Still Impressive


Boyd Hill Nature Preserve, St. Petersburg, Florida September 2020

I was pleasantly surprised to encounter this Bald Eagle (Haliaeetus leucocephalus) last week. It was truly only a matter of time since there are over 1500 nesting pairs of them in Florida (the highest number outside of Alaska).

This eagle’s imposing presence explained why the south side of Lake Maggiore was so quiet that day – all the Ospreys were giving the area a wide berth!

After spending time in the Pacific Northwest (mostly recently on the Central Oregon Coast and years earlier, the Alaskan Coast) I can see that there is a sizable difference between the birds of these discrete locations. This biological phenomenon is known as Bergmann’s rule; members of a species increase in size when living further from the Equator.

Mainly observable in birds and mammals (and also a few plants), it is related to the surface area to volume ratio. In warmer climates, body heat needs to be released rapidly while in colder climates it behooves the animal to store the heat (perhaps counterintuitively, larger animals emit less body heat).

In this case, Florida Baldies average just over nine pounds, while in Alaska they top the scales at fifteen. No matter what the size, Bald Eagles are still majestic!

Unfortunately, it was not that impressed with me…

Categories: Nature Notes

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