226 November, 



SOME NOTES ON THE WEIGHT OF BIRDS' EGGS. 



BY W. H. WORKMAN. 



Reading, some time ago, in Miller Christy's book on Birdnest- 

 ing that it would be an interesting thing to have some record 

 of the weights of eggs of our British birds, I thought I would 

 make a start last season and get as many examples as possible 

 which, I am sorry to say, are very few. In all, I got ten 

 species. One living in town has very little chance of getting 

 any but the very common eggs ; but, next season, I may 

 get more, and other observers who have more time on their 

 hands might take the subject up. I used a pair of chemical 

 balances weighing down to J grain ; this, I should think, is 

 quite low enough for ordinary purposes. Of course much finer 

 and more expensive balances can be got. I have taken the 

 greatest care in weighing and measuring the eggs given below, 

 so as to make my statements as accurate as the means in my 

 power would admit. 



A great many people, in fact the majority by a long way, 

 have no idea of the weight of eggs at all, still fewer know 

 that there are great differences in the eggs of one clutch. 

 I have come on some with as much as 10 to 21 grains 

 difference in the one clutch, and, taking one nest with another, 

 the differences will be found much greater. I have only 

 come across one other paper on the weights of birds' eggs ; it 

 appeared in the Zoologist of this year. I give the length and 

 breadth after each egg, as, of course, it has a lot to do with 

 the weight, but not as much as one would expect, for, as 

 will be seen, some eggs with the same, or nearly the same 

 measurements, have very different weights. This may be due 

 to a difference in the thickness of the shell, or perhaps the 

 yolk in some cases may be heavier than in others, or the yolk 

 may be larger and the little air bubble less. Another question 

 arises here, which is the egg with the greatest weight ? the 

 one laid first or the one laid last ; one would naturally say the 

 first, but I have not been able this year to look into this 

 question. 



