Friday mystery object #179 answer

On Friday I gave you this really tricky mystery object to identify:


Despite it being one of the hardest so far, Barbara Powell managed to not only work out what piece of morphology this specimen represents, but the species it came from. Remarkable skills Barbara!

These plates of bone fit together to make a ring like this:


You probably have a better chance of identifying the structure when it’s assembled like this and the tubular shape is characteristic of a particular order of birds. This is the sclerotic ring of an owl, more specifically a Eurasian Eagle Owl Bubo bubo (Linnaeus, 1758).

Eurasian Eagle Owl (Bubo bubo), Poland by Kamil

More on sclerotic rings in this 1938 paper by Curtis and Miller [pdf]. When the ring is in situ it  supports the eyeball and in the case of owls it forms a tube that holds the eye in place:



This means that owls are unable to move their eyes independently of their head – fixing their gaze straight ahead. This is part of the reason why owls are able to rotate their heads to such a degree, as without the extreme rotation their field of view would be very limited. It is also the reason why owls exhibit remarkable head stability, since their eyes can’t adjust for changes in body position, as shown in this rather odd video:

Owls are awesome!

6 thoughts on “Friday mystery object #179 answer

    • I have to admit that owls are a special area of interest, ( it was analysing barn owl pellets that got me hooked on collecting bones) and I see at least one eagle owl most days as my neighbour keeps a breeding pair.)

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