Blog #275 Growing like Weeds

 Some say you can watch the corn grow over night in Lansing. So too it is with Osprey  nestlings. The two nestlings at Salt Point are growing before our eyes in a race against  time—the sooner they grow, the more time the fledglings will have to become  accomplished hunters before they must leave on their southerly migration alone.  

Hope (L, 18 days) and Lucky (R, 15 days) feeding. Note the swollen crops of the well-fed chicks.  Screen shot from the Salt Point Osprey Nest Cam. 

Compare the screen shot below taken just a few days earlier to see the tremendous  transformation of growth and muscular coordination in both nest mates.

Hope (L,14 days) and Lucky (R, 11 days) feeding. Screen shot from the Salt Point Osprey Nest Cam. 

Today, Hope at 18 days old is mid-way in its exponential growth spurt and routinely  pokes its head up to see the world. Lucky, at 15 days old, just entered the reptilian  phase and this period of exponential growth represented by the "sigmoidal” or S-shaped  growth curve typical of many young raptors. 

The exponential sigmoidal growth spurt of osprey nestlings, courtesy of Dyfi Scotland.

Osprey chicks grow slowly during their first days after hatching. At about ten days, their  growth accelerates exponentially for about 20 more days until they approach their adult  size at day 30. At day 35, the growth of the male chicks levels off, while the females  continue to grow, becoming much bigger than the males as adults.  

Meanwhile, the nestlings, when still, are well camouflaged from above; their light spinal  stripe and dark sides look like twigs when seen from the air. Ophelia has taught the  chicks to lay flat and still in the nest as a defense from aerial predators: both nest mates  assume this posture with one sharp warning call from Ophelia—a harsh Cheerp!  

Nest mates are camouflaged against the twigs and grass backdrop of the nest. 

Screen shot from the Salt Point Osprey Nest Cam. 

Some researchers refer to the nest mates’ behavior as “playing possum” or feigning death, a behavior found in many parts of the animal kingdom. Since most predators  seek living prey, pretending to be dead makes the prey less appealing. However, I  disagree that this adaptive form of animal deception, also known as tonic  immobility or thanatopsis, is at work in the Osprey nest. Rather, simply by staying still,  the nest mates’ protective coloration perfects their ability to stay camouflaged and go  undetected by predators. 

Eyes to the sky! 

Candace

Candace E. Cornell  

Friends of Salt Point  

Lansing, NY 

cec222@gmail.com 

Read!  

On Osprey Time (blog) 

Ospreys of Salt Point 

  

Explore! 

Cayuga Lake Osprey Trail  

  

Watch!  

Salt Point Osprey Nest Cam

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