The kiwi’s egg

My colleagues incredulously rejected the notion that the chicken-sized kiwi lays eggs six times the size of a chicken egg. Well, it wasn’t just a fancy, it really is the case. A couple of days before the egg is laid, it assumes so gigantic proportions that it fills the female’s whole body cavity, forcing the bird to fast. It’s a huge burden for the kiwi, while developing the egg, it needs to eat three times as much as usual. The kiwi has the largest egg-to-body ratio (1:5) among all birds.
kiwi with egg

I wonder what adaptive advantage this bird gains by producing such a monster egg. I think the answer lies in the lack of natural predators. No native mammals exist in New Zealand (except for bats) that could prey on them, which is the primary reason for the loss of most of the birds’ ability to fly (think of the kakapo or the takahe, all flightless) on the island. The energy necessary to fly is turned over to producing enormous eggs. Not incidentally, the lack of predation allows for the birds to have very low reproduction rates, raising only one chick per season. As a matter of course, the whole agenda is turned upside down by the introduction of invasive species like rats, pigs and feral cats, wreaking havoc in the bird nests and effectively reducing the population size of these wonderful, but hapless birds.

An X-ray image:
Kiwi egg


  1. trialofash said,

    July 30, 2009 at 15:30

    This is really interesting!

  2. March 20, 2010 at 04:09

    […] kiwi: are, dintre pasari, cel mai mare ou comparativ cu corpul. Merita vazute imaginile de aici: E cit o gaina, dar oul e cit 6 oua de gaina. Restul e un fel de gradina ornitologica de calitate, […]

  3. Kiwi Lovr said,

    April 9, 2010 at 05:15

    Kiwis rule i wish i was a kiwi then i would come out of a monster egg and eat trees and live in tree hollows and play with the fairies.!

  4. Kiwi Lovr said,

    April 9, 2010 at 05:17

    iii snort

  5. adria garriga said,

    January 19, 2012 at 20:02


  6. Eugene said,

    June 22, 2013 at 16:27

    Great article. I am facing many of these issues as well.

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  8. June 29, 2013 at 13:50

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  9. June 25, 2014 at 09:16

    […]  Also, the Kiwi bird has the largest egg-to-body size ratio (1:5) among all birds.  Look at this:  (I got this x-ray photo off the […]

  10. September 3, 2017 at 21:28

    I really like looking through an article that will make people think.

    Also, many thanks for permitting me to comment!

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