Blog #262 Three Precious Packages

Changing of the guard, Ophelia about to incubate her three eggs. Snapshot from the  Salt Point Osprey Cam. 

At first there was just one egg with chocolate, cinnamon, and rust blotches along with  some swirls. The second was much lighter mahogany spots and cinnamon flecks on a  creamy background. The third egg, laid around 7 am. on April 20, was a mix of the other  two, with a russet glow, making all three eggs highly distinguishable.  

The coloring of Osprey eggs, and birds eggs in general, is an interesting topic. Egg  patterns—the distinctive, fantastical blotches, swirls, streaks, speckles, flecks, and  spots—are created by protoporphyrin pigments absorbed by the porous eggshell during  its passage through the female’s oviduct and are as individual as a human fingerprint. 

Closeup of Ophelia’s three eggs. 

No two Osprey eggs are alike and each female produces her own shell patterns, which are distinguishable by the breeding pair. Within each brood there is some similarity  between the eggshell patterns, but each is one unique. The random coloration of  Osprey eggs imparts protective camouflage, making them difficult to see from above by  flying predators, as the eggs blend into the background patterns of twigs, grasses, and  urban detritus in the nest. 

Assorted Osprey eggs illustrating the variation in the eggs, courtesy of Flicker.

Ophelia has laid three eggs this year as she has every year she has nested, although  she may be capable of laying a fourth. The number of eggs in a brood is determined by  a number of factors. Too many eggs could stress a female, leaving her too weak to  survive the winter, whereas too few eggs risks losing the brood to accidents and egg  failures. The number of eggs is dictated by the amount of food the father can supply. Where the environment will support larger populations, parents adjust their brood’s size.  The brood size is ultimately limited by the size of the Osprey’s brood patch, which  transfers the adult’s body heat directly to warm the eggs. Feeding a fourth chick would  require up to an hour of additional fishing each day by the already busy father. The only  nest in this area that has produced four offspring is proximate to the fish-filled Cornell  Research ponds. 

A female Osprey with her naked abdominal brood patch exposed, courtesy of Flicker. 

Egg shells in themselves are a source of wonder, delicate yet tough, and able to  perform amazing balancing acts. Egg shells must be strong enough to withstand the  weight of an incubating adult yet not too thick to prevent the hatchling from breaking  free of its confines. Harmful pesticides and other chemicals in the environment work  against this process, thinning eggshells and causing breakage and egg loss. 

Watch the action live on the Salt Point Osprey Nest Cam.  

Eyes to the sky! 

Candace

Candace E. Cornell 

Friends of Salt Point 

Lansing, NY 

cec22@cornell.edu 

Errata: The Guest photographer for Blog # 261 was Cassandra Rooney-Monger.

Read!  

On Osprey Time 

Ospreys of Salt Point 

Explore! 

Cayuga Lake Osprey Trail 

  

Watch!  

Salt Point Osprey Nest Cam


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