Why do chicken eggs have thinner shells in the summer

Why do chicken eggs have thinner shells in the summer  

Egg shells are made of calcium carbonate, CaCCE. The chicken ingeniously makes shells for its eggs by a process involving carbon dioxide dissolved in its blood, yielding carbonate ions which combine chemically with calcium ions. An equilibrium is soon established between these ions and solid chalk, according to 

Unfortunately, chickens have no sweat glands, so they cannot perspire. To dissipate any excess body heat during the warm summer months, they must pant just like a dog. Panting increases the amount of carbon dioxide exhaled, itself decreasing the concentration of CO2 in a chicken s blood. The smaller concentration [CO2 ] during the warm summer causes the reaction in Equation (4.60) to shift further toward the left-hand side than in the cooler winter, i.e. the amount of chalk formed decreases. The end result is a thinner eggshell. 

Chicken farmers solve the problem of thin shells by carbonating the chickens drinking water in the summer. We may never know what inspired the first farmer to follow this route, but any physical chemist could have solved this problem by first writing the equilibrium constant K for Equation (4.60)  

The value of ST(Sheii formation) will not change provided the temperature is fixed. Therefore, we see that if the concentration of carbonate ions (see the bottom line) falls then 

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