Blog # 444 The Great Race Against Time

 

“Mombrella” Ursula shading her three chicks (two are visible), courtesy of Cynthia Sedlacek.

The Salt Point nestlings are growing like lightening, as they double their weight every week. In their third week, their staggered birth order is evident. Daily changes are visible as the young birds grow adult feathers and gain muscle strength and coordination. The three offspring are imprinting and forming critical attachments to their parents, and learning the finer points of being an Osprey. It is a race against time: the sooner the young mature, the more time they will have to learn critical life skills—flying and fishing—that must be mastered before migrating thousands of miles in September.

Weeks four through six is a very intense period of rapid growth and behavioral development during which the nestlings practice flapping and helicoptering into the air. They approach their adult size by day 30. Food demands are highest during this rapid growth phase making fledglings vulnerable to starvation keeping Orpheus busy. As shown on the graph below, the growth of male fledglings tapers off at 6 weeks but

S-shaped growth curve showing the rapid growth period, courtesy of Dyfi.

females continue to grow another two weeks resulting in the females being larger than the males. This type of sexual dimorphism is common in raptors.

The three-week-old nestlings are well camouflaged—a light spinal stripe and dark sides make them resemble twigs in an empty nest. One sharp warning call—a harsh Cheerp!—from Ursula and the chicks lay flat and still in the nest—their defense against predatory bald eagles and great horned owls.

Some researchers consider this defensive behavior as feigning death or “playing possum,” a common behavior in the animal kingdom. Pretending to be dead is thought to make the prey less desirable to predators that hunt only living prey. However, eagles eat both live prey and carrion so there is no reason to carry on this ruse. The purpose of staying still is most likely to enhance the deception of the camouflage. With feathers imitating the shades of twigs, the motionless nestmates usually go undetected when unattended in the nest. Ursula is a good first-time mom, but she is not as attentive to her brood as Ophelia was in her early years. Unlike Ophelia, Ursula takes 1 to 3-minute breaks numerous times during the day, regardless if Orpheus is nearby leaving the

At 3.5 weeks, the eldest chick is on the left and the youngest at the left, courtesy of the

Scottish Wildlife Trust. Note the white strip down their nestlings’ backs offering camouflage.

young exposed to the elements. Ursula often took frequent breaks during incubation as well, but the eggs were fine and the nestlings are thriving.

Until they learn to fly, the young nestmates will be vulnerable to predators. Besides the two avian predators mentioned above, Ospreys must be wary of climbing nest raiders such as red squirrels, raccoons, and snakes that take eggs and young birds. The best protection a nestling can get is hiding under its mother’s mantling—partially held out— wings.

Over the next 3 weeks, the hatchlings will do little other than sleep, consume colossal amounts of fish, sleep again, and rapidly transform into magnificently adult Ospreys. Wing-flapping practice begins at 3 weeks old and becomes quite comical as the nestlings struggle to gain muscle strength and coordination. The chicks are halfway to fledging. In 3 more weeks, the nestlings will be so close to fledging that they’ll be able to taste it. To fly… to fish…to be an Osprey. The race against time is on.

Eyes to the sky!

Candace

Candace E. Cornell

Friends of Salt Point

Cayuga Osprey Network

Lansing, NY

cec222@gmail.com


Two of the three youngsters peeking over the nest, courtesy of Cindy Sedlacek.

EYES ON OSPREYS

WATCH!

Salt Point Osprey Nest Cam 2022

2023 out of order

READ!

 On Osprey Time: Ospreys of the Finger Lakes

VISIT!

Cayuga Lake Osprey Trail Nests Driving Tour

Complete Cayuga Lake Osprey Trail

HELP PROTECT OSPREYS

  • Avoid getting too close to nesting sites during the breeding season. If an animal vocalizes when you're near, you are too close! Back off Immediately.
  • Carry binoculars to view wildlife from afar.
  • Restore, clean, and preserve lakeshore and wetland habitats. 
  • Recycle used fishing lines, which can be hazardous to Osprey.
  • Join the Cayuga Osprey Network and volunteer to help monitor Osprey nests. Write to: cec222@gmail.com.



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