Saturday, November 29, 2014

Climate Change Part 12: Where Oil Comes From Part 2


Note: This program first aired on November 29, 2014.

Last week’s show was a bit of a climate change cliff hanger. We were looking at where oil comes from, and we ended last week talking about primary productivity in the ocean, the process where by plants fix inorganic carbon from the atmosphere and incorporate it into their bodies transforming it into organic carbon. Part of this process fixes the sun’s energy and turns it into chemical energy, the energy we liberate when we eat food or burn gas in our cars.

That process is usually thought of as part of the “fast carbon cycle”, carbon travels from the atmosphere into plants and then up the food web into the bodies of other organisms, and all along the way it gets returned to the atmosphere as that chemical energy is burned and carbon dioxide is exhaled or released. It is a tight loop. Yesterday’s atmospheric carbon dioxide is today’s plant is tomorrow’s cow is next week’s atmospheric carbon dioxide, and the cycle repeats. In the ocean carbon is fixed by phytoplankton, some of which are eaten by zooplankton and small fish, and that carbon proceeds up the food web. Some of the phytoplankton dies without being eaten, and that plankton slowly sinks to the bottom, where it can be decomposed by decomposing organisms. In the ocean these are typically bacteria. On land fungus joins bacteria as one of the two primary decomposers. Decomposing is just another name for getting eaten, but by things that don’t have mouths. Chemically generally the same thing happens as when an animal eats, chemical energy is liberated from the body of the dead phytoplankton and one of the break down products is carbon dioxide.

Now knowing that there is a “fast” carbon cycle might clue you into the fact that there is a “slow” carbon cycle as well, and this is where the formation of oil comes in. In the slow carbon cycle, instead of getting eaten or decomposed, carbon moves out of the biotic realm and is sequestered into the rock cycle. The carbon can build up as calcium carbonate deposits in certain areas of the ocean (also known as lime stone), or can build up as organic deposits on the ocean bottom. This is where oil comes from.

Typically, when plankton dies without being eaten at the surface of the ocean, it slowly sinks to the bottom, where it can be decomposed, as we just learned in the fast carbon cycle. Sometimes though, things can go a bit haywire and the balance of carbon in and carbon out gets disrupted. There are places in the ocean, places like the Gulf of Mexico for example, where there are both lots of nutrients and lots of light, the two things that limit phytoplankton growth. The light comes from being at a sub tropical latitude, the nutrients come from a. being a coastal environment and b. being at the mouth of one of the largest river drainages in the world. The Mississippi River drains much of the central United States, and winds its way through much of the country’s agricultural zone. That is a lot of top soil and a lot of fertilizer that ends up in the river. With all that extra nutrition, the phytoplankton in the Gulf of Mexico go crazy and reproduce prolifically. They reproduce so much that they can’t all get eaten, there’s so many of them. So they die without being eaten and float down to the bottom on the continental shelf. There they start to be decomposed, but again, there are so many of them that the bacteria has a huge job to do, and consequently so much decomposition happens that the bacteria use up all of the oxygen it the water. Its like a fire burning in a closed space. Once it uses up all the oxygen, what happens? The fire goes out, as does the decomposition. This is called a dead zone, because anything that can’t swim or crawl away from this area of the ocean floor will die due to lack of oxygen. Dead zones form in coastal waters in many areas seasonally, and they aren’t all due to human influence, though the regularity with which this happens in the Gulf of Mexico is certainly tied to industrial agricultural practices and the subsequent nutrient load the river carries to the sea.

If dead zones happen repeatedly in the same area over time, those little phytoplankton bodies build up in the sediment without being decomposed, and all the carbon contained in their tissue is locked away. This process pumps carbon out of the atmosphere, and results in a decrease of atmospheric carbon dioxide. Over time, and it doesn’t have to be that much time, thousands to hundreds of thousands of years, and with heat and pressure that result from ongoing sedimentation on the continental shelf, that organic matter is transformed into gas and crude oil. The process goes on today, though at a much slower pace than we are using up the oil. Right now we are pulling that carbon back out of the rock reservoir and pumping it back into the atmosphere much faster than it was taken out, hence, the rising levels of atmospheric carbon dioxide.

So that is where oil comes from. Much like coal, it is photosynthetic material that is deposited in sediment without being decomposed. It’s a naturally occurring process, one we really aught to be paying more attention to.

Read the whole Climate Change series here.

References:
About making crude oil in the lab from plankton: http://www.gizmag.com/algae-crude-oil-process-pnnl/30235/

Not really about where oil comes from, but a great graphic from the BBC showing how it is refined: http://www.bbc.co.uk/schools/gcsebitesize/science/ocr_gateway/carbon_chemistry/crude_oilrev4.shtml


Climate Change Part 11 Where Oil comes from Part 1


Note: This program first aired on November 22, 2014.

At last! A return to the Climate Change Series!!
It’s been many weeks, even months since we last talked about climate change, but I haven’t forgotten that I never finished that series. Today we start to rectify that. When last I looked at climate change, we were talking about the formation of the massive coal beds that fueled the beginning of the industrial revolution. Coal is still big business and a significant environmental issue today, especially in electricity production, air quality and destructive mining practices. Coal has been surpassed by oil in both the popular imagination and in the carbon dioxide emissions data as the number one climate change villain, and it is to oil that we turn today.

Where does oil come from? It doesn’t have its own neat and tidy geologic era like coal does, and the processes that form oil are still going on today. People have been arguing about the origins of oil since we discovered it. One camp holds that oil forms abiotically, meaning it can form from inorganic sources of carbon in the absence of life. The other posits that oil is formed biotically, from carbon found in once living organisms. It turns out both theories are correct, though one explains the vast commercial deposits of oil we exploit better than the other. Hydrocarbons can be created inorganically, that’s how Saturn’s moon Titan can have lakes filled with liquid methane on its surface, or meteorites can contain organic carbonaceous materials. The vast majority of hydrocarbons here on Earth though, are formed through biotic processes.

When oil is found in large deposits, it is always found in sedimentary rock that is marine in origin. Whether it is a sedimentary deposit that is still under water, or a much more ancient deposit that is now far inland, that rock deposit originated as terrestrial sediment that was washed into the ocean and deposited along the coastal margins of the continental shelf and continental slope. Its what gets buried along with that sediment that makes up the oil that we burn so freely today. And for that we need to talk about productivity.

Virtually all energy that flows through living organisms and biotic systems originates from the sun. This is true for your breakfast, its true for your dog food, its true for the gas in your car. The sun’s energy comes to Earth in the form of light, in your breakfast, dog food and gasoline, it has been transformed into chemical energy. Plants are the means by which that energy gets changed from wavelengths of light to chemical bonds, a process we all know as photosynthesis. Plants absorb light energy and rearrange the bonds of water and carbon dioxide. They form new molecules from those atomic ingredients, and in the bonds of the new molecule, aka glucose, the sun’s energy is stored chemically. Ecologically this is known as primary productivity. The more primary productivity going on, the more energy is entering an ecosystem. 

In the ocean primary productivity is limited by two factors; light and nutrient availability. At the surface of the ocean there is usually plenty of light, so what tends to limit productivity in most parts of the ocean is nutrient availability. When we say nutrients, we mean the same kinds of things that plants everywhere need: nitrogen, phosphorous, potassium, iron and a wide range of other minerals in very small amounts. Nutrients are quite limited at the surface of the ocean in most regions, so while there can be plenty of light to drive productivity, if there are no nutrients, there is no action. The coastal ocean however has access to nutrients that the rest of the ocean does not. These nutrients come to coastal waters through run off from land, sediment washing from land to water in a constant and inevitable flow. If you look at a map of global sea surface chlorophyll levels, chlorophyll, as the photosynthetic pigment in plankton is a proxy for primary productivity, the pattern is clear. Productivity along coastlines is high on virtually every shoreline world wide. What this has to do with the formation of oil, you’ll have to wait until next week to find out.

References:


From the GRID Arendal Center in collaboration with United Nations Environment Programme, figures on the proportions of Carbon Dioxide from oil, coal and natural gas:


From the Louisiana Department of Natural Resources:




Electricity

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Note: This program first aired November 15, 2014.

These past weeks have been a challenge for us modern humans, living in these temperate latitudes, walking a delicate balance between the natural realities of life nearing the winter solistice at 45 degrees north, and the demands of our computers, smart phones, freezers and livelihoods here in 2014. For many of us, the November Nor’easter pushed that balance towards one end of the human spectrum, into the realm of wood stoves and water sources, candles and bees wax, propane, lamp oil and natural darkness. Knitting by candle light, reading by head lamp and early bed times accentuated these lengthening nights.  We live most of our days now far on the other end of that spectrum, with 24 hours of light if we like, cooking our food with electricity, maintaining our communities through waves and wires instead of eye contact and helping hands. When the power went out, we knew what to do, even if we didn’t want to do it, or believe we had to do it. After 12 hours without electricity, you either get with the program or jump ship for a place with a generator.

This temporary lack of our simple modern convenience made me wonder about the material reality of electricity. What is it exactly? This invisible force that has the power to abruptly alter our lives so profoundly, here one moment, gone the next?

It turns out that electricity isn’t so simple. Google electricity and you find out it is made of particles, or not, no its actually waves, or not. The variety of units associated with electricity is dizzying; volts, watts, amperes, coulomb, joules. What I am interested in is what is happening, or not happening, when the power goes off. What is actually moving through the power lines, and what happens when they break? When you work at an engineering college, there are lots of people around who can answer these questions, and when I put these questions to one of my colleagues he replied unequivocally “electrons”. It’s electrons that are moving through the power lines.

Electrons are negatively charged particles, they actually have mass, though not very much of it. They are one of the three types of particles that make up atoms, the others being protons and neutrons.  The protons and neutrons make up the core or nucleus of the atom, and the electrons fly around the outside and form an energetic shell around the atom’s nucleus. The outer most electrons, the ones furthest from the nucleus are called valence electrons, and when we talk about electrical current, those are the ones we are interested in. They can move relatively freely from atom to atom, and in a simple way to think about electricity, it is these valence electrons that are moving through the wires. Its important to note that powerplants don’t make electrons, the electrons are already present in the metal the wires are made of, in fact, electrons are present everywhere in all atoms! All the powerplant does is get the electrons moving, that’s why it takes energy to make electricity. When we say electricity, we really mean electrical current, which in this simple example is moving electrons through a wire. The electrical current requires a circuit, which simply means a loop. Electrons are set in motion at the powerplant, and they return to the powerplant after looping through your house and doing some work there. If there is a gap anywhere in the loop, the current stops flowing. This applies to powerlines downed by broken trees, and to the light switch in your kitchen. When the light switch is off, the circuit is purposely left open, so no current flows. When you switch the light on, you physically close the circuit, and the current flows through the lightbulb or stove top or whatever appliance or gadget you are operating.

And Google was right when it told me that electricity is a particle, no it’s a wave. It’s both. In DC, or direct current systems, it really is the electrons moving, as in our simple example. In AC or alternating current systems (which most of us have in our homes) the electrons in the wires are transmitting a wave of energy, and just like with ocean waves, the electrons don’t have much net transport as the wave passes by.

However I look at it though, I am grateful the circuit is repaired and the electrons are flowing back through my house. But I also find myself grateful for that week of darkness. Electrical power makes our lives infinitely easier than those of generations past, and enables the frenetic pace of life we tend to run at. Sitting in the dark that long week, reading by the light of the oil lamp, doing the dishes by candle light with water heated on the woodstove—these moments pulled at something old inside me. Something old and slow and precious. So don’t despair when the lights flicker and that electron flow is impeded. You remember how to do this.

References:

The internet standard for basic physics info:


Weirdly written (perhaps translated?) but with some good basic stuff: http://www.leonics.com/support/article2_2j/articles2_2j_en.php


Bears love donuts, and so do we


Note: This program first aired October 25, 2014.
 
I’ve been trying to avoid election propaganda and advertising this election cycle, not having a TV goes a long way towards that goal. As a naturalist though, it is hard to miss the rhetoric around the upcoming referendum about bear hunting methods here in the state of Maine. Bear baiting in particular got me thinking about how we’re really not so different, the bears and us.

Bear baiting is a hunting method where by food is left in the woods consistently in an attempt to attract the bear and train it to return to the same spot repeatedly during the hunting season. The hunter hides in a blind near by and shoots the bear when it returns. Here in Maine the season for hunting with bait is most of the month of September, and the baiting/habituating process can begin as early as the end of July. Typically the food used is old fast food, fryolator grease, and donuts and pastries, though really anything can be used.

So why does bear baiting work? And by work I mean, bears come to eat the food. The obvious answer is that they are hungry. As wild animals they spend their entire lives looking for something to eat. For bears, their need is even more extreme. They need to eat enough to not only survive, but also get obese enough to survive a winter of not eating. In the wild they work hard to get these calories from berries and other fruits, insects both adult and larval, live prey and scavenged carrion. Up to 90% of their diet is plant based, mainly fruits, which come in waves during the growing season. Strawberries, then pin cherries, then blue berries, then raspberries, then choke cherries, you get the idea. With this in mind it isn’t a great leap to hypothesize that bears are adapted to seek out sweet flavors, if fruits make up as much as 90% of their caloric intake.

I know another animal that seeks out sweet flavors, and like the bear, this habit can be its undoing. Humans are adapted by evolution to seek out sweet flavors, salty flavors and fats. These three tastes represent nutrients that were extremely limited or difficult to come by in our evolutionary history. By evolving a preference for them we have trained our cells to seek them out. This by the way is another way to define addiction, and it is no exaggeration to state that humans are addicted to sweet, salts and fats. But being addicted to something that is very limited in the environment, not to mention also beneficial in small quantities, isn’t so bad a thing. The problem of course is that these nutrients are no longer limited in the environment, but we are still addicted to them. This fact, along with changes to our microbiomes, sedentary lifestyles and increases in chronic estrogenic chemical exposures have led to the obesity epidemic we face today.

Bears, just like us, seek out sweet and fat, a slave to their genes. They, unlike most of us, are seeking obesity. Baiting bears with donuts holds up a strange sad mirror, reflecting poorly on our own sad lives. Their weakness, their physiologic need mirrors our own, with bad results for both of us. Bears love donuts, and so do we.


References:




Coyotes


Note: This program first aired on October 18, 2014.

I haven’t been sleeping well this fall. The transition from summer’s expansive freedom to the structure and busy schedule of fall is always a rocky one. But above and beyond the stress of 21rst century living, a more practical matter is keeping me up at night. The weather the past month has been mostly cool and crisp, the air dry and clear. As a result, the moon has been exceedingly bright and it shines in my window with a direct hit on my pillow night after night. And if the night time noises I am hearing through my still open window are any indication, I’m not the only one awake in the moonlight.

Nearly every night for the past month our neighborhood has been serenaded by a group of coyotes. They aren’t singing for our benefit or enjoyment of course, biologists think coyotes vocalize to maintain contact with pack members and reinforce their claim to their territory. Whatever their reasons, they have been doing it a lot. If the yipping and howling really is a contact call, it makes sense to be hearing it so much as they move from place to place in their territory.

Announce that you have coyotes in your neighborhood and you will get one of two reactions: people who want to see or hear them and people who want to kill them.  We have a long standing tradition in this country of not only over exploiting wildlife, but especially over exploiting apex predators, removing them from the ecosystem so that we can ostensibly take their place. That’s why coyotes are here and in such numbers in the first place, they moved in to the north east to occupy the ecological niche opened when wolves were exterminated here in the 19th century. That is a clue to both how ecosystems function and their resiliency, when one member of the cast disappears, an understudy quickly moves in to fill the role.

Coyotes will eat anything, making them opportunistic omnivores instead of pure carnivores in a strict trophic category sense. Their go to food item is mice and other small rodents. These are a year round staple on the coyote menu. If you know anything about lyme disease, you know that anything that eats mice is a good thing, they are the most common intermediate host for the disease. Keeping rodent populations in check is critical to slowing the spread of Lyme and coyotes are doing their part. In the late summer and fall, when we are picking berries and apples, coyotes are too, they’re no dummies. Two days ago I found coyote scat that was solid apple peel and studded with apple seeds and cherry pits.  Coyotes will also prey on other mammals including snow shoe hares as well as scavenge on carrion of all types.

The elephant in the room of course is that coyotes also eat deer, and this is why they are so reviled by hunters. The degree to which coyotes rely on deer for food varies from region to region, and time period to time period, so what was found in a study one place at one time may not hold true somewhere else. Traditionally we are taught that wild predators take the weak and the old individuals of prey first; these individuals will be the easiest to catch. Hunting takes energy, and energy is at a premium in nature. Any advantage a predator can take to conserve energy is worth while. Studies have shown though that coyotes sometimes take deer that are in fine condition, good condition even, particularly if the hunting group is large, so the romantic view of the noble predator culling the herd and improving the gene pool is somewhat naïve. There is a natural economics in play  here, coyotes will maximize their resources and get the biggest deer they can with the resources they have, they are in business to stay alive.

And it is a dirty business sometimes, staying alive. Death supports life, in every way you can imagine. Every bite we take begins with the death of something, be it the plant that became the bread, the fruit that bears the seed, the animal that became the meat. I can’t begrudge the coyotes their meal, they are no risk to me, and if I am smart with my pets and livestock, coyotes are no threat to them either. We humans like to think that we are the new apex predators, but we can’t actually fill that niche ecologically. Yes, some humans like to kill deer, but most of us are not also living off eating rodents and other small mammals. An ecosystem missing its top predators is an ecosystem overrun with herbivores and rodents and nowadays, Lyme disease. I’ll take the coyotes over the ticks any day.

References:

Just the facts ma’am (from Maine Dept. of Inland Fisheries and Wildlife: http://www.maine.gov/ifw/wildlife/human/lww_information/coyotes.html

The Wildlife Conservation Society’s review article on coyote biology: http://s3.amazonaws.com/WCSResources/file_20110518_073403_WCS_WorkingPaper17_Gompper_kTiIyc.pdf


Geri Vistein’s site about coyotes in Maine: http://www.coyotelivesinmaine.com/

And in case you were wondering about coyote hunting, here’s a fact sheet from SAM: http://www.sportsmansallianceofmaine.org/PDF/Coyote_hunting_laws_handout.pdf  (short summary: you can hunt and kill them pretty much every way except snaring them—that includes baiting, trapping, hunting with dogs, hunting at night)

Succession and the Bucksport Mill


Note: This program first aired October 11, 2014.
 
If there is anything you can be sure of in nature, it is that things will change. The natural world is not static and nothing remains untouched by this truth. As soon as mountains are formed, they begin to erode. The temperature falls and rises, ice covered this landscape, not once but many times, the ocean has left its mark too. Forests we experience as known communities are as ephemeral as spring flowers, in the grand scheme of things here on Earth.

Knowing this truth of the world did not make this week’s news from Bucksport any easier to hear. The paper mill that opened there in 1930 formed the economic and social backbone of Bucksport and many neighboring towns. The paper mill that will be closing there at the end of 2014, 84 years later, leaves a hole not only in the tax base but also in the fabric that stitches that community together.

The make up of a natural community is determined by many factors, the most fundamental of which are the external environmental conditions present. If the climate is cold, we expect to see cold adapted plants and animals, if the climate is dry, we expect to see succulent plants or fire adapted plants. When the environmental conditions change, we expect to see the ecological community change as well. On a landscape freshly cleared, whether by wild fire, glacial melt, sea level drop or some other disturbance, we see the successive changes in community composition coming in an orderly procession; fast growing opportunistic species first, more slow growing and complex assemblages later. In classical ecology we are taught to recognize the climax community, the culmination of successional change that started with our blank slate, and progressed to a fully articulated rich and diverse ecological community. The implication is that once climax community is reached, it is self sustaining unless environmental conditions change, thus changing the playing field and potentially favoring species other than those on the climax community cast list.

My father worked at the mill for 22 years, in it’s hay day, when all four paper machines ran twenty hour hours a day, the employee parking lots so full we might not be able to see Dad’s car when we drove by on the way to my grandmother’s house, when men and women took what now seems an old fashioned pride in their work, when unions fought for workers rights and won. That mill lifted my family from the threshold of poverty, gave me amazing health insurance, put my sister and me through college. It was not easy work, but making paper provided a living that supported countless families year in and year out.

Red oaks dominate the forest around my house, they are the prevailing species in the Oak and Northern Hardwood forest climax community that typifies my neighborhood. They provide food for thousands of creatures, insects that feed as parasites on the growing acorns, grackles and blue jays who eat acorns right off the tree, the myriad of forest animals large and small who eat the acorns once they fall to the ground. These animals depend on this tree in an existential way, if these oaks were to die out due to changes in the environment, these animals would need to adapt to a new way of life, new food sources, a new community in an old place.

Bucksport sits now right on the edge of the end of its climax community. Much like we see the changes ahead due to climate change, Bucksport must ready itself for a fundamental shift away from the very thing that has been the organizing structure for the town for the past 84 years. By nature’s clock that isn’t a very long time, but its long enough for a field to turn into a forest. Perhaps the grasses mourn the loss of the sun when the first woody shrubs grow above them and spread their leaves. Perhaps the shrubs cry out their loss when the mighty oak’s branches cover the sky. Change is the only thing worth betting on, we can’t hold the natural communities around us frozen in place any more than we can keep a mill from closing, though it may break our hearts to see it go.

It’s been 16 years since my father died, and the mill’s death spiral started not long after, machines were shut down, shifts were cut. The parking lot got smaller. The truth is, this has been coming for a long time, just like the changes in global climate we as a society, are doing our best to ignore. And just like communities in nature, a new reality will grow in Bucksport, one calibrated to the economic and ecological conditions dictated by not only life in the 21rst century, but by the very people who call that place home.


References:

Want to try your hand at keying out Maine’s different natural communities? Check out this classification key: http://www.maine.gov/dacf/mnap/features/communitykey.htm



Blue Jays and Hunger


Note: This show first aired September 27, 2014.
 
I have red oaks around my house, which means this time of year, I have blue jays. I watched them the other day from my desk, looking out my window at the rain. They hopped and flapped from branch to branch at the top of the trees I see from my third story vista, searching for acorns, their preferred food this time of year. Hence the correlation: oaks and jays. Spending time beneath these branches is a bit of a risk, acorns frequently rain down, dropped accidentally. Jays hold the acorns in their claws and pound away at them with their thick beaks, cracking them open to access the nutritious nutmeat inside. This time of year, it’s likely to be all that they are eating.

There’s a reason we humans think about eating all the time. In the natural world, in the world we evolved in as animals (the animals we still are despite our computers and phones and refrigerators), what else is there to think about except finding food? Food is the constant vocation for wild animals, the number one job of all consumers is just that, to eat. Without enough food, there is nothing, no energy to run the metabolism that drives the fulfillment of genetic destiny. Food first, sex later.

I imagined what that would be like, to wake up in the morning like a wild animal, each and every morning of every day of your life thinking about food. Everyday a new day, a fresh opportunity to eat, or starve. Imagine getting out of bed in the morning in a house with no kitchen. No cupboard, no fridge, no food stores of any kind. Your day starts with you going outside to find something to eat. Every day starts that way. Reality TV aside, this is a marginal existence, an existence that honed us through natural selection oh so many years ago. An existence we pay no attention to now, unless you are a neo-aboriginal, experimenting with “rewilding light”, or desperately poor.

It turns out that Blue Jays, though they live the life of wild creatures everywhere, have a strategy for food scarcity, a strategy to cushion the pangs of hunger. They cache food, acorns and other mast crops from the forest. They can move hundreds of acorns a day, thousands a week, hundreds of thousands during a season. They bury them in small groups in the soil of the forest floor, and have a retrieval rate, according to one study, of about 30 %. That leaves about 70% for other animals to eat, or to germinate, dispersed so widely and nicely from the parent tree. Other studies show that Blue Jays are real foodies, picking only the healthiest and most viable acorns for caching, which means in practice, oak trees have come to depend on this noisy bird for dispersing their seeds. The idea is out there that Blue Jays are at least in part responsible for the rapid reforestation that occurred after the last of the glaciers left New England twelve thousand years ago. That’s a mighty job for a small blue bird. Americans are estimated to waste about 40% of the food we buy, and our food waste doesn’t feed other animals or grow forests, most of it rots in land fills (compost piles not withstanding). It’s a statement of how far out of the system we’ve come.

If I can’t think of the Blue Jays as facing each day with an empty belly (though in practice, even with food stored away, there are not guarentees), there are certainly other animals that wake up each morning with a clean slate. The coyotes I have been hearing around my house every night for the past two weeks don’t cache food. They spend all their time searching. What if I lived more like a coyote instead of a blue jay? What if every day that dawned was a brand new challenge to fill my stomach, as unconnected from the day before as to the day ahead. Each day an individual exercise in survival, life a series of these days strung together, one after the other, going on until I fail.

The blue jays I see this fall I watched fledge in July. Fledging day dawns with a ruckus coming from those same tree tops outside my 3rd story window, the young hop and flutter from branch to branch all the while encouraged by the screeching calls of the adults. I imagine they are saying “come on come into this world, where your pursuits must be single minded, and your eyes clear”.


References:


Good citations to studies if you are a paid subscriber to the Birds of North America site

Nice article with a few more details about cache retrieval rates (presumably from the above studies) http://www.courierpress.com/lifestyle/blue-jays-cashing-in-on-caches-to-survive