Fish Eaters!

Osprey - Pandion haliaetus  

inset: Coastal Rainbow Trout - Oncorhynchus mykiss irideus

A wide variety of wildlife eats the fish in our river! The fish are preyed on during all stages of their life cycle, from eggs to adults. Their predators range from tiny dragonfly nymphs to large Black Bears! For some species of wildlife, fish make up more than 90% of their diet. For other species, fish are just one of their food sources. The most commonly seen fish in the North Yuba River are Coastal Rainbow Trout (inset above), which are native to California, but have been planted locally by the California Department of Fish & Wildlife. There are also non-native German Brown Trout, that swim up to spawn from Bullard's Bar Reservoir. Occasionally you might also see a non-native Brook Trout that has flowed out from a higher elevation lake, during the high water of Spring.

I spotted the Osprey above, eating a fish one morning this week! It was holding the fish with its left foot. Look closely and you'll see the fish tail! About 15 minutes later, I was about 1/4 mile down river and the Osprey flew overhead with another fish! Wow!!!  Ospreys catch fish by diving feet first into the water! The pads on the bottom of their feet are barbed for holding slippery fish. They are usually successful in 1 out of every 4 dives.  Fish make up 99% of their diet!  

Great Blue Heron - Ardea herodias

  These large Herons search for food day and night!  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.

Great Blue Heron - Ardea herodias

Just about every morning, I see this Great Blue Heron standing in the rapids, up-river from the bridge.  Last week, I watched it catch 2 fish in just 10 minutes!!!  In the pictures above you can see a fish in its beak on the left, then you can see its swollen gullet on the right!  It was amazing!!!

Green Heron (juvenile) - Butorides virescens

I spotted this juvenile Green Heron just yesterday morning on the edge of the river!  As soon as it saw me, it flew up into a tree.  I have never seen one of these birds ever before!  In fact, it is really unusual to see a Green Heron in our neighborhood.  They are usually found in foothill and coastal areas.  Their preferred habitat is a lake, pond, marsh, or stream, that is shaded by riparian trees.  However, they are known to pass through the Sierra during their southward migration.  These herons are much smaller than Great Blue Herons, that can be up to 4' tall.  Green Herons only measure 16.5"-18" in body length, and have short legs.  They eat small fish, crustaceans, insects, frogs, and rarely small mammals.  They hunt for prey day and night!  They wade into shallow water and wait patiently for prey to pass by.  They will also dive for prey from a perch, head first, and become totally submerged!!!  I was so excited to see this unusual and uncommon, 

beautiful bird in our neighborhood!  I hope I see it again soon!

Belted Kingfisher (male) - Megaceryle alcyon

Another fish-eating bird in our neighborhood is the Belted Kingfisher.  These beautiful birds dive from perches into shallow water for small fish, tadpoles, and crayfish.  In the morning, I hear their loud rattling call along our river corridor.  They are one of my absolutely favorite birds!  Such beauty!

Common Mergansers -  Mergus merganser

Common Mergansers are diving ducks that feed on mollusks, aquatic insects, crayfish, worms, frogs, small mammals, other birds, plants and fish!  They mainly eat fish in the winter, when aquatic insects, frogs, worms, and crustaceans are less active. The mergansers on our river molted their flight feathers all at once about a month ago. Flight feathers are the long, stiff feathers in their wings and tail.  The feathers  have since grown back and now they can fly again! 

River Otters -  Lontra canadensis

90% of a River Otter's diet is fish!  They can eat 2-3 lbs of fish daily!  They will also eat frogs, newts, garter snakes, ducks when molting, aquatic insects, and turtles!  I took this photo a few weeks ago from our bridge, when these two Otters swam by!  I haven't seen them since then, but hope I will soon!

  

Aquatic Garter Snake - Thamnophis couchii     Dragonfly Nymph - Odonata sp.

Aquatic Garter Snakes primarily live in the river.  They eat small fish, toads, frogs, tadpoles and fish eggs!  Dragonfly Nymphs live in slow-moving parts of the river, where they are predacious on small fish and aquatic insects!

Fish Eaters Summary: 

With all these critters eating fish it's a wonder that there are any left in the river!  It's also amazing that the "fish eaters" can survive in the wild!  The competition must be fierce out there!

Sunflower head and seeds - Lesser Goldfinch - Carduelis psaltria

Seed Eaters!

Okay, so I tried to figured out how many seeds a Lesser Goldfinch might eat in a day.  My research was based on the information that birds eat 1/2 to 1/4 of their weight daily, and that a Lesser Goldfinch weighs about .33 oz.  I pried the sunflower seeds from the dried flower heads (It's not as easy as you would think!) and found out that 37.5 seeds add up to .01 oz. in weight.  However, the seeds I weighed were still in their hulls.  The actual weight of JUST the seeds is probably at least half that weight.  So I assumed that it would take 75 seeds to add up to .01 oz of weight.  So, if a Lesser Goldfinch ate 1/4 of its weight (.0825 oz) in a day, it would need to eat approximately 619 seeds.  If a Lesser Goldfinch ate 1/2 of its weight (.165 oz) in a day it would need to eat approximately 1,238 seeds!!!  WOW!  That is a lot of seed hulling!  It also explains why they appear to eat continuously during the daylight hours!  This is just an estimate, but it was fun to figure out!  

Fruit Eaters!

Lately the Black Bears have been feasting on the apples, grapes, and plums that grow in our neighborhood.  Every morning, there's fresh bear scat on our road.  We've been careful to keep our garbage inside, and out of the reach of bears.  I haven't seen them in person, but I don't go looking for them at night either!  Maybe I'll get lucky and see them one of these mornings!

  Who is this?

Where are the foxes?

I'll explain what American Dippers and Great Blue Herons have in common next week!

That circular, yellow-green mystery I posted last week 

was crustose lichen on a rock!

Those skeletonized leaves that I posted last week, were in a California Tent Moth colonial web.  I'll explain more next week! 

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

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