What Eats This?

There's a tall Fremont cottonwood tree (Populus fremontii) planted at the Plum Pond on the Dipper Ranch. After hiking all the way down there, it's nice to sit next to the pond and relax while watching the dragonflies flit across the pond surface in sync with the fluttering cottonwood leaves. Trees in the Populus family (including the quaking aspen) have long flattened stems and wide blades which cause them to move in the slightest breeze.

In September, I noticed many of the fallen cottonwood leaves had a bulge at the base of the leaf blade. I've frequently planted and hiked among several species of cottonwood trees and never noticed this before. On closer inspection, I found that all the swollen bumps had a small slit on the side. I realized they were probably galls.

Galls are abnormalities in plant tissues caused by some other organism, often an insect. The insect chemically or mechanically stimulates the plant tissue to produce extra plant hormones which in turn greatly increase plant growth in a localized area (like cancer) and this results in a new structure - the gall. Guess what happens inside the gall. The insect either moves into or lays eggs in this new structure. Thus, the insect has caused the plant to create a bug birthing chamber or bug condominium. Certain aphids do this to cottonwood and poplar leaf stems. Ah-hah.

But there's more. The Poplar Petiole Gall Aphid (Pemphigus populitransversus) bears live young inside the cottonwood gall, that turn into winged females who leave the cottonwood to give birth to more female aphids that eat mustard plants. See the naturebyte video at the end of this posting for a fascinating and gross video of the fat, warty mom aphid swarmed by her winged offspring, all sucking inside the gall. The lady mustard version of the family flies back to the cottonwoods in the fall and has a generation of both female and male aphids who lay eggs in the cottonwood twigs or bark since cottonwoods are deciduous and drop their leaves in the fall. In the spring, the leaf buds break, the aphid eggs hatch, the little aphid nymphs chew on the new cottonwood leaf stems causing the galls to form and the whole thing starts over again. Whew.


But there's still more. Today I saw a small bird busily picking gall-laden leaves in the cottonwood tree at the Plum Pond and I saw and heard it peck at each leaf and then drop them. The bird was greyish and seemed to have a small crest. It was getting dark, and as always, I was nervous about the approach of mountain-lion hours, so I couldn't stay for long, but I think it was an oak titmouse (Parus inornatus - photo by Gary Kramer, US Fish & Wildlife Service). A quick internet search finds many research studies on poplar gall aphids, types of poplars infested by them, birds who eat the aphids, and why they occur, where, at what numbers, or not.

This planted cottonwood tree is the only one at the pond or anywhere nearby. Still, the aphids find it, go through their complicated life cycle and the birds find the galls with the aphids. Next time I'm relaxing at the Plum Pond, I will try not to be unnerved by the busy and complicated natural world above me or maybe I will sit under the sycamore tree instead.

See:
Insect and Mite Galls, Univ of Minnesota Extension Service
Backyard Nature with Jim Conrad
Gross & Fascinating Aphid Video by Henry Shenkman
Field Guide to Plant Galls of California and Other Western States, Ron Russo, University of California Press, 2006.

Winter is Green and Orange

A few weeks ago, the first big rains finally started in coastal California. With rain, the grass sprouts, the hills turn green and the newts start marching to their breeding ponds. On November 11, I pulled a yellow-eyed ensatina (Ensatina eschscholtzii xanthoptica) from the springbox, a little fellow, shiny orange jewel. Notice the skin on this bright salamander is smooth and there are narrow lines running up his sides and across his back. They live mostly in the damp woods among leaves and logs.
As I was releasing the ensatina at the closest pond, we stumbled upon a coast range newt (Taricha torosa torosa) plodding along in the same direction. He looked like a brute next to the ensatina. Later I learned that while coast range newts breed in ponds, ensatinas lay their eggs and brood them in moist logs or burrows until they hatch fully formed. So I guess this ensatina just had to turn around to find another moist spot.

The male coast range newts head to the ponds first. This one is a male as shown by his swollen vent. Once he spends time in the water, his skin will get smooth and his fat tail will flatten to an effective swimming blade. This coast range newt subspecies of the California newt species is detected by the way the eyes extend beyond the outline of the head as seen from above and the yellow coloring of the skin under the eye. All subspecies of the California newt are poisonous and sometimes secret the neurotoxin through their skin, so either don't pick them up or wash your hands before you lick your fingers.

More info and photos of these salamanders later as the rains pick up and the newts get busy. I spent quite a bit of time with newt eggs and aquatic larvae over the past year. Ever try to feed a bunch of baby newts?

Part IV - Cracking the Nuts

I spend winter evenings cracking walnuts while I watch movies. Then I seal the kernels in vacuum-packed pouches and store them in the freezer or give them away for holiday presents.

This is my cracking technique. Line up the nutcracker perpendicular to the slit in the shell. Grasp the free ends of the walnut firmly in your other fist (even tighter than shown in the photo) and gently apply pressure with the nutcracker just until you feel the slit widen and hear the first crack. Roll the walnut 180 degrees and reposition the nutcracker diagonally across the top and bottom of the shell. Slowly apply pressure again until you hear another crack. Usually by this point there are enough cracks in the shell that you can pull one hemisphere off and then firmly pluck the nutmeat out of the remaining cup of the shell. Either pull out the papery packing tissue between the kernel halves or use your fingers to split the nutmeat in half and flick off the packing tissue which should be brown and stiff if the walnut is ripe.

I challenge myself to crack the walnut shell so the kernel comes out whole. Then the nutmeat looks like a brain with its wrinkled double hemispheres. Indeed, in the 16th and 17th centuries, herbalists encouraged the eating of walnuts to boost one's intelligence and heal other ailments of the head and heart. Modern-day research has found that walnuts are loaded with omega-3 fatty acids and have multiple health benefits (www.walnuts.org).

Other animals frequently harvesting both acorns and walnuts on the Dipper Ranch are deer, Stellar jays, scrub jays and ravens. If I sleep late on these brilliant autumn days, the Stellar jays get me up by rapping shells on the roof to peck a hole through to the nutmeat. On the other end of the day, the deer gather in the willow thicket below the barn at dusk, waiting for their chance at the walnut-strewn yard. Since the deer rutting season and acorn drop occur at the same season, careful driving is required this time of year as the deer recklessly cross roads at night to socialize under their favorite oak trees. The deer look ridiculous eating acorns. To eat these big nuts, they must open their mouths so wide, they lose all their daintiness.

Everywhere I go these days, I carry bagfuls of walnuts and give them away. The birds are carting off acorns overhead to family and hiding places. It's amazing these trees can produce so much food in their own little packages.

One final amazing fact about acorns - you can make a loud whistle with an acorn cap.

Part III - Harvesting & Hoarding

Every few days between Halloween and Thanksgiving, I scoop up any brown shells from the ground under the walnut trees and toss any fallen nuts still encased in hulls against the red barn to let the outer coating weather itself off. That way, I avoid staining my hands black from the phenol chemicals in the hulls. Some people use walnut hulls for making black or brown dye.

I wonder if the chemical in the walnut hulls also reduces the number of predators willing to chew through to the nut. Squirrels seem to be immune. Although English walnuts are not native to the North American continent (they originate from southwest Asia and are sometimes more correctly called Persian walnuts), our local wildlife collect them from yards and orchards. Squirrels are famous for stripping my friends' urban walnut trees. I am fortunate that the farmyard is surrounded by a broad band of grassland which the native western grey squirrels are not willing to cross from the hillside forests. There are, however, rodents that apparently collect walnuts at night because throughout the winter I find emptied shells in the barn with small holes chewed through the end.

Most nuts for human consumption need to dry for days to weeks before they are eaten. Last winter, I dried my walnut crop in the garage in open cardboard boxes covered with metal wire refrigerator shelves. Eventually, however, rodents raided the stash and the garage floor was strewn with broken shells. At first I couldn't figure out how the mice got the fat shells out of the boxes which were still sturdily covered with the wire shelves. Then I decided extra skinny mice had been assigned the mission to slip through the wires, crack the nuts inside the box and toss the pieces through the bars to their hungry families waiting outside.

This year, I am pouring the collected walnuts onto an old screen door suspended between picnic tables under the maple trees. I clamp a set of window screens on top to discourage raiders. So far it is working, although at first, I expected to hear crashing noises from the clever raccoons unscrewing the clamps some night. The raccoons (who ate my entire pear and persimmon crops this year) haven't shown up, so maybe their smirky mouths and sneaky hands aren't strong enough to crack open walnut shells. I hear the great-horned owl every night now, and sometimes a pair of screech owls, so they must be keeping the skinny mice away.

Every few days, I turn the walnuts to ensure thorough drying. It's a meditative process rolling the walnuts and lining them all on their long sides so the top screen will clamp down firmly. The other day while I was rolling walnuts, the local flock of acorn woodpeckers landed in the maple trees above me, chattering about their day of acorn harvesting. It reminded me about their special techniques for storing and drying acorns in a pecker-made granary.

Acorn woodpeckers work in extended family groups to harvest acorns and store them in their own granaries - tree trunks, power poles and fence posts that they have riddled with long rows of holes. They check the granary every day and since the acorns slightly shrink as they dry, the woodpeckers will move any loose acorns into tighter holes to prevent other animals from robbing their stash. I haven't found the acorn woodpeckers' cache on the Dipper Ranch, however, every morning they visit the maple trees by the house and conduct a short shouting match with the earlier arriving Stellar jays, so the yard must be somewhere between their nighttime roosts and granary trees. (Painting of acorn woodpecker above by Bob Hines, United States Fish and Wildlife Service)

Ninety-nine percent of the US supply and two-thirds of the world supply of English walnuts are produced from extensive orchards in the Central Valley of California (www.walnuts.org). Commercial harvest of walnuts is largely mechanized. First the orchard floor is rolled or dragged clean, then the walnuts are knocked loose from the trees by large shaking machines, and finally the fallen walnuts are blown into a row and swept up my mechanical harvesters.

I'm glad I get the chance to pick up the walnuts by hand. They make a lovely sound when they plunk into the bucket and many of my friends and family while talking to me on the cell phone in the fall, exclaim, "I hear walnuts. Will you save me some?"

For a hilarious description of the hippy lifestyle of California's acorn woodpeckers, see the Bird Watcher's General Store.

Part II - The Nut Leaves Home

By late summer, plump green hulls hang heavily in the walnut canopy. As the hulls slowly split, they reveal promising peeks of brown shells. By early fall, the hulls release their cargo and brown shells plop to the ground. On windy days, some nuts may drop still encased in their hulls.

In our area, the general order that acorns ripen in the fall is valley oak, black oak, tanoak, coast live oak, and then canyon oak. The acorns of species in the white oak group take 6 months to ripen (pollinated in spring, full acorn formed in subsequent fall), whereas acorns of the black oak group take 18 months to grow and ripen. On branches of the black oaks, you will find first-year acorns looking like shingled buttons, and second-year acorns fully formed. The first crop of acorns dropped is usually the damaged acorns, ones with weevils or mold or otherwise underdeveloped. They are still good eating for wildlife, but if you are collecting acorns to grow oaks, wait a few weeks for the second drop when the healthy, heavy acorns are finally released from their caps and fall and roll to their future destination.

Part I - A Sum of Nut Parts

English walnuts have 3 layers: the outer fleshy hull, the hard woody shell, and the inner eatable kernel. If you have just seen walnuts in holiday baskets, you wouldn't know about the thick, green hull that has to peel open to release the brown-shelled nut. As an extra layer, the hull discourages early consumption of the nut from some bugs and other potential consumers.

The acorn seed is enclosed in a leathery, bullet-shaped casing that emerges from a shingled cap. Each oak species has an acorn cap with a slightly different design, their own signature beanie or architectural roofline. The cap depth can vary from shallow to deep and the shape of the shingles covering the cap can be distinctly flat or warty depending on the species of oak.

Both the walnut hull and the acorn cap derive from bracts originally enclosing the flower buds. These plant parts modify their function through the reproductive stages, first protecting the developing flower (and perhaps controlling the timing of wind pollination in a way that may increase the genetic diversity or food quality of the seed crop) and then protecting the fertilized seed as it swells with food transported from the mother tree and stored in the developing nut - future nourishment once the nut breaks away and starts its separate life or becomes a menu item.

THE WALNUT AND THE ACORN

- A Serialized Story about Big Nuts -

My friends and I are collecting English walnuts in our farmyards while the local wildlife is harvesting acorns on the surrounding hillsides. In this autumn series, I'll compare these two large-sized nuts and their consumers.