Blog #289 Post-fledging Behavior

In their ninth week, Hope and Lucky have begun the post-fledging dependence period— the time after leaving the nest during which Osprey fledglings still depend on their parents for protection and food. This period, spent learning to fish, can last from several weeks to a month or more as the fledgling gradually perfects this innate skill.  

Hope sitting on a cottonwood limb, courtesy of Karel and Cindy Sedlacek. 

Hope is mad for flight and literally cannot get enough of it with Lucky not far behind. The  fledglings have attained an adult body size, but their flight feathers still need time to fully

Awkward flight of the Salt Point fledgling with dangling legs, courtesy of Karel and Cindy Sedlacek. 

difficulty during take-offs. The feet often dangle, dragging in the air, until the bird closes  its talons and brings its legs close to the body. Such awkwardness vanishes in time.  Now the Salt Point young share the sky with fledglings from neighboring nests on Myers  

Salt Point fledgling not holding wings straight. Courtesy of Karel and Cindy Sedlacek.

Hill, Church Hill, Cargill, and Portland Point Road as they explore the area and interact playfully with one another. The young spend their airtime perfecting the art of play, flying in circles, steering amongst the trees, changing altitude, and learning to bank while turning. Proper landing techniques and balancing on perches comes easier to some fledglings than other, but all must practice this crucial skill.  

Lucky attempting to balance on a thin branch, courtesy of Karel and Cindy Sedlacek. 

The fledglings have to learn which branches are for perching and which won’t support  their weight. It’s comical to watch them recover from a minor tumble off a flimsy branch  that gives way under its weight. While perching, the young birds continually adjust their  balance and footing with the help of their wings. If a fledge falls backwards, it counters  by rowing its wings backwards as fast as it can until righted.  

Life is not easy when there is only room for one foot on the branch tip, and you have  two very large feet. Adult ospreys are noted for their ability to stand on one foot for long  hours, but the fledglings have not discovered this pose yet.  

Hope and Lucky are often found in the cottonwoods overhanging the mouth of Salmon  Creek perching, preening, and resting between flights around the point. When not at 

play, the fledglings sit in the trees for hours cooling off and staring at the water as they  develop search images of the fish they will soon hunt. Clinging to branches in the wind,  they exchange distinctive low, repetitive whistles and chatter to each other as they fly  around and change perches. The sound gets louder as they repeatedly trade places,  playfully switching positions between the trees and the nest.  

Orpheus delivering a fish at the same time siblings arrive. Salt Point Osprey Cam screenshot. 

At mealtime, Ophelia and the young gather around the nest in anticipation. The din of  their begging calls is constant as they clamor for food. Orpheus heeds their calls and  flies off seeking their object of their desire—a big, wriggling fish. Not until his return with  the meal does the racket cease. The fledges still eat at the nest, but with increasing  frequency, they will take part or all of the fish to eat in a tree.  

At lunch, Hope took command of the fish Orpheus left in the nest and mantled it with her  wings, preventing Lucky access to it. Every once in a while Lucky would grab a small  piece of the fish, but Hope essentially at most of it. Orpheus will most like get another  fish fairly soon, which will be all for Lucky to eat.

Hope takes the fish from Orpheus’ talons. Salt Point Osprey Cam screenshot. 

Hope and Lucky grapple to see who will get the fish. Salt Point Osprey Cam screenshot.

Hope mantles the catch with her wings barring Lucky from the fish. Salt Point Osprey Cam screenshot. 

Two types of play are most commonly seen in Osprey fledglings. “Social play” during  this critical period takes the form of feigned or fictitious attacks, chases, or games of tag  with siblings, unrelated fledglings, or other birds and mammals, apparently without any  intention of capturing or hurting the other individual. Hope is keen on chasing gulls over  the water, but she is out-maneuvered easily by them. However, occasional chases are  given in nest defense against intruders or predators. Both Hope and Lucky have been  raising alarm calls when neighboring fledglings fly overhead and sometimes give chase.  During ‘object manipulation play,’ fledglings use inanimate objects to practice different  maneuvers related to the capture, transport, and consumption of prey. 

Hope and Lucky frequently play with objects, dragging their feet across the water,  picking up clumps of water plants and other found objects in the flotsam by the shore.  They comb the point and dive to retrieve moss, grasses, feathers, stones, sticks,  leaves, and other interesting objects—shoreline refuse—to bring to the nest. The  materials are for play only and do not contribute to the nest structure. Researchers think  play helps the fledglings hone their ability to fly and to capture and manipulate fish. Play  maneuvers also train the muscles necessary for these activities. 

Fledgling trying to hoover to fish, courtesy of Andy Morffew. 

There are few detailed studies on the maturation of hunting behavior in raptors. In 1954 Meinertzhagen reported that young Ospreys learned to fish by observing their parents.  While this does occur in some avian species, it is not true for Ospreys. Regardless, this  

erroneous belief persists today. In 1982 researchers reported that Osprey hatchlings  raised in isolation easily learned to identify fish as prey and readily learned how to hunt  without any demonstrations. Thus, the act of fishing is an innate behavior in Ospreys,  although the techniques must be developed. 

A detailed study in 1989 corroborated that fishing is an innate skill in Ospreys and  verified that young do not learn by following their parents on fishing trips. These researchers did observe “social facilitation,” where fledglings with siblings learned to fish  faster than singletons. The fledglings also tend to imitate only the successful fishing  techniques. In that way siblings develop similar hunting techniques. However, they do  learn where to fish by following their parents to preferred fishing grounds. There is no  explanation, however, for why some young Ospreys, siblings or not, are faster learners  than others, as it can take anywhere from 2 to 6 weeks to become competent enough  for the bird to become an independent juvenile ready for migration. 

Eyes to the sky! 

Candace 

Candace E. Cornell  

Friends of Salt Point  

Lansing, NY 

cec222@gmail.com 

Guest Photographers: 

Karel, a Senior Data Analyst, and Cindy Sedlacek (aka BOGette), a Director of  Data Administration and Reporting Sedlacek, are long term at Cornell University employees. (BOGette stands for Birder on the Ground). They were introduced into the  wonderful world of raptors after watching the 2012 Lab of Ornithology's Bird Cams -- Big  Red and Ezra and Stanley and Iris. Since that introduction they have spent their free  time documenting the lives of local Red-tailed Hawks and Ospreys via livestreaming  and photography — https://livestream.com/karelsedlacek —at Cornell and Syracuse  Universities.  

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