Blog # 337 Fast Track Growth Spurt

 

One month old chicks with rusty-cinnamon nape of neck, courtesy of Andy Morffew.


Rosie is a day shy of being a month old, and the others are close behind. They are already 70-75% of their adult weight and are quickly developing to resemble adult birds. Rose’s camouflaging brown and buff feathers set off a handsome collar of rusty-cinnamon feathers. Olan also shows hints of this collar. Lilibit is still in the reptilian phase.


The chicks spend the majority of their day laying in the shade of their mother, digesting their food, and sleeping. Periodically wings will flex or a leg may stretch, but the activity is held to a minimum in the hot weather. However, the second that Orpheus arrives with a fish and gives it to Ophelia, they come to life and waddle over to the food. Ophelia may eat some of the fish before sharing it, or she will wait for the 


Fish deliveries cause much excitement at the nest.


young to feed first. Typically Rosie gets the initial feedings, but Olan and Lilibit get their fair share.


Hiding in mother’s shade.

These helpless nestlings with their clumsy big feet and useless long wings sleep for hours on end in Ophelia’s shadow. Why are the nestlings sleeping so much? Because they have been spending all their energy on growing. Thirty days marks the beginning of the super growth phase in Osprey nestlings during which they will sleep all the more. 


During this fast track growth spurt fueled by their very high protein diet of fish brought in by Orpheus their bodies transform into fully feathered and formed adult-like birds. The siblings’ skin is now covered with feathers and no longer sensitive to the sun, which allows for lounging around in the nest. 

Month-old nestlings with mother, showing their downy breasts, courtesy of Andy Morffew.


With fledging only a month away, the nestlings have much to do. Their body growth will slow as they put on mass and become fully feathered. Significant muscle strength must be developed in their wings and back, and neurological connections and muscle coordination must be practiced. 


It will be possible to sex the offspring after this super growth period using a few indicators. The culmen is the ridge along the top of the upper mandible of a bird’s beak and grows at a steady rate. Therefore, the culmen’s length may be helpful in determining the chick’s age. (The shape of the culmen or its coloration is often a helpful

clue in the identification of certain bird species.) At the age of 20 to 35 days, the females, which are heavier as adults, start gaining weight much faster than the males.

Chart mapping the exponential growth rate of ospreys, courtesy of Lyn Adair.


Thus, body weight is used as a reliable criterion for sexing the chicks more than 30 days old. If I had to guess now, I’d say Rosie and Olan are females leaving Lilibit a male.

           

                 

Eyes to the sky!

Candace 


Candace E. Cornell 

Friends of Salt Point 

Cayuga Osprey Network

Lansing, NY 

cec222@gmail.com 

EYES ON OSPREYS

WATCH!

Salt Point Osprey Nest Cam 2021

READ!
On Osprey Time—A Blog  on the Ospreys of Salt Point


VISIT!
Cayuga Lake Osprey Trail



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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 habitat. 

  • Recycle used fishing line, 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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