Strange bones #11: The buzzard skull that wasn't

On Tuesday me and Dad went on a walk in Suicides Graves wood. First of all we went down to the south-east corner where there is sometimes a herd of red deer, but although we saw lots of tracks, we didn't see any deer. Then we worked west through the wood, following red deer tracks and paths, and looking for bones.

We found a lot of bones, including something that was either a lamb or a red deer calf, but nothing worth bringing back. That was until we were at the edge of a clearing when dad spotted this at his feet. We searched around but couldn't find any other bones near it.

It was a strange bone but I thought I knew what it was straight away. It looked like the back part of a bird of prey skull .

It felt strange, though. It feels flimsy and not strong like bone usually is, but more like polystyrene.  The beak part is missing (it should be on the right in the above photo) and there is a hole in the skull at the top where the top of braincase looks like it was crushed in.

This is a close up of it. It looks like a flap has been pushed in. If it was alive when it happened, it would have been killed by it because it would have damaged a big part of the brain. But it could have also happened after death. You can see the honeycomb part of the bone in the bit that's broken.

So what is it ?

It was definitely a bird, and it is big. The bit I have is about 4cm long and 4.5cm wide, so the entire skull must be about 5cm to 8cm long. It seemed like it was a bird of prey.

At the time my first guess was that it must be a buzzard because of the size, and because buzzard skulls are the most common bird of prey about these woods. A buzzard skull is normally about 7cm long and about 4cm wide. Here is the back of the mystery skull (on the right) next to a buzzard skull.

They look similar but there are differences. Both braincases have a line going from front to back with two bumps rising from it on either side, but the mystery skull is smaller overall but the bumps are bigger. The bumps and grooves above the spine hole are bigger on the buzzard.

On the underneath, the spine hole is bigger on the buzzard (on the left)  and the triangle of bone in front of the spine hole is bigger on the mystery skull. The biggest difference is that the mystery skull has two bits of bone underneath the eye sockets that stick out to the side. The buzzard doesn't have those, so the mystery skull isn't a buzzard.

What is it if it's not a buzzard ?

When I realised it wasn't a buzzard then I thought it might be an owl. I have two owl skulls. One is a barn owl skull, and one is a short-eared owl. Here is the mystery skull on the right with the barn owl skull at top left and the short eared owl at bottom left:

It looked more like the owl skulls than the buzzard skull, but it looked different because the braincase looked much bigger. So then I started thinking that it maybe an owl, but one that I didn't have. I looked up owl skulls in my book "Tracks and Signs" and it said the usual sizes for owl skulls were:

• Eagle Owl: 95mm-108mm long
• Snowy Owl: 85mm-90mm
• Short-eared Owl: 55mm-59mm
• Long-eared Owl: 53mm-58mm
• Scops Owl 38mm-42mm
• Little Owl: 46mm-50mm
• Tawny Owl: 63mm-71mm
• Barn Owl: 65mm-68mm
• Ural owl: 75mm

I guessed that my mystery skull was between 6cm and 8cm long.It could be a juvenile, so it means the skull couldn't be anything smaller than that, which leaves.

• Eagle Owl: 95mm-108mm long
• Snowy Owl: 85mm-90mm
• Short-eared Owl: 55mm-59mm
• Long-eared Owl: 53mm-58mm
• Scops Owl 38mm-42mm
• Little Owl: 46mm-50mm
• Tawny Owl: 63mm-71mm
• Barn Owl: 65mm-68mm
• Ural owl: 75mm

Then I checked whether the owls live in Scotland. Eagle owls, snowy owls and ural owls are rare, so that left just Tawny Owls and Barn owls. This is it next to my barn owl skull:

I thought there were too many differences between them to be the same, so I looked up Tawny Owls at Skullsite.com, and it looked almost exactly the same ! So do you think I have got it right ?

I have never seen a tawny owl, but here is a picture of one from Wikipedia taken by K.-M. Hansche and licenced under a Creative Commons Attribution-Share Alike 2.5 Generic license.

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