Today’s comparative mini-post comes from a question I received from Trisha J. (thanks Trisha!), who asked for a bit of a comparison between rodent and bird bones. Now, while I have written about both rodents and birds before, I’ve never actually compared the two in one of these posts – which is a bit of a surprise, as I totally get the confusion between them! They can look pretty similar,
Before we start, let me first preface this by saying we’ll be looking specifically at small bird bones – obviously, as you can see in the photo below, birds come in a wide variety of shapes and sizes! So we will be working under the impression that it’s easier to confusion small bird bones with rodent bones…unless you’re working with Rodents of Unusual Size, I guess?
Unfortunately there isn’t an easy tip for differentiating between bird and rodent bones quickly – although bird bones are known for being particularly light in weight to allow for flight, rodent bones have a similar weight due to size. Thankfully, bone shapes are pretty distinct between the two. See some of the example photos below to see how each differ!
If you’re dealing with bone fragments that are similar in size to either a small bird or rodent, I would highly suggest using some form of reference (photo or physical) to base your identification off of. They can certainly be quite tricky! You can also use small variations, such as the presence of “nubs” on bird ulnae, to help differentiation. Also remember that birds have bones that are not present in rodents (tibio-tarsus, furncula, etc.), so memorising their general shape will be helpful.
With skulls, if you have complete specimens, it’ll be pretty easy – the bird will usually have a beak attached!
Of course, life isn’t fair and you will often have a skull fragment on your hands. In that case, remember that bird skulls, in particular the cranial vaults, have very rounded and bulbous skulls (see below).
And if you’re unlucky enough to have vertebrae and ribs on your hands…well, good luck! Well, maybe at least with the ribs…vertebrae can be very tricky, especially when they’re very small. However, bird vertebrae tend to have a “body” (the thickest part of the vertebra) that curves inward and are a bit more narrow in shape.
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Cohen, A. and Serjeantson, D. (1996) A Manual for the Identification of Bird Bones from Archaeological Sites. Archetype Publications Ltd.
Prehn, N. et al. (2018) Beginner’s Guide to Identifying British Mammal Bones. Natural History Museum. http://www.nhm.ac.uk/content/dam/nhmwww/take-part/identify-nature/british-mammal-bones-ID-guide.pdf