Avian Dinosaurs: Bald Eagles at the Sacramento National Wildlife Refuge

Sometimes I am reminded that the dinosaurs never actually went extinct. They were decimated certainly, and their present-day species don't look all that much like their ancient ancestors, but there are occasional clues to their dinosaurian past. The claws of a Bald Eagle (Haliaeetus leucocephalus), for instance. We were at the Sacramento National Wildlife Refuge just before Christmas, and saw several of birds at close quarters.

How close are the birds to the dinosaurs? Dinosaurs are classed as reptiles, but the reptiles we know today, the lizards, snakes, turtles, and crocodiles, were separate evolutionary lines in the Permian and early Triassic, before the dinosaurs even arose. The crocodilians are the closest of these ancient relatives, but they were already on their own evolutionary path during the Jurassic and Cretaceous periods when the dinosaurs were dominating the terrestrial habitats of the planet.

The birds on the other hand developed from the dinosaurs, descending from small theropod carnivores similar to the Velociraptor or Deinonychus, monsters made famous in the Jurassic Park movies. Evidence has emerged in recent decades that many dinosaurs may have in fact sported feathers (which are modified scales). Many bird embryos support teeth that are later resorbed during development.

In any case, that's what I was thinking about as we came across at least three Bald Eagles while traveling the auto tour route at the Sacramento Refuge. There were a couple of immature individuals and one adult. They were accustomed to automobiles passing by so they didn't retreat as we passed by, enabling me to get a zoomed view of their claws.

One juvenile was still hanging out with mom, while the other was on its own. They were a sight to see in the rain (that's why they all looked a little scruffy; they were generally soaked).

Bird of the Day: Sandhill Cranes at the Merced Unit

Sandhill Cranes (Grus canadensis) were my bird of the day only a few weeks ago, but these extraordinary birds will no doubt show up often on these pages. They are intriguing residents at the Merced Unit of the San Luis National Wildlife Refuge. There will be 20,000 of them here in a few weeks, and thousands have already arrived.

The Great Valley for the most part little resembles the valley that existed here prior to agricultural development, but the ancestral environment is being reconstructed in a few places to provide and maintain wintering grounds for the rich variety of migratory birds who come here each year. The Merced Unit is a marvelous introduction to the birds with a five mile long auto loop providing excellent access. We'll be visiting often through the winter and coming spring, so expect more updates!

I'm going to keep trying to get some quality shots of the Sandhill Cranes. They keep their distance from the road and trails and are fairly skittish when tall humans like me are around (no, I don't go chasing them; these shots are from the viewing areas or from the inside of the car). All of today's shots are at an extreme zoom (60x), so they continue to be a bit fuzzy.

The cranes are an ancient line of birds, with a fossil record extending back at least fifty million years. Thirteen species are known today, with seven others that have gone extinct. The Sandhill has features that suggest that it most closely resembles the ancestors to all the cranes. There are six distinct subspecies, including the Lesser Sandhill Crane, which was the type we were seeing yesterday at the Merced Unit.

Birds are generally recognized as a subset of the dinosaurs, the only group of dinosaurs that survived the great extinction event of 65 million years ago. Many of the dinosaurs even supported feathers (but they didn't fly; the flying pterosaurs were not closely related to dinosaurs or birds).

I look at these avian dinosaurs in the meadows of the Merced Unit and can't help imagining their much larger forebears. We've come to understand that dinosaurs traveled in large herds or flocks, and that they cared for their young the way present day birds do. I'm just glad there aren't Velociraptors and Tyrannosaurs running around after them!

In the waning hours of the day, more and more of the cranes were taking flight and disappearing somewhere. I didn't give a whole lot of thought about where they were headed, but as we drove up the road we heard a lot of noise coming from the other side of the Cottonwood wind break. We stopped and looked over to see a truly stunning sight, thousands upon thousands of Sandhill Cranes grazing in a large field.

This is not the finest video I've ever taken, so I suggest keeping it small so you won't get dizzy. The mechanical noise is coming from a groundwater pump we needed to stand behind. It shows the full extent of the flock of grazing cranes at the Merced Unit. It is an astounding sight, especially for those of us (me) who took our Great Valley for granted while exploring other flashier places. This is one of those places that can be called America's Serengeti...