Black Oaks

California Black Oaks - Quercus kellogii

California Black Oaks are one of the many native, deciduous trees in our forests. Even though it has been an extremely dry year, the local oaks still changed color this Fall. Right now they are incredibly beautiful in their golden-yellow autumn foliage!   

Acorn crops vary greatly from year to year.  This year there is a bumper crop of acorns.  There are 1,000's of them on the ground!  Some scientists have actually estimated that in a high yield year, there can be as many as 250,000 acorns per acre!!!!  Bumper crops apparently occur, on average, 2 out of every 10 years.  Since so many critters eat acorns, scientist think that oaks may vary their acorn production levels to control critter populations.  If they had bumper crops of acorns every year the critters that eat them would also increase in population.  This population increase could potentially decrease the amount of new trees sprouting from uneaten acorns.

California Black Oak acorns - Quercus kellogii

When I cracked some acorns open, I was surprised to find that the shell was leathery and pliable, not dry and brittle!  The size of the nutmeat inside was impressive!  About a third of the acorns I opened were damaged.  It turns out that a variety of insects eat and live in acorns!  

While an acorn is still attached to a tree branch, an Acorn Weevil will drill a hole into it (center photo, below) and then lay an egg!  In about 2 weeks, the larva hatches from the egg and feasts on the nutmeat, until the acorn falls from the tree. Once the acorn lands on the forest floor, the larva emerges from the acorn and digs down about 12" into the ground.  The larva then lives underground for up to 5 years, before it pupates and emerges as an adult!

An Acorn Moth lays an egg near the hole an Acorn Weevil has made, but only after the weevil larva has left.  In a few days the Acorn Moth larva hatches and crawls into the acorn, via the hole the Acorn Weevil made!  The larva then builds a web across the hole to keep others out!  It remains in the acorn, eating the nutmeat, until the following spring when it pupates and emerges as an adult.

Lots of insects will live in emptied acorn shells, including ants, snails, wasp larva, and slugs.  These in turn can be eaten by predators, such a centipedes!  WOW!  What a complex little ecosystem an acorn can be!  

   

Canyon Live Oak acorns (uncut - left, cut open - right) - Quercus chrysolepsis

Center photos:

 acorn with weevil hole - interior filled with frass & partially eaten nutmeat

Band-tailed Pigeons - Mule Deer 
Columba fasciata - Odocoileus hemionus

Acorns are also eaten by a variety of birds and mammals. Mammals grind them up with their teeth, but birds use their gizzards! A gizzard is a muscular organ found in the lower stomach of many birds and reptiles, that grinds food, usually with the aid of ingested gravel or grit.  Mountain Quail, Steller's Jays, Band-tailed Pigeons, and some woodpeckers eat acorns.  Raccoons, Flying Squirrels, Black Bears, Deer, Gray Squirrels, and rodents also consume acorns.  Oak trees also provide housing and a place to forage for many more species. 

To quote Wikipedia:  "The California black oak is a critical species for wildlife. Oaks may be the single most important genus used by wildlife for food and cover in California forests.  Cavities in the trees provide den or nest sites for owls, various woodpeckers, tree squirrels, and American black bears.  It is a preferred foraging substrate for many birds.  The parasitic plant which commonly grows on this oak, Pacific mistletoe, produces berries which attract birds as well."  

 Mountain Quail - Western Gray Squirrel 

Oreortyx pictus - Sciurus griseus

Bedrock Mortars - Halls Ranch Trailhead - Tahoe NF

Acorns are also an important part of the past and present-day life of the Nisenan, the local Native Americans.  The Nisenan lived in this area for thousands of years. They hunted, fished, and gathered many plants and seeds.  Acorns were one of their main winter staples, which they pounded into flour using pestles and bedrock mortars.  The resulting acorn flour was made into cakes, breads, soups, and mush.  A typical Nisenan family would gather 500+ lbs of acorns, to get them through a winter!  You can see some of their mortar holes (photo above) at the Halls Ranch Trailhead on Hwy. 49.  The oak trees were also used for construction materials, dyes, and medicines.

 It is estimated that in the past the Nisenan tribe had a population of approximately 7,000 individuals.  In the 1800's, the settlers and government of California decimated this Native American population through rampant genocide and disease.  Today there are only 147 Nisenan in existance, but they have been actively bringing their culture back to life.  An excellent article on their past and recent history, accompanied with beautiful photographs, can be found at https://www.vice.com/en_us/article/vbyxnx/the-california-tribe-the-government-tried-to-erase-in-the-60s-456.

Northern Flicker (male - left, female - right) - Colaptes auratus  
Inset: possible hybrid

Woodpeckers!

Two weeks ago, I posted photos of two unidentified woodpeckers. I also posted the photos on inaturalist.org, hoping that someone would identify them. So far inaturalist.org commentors have identified the genera they are in, but not the species. 

The bird in the insert above is a type of Northern Flicker. The odd thing about it is that it has a red band on the back of its head, and red malars (facial stripes). Usually only the Yellow-shafted subspecies has a red band on the back of their head, but they have black malars. The Red-shafted subspecies, which is commonly seen in my neighborhood, has red malars but no red stripe on the back of their head. Although these two subspecies have been known to interbreed, one commentor on inaturalist.org thought that my neighborhood is too far south for Yellow-shafted Flickers! So it's still a mystery bird, but I'll keep you posted on further developments!

  Red-breasted Sapsucker - unknown Sapsucker

Syraphicus ruber - Syraphicus sp.(?)

The Red-breasted Sapsucker (above left) is the most common Sapsucker in my neighborhood.  The other Sapsucker on the right is harder to identify, because I wasn't able to get a full view of its head.  The initial obvious difference between them, is the lack of red on the head of the unknown species.  There are 4 possible Sapsuckers it could be, but two of them are extremely rare in my area.  Commentors on inaturalist.org have only identified it as in the Sapsucker genus, but not the species.  Hopefully, I'll see it again soon, and get a better photo. 

Black-necked Stilt - Northern Pintail - Greater White-fronted Geese  
Himantopus mexicanus - Anas acuta - Anser albifrons

California Wetlands!

I stopped by the Colusa NWR in my travels last week. I had never visited one of these refuges this early in the season, and was thrilled to see thousands of birds in the wetlands all squawking at once! White-fronted Geese were the dominant species. These geese migrate down to California's wetlands, from their arctic breeding-grounds, to spend the winter! These refuges are great places to see all kinds of migratory birds in winter. If you haven't visited one, I highly recommend that you do! Check out their website at https://www.fws.gov/refuge/Sacramento/. 

Here's some information from the Colusa NWR website: "Colusa NWR is just one of the 5 National Wildlife Refuges/3 Wildlife Management Areas that make up the Sacramento National Wildlife Refuge Complex. Colusa NWR was established in 1945 as a refuge and breeding ground for migratory birds and other wildlife and to reduce damage of agricultural crops caused by waterfowl. 

Flocks of shorebirds begin arriving in August and September as the water begins to flow back into the wetlands. Northern Pintails are the first ducks to arrive and signal the beginning of fall migration. White-fronted geese will follow. White geese begin to appear in October. Colusa NWR typically supports wintering populations of more than 200,000 ducks and over 75,000 geese. Many birds including nesting wood ducks and mammals can be seen year-round."

 White-faced Ibis - Plegadis chihi

 Shorebirds & Waterfowl - Colusa National Wildlife Refuge

  Cattle Egret - Great Egret

  Bubulcus ibis - Ardea alba

 What kind of "skipper" is this?

What kind of fungi is this?

Where are those lovely foxes?

Next week I'll talk about where the trout go when the river gets low and cold.

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

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Your questions and comments are greatly appreciated!

Please email me at northyubanaturalist@gmail.com