[00:00:00] Griff Griffith: Growing up my grandma was my best friend. We even made up our own religion called the Church of whatever and Oak Trees. We were the only two members. The Valley Oak was our symbol. We even had a sacred book that only existed in our heads, but it was called the Gospel of the Oak as an 8-year-old. My most sacred place was on a wooden palette that was lodged in the branches of an ancient valley oak.

My grandma couldn't climb this tree, and anyone else who tried was pummeled with acorn grenades and or oak gall bombs.

 We chose the oak as our religion symbol, not just because they're beautiful trees, but also because my grandma told me that our ancestors only survived Ireland's potato famine because they ate acorn mush up until the moment they stepped on the boat that brought them to America.

Grandma assured me that the more time I spent among the oaks, the more mysteries I would discover. And she was right first time I found an acorn Woodpecker's Grainery, I thought that someone had [00:01:00] shot that dead tree with a machine gun that used acorns as bullets. But it wasn't long before I noticed Acorn Woodpeckers standing guard over them even fitting the seeds into place.

I called the old snag woodpecker's kitchen and gave the birds plenty of space.

Years later, as a Nature Conservancy restoration intern. Part of my job was to collect acorns for our restoration site . . My boss said we were lucky 'cause the oaks along the Sacramento River were masting that year. I nodded. Like I understood, but I really didn't. It was the first time I remember hearing that word, but once I was crawling around in the grass and Finding tons of acorns to drop into the bucket . I figured out what Masting meant. It wasn't just one oak tree producing a monster amount of acorns that year. It was all the trees in the area.

If each acorn were a quarter ,, I would've been a millionaire.

It took little time to fill 10 buckets and I never felt like I was stealing wildlife's food. There were more than enough acorns for all of us.

These [00:02:00] synchronized boom years or masting events are a fluke of nature, a manifestation of weather.

Or a carefully derived strategy among oaks. Wherever the evidence takes you, you will immediately see that the benefits to the oaks is obvious, overwhelm the scene, with numbers, and some acorns are bound to sprout.

In the gospel of the oak chapter 10, verse 15, it says, an oak or a grandson that tries to mast every year wears itself out. Learn when to store your energy and when to share it.

That's how you last long enough to shade others.

Today's episode is part of a playful experiment in community podcasting.

Six different shows are each producing their own stories about, or inspired by the mystery of masting and releasing these episodes at approximately the same time. It's a critical mast of podcast, if you will.

so be sure to check out Future Ecologies, Golden State Naturalist, Outside/ In and Learning from Nature, [00:03:00] the Biomimicry Podcast for their releases. And you can hear the full interviews with our guest today on the Nature's Archive Podcast. And by the end of this episode you will be a master about masting. Get it? Okay. Sorry. Let's jump in.

 I'm Griff Griffith, and welcome to Jumpstart Nature. 

 Quick heads up. Our founder and producer Michael Hawk is the one who facilitated these original interviews. So to give you the most cohesive story today, Michael's going to personally guide us through the clips. Take it away, Michael.

[00:03:47] Michael Hawk: Do you remember childhood encounters with acorns? They're Robust and polished, like a classic artist carving with cute caps that can hardly be ignored and from the acorn grows a tree sometimes immense, sometimes [00:04:00] living hundreds of years. Other oaks might only grow a few feet tall when considering the 90 species of oaks native to the United States and the 500 worldwide.

I could rattle off superlatives all day long. But some of the most important facts about oaks are harder to see. Life on earth nearly always begins with sunlight, and somehow the sunlight's energy has to be converted to calories for plants and animals. Of course, that begins with photosynthesis.

When ecologists look at ecosystems, they estimate that about 10% of the energy produced by plants gets passed along to herbivores the plant eating animals.

[00:04:38] Doug Tallamy: The 10% is a general estimate that has been challenged for about 50 years, . Um, it could be somewhere around there

[00:04:46] Michael Hawk: You might recognize that voice. It's Dr. Doug Tallamy, author of The Nature of Oaks.

[00:04:52] Doug Tallamy: but yeah, I, I would say definitely the oaks are punching above their, their weight class. You know, it's about how much of the energy [00:05:00] from the sun you are willing to share with other organisms.

Oaks share a lot.

there are other plants, even other native plants that share very little, like ferns, for example, ancient, ancient plants. But they, they're really good at protecting themselves.

They, they grab that energy and they don't share it. So, uh, if you're trying to support a food web in your local ecosystem, you're not gonna do it with ferns. You are gonna do it with, with oaks

[00:05:24] Michael Hawk: I know one big area of focus is their larval food plants for, a great variety of insects. 

[00:05:31] Doug Tallamy: Right. And that is, that's really, uh, one of the primary reasons, , I got interested in oaks. It's not just insects, it turns out it's caterpillars. Um, caterpillars transfer more energy from plants to other organisms than any other type of plant eater.

So if you don't have a lot of caterpillars in your ecosystem, you, you essentially have a failed food web.

Why do we need so many caterpillars? Well, let's just focus on birds. It takes thousands and thousands of caterpillars to make one clutch of breeding bird. You know, we, we got a lot of data for chickadee, but there's data on a [00:06:00] number of other things.

6,000 to 9,000 caterpillars to get one clutch of a bird that's a third of an ounce through to independence, actually just to, to fledging. And then the parents continue to feed them caterpillars another 21 days. So you're talking about tens of thousands of caterpillars required to make a nest of chickadees.

nationwide Oaks support more than 950 species of caterpillars

[00:06:22] Michael Hawk: The impact of caterpillars is undeniable, but one of my favorite things about oaks are growths called galls. Sometimes tiny and cryptic. Other times, boastfully large and colorful.

They can sometimes adorn an oak tree by the thousands. Now, just a few seconds ago, I called them growths. But that simple characterization really shortchanges what they are.

[00:06:43] Doug Tallamy: People have likened galls to cancerous growths on plants, but I don't like that analogy because cancers grow.

I mean, tumors just keep growing in an uncontrolled way

[00:06:55] Michael Hawk: It all starts with a tiny wasp. In fact, it's a special group of wasps who rather than [00:07:00] sting have unique ovipositors. Think of it like an egg laying tool. These wasps seem to emerge at just the right time when the oak tree has buds at just the right stage or when a leaf is at the perfect stage.

[00:07:14] Doug Tallamy: the female wasp injects into the buds of the. The ma thematic tissue. The bud of an oak is like, like stem cells. You can make it into anything you want.

And they inject, hormones in different ways that create the shape and the size of this species specific gall. So it's, it's highly defined. You can identify what species of wasp it was that made the gall just by the shape of the gall.

[00:07:38] Michael Hawk: Yes, the wasp through some sort of chemical alchemy developed through eons of evolutionary experimentation, instructs the tree to grow a very specific growth inside of which the wasp larva set up shop in their new home. They have protection and free food courtesy of the tree. And the galls, depending on the species, [00:08:00] can look like strawberries, tiny red volcanoes, little convoluted brains or large apples, just to name a few of the shapes and sizes.

While oaks haven't covered the gall real estate market, there are other trees that do this as well, and other plants for that matter, they are some of the most prolific gall supporters and where there are defenseless larva, there are sure to be predators of all shapes and sizes as well.

I've even seen woodpeckers probing inside of Galls looking for a treat. Maybe a bit like nature's gumball machine, but when we think of woodpeckers and oak trees, one species stands out.

That's the sound of an acorn woodpecker, a gregarious bird found in the southwest and western United States. And in fact, all the way through Mexico and down into Colombia.

[00:08:53] Dr. Walt Koenig: they are quite vocal They make a lot of fun noises that make them very conspicuous,

acorn [00:09:00] woodpeckers are typically described as being clown faced. They do have a clownish type of visage, if you will

[00:09:09] Michael Hawk: Dr. Walter Koenig is perhaps the world's leading expert on acorn woodpeckers.

I 

[00:09:13] Dr. Walt Koenig: they have these tongues, that go all the way around their heads so that they can stick them out, strikingly long distances. Back when I used to have a bird that I could show people, I would pull out his tongue and, it would go an amazing distance given that,

 as birds, they aren't that big.but they use that. They have a little barbs at the end. Uh, most woodpeckers, which are wood boring and are pecking into wood, looking at wood, trying to find wood boring insects will use that to pull out those insects

 Acorn woodpeckers are what we call cooperative breeders. Cooperative breeding is, not terribly unusual, but pretty interesting social behavior [00:10:00] found in maybe 10 percent of bird species, but it's quite uncommon in North America.

[00:10:06] Michael Hawk: Part of the reason why acorn woodpeckers love oak trees is because old mature oaks often have lots of holes, perhaps where branches fell off or maybe where other woodpeckers excavated.

[00:10:17] Dr. Walt Koenig: Acorn woodpeckers are cavity nesters, and they also roost together in cavities throughout the year.

They are communal roosters. They live in family groups, and In some cases, the entire group will roost together in the same nest cavity, though sometimes they'll split among more than one roost cavities on their territory.

[00:10:39] Michael Hawk: and surprisingly,

[00:10:40] Dr. Walt Koenig: Acorn woodpeckers are largely fly catchers, so they're spending a lot of time fly catching up in the air.

They also leaf glean and bark glean in particular. One of the old names for them was ant woodpecker, and in fact they eat a lot of ants, which are often on the trees, living up in [00:11:00] the trees around here.

[00:11:01] Michael Hawk: oaks in their habitats support lots of insects. So it makes sense. But their name, Acorn Woodpecker came about from a much more obvious reason. Yes, they do eat acorns too.

In fact, acorns are their foundational food, perhaps like rice and wheat are for people.

[00:11:18] Dr. Walt Koenig: Acorn woodpeckers are tied to acorns and oaks, and part of it is that they have developed a striking habit of drilling individual holes in, 

[00:11:30] Michael Hawk: And was that a pun by the way, a striking 

[00:11:33] Dr. Walt Koenig: I mean, well, yeah, okay, I'll accept it. A striking habit of drilling these These individual holes in the dead tissue of trees. Uh, and other structures. They, of course, are well known for doing this in buildings and, and people's houses Telephone

poles. so they'll drill these individual holes that they'll then harvest acorns in the fall as they're [00:12:00] maturing and put them in these little holes. Now, the point of that. as I said, is that it has to be in the dead tissue of a tree. So it's always in dead limbs or the bark. It has to be in a species of tree that has relatively thick bark where they aren't piercing into the living tissue of the tree, because they, the whole point is that they're doing this in the late fall, early winter, when around here in California, uh, that's when it starts getting wet and cold and rainy. And the whole point is to allow these acorns to dry out and to not rot and mold during the winter

[00:12:42] Michael Hawk: Now when you think of woodpeckers, of course you imagine them drilling holes, but surprisingly,

[00:12:47] Dr. Walt Koenig: They aren't really good at drilling holes, cavities, but they, they do it. And so they'll drill a few dozen hundred of these a year, and they'll just keep doing it. They'll reuse these [00:13:00] these holes over and over again during the winter and each year when the acorn crop matures. And so if they happen to have a nice. tree, that is going to be around for a while, they can end up with a, granary, as we call them, that has tens of thousands of holes. These big granaries, , which end up being kind of famous because they can be pretty striking,are not all that common because These birds are trying to drill these holes as fast as they can, just to make up for holes that are being lost for one reason or another, because often the limbs are falling during the winter, the tree is falling apart, You know, they have to work pretty hard to maintain a granary that's going to have a thousand, a couple thousand holes, and allow them to last through the winter and the spring.

[00:13:54] Michael Hawk: kind of like with gall larvae, we're now talking about a great food source stuck in one place. [00:14:00] No wonder Acorn woodpeckers live in family groups.

They need labor to protect and manage the granary.

[00:14:07] Bernard: Good Morning Ralph

[00:14:08] Vernon: Good Morning Sam 

[00:14:10] Dr. Walt Koenig: They certainly check on the acorns. as they dry out, they shrink, and the birds spend a lot of time in in the winter just sort of checking on them, and if they don't fit very well anymore, they will pull them out and move them to a hole where they fit better, because then they do also spend a lot of time defending them against the titmice and the quail and the ground squirrels. And everything else that might come and want to steal those acorns when they are no longer available on the oaks themselves. Because by the time you get to January, and February, and March, and later, in a typical year, those are the only acorns that are going to be around. And so there are a lot of animals out there that would like to get those acorns. And of course, having them, Carefully packed in those [00:15:00] granaries makes them difficult for anybody else to get them, and the birds then defend them against all these other species. As well as other acorn woodpeckers that might want to come and try to steal them.

One of the really interesting things about the geographic distribution of acorn woodpeckers, is that they are not, strictly speaking, restricted to places where there are oaks. They tend to only be found in places where there are at least two species of oaks,

[00:15:30] Michael Hawk: And this brings us back to masting.

[00:15:32] Dr. Walt Koenig: The reason for that oaks, are masting species. They produce a lot of acorns, a lot of seeds some years and very few seeds other years. And if you're living in a place where there's only one oak species, you're going to have what amounts to an acorn crop failure fairly regularly, once every three or four years, which is basically once a generation, if you're an acorn woodpecker. And acorn woodpeckers just apparently are not able to make it [00:16:00] in most such places. Whereas if there are two or more species, the species do not necessarily produce acorn crops synchronously.

[00:16:07] Michael Hawk: Dr. Koenig has spent many years studying masting.

[00:16:11] Dr. Walt Koenig: So masting is the variable and synchronized production of seeds of plants, and so, I'll talk mostly about trees because that's where it's been most studied and what I've been most interested in.

So the interesting thing about masting is it's not strictly speaking something that an individual tree does. So a tree may produce a lot of acorns one year and not very many or no acorns another year. But masting is a population level phenomenon. It's something that all the trees in the population are doing more or less at the same time. So in a good mast year, all the individuals Of whatever species we're talking about, are going to produce a relatively good acorn, crop whereas in a bad mast year. [00:17:00] none none of them, or very few of them, are going to produce any acorns at all.

how does a population of trees decide when it's going to produce to put all its energy into acorn production?

[00:17:11] Michael Hawk: I'm sure that's the question we were all thinking.

[00:17:14] Dr. Walt Koenig: those factors can be similar among some species so that you can get some synchrony in acorn production among different species. But one of the things that really sparked my interest early on was this definition, which was synchronous production of seeds by a population of trees, but what no one seemed to really care too much about or have spent a lot of time studying was how big a population we were talking about. So was it just the trees right here at Hastings? These trees that we have here, including Valley Oaks and Blue Oaks, found all around the state, around the Central Valley of California. So they cover millions of [00:18:00] acres. And so if it's a good acorn year for Blue Oaks here in Hastings, is it a good year up in the Bay Area around Oakland and the Berkeley Hills?

Is it a good year in the foothills of the Sierras?

so it took us a long time before we kind of realized that, in fact, the population we were dealing with was much larger than people had suspected. And, in fact, for some of the species, at least, it pretty much encompasses their entire geographic range

[00:18:32] Michael Hawk: So what is driving this large scale event?

[00:18:35] Dr. Walt Koenig: the 2 things that are the most important for, say, the valley oaks, or the blue oaks, uh, which are species, which at least a lot of your listeners here in California will be familiar with, conditions during the spring, when they're flowering, so these are species that are flowering in February and March and April, and then those flowers that are what, then mature into [00:19:00] acorns the next, fall. And so the conditions during the spring are very important. And then the complicating factor and the one that sort of really makes things difficult is that it also depends on, what the acorn crop was the year before

So if they put a lot of energy into and had a very good acorn crop last year, then they tend not to have a very good acorn crop this year. And this is what really tells us at some level that part of the story is that they're storing energy somewhere in the tree

[00:19:34] Michael Hawk: so the weather's the main driver,

[00:19:37] Dr. Walt Koenig: In fact the weather is probably the main driver of what's going on.

[00:19:42] Michael Hawk: So the oak trees need to have the right weather conditions to build up energy and the right conditions to allow for pollination and production. Of course, the cycles might be a bit different where you live, but the principle remains the same.

We only talked about acorn woodpeckers, but so many other animals partake in [00:20:00] acorn treats from blue jays and scrub jays to crows and turkey, squirrels, wood rats, and mice love a good acorn too. But did you know that white-tailed deer are some of the most prolific acorn eaters? And black bears can gorge up to 10 pounds of acorns per day when preparing for hibernation?

But despite all of the connoisseurs, a great many acorns will end up lost, buried by a squirrel or a jay and sprout into the next generation of oaks continuing this ancient cycle.

[00:20:30] Griff Griffith: So what's the big lesson we can take from today? Well, masting is a reminder that the natural world operates on long, complex cycles that we don't often even see. It takes years for an oak tree to budget its energy for that giant synchronized boom year, and when it happens, the entire ecosystem from the smallest ground squirrel to the amazing Acorn woodpecker is riding that wave.

We're all part of this massive, invisible, critical event.

My call to you is [00:21:00] simple. If you want to support this whole, beautiful, ancient, complex system right outside your window, plant an oak. It's a gift to the future and a keystone home for hundreds of species.

Be sure to check out our show notes for links to resources to help you find the right sized and right species of oak for your area. check out the full interview with Dr. Walter Koenig over on Nature's Archive Feed right now. There is so much more to the fascinating story of acorn Woodpeckers that you just have to hear to believe.

[00:21:29] Michael Hawk: The Jumpstart Nature Podcast was created and produced by me, Michael Hawk.

Special thanks to Kat Hill who provided editing support on the Walter Koenig interview, and of course, Griff Griffith, our host. 

Thanks for listening.