Little Blue Penguin Skull sizes

After finding a few dead Blue penguins washed up on a beach and examining them, I have noticed that two of the skulls easily fit onto my index and middle finger’s, but the third was the size of my palm. I can confirm these were all LB penguins as there were other bird nerds in my group and all there were found with a full body. The two smaller skulled specimens had full blue adult plumage, and the bigger looked very brown (a light brown). We also think the bigger skulled one might be the white-flippered penguin subspecies if that is any help.

I am just a big curious as to why the skulls are such vastly different sizes for the same species.

Thanks.

Sexual dimorphism and age immediately comes to mind. And even if all three specimen were adults, an older adult can have some size on a young one. Both of those factors in conjunction can cause pretty decent size variation within a species, and being a different subspecies could help. I imagine the size difference between a younger female grizzly bear skull and older male kodiak bear skull would have a similarly impressive side by side size difference.

Granted, that’s a sweeping generalization. I don’t know much about penguins, if the little blues really aren’t sexually dimorphic and if the subspecies doesn’t run much bigger, I’m not sure age would make sense as the only factor to cause such variation.

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