does a bird egg gain any weight at all as it matures into a chick?

seems like a obvious no, however, when I was a child and raised pigeons, It seemed to me that the eggs got a little heavier as they got closer to hatching. they seemed to gain in mass weight.
I do realize that it is a closed system, I guess that is what interested me as a boy. I always meant to wieght an egg each day, but I was to busy chasing lizards and snakes etc.in the creeks.
thank you all for great input, special thanks to Maverick for a most detailed answer..

No.
Now let us look at the question deeply.

1)THE SHELL — When an egg is laid, it has an outer shell of calcium carbonate. This shell will NOT increase or decrease in its weight any time after it is formed till the chick is hatched and even after that.The shell only protects the egg and allows gaseous exchange and plays no other role.

2)THE YOLK & THE ALBUMEN — This part of the egg contains two important things viz. the fertilized nucleus and the reserve food for the growth of the embryo/chick.
The fertilized nucleus is embedded in the yellow yolk and can hardly be seen with the naked eye initially ;but as the embryo begins to grow ,this embryo can be seen with the naked eye with its beating heart and the web of blood vessels (but you have to break open the egg and then it is a waste.)

The raw material for the growth is drawn from the yolk(the yellow of the egg ) and the albumen ( the white of the egg. ), i.e. the reserve food is converted in to embryo and then the chick. There is no loss or gain of weight here.

Now comes the crux of the problem.

3)THE ENERGY OR THE FUEL FOR THE DEVELOPMENT — The energy required for this development also comes from the SAME reserve food material (Yolk & Albumen).
This conversion of food in to energy means LOSS in the weight.

Thus, if you weigh a newly laid egg and newly hatched chick with the tattered shell the egg will weigh more. (you can discount the weight of the shell from both the readings).

4)THE CONCLUSION — The chick does not gain any weight in fact it has less weight than the egg. It begins to gain weight only when it begins to feed on its own.
This is applicable for all the birds.

First Hatch

AUS-1932 Emperor Penguin – father staring down at egg as the chick makes its Photo Mugs AUS-1932 Emperor Penguin – father staring down at egg as the chick makes its first break in the shell Antarctica Aptenodytes forsteri Fred Olivier / Auscape / ardea Auscape Please note that prints are for personal display purposes only and may not be reproduced in any way. contact details prints ardea tel and 44 (0) 20 8672 2067 ….

Chicken – Hatching Photo Mugs PM-5565 Chicken – Hatching Pat Morris Please note that prints are for personal display purposes only and may not be reproduced in any way. contact details prints ardea tel 020 8672 2067….

Chicken chick – hatching from egg Photo Mugs LA-2612 Chicken chick – hatching from egg Jean Michel Labat Please note that prints are for personal display purposes only and may not be reproduced in any way. contact details prints ardea tel 020 8672 2067….

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