February on the North Yuba River

North Yuba River 2/20/20

The North Yuba River is a beautiful clear glass-green in the winter. It's gorgeous! The water clarity is amazing! Most of the winter the river water is quite cold, about 42 degrees! Despite the cold, there are animals that live in and on the river in winter, including River Otters, American Minks (which I haven't seen in years), Waterfowl, Herons, Dippers, trout, crayfish, and aquatic insects. Each one has a specific way in which they deal with the frigid water.

(Use the "search this blog" bar, on the top right of this page, for more information from past blogs about these species.)

 

Common Goldeneye (male) - Bucephala clangula

River Birds

In California, Common Goldeneyes are the only ducks that regularly spend the winter on rivers and lakes above the foothills of the western Sierra. They, like most waterfowl, have several ways to survive the cold of winter, including dense layers of insulating feathers, counter-current blood flow to reduce heat loss through their feet and legs, behavioral modifications to reduce exposure to the elements, and the ability to carry large fat reserves.

Common Goldeneyes underwater - Bucephala clangula

They are diving ducks and eat fish, aquatic vertebrates, seeds, and tubers. When diving, they keep their wings pressed to their sides underwater, and swim with their webbed feet! 

Common Goldeneye (females) - Bucephala clangula

This species can fly up to 40 mph, and the wind "whistles" through their wing feathers! They will spend the rest of the winter here. In the spring they will leave for their northern breeding grounds in prairie-pothole regions of Alaska and Canada.

Great Blue Heron - Ardea herodius

There is one Great Blue Heron that lives here year-round. You'd think it would be hard for a Heron to stand in the cold river for any length of time.  However, birds' feet don't get frostbit or even close to freezing because there's not much fluid in the cells of their feet. Their feet are mainly made up of tendons and bones, and don't have much muscle or nerve tissue. Also, the two blood vessels that carry the blood from the bird's body to its feet and back, are right next to each other. The cooled blood returning to the bird's body, is warmed by the body-warmed blood going to the feet! Also, their circulation is so fast, that the blood doesn't stay in their feet long enough to freeze! Wow!!

American Dipper (adult) - Cinclus mexicanus

There are a few American Dippers that live here year-round. They are absolutely amazing birds! They dive underwater and swim with their wings to find aquatic insects and larvae to eat! They, like all birds, have an extra lens (nictitating membrane) over their eyes that works like goggles underwater. This lens is hinged at the inner side of the eye and sweeps horizontally across the cornea. They also have special muscles that close their nostrils underwater!

American Dipper Underwater (adult) - Cinclus mexicanus

American Dippers are the only aquatic songbird in North America! Lately I've been hearing them sing some amazingly varied songs! It turns out that fall, early winter, and early spring are when they sing the most. They are quiet in spring and summer when raising their offspring. They have enlarged oil glands, which contain oil for waterproofing their feathers. They also have a thick coat of downy feathers, below their outer feathers, that keeps them warm in cold water. 

 

Northern River Otter - Lontra canadensis

River Otters

One morning this week I spotted a Northern River Otter in the river!  It was catching fish and eating them while I watched!  At one point it swam to shore with a medium sized fish, got out of the river and proceeded to eat the fish!!!  I've since read that they eat small fish in the river, and large fish are brought to shore.  In the river they raise their heads vertically and chomp away at their catch. Makes me wonder if they're treading water with their legs while they're eating in the river, or if they're just floating!  I watched this Otter for a good 15 minutes before my fingers froze and I had to leave!  

Northern River Otter - Lontra canadensis

Northern River Otters are not commonly seen in our river, because there are not a lot of them. They need a lot of food daily, and consequently need a large area in which to hunt. If food is scarce a female otter may travel 19 miles in one day, and a male may travel 37-56 miles! Usually they only travel 1.5-3 miles in a day. 

Northern River Otter - Lontra canadensis

90% of an Otter's diet is fish, but not just trout. They will also eat sucker fish if they are available. Most of the local, native sucker fish have been depleted by the otters.  In addition to fish, River Otters will eat garter snakes, clams, mussels, turtles, crayfish, molting ducks, frogs, aquatic insects, and newts.

Northern River Otter - Lontra canadensis

River Otters are "at home" underwater. Their ears and nose are closed when they are submerged. They can swim at 6-8 mph, and can hold their breath for 8 minutes! They can dive to a depth of 68 feet, and can swim the length of a football field without surfacing! They have a layer of fat and a thick undercoat to keep themselves warm in cold water.  Their outer fur is waterproofed by oil applied from their oil glands, and their underfur is very dense, averaging 373,000 hairs per square inch!  WOW!

Northern River Otters are active year-round, and are most active at night, dawn, and dusk. Typically they become much more nocturnal in the spring, summer, and fall seasons, and more diurnal during winter. At night their whiskers help them detect prey! They are large, strong animals weighing 11-31lbs. They range in length from 35"-51", with their tails an additional 12"-20"! How lucky I was to watch these uncommon, amazing animals in their home!

Northern River Otter - Lontra canadensis

The following afternoon my husband and I were out walking when we spotted an Otter in the same pool as the day before!  It too was hunting and chomping up fish in the river!  It was probably the same Otter!  At one point it swam to shore and climbed up on land, but it didn't have a fish!  This time it rubbed and scrubbed its back on the mossy rocks!  You could sense the pleasure the otter was experiencing through his exquisite body language!

Northern River Otter - Lontra canadensis

Luckily I was able to make a short movie of him scratching his back on the rocks!  I apologize for the amateur quality of the movie (hard to handhold the camera steady), but it's fun to see!  I never saw this behavior before!  What JOY!  Wikipiedia states that Otters "dry themselves and uphold the insulative quality of their fur by frequent rubbing and rolling on grass, bare ground, and logs."

Northern River Otter scat and tracks - Lontra canadensis

I've frequently come across Otter poop and tracks along the river's edge.  The poop seems to be mainly composed of crayfish exoskeletons.  I don't know why there aren't a lot of fish bones in the poop as well.  Perhaps crayfish are more readily available.

Signal Crayfish - Coastal Rainbow Trout

Pacifasticus leniusculus - Onchorhyncus mykiss irideus

Being coldblooded, trout, crayfish, and aquatic insects become less active when the water temperature drops below 40 degrees. Their metabolism and respiratory rates slow down. Adult trout usually stay in deep, slow moving pools during fall and winter, while Crayfish sequester themselves in underwater burrows.  These burrows are a series of interconnecting tunnels that can be two meters deep!  Aquatic insects also become inactive and shelter under rocks.  All these river dwellers eat less and move around less in winter. 

As water temps continue to decline, trout are less likely to expend precious energy chasing down prey, so small fish become a less frequent item on the menu. In Winter, small fish usually stay away from adults, and retreat into areas of shallow water with overhanging shrubbery.  Aquatic insects will make up most of a trout's diet as they sit stationary in the current and wait for bugs to drift by, providing an easy meal.  Midge larvae are probably the most important aquatic insect for trout during the winter.

American Mink - Neovision vision

American Mink

It's been several years since I've seen an American Mink in the river. Nevertheless, they do inhabit the river so I thought I should mention them. I photographed this female with her three offspring back in July of 2019. American Minks aren't seen that often because they are mainly nocturnal, and are especially active at dawn and dusk. They are called "aquatic weasels" because they can pursue prey underwater. They eat muskrats, crayfish, frogs, ducks, waterfowl, and fish, in rivers, streams, ponds, and lakes. They can swim a distance of 100' underwater, and can dive to a depth of 15'!!! They also hunt on land and eat shrews, mice, and rabbits. They are much smaller than Northern River Otters, weighing 1.5 to 4lbs, and approximately 2' in length, including a 12" tail.

Common Raven Couple - Corvus corax

Happy Valentine's Day!

Some birds mate for life such as Bald Eagles, Ospreys, Red-tailed Hawks, Tundra Swans, Sandhill Cranes, Snow Geese, Canada Geese, Barn Owls, Pileated Woodpeckers, and probably Common Ravens! Most birds only mate for one season or a few more. Many birds have several mates in one season. There is monogamy (one mate in a season, eg. Goldfinches and most songbirds), polyandry (when a female has more than one mate in a season, eg. Spotted Sandpipers), and polygyny (when a male has more than one mate in a season, eg. Hummingbirds).

The birds that tend to mate for life are large birds. Some scientist think that this is because large birds tend to have large territories to defend and it's better to not waste time on finding a new mate every year. Scientists don't think "love" is an issue with birds, rather it's all about procreating and survival of the species. However, we non-scientific humans tend to see "caring" between birds and their mates. Are we projecting our emotions on wildlife? Probably! However, when I watched two Ravens allopreen each other it really seemed so gentle and loving to me! I remember a story Loren Eisley wrote, called the "Star Thrower", in which he realized "caring" of offspring was quite possibly an additional reason for wildlife survival, not just its genetics. Who knows for sure? In the meantime, I am absolutely amazed that a Sandhill Crane can live up to 35 years in the wild, travel hundreds of miles annually in migration, and stay with the same mate the whole time! WOW!!!

Storm Clouds

Damp Earth Art

We had unseasonably warm days into the 70's this week along with intermittent wind!  It was very disconcerting.  The lack of rain is increasingly worrisome.  There's a 40% chance of rain this coming Monday night!  My fingers are crossed that this may open the "storm door" and more storms will come.  Please join me in my continuing hope for precipitation!  Perhaps our collective efforts may help it happen.  I'm going to keep posting rain inspired writings, art, etc. on my blog at dampearthart.blogspot.com.  Any submissions would be greatly appreciated.

What's happening up at Yuba Pass?

Is anything blooming?

Check back next week for the answers to these questions and more.

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