North Yuba Naturalist: The one that got away!

Rainbow Trout (fingerling) - Oncorhynchus mykiss irideus

I don't fish, but I went looking for them in the North Yuba River this week! I found a few "fingerlings" (above) in the shallow, slow waters along the river, as well as lots of "fry" (below). I also spotted a medium size fish in some shallow water but it spotted me too, and zipped right out of that area before I got a photo! Rats!

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.

It sounds like the most common fish in the North Yuba River are Coastal Rainbow Trout, which are native to California, but have been planted locally. There are also non-native German Brown Trout, that swim up to spawn from Bullard's Bar Reservoir. Occasionally you might also find a non-native Brook Trout that has flowed out from a higher elevation lake, during the high water of Spring.

Maybe all these fish will attract a River Otter to our local stretch of the North Yuba River! I'll keep my fingers crossed!

Rainbow Trout "Fry"- Oncorhynchus mykiss irideus

Signal Crayfish claws - Pacifastucus leniusculus

top side (left) & under side (right)

Crayfish or Crawdads?

I also found the claws of a Signal Crayfish in our river! Signal Crayfish are freshwater crustaceans, that are native to Washington, Oregon, and Idaho. They were introduced to California in 1912, and have spread throughout the state. I only noticed them in our river, about 4 years ago, at the beginning of the California drought. I don't see lots of them, but they are definitely residents. Large fish, raccoons, minks, river otters, and Great Blue Herons all eat adult crayfish. I don't know who got this one!

Crayfish mate in the Fall. After mating, each female lays 200 to 400 eggs, which she carries under her tail until they are ready to hatch the following Spring. The eggs hatch into juveniles and molt 3 times before they leave their mother! The main predators of crayfish eggs and young, are other crayfish and fish. They reach sexual maturity in 2-3 years, and can live as long as 20 years! As youths and adults, crayfish feed on animals and plants, living or deceased, and detritus. They are omnivores!

A Crayfish is the same thing as a Crawdad! They are also commonly called Mountain Lobsters, Freshwater Lobsters, Mudbugs, and Yabbies!

Water Strider Nymphs - Gerris sp.

Water Striders!

I also found 100's of these tiny, wildly spinning bugs on top of the water, in a side pocket of the river! I looked and looked through all my natural history books and couldn't figure out what they were! Looking on-line I found a website, www.whatsthatbug.com, and they had an "Ask Us" section! So I emailed them this photo (above) last night, and this morning they emailed me the answer! WOW, that was fast!

It turns out that they are the nymphs of Water Striders! Water Striders start out as eggs which 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!

Hummer Summer!

My neighbor is gone on vacation, and I'm keeping her bird feeders full of sugar-water, for all the local Hummingbirds. I'm not sure that I've identified them correctly, but most of them appear to be Anna's Hummingbirds. It has been a blast watching them! They are also feeding on flowers in our garden, especially the Bee Balm! I have really enjoyed photographing them! Check out the Hummer's feet in the photo below! Wow!

Anna's Hummingbird (female) - Calypte anna

Hummingbirds have the highest metabolism of any warm blooded organism! They have to eat a lot to stay alive, but they actually spend 75-80% of their day perching, and only 10-15% of their time eating! The wildflower nectar that they eat is 55% sucrose, 24% glucose, and 21% fructose! They also supplement their diet with insects, such as mosquitoes, gnats, aphids, and spiders! At night they go into a state of torpor, to conserve energy, which slows their metabolic rate to 1/15 of their normal rate! Torpor also causes their body temperature to drop from 40 degrees to 18 degrees, their heartbeat rate drops from over 1,000 beats per minute to 50-180 beats per minute, and their respiration rate (normally 250 breaths per minute) slows down as well! If you want to feed hummingbirds sugar water, use only white granulated sugar, diluted to 1 part sugar to 4 parts water. Food coloring is not needed to attract them, and can be harmful to hummingbirds!

Hummingbirds beat their wings at an amazing 50 beats per second! I used a slower shutter speed on my camera to create the "ghost" wings in the photo above. The wings move so fast, that at a slow shutter speed they disappear! During their courtship displays the male hummers ascend an incredible 35 meters, then they dive down and up past the female, going 27 meters per second! That's twice the speed of a Peregrine Falcon in pursuit of prey! Wow!! Hummingbirds also travel long distances during Fall and Spring migrations. Most migrate south from North America to Mexico, and Central America. One of our local hummers, the Rufous Hummingbird, travels an incredible 3,900 miles from Alaska to Mexico in late summer!

Above is a photo of a female Anna's Hummingbird in the sun (left) and in open shade (right). In the bright sun some of her feathers are shimmery and iridescent, but in the shade the same feathers look black and gray. This is because Hummingbird feathers get their color from some pigment in the feathers, as well as from structural coloration. There are prism-like cells within the top layers of feathers of the head, throat, breast, back, and wings. When sunlight hits these cells, it is split into wavelengths that reflect back to the viewer in varying degrees of intensity. By merely shifting position, some plainly colored Hummingbird feathers can instantly become flashy red/magenta or brilliant green! Amazing!!!!

Rock Creek!

Rock Creek is one of the two creeks that join together and flow behind our house. I hadn't been up there in years, because of all the poison oak, but decided to check it out this week. It was well worth the effort! It is an incredibly beautiful sculpted bedrock creek-bed, with lots of small waterfalls, and clear deep pools, lined with Indian Rhubarb plants! So lovely! We reached the waterfall (above) after hiking for about an hour, along with some easy climbing up a few bedrock walls! The water was ice cold but felt great in the heat! Unfortunately, we didn't have much time to really explore and look for wild critters, but came away filled with beauty! I'll have to go back up there again soon!