It is winter here now, with about five inches ( 127 mm) of snow on the ground, with wind chills around zero F ( -18C). Pretty typical for a Wisconsin winter.
Plenty of activity around our bird feeders, especially the juncos hopping around on the ground. Since retirement, I spend a bit more time just watching and trying to grok the natural world around me.
The thought that keeps coming to mind as I watch from my warm home is how amazing it is that these little balls of fluff can survive and thrive in the cold, with so little food easily accessible. They enjoy the bird feeder, but do just fine without it. Their existence proves that their ancestors for millions of years managed without birdseed from the hardware store.
The same applies of course, to the other creatures that stay active all winter, but to me these little guys epitomize the ability to find a way to survive in marginal conditions. Heat loss is a function of the ratio between volume and surface area, so small birds are playing a tough hand in that respect.
The world, and the universe itself, for that matter, is a big old entropy generating engine, and we are all busy doing our part, consciously or not. I imagine there is some soil bacteria species that will find sustenance even in the tiniest spec of junco poop.
I'm no paleontologist, but my mental image of evolution goes like this:
The planet has many different energy flows happening continuously, with sunlight being the main one driving living systems, once plants figured out how to photosynthesize. Boy, wasn't that a great leap forward.
Then, as plants multiplied and got to crowding each other, evolutionary forces kicked into overdrive, with some plants growing taller to grab the sunlight first, or others changed other features to get enough energy to reproduce.
Before you know it, the tropics were packed, and some plants figured out how to withstand freezing by going dormant each winter or changing their internal chemistry. Thus plants crept toward the poles, covering more and more of the land. ( hmm, wonder what might have happened without our 23 deg. tilt?)
Insect and animal life came along over time, and they all figured out a way to harvest energy and reproduce as well. All along the way, more and more subdivided niches were filled, as one species or another found an energy flow to exploit.
And then Homo Sapiens came along. Our unique assemble of traits mean we are a generalist that can exploit many energy flows. Even fossilized carbon from millions of years ago. Oh, we'll finish extracting all that energy soon, and the food web will adjust accordingly.
The thing to keep in mind, with all these energy flows, is that each species finds a balance between population levels and the energy flow they are a part of. At the geological scale, our use of fossil carbon is a one time brief blip, and our numbers will readjust to the available energy, as the food web hopefully restabilizes in a complex, diverse new balance.
I'm thinking juncos will still be part of it.