Blog # 324 An Egg is Patience

Changing of the guards as Ophelia takes off for exercise. 

It’s will happen this week. Faint peeps from within the egg will be the first sign hatching is about to begin. These peeps are the embryo’s way of communicating with its sibling embryos and its parents, from inside the egg. These faint “care–soliciting” peeps prompt the adults to turn the eggs more often, build up the nest sides, and spend more time incubating.  

Osprey eggs require 32–45 days of judicious incubation, keeping the eggs at 98–99 ºF  with frequent rolling to insure the embryos develop normally. Ophelia’s first egg was laid  on April 18, making today Day 32. Ophelia’s eggs usually hatch beginning on Day 37,  which is this Saturday, May 29, and will most likely occur in the early dawn before the  nest camera turns on.  

What trigger tells the embryo to start the hatching process? As hatching approaches,  the embryo is so large that it nearly fills the entire egg and starts to retract the residual  yolk into its body cavity. Until this point, the embryo had been respiring using the chorio allantoic membrane (CAM), diffusing O2 in and CO2 out through the eggshell and the  CAM illustrated below. However, the embryo’s oxygen demand increases along with its  growth and activity while oxygen supplies from the CAM run short. 

Cross section of a bird egg showing the CAM and air pocket, courtesy of Brainly, Inc.  

The shortage of oxygen triggers the embryo to start lung respiration. The embryo  instinctively puts its head under its right wing with the beak pointing toward the  membrane separating the egg contents from the air pocket. A few days before hatching,  the embryo pierces the inner membrane and starts lung ventilation in the air pocket.  This is called internal pipping. Even though the first lung respiration has started, the  CAM remains important for respiration for a few more days.  

About 12 hours after it pierces the inner membrane, the embryo starts tapping the  eggshell repeatedly with its egg tooth, a sharp, white, chisel-like temporary structure on  the top of the beak. Repeatedly tapping the same spot in the eggshell eventually causes the shell to weaken and break. This is called external pipping.  

Pipping is exhausting. The “pipping muscle,” a neck muscle used to make this specific  movement, bulges by the time the embryo has hatched. From the outside, a small star shaped crack or hole in the eggshell appears 2–3 days before hatch day, sometimes  with the point of a beak sticking out. After external pipping, the embryo takes a rest.  

The embryo has one last challenge ahead: breaking free of the eggshell, which can take  another 12 hours after external pipping to hatch. The parents typically watch as the  embryo cuts the blunt end of the eggshell with its egg tooth, turning inside the egg,  while using its wing for direction and legs to apply force. Once a near circle is cut, the  

embryo tries to push itself out of the egg stretching its legs. This causes the last bit of  the shell cap to break loose, allowing the embryo to push itself free. New hatchlings are  wet, tired, and vulnerable. Hours after hatching their down feathers dry, and they 

become fluffy. After they’ve recovered from the hatching process they become more  active.  

Hatchling resting, courtesy of Landings. The pointed white egg tooth can be seen on the top of its bill. 

The parents will watch as the exhausted hatchling struggles to remove itself from the  confines of the egg shell and dry off in the air. The newborns are semi-altricial (semi 

Ophelia stretching her wings after rolling the eggs.

helpless) at birth and unable to thermo-regulate their body temperature. (That is  because precocial species are completely developed when they hatch whereas the  altricial birds have more developing to complete.) The hatchlings are capable of limited  motion, have their eyes open, and are covered with down at birth. However, they are  able to beg for food in a matter of hours and instinctually know to defecate over the side  of the nest and may try to do so on Day One. 

You can tell from the mother’s behavior when an egg has hatched. From the moment  the first egg hatches, Ophelia will no longer leave the nest to eat. She’ll stay with her  precious brood and will not leave for several weeks. You will also see the parents  staring at the inside of their nest as if they were admiring something. 

Eyes to the sky! 

Candace  

Candace E. Cornell  

Friends of Salt Point  

Cayuga Osprey Network 

Lansing, NY  

cec222@gmail.com 

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. 

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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