, but they will normally target a fish in the 14-22 ounces range.
The osprey will hunt for fish in both fresh and saltwater, making their selections based on size and accessibility from the surface, as ospreys can only dive about three feet under the water. The osprey is a connoisseur of live fish and is not normally a carrion eater. In the Chesapeake Bay region the osprey's food preferences include shallow-water fish such as carp, bullhead catfish, menhaden, perch, and gizzard shad.
Our young cam ospreys will soon be working on their fishing skills with the hope of becoming as accomplished as their parents. Ornithologists report that siblings will hunt together after fledging and will develop their hunting skills faster than single juveniles do, although by the time the juveniles head south, the single chicks will show no difference in hunting ability or success.
Below you'll find a link to our Osprey Fishing Slide Show, which gives our cam watchers a chance to see in detail what they can't see on our Osprey Cam -- how the osprey catches its meals. The photos are courtesy of Vince Rees, one of our talented cam watchers; much thanks to Vince for the loan of his wonderful photography.
Click on the link below to open the slide show window. Use the buttons to navigate through the 14 slides. If you have dial-up Internet access, the photos might take a few seconds to load. Watch for the little green "ready" light to see when each has loaded. At the end of the show, click Restart to watch it again (it will load more quickly on subsequent viewings). Close the window when you're done.
This is the first time we've used jClicker Slide Show to display sequential photos. If anyone has comments about its operation -- good or bad -- please feel free to share them.
Until next time,
Lisa - webmaster (contact)