North Yuba River - 8/23/23
This week I finally spent a day on the North Yuba River that runs through our neighborhood. It's been a while since I had the time to linger on the river. It is such a beautiful river, clear glass-green in color, running over miles and miles of water-sculpted bedrock and river rocks, bordered by willows, grasses, and giant-leaved Indian Rhubarb, surrounded by conifer covered ridges, and filled with wildlife of all types!
For several years there has been a dead tree trunk in the river, down-river from the bridge. In the high water of last winter it got washed downriver and ended up on top of this big bedrock boulder! I've seen Canada Geese on this rock, as well as Spotted Sandpipers, and Black Phoebes. River Otters are occasionally present here, as the water is deep and trout are sometimes abundant. Almost daily in the summer, Common Mergansers swim by with their ducklings. Kingfishers and Ospreys often fly overhead. It is just one of the many magical spots on the North Yuba River and it has been our swimming hole for 30+ years! We affectionately call it "Big Rock"!
Cooper's Hawk - Accipiter cooperii
River Birds
On the morning of my day on the river, I was astounded to see a Cooper's Hawk land on the dead tree trunk perched on Big Rock! WOW! It actually stayed on the log for 20 seconds, looking all around before it took off! I've never seen one on the river before. Cooper's Hawks are uncommon and mainly live in dense forests, but can also be found in open fields. Their main food is other large birds such as doves, pigeons and robins. They will also prey on squirrels, rabbits, mice and reptiles.
Cooper's Hawk - Accipiter cooperii
They can readily pursue prey through dense thickets or forests. Their short wings and rudder-like tail makes them able to make quick, sharp turns. They grab prey with their feet, and will drown or squeeze them to death! They can see 2-3 times farther than humans! It's a rare event that a Cooper's Hawk doesn't catch its prey, unless a tree intervenes! Almost one fourth of the museum specimen Cooper's Hawks that have been examined, have breastbones that have healed fractures! These hawks are uncommonly seen in our area, although they live here year-round. How lucky to see this beautiful raptor on the river!
Osprey - Pandion haliateus
Lately there has been an Osprey on the river. I love looking for it every day. They are such handsome birds!
Their are many classifications (or subgroups) of raptors, such as accipiters, buteos, falcons, eagles, harriers, kites, ospreys, and owls. Ospreys are the only bird in their classification! They are unique among raptors in their hunting method of diving feet-first into water to capture fish. They are usually successful in 1 out of every 4 dives. No other raptors use this method of hunting. They also have small barbs on the pads of their feet to help grab slippery fish. After they have caught a fish and are back in the air, they maneuver the fish to face forward, using the fish’s streamlining to reduce aerodynamic drag. They then carry the captured fish to an elevated and prominent perch to be eaten. 99% of their diet is fish. They are large birds with a wingspan of 63", a length of 23", and a weight of 3.5lbs!!!
Common Merganser female & duckling - Mergus merganser
There's a nearby creek that feeds into the North Yuba. It's usually cooler than the river, but there's a great swimming hole where they join. I often go down in the late afternoon to jump in! Right now it's a little chilly for me, about 58°, so I've been wading along the shore instead of swimming. To my delight I spotted a Common Merganser family near the shaded mouth of the creek! I quickly hid in the willows and waited to see if they would come out into the river.
Common Merganser female & ducklings - Mergus merganser
Within a few minutes, they came out of the creek and sped off downriver! How fun! The average brood size of the Common Merganser is 9-12, but they have been known to have as many as 17 ducklings! This spring was probably a tough time to raise ducklings, with the river being fast, high, and cold. So the survival rate of ducklings was probably low, or maybe the females didn't lay as many eggs. For quite a while I thought that they weren't going to have any ducklings, so I'm happy to see this trio of ducklings with their mom!
Within 1-2 days after the ducklings leave their nest, they are capable of swimming, diving, and feeding on their own! The mom will stay with them for approximately 2 months, warding off predators such as minks, otters, foxes, and herons! In the Fall, they will migrate to southern California or Arizona for the winter.
One of our year-round river residents, the Belted Kingfisher, is always a joy to see. This once perched nearby and spent some time watching me! Like the Osprey, Kingfishers mainly eat fish, usually small ones in the shallow water. They will also eat crayfish and tadpoles.
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Great Blue Heron (adult) - Ardea herodius
Another year-round resident, the Great Blue Heron flew over as I lingered on the river. These large Herons search for food day and night! They are 46" in length, with a wingspan of 72"!!! In addition to fish, they eat crayfish, frogs, aquatic insects, amphibians, small mammals, and other birds! They are usually solitary except during breeding season. They are the only species of Heron seen above the foothills.
Willows and airborne seeds - Salix sp.
Along the river shore are thickets of willows. Right now the last of their fluffy seeds are being blown off the bushes and into the air. One bush probably produces a million seeds annually! Just lovely to watch!
Dragonfly Wing
Dragonflies!
At this time of year, there are also hundreds of dragonflies flying above the river! At the end of the day they glint and flash in the sun, as they pursue and capture insect prey. I can watch them for hours!
Dragonflies are in the order "Odonata", which means "toothed ones"! Their sharply serrated mandibles earned them this name! They will catch an insect in the air, tear off its wings with their mandibles, and eat the prey while still flying! Dragonflies can move each of their wings independently and can fly in any direction, including sideways and backwards. They can also hover in one spot for a minute or more! Some dragonflies can fly fast, up to 18 mph!
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Autumn Meadowhawk - Flame Skimmer
Sympetrum vicinum - Libellula saturata
Most of the dragonflies above the river look coppery, red, or green in color.
Here are my guesses as to what they are!
Common Green Darner - Anax junius
Dragonfly eyes are huge, and have 30,000 facets and near 360 degree vision! They also see in color, usually up to 4x more colors than humans see!
Rain Bejeweled Dragonfly Wing
Rainbow Trout (fry) - Oncorhynchus mykiss irideus
Tiny River Critters
I don't fish, but I went looking for them in the North Yuba River this week! I found lots of tiny "fry" in the shallows, but no big trout.
Fish start as eggs which hatch into larvae. The larvae are not able to feed themselves, and carry a yolk-sac in their bellies which provides their nutrition. At this stage they are called "alevins". When they have developed to the point where they can feed themselves (mainly zooplankton), the fish are called "fry". When they develop scales and working fins they are called "fingerlings". This juvenile fingerling stage lasts until the fish is fully grown, sexually mature, and interacting with other adult fish.
Water Strider Nymphs - Adult Water Strider - Gerris sp.
I also found 100's of these tiny, wildly gyrating bugs on top of the water in a side pocket of the river! They are the nymphs of Water Striders which start out as eggs that hatch into nymphs. The nymphs have 5 instars (periods of growth) between molts. In about 60 to 70 days the nymphs become adults. As adults they prey on spiders and insects that land on the water, as well as nymphs of their own species! Birds are the main predators of the adults. To avoid predation the adults can fly away or dive under water!
Water Striders are known for their curious ability to "walk-on-water"! They are able to do this for a variety of reasons. They use the natural surface tension of water, along with a water-repellent body covered in LOTS of fine hairs (up to several thousand hairs per mm), as well as long thin legs that distribute their body weight over a large area. The round shadows they cast, from the tips of their legs, are caused by the dimples their feet create on the surface of the water!
Scarlet Monkeyflower - Blazing Star
Mimulus cardinalis - Mentzelia laevicaulis
Wildflowers
These beautiful wildflowers are blooming right now among the dry river rocks. There aren't a lot of them, just a few clusters scattered here and there. Such beauty!
Dark storm clouds last Week
Stormy Weather!
We had stormy weather a week ago, with a total rainfall of .50"!! Yay! This brings our water-year total to 83.53"!!! Yahoo! It poured off and on for days! A real SOAKER, just when we needed it. The forest was getting crispy! Additionally, this week the temperatures have lowered into the 80's and the nights are in the 50's, such a wonderful change in the weather! I hope the rainstorms keep coming, and keep the fire danger down.
One evening we decided to drive up to the Lakes Basin to see the clouds and rain and sunset skies. It was gorgeous! I'm not often up there at that time and it was such a delight! On our way home we came upon this incredible rainbow, that lasted for a few glorious minutes! Such amazing beauty!
On another rainy afternoon in our neighborhood, this beautiful pastel rainbow appeared! WOW!!!
Who's scat is that?
What's happening in the Lakes Basin?
Check back next week for the answers to these questions and more!
Your questions and comments are greatly appreciated!
Please email me at northyubanaturalist@gmail.com
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