Largest egg in comparison to body size [birds]

dillotest0

dillotest0

Well-Known Member
5+ year member
It is enshrined in popular knowledge at this point that kiwis lay the largest egg of any bird in comparison to their body size.
The Northern Brown Kiwi, which weighs in the region of 2700 grammes; and the egg weighs about 450 grammes.
So this is in the region of 17%.
A great spotted kiwi weighs in the region of 2000 grammes; and if the egg weighs the same then it's 22.5% weight of the bird.
So not quite the clean and dry quarter as often stated... which is an exceptional case.
So whatever the number is, it's still a damn large egg.
But then...
The Xantus' Murrelet* weighs about 160 grammes; the egg about 37 grammes.
This is about 23%, and if rounded up then it becomes 25%.
The Storm Petrel weighs about 25 grammes; and the egg about 6.8 grammes. This is even greater than a quarter at 27%.
So now I do wonder which bird it truly is that is best suited to this title... even if kiwi can be said to be the terrestrial bird whose egg weight is largest compared to body weight.

I do realise the irony here.

*Scripps and Guadalupe Murrelets - numbers are smiliar
 
dillotest0 said:
I do realise the irony here.
Click to expand...
What is the irony?

dillotest0 said:
The Northern Brown Kiwi, which weighs in the region of 2700 grammes; and the egg weighs about 450 grammes.
So this is in the region of 17%.
A great spotted kiwi weighs in the region of 2000 grammes; and if the egg weighs the same then it's 22.5% weight of the bird.
Click to expand...
Kiwi eggs are generally around 15-20% of female body weight. Where are you getting your figures for body weights from?

Kiwi vary a lot in weight, depending especially on time of year (a winter bird is much heavier than a summer bird), and a bird carrying an egg is obviously much heavier than one which isn't, and mountain birds are heavier than lowland birds. Female birds are also much larger than males, so averaging weights is going to give skewed results for egg-to-bird ratio if containing both sexes in the total. However, your "in the region of 2000 grammes" for a Great Spotted Kiwi is really low.

HANZAB has average weights for female Great Spotted Kiwi as 3270g (of seven individuals) and 2418g from 12 individuals (one emaciated individual weighed just 389.3g which skewed the average).

For female North Island Brown Kiwi averages given are 2490g (21 individuals), 2535g (26 Individuals), and 2711g (9 individuals), although again some emaciated birds skewed the averages and weights differ depending on time of year; the heaviest female in the studies weighed 3850g

For female South Island Brown Kiwi 2725g (four individuals, including an underweight bird) - heaviest female of the four was 3433g.

For female Stewart Island Brown Kiwi there is an average of 3115g (ten individuals) - the heaviest bird weighed 3500g.

The kiwi which lays the largest egg relative to body weight is the Little Spotted Kiwi, which has an average female weight of 1351g (41 females outside the breeding season) and an egg weight of about 300g (i.e. about 22%).
 
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