Blog #291 Not as easy as it looks!

Hope trying to do a hover dive over the lake. 

Interviewer: Now that Hope and Lucky are free flying birds, what is next? Ospreyologist: Learning to feed themselves.  

Interviewer: How and why should they learn to fish if their father feeds them  regularly? 

Ospreyologist: Fishing is instinctual. The hunt, or rather fishing, is in their blood, in  every cell of their body, just like flying. You can’t hold them down. Their very being  tells them to do it. 

Interviewer: When will they stop taking handouts from Orpheus? 

Ospreyologist: When they are good enough at fishing that they don’t need  supplements. 

Naive Ospreys Hope and Lucky are fascinated by the water, captivated by it,  frequently dragging their talons along the lake’s surface to get a feel for this unique  medium. They practice targeting and swooping down on floating sticks, snatching  them up like they would a sunfish. 

There is much that goes into the nuances of fishing: The young must integrate  information such as sun glare, water clarity, wind direction, current, and incidence  of light into their dive. Fishing involves both innate and learned behaviors.  Fledgling awkwardness is evident while attempting this complicated series of  behaviors.

Both Hope and Lucky spend hours perched on the open branches overhanging  Salmon Creek and Cayuga Lake watching the water and everything living in it. They  ready themselves for the hunt by developing appropriate search images of their prey,  learning to recognize in a split second what fish look like in both clear and muddy  water. It is thought that fledglings raised together learn faster by modeling each other  than those raised as singletons. Sibling nestmates also exhibit similar foraging  techniques and have greater success over time relative to singleton birds.  

Fledgling about to snag a fish, courtesy of Douglas Brown. 

Young Ospreys begin their fishing careers by learning to plunge-dive wherein the  raptor sitting on a perch drops to the water feet first to grab a fish and flies off with 

the fish to a perch or the nest. Hope snagged a “minnow” plunge-diving this  morning—not much of a meal but still a success—underscoring the importance of  Orpheus’ meal deliveries to the nest. Orpheus must bring 5–6 fish a day for the  fledglings, as they continue to depend on Orpheus until they are totally self-sufficient.  However, Orpheus will begin to taper the amount of fish he supplies in a few weeks to  promote independence in the young. 

Meanwhile, Ophelia has begun feeding herself, but she still takes a nibble of fish if  there’s some at the nest. Soon she will migrate to South America most likely this  week. By the time Hope and Lucky leave the Finger Lakes for the tropics, usually in  mid-September, their fishing skills will be sufficient to live independently. However, up  to 50 percent of the fledgling Class of 2020 will perish due to the rigors of migration,  starvation, use of toxic chemicals in South America, and being shot by Latin and  South American subsistence fish farmers when the Ospreys raid their fish farms.  

As stated, fishing relies heavily on innate skills, as evidenced by Ospreys raised in  isolation becoming competent hunters. As with flying, fledglings perfect their fishing  techniques by imitating their siblings and their father. Orpheus will not show his  offspring how to fish, but he will guide them to his favored fishing spots at the best  times to fish.  

Orpheus delivers a goldfish to Lucky in the nest. Screenshot from Salt Point Osprey Cam. 

Orpheus does a large percentage of his fishing in the early morning or late afternoon  when the sun is low on the horizon as it lessens the glare off the water. Cayuga’s 

many coves offer calm, secluded waters good for yellow perch, and the tributaries,  like Salmon Creek, are good for bullheads and suckers. The best place to fish on  calm days is over the shallow shelf that extends off Salt Point. On stormy days,  Salmon Creek provides more sheltered fishing. Orpheus is able to catch bullheads in  the muddy creek, presumably by detecting their motions. 

The elegant hover dive, comprised of an intricate series of complex behaviors, is an  important technique to learn for young Ospreys. It will be their last major skill to  acquire before migrating to South America. Perfecting the hover-dive, which is crucial  for marine fishing, will take all of the fledglings’ efforts during the winter months in the  tropics. For now, the low-energy, less accurate plunge-dive from a sitting position will  suffice and be their key to independence in September. 

Feed Me! begs Hope. Screenshot from Salt Point Osprey Cam. 

It’s mealtime and Orpheus is called into action: Eyes to the sky as Orpheus hovers  above the calm waters about to marshal his attack. Diving straight down at about 40  mph until just above the water, he pulls back his wings above his head, legs trained  on the fish, talons open, and his head between his feet keeping aim on the target.  Orpheus hits the water with such force he submerges three feet below the surface.  His buoyant body is covered in oily, water-repellent feathers, preventing him from  sinking further and propelling him back to the surface.

Fish in his grasp, Orpheus takes off by making figure-8s with his wings, enabling him  to rise vertically out of the water like the V-22 Osprey airplane. Once airborne,  Orpheus re-positions the fish to face forward, reducing the aerodynamic drag on the  fish and making it easier to fly. When especially water-logged, Orpheus will do a mid air “doggie shake,” imitating a wet dog shaking itself dry.  

When Orpheus’s feathers get wet, water stays on the surface of the feather because  their oily water-proofing and miniscule grooves trap air around the feather preventing  liquids from attaching to the wing surface. The "doggie shakes" with forcibly twisting  

and shaking of his body breaks the weak chemical bonds to the water. (Such physical  bond cleavage is called “mechanochemistry.”) This remarkable feat, done while flying  and holding a struggling fish, is examined in Blog #165 The Physics of Doggie Shakes. 

The classic Osprey “doggie-shake,” courtesy of Kristofer Rowe. 

Adult Ospreys are excellent hunters and use the hover dive to catch up to 70% of  their intended prey. This makes Ospreys the most accurate and talented fishing hawk  in the U.S., far exceeding their rivals, the Bald Eagles. But Ospreys were not born that  way. It’s taken years of practice to become an awesome authentic amazing apex  aerial angler. 

A combination of nature and nurture is involved in many important skills for  survival. For example, all flying birds orient their flight relative to the wind to save 

Photo sequence courtesy of Tanja Clendinen illustrates the young bird’s unsteady approach. 

energy. This innate behavior that is nearly automatic in the Osprey is improved by practice. Using both innate and learned skills during plunge-diving allows them to  vary the altitude while foraging, increasing the number of available and types of prey. These and countless other behaviors take the young time to develop and  will be their focus during their juvenile gap year in the tropics.

Below is a sequence of photos illustrating a fledgling’s unsteady approach while doing  a hover dive and rising with a fish that it later drops.  

Osprey diving underwater (head left, white eyelid shut, wings straight up), courtesy of Archive. 

Salt Point fledgling about to fly loses her catch, courtesy of Karel and Cindy Sedlacek.

This is a great, albeit noisy, time to watch the adult and fledgling Ospreys do their magnificent dives around the shallow ends of the lake and above the shelf off Salt Point. They cry out in—and at the nest  where the young clamor enthusiastically for meals. Some devoted Osprey followers liken the non-stop  begging call of the fledglings to a sweet songbird chirp, whereas others find it grating. 

Eyes to the sky! 

Candace 

Candace E. Cornell  

Friends of Salt Point  

Lansing, NY 

cec222@gmail.com 

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