I'm a Heterotroph

Note: This program first aired September 26, 2015


I am a heterotroph. This means that I eat food, food that comes from outside of my body. Unlike plants, which are able to make their own food within specialized cells within their bodies. I can’t do that. To live I have to eat, and what I eat is important to me.

One of the things I eat is meat, though not very much of it, and mostly meat I have looked in the eyes. In the yard behind my green house are two tidy wooden houses. One is fully of baby chickens, the other full of baby ducks. A few of these birds will join my flock of laying hens, or go to live as slug eating garden ducks for my neighbor, the majority will end up in my freezer, sustaining me and my husband over the winter. I’ve participated in this process for several years, raising or helping to raise the meat that fills my freezer, and when the day comes deconstructing the animals from which I derive my nourishment. I do this not without pause, in many ways I would prefer not to eat animals at all. Watching the ducks embody their inherent duckness, splashing in their water with apparent pleasure, watching the chickens doing what is theirs’ to do, scratching in the soil looking for invertebrates, its hard not to appreciate watching an animal do what it is designed to do.

By all measures I am a greenhorn when it comes to my small homestead. And this fall has highlighted this fact. This fall the “raise your own meat” story didn’t exactly follow the script. It started with a text from my husband that simply read “we may lose a duck”. He went out to do the morning chores and found one of the ducks on its back, waving its legs, unable to stand. He flipped it over but it was unable to stand, and it flopped back over on to its side. We isolated it from the flock by bringing it inside in its own quarantine box in the bathroom. It wouldn’t eat, could not sit upright or bend its legs and would drink only if you put its beak in the water. Its condition worsened and the duck was dead by nightfall. Two days later the process repeated, only this time the duck survived the night, flopping around in its box all night, only to die in the morning.

It wasn’t easy to watch those animals die. They suffered, and the only thing that would perhaps have made them feel better would have been to be reunited with their flock, something we couldn’t do because we suspected that what was killing them was contagious. Using the hard economics of a small homestead, we had to decide how much money to spend to save a duck that we were going to kill in 8 weeks anyway. But even though their fate is the freezer, I care about those animals, I enjoy watching them embody their duckness, and it is critically important to me that they are able to do the things most important to them-wander about in the fresh air, splash in the water, snuggle with their flock mates. Watching an animal suffer when you don’t know what is wrong and are powerless to provide comfort is a reality check indeed. Ultimately we brought the second duck to the University of Maine for a necropsy and bacterial culture to try to get some answers, and while we were waiting for the results a third duck fell ill.

This story though has a happy ending. The third duck spent the night in the house with us, and was able to eat and drink the whole time. He maintained the ability to walk, and was well enough that in the morning I put him outside in a small quarantine pen. He had recovered enough that evening that I reunited him with his flock, and when they came out of the duck house the next morning, I couldn’t tell which one had been sick the day before. Cue the happy music.

Being an active participant in your own food chain isn’t always easy but it will challenge you in all the best ways, and provide endless opportunities to examine your own values and priorities. It may change the way you eat. I’ll always be a heterotroph, but I’m not sure I’ll always be a meat eater. The ducks may have more to teach me still.

Blackberries and Summer

Note: This program first aired August 29, 2015.

Late summer is one of my favorite times of year. The expansive energy of summer starts to wane as plants start their journey to winter dormancy. Birds cram in the as many fat and juicy insects as they can, and start making their way to warmer climes. For many of us humans the school year is starting back up and though we mourn the end of summer the structure of fall is just what we need. And most importantly, late summer is when my favorite wild fruit ripens and is there for the taking, road side and trailside.

Blackberries are a common late summer fruit here in Maine, coming after the strawberries of early summer, the blue berries and raspberries of mid to late-ish summer. Blackberries mean the end really is nigh. Some summers in recent memory, the chill of fall started before the blackberries were able to fully ripen, and we never got our end of summer treat.

When we say “blackberries” we are really talking about several species of plants in the genus Rubus. Rubus is a real head ache for botanists, as the species are difficult to tell apart and hybridize (or cross breed) in the wild readily. This cross breeding ability has made it easy to develop all kinds of interesting agricultural cultivars, but it makes sorting out the taxonomy of wild plants very difficult. Estimates for the number of Rubus species world wide range from 250 to 700 because different botanists treat the genus with differing degrees of discernment. On the one hand we have the “megaspecies” approach, lumping many disparate species together based on one common characteristic. On the other hand, similar plants can be separated into different species based on minute or inconsistent characteristics. Hence the range, the taxonomy of Rubus is still an open debate.

Regardless of exactly how many species are in the genus, Rubus includes along with blackberries and raspberries, plants with dreamy sounding names like dew berry, cloud berry and baked apple berry. All of these berries are technically aggregates of a type of fruit called a drupe. Drupes are stone fruits, consisting of a fleshy pulpy layer surrounding an inner hard seed, think a peach, plum or avacado. Blackberries and their kin are made up of lots of little drupes, called drupelets, clustered together in one delicious berry. These berries mostly share another characteristic in their growth form. They are perennial, growing from multiyear root system, but the above ground portion of the plant is a woody cane that lives as a biennial, or for two years. The first year the cane grows it is called the primocane. It has lots of leaves but no flowers or fruit. Think about all the lush green leafy blackberry brambles you have seen and wondered why there were no berries. They were primocanes, that’s why. The primocanes overwinter and produce lateral branches that flower and fruit the second year. These flowering canes are referred to as floricanes. And if you want to take on the challenge of identifying Rubus to species, knowing the difference between floricanes and primocanes is essential. In any given patch of blackberries, there should be both primocanes and floricanes, so this year’s lush fruitless bramble of primocanes should yield some fruit next year, but its root stock will also put up more primocanes next year, which may explain why some blackberry brambles I watch never seem to produce fruit. It also may be that black berry floricanes especially sensitive to cold, much more so that red raspberries for example. And after last year’s cold winter, I notice that the wild raspberry crop this summer has far surpassed what it usually is, and blackberries, sadly are harder to come by in my yard.

I grow cultivated raspberries, enjoying them from the freezer all winter long. The blackberries though, have defied my attempts at domestication. And once in a bumper crop year I froze some, only to find them disappointingly tasteless when thawed in December. For me blackberries are a fruit that demand to be appreciated on their own fleeting terms—on the side of a dirt road, ideally warmed by the sun, going directly from cane to mouth, staining fingers inky purple. Enjoy them in the present as a foraging wild animal, it’s a marvelous way to spend the last few days of summer.

References: 

GoBotany is a great place to start learning about the different Rubus species in New England

https://gobotany.newenglandwild.org/genus/rubus/

Arctic Oil Drilling and Climate Change: Connecting the Dots

Note: This program first aired August 22, 2015.

If you haven’t noticed lately, its been kind of hot here in Maine. Hot like it hasn’t been all summer, or even in a year or two. While the rest of the world has been heating up, the Northeast has generally been running a bit cooler than most everyone else. We knew that for sure last winter, but the same has held true for the past couple of summers as well. Exactly why we’ve been cooler while everyone else has gotten hotter, as predicted by climate models, is not entirely understood. The wandering of the polar vortex that has graced our past two winters results from latitudinal changes in atmospheric pressure gradients, which change the jet stream, allowing it to run more north and south than the typical east and west. The summer coolness may just be coincidence, or may not. Rapid melting of Arctic sea ice and the Greenland Ice sheet have put large quantities of cold fresh water into the north Atlantic and changed aspects of the circulation of the Gulf Stream. Less warm water is going north, and less cold water is coming south. The resulting cold area in the north Atlantic may be having something to do with our coolness relative to the rest of the world. Or not. It just isn’t clear.

While we’ve been living in our cooler than average bubble here in Maine (present heat wave notwithstanding), temperatures on the rest of Earth have been rising. In fact the first half of this year has been the warmest on record, wiping out the “warmest year on record” status held by last year. And we know why this is, we’ve talked about it ad nauseam here on the show before. Increased levels of atmospheric green house gasses are trapping more and more heat in the Earth’s atmosphere. The primary green house gas is of course, carbon dioxide—one of the key nutrients necessary for photosynthesis and one of the products of energy liberating chemical reactions, like deconstructing glucose for metabolic energy or burning oil, coal or gas to yield mechanical energy. Anything we do that diminishes photosynthesis or increases energy liberation increases carbon dioxide production.

As has been clear from the past two winters here in the northeast, the impacts of climate change are not distributed uniformly across the surface of the Earth. We were buried under feet of snow, and when it wasn’t snowing it was well below zero, while my uncle in Alaska dealt with rain and temps in the 50’s all winter. One of the regions being hardest hit is the Arctic, a region of the world that has been an ice covered ocean for at least 700,000 years, if not more. Each summer the sea ice melts a bit, and each winter more ice forms. Lately though, due to all this carbon dioxide mediated warming, more and more ice has been melting in the summers, and less is refreezing in the winter. The ice is getting thinner, and the overall coverage is diminishing. This is problematic for many of the organisms that make the Arctic their home, as well as for the havoc that it wrecks on global weather patterns (Snowmageddon anyone?). There are some people out there though, who think this lack of Arctic ice is pretty good news. The petroleum company Royal Dutch Shell has been working for many years to secure all of the equipment and permissions required to begin exploratory well drilling in the Arctic Ocean north of Alaska. Because this is US territorial water, it required the permission of the federal government, which it just received. 

One of the things we talk about when looking at climate change is the feedback loop. Feedback is when one thing impacts another, which can then impact the original event which can then impact the secondary event, and on and on. What we have set up here in the Arctic now is a feedback loop. We burn fossil fuels and pump carbon dioxide into the atmosphere, which warms it, which melts the Arctic sea ice, which opens access to the Arctic Ocean for offshore drilling, which gets us more fossil fuel. Perfect. I feel like that character in the movie Zoolander, who, at his wits end screams out “I feel like I’m taking crazy pills!” Aren’t we worried about the impacts of climate change?  Then why are we green lighting a scheme to get even more climate change causing oil? Not to mention the potentially horrific impacts of an oil spill in the Arctic. Someone didn’t connect the dots here. As we stew in our 100% humidity here in Maine, for a few weeks we join the rest of the world in feeling the heat. I suspect that when President Obama visits the Arctic later this month, he will be feeling the heat as well.

References:

http://bangordailynews.com/2015/08/17/news/state/heat-wave-triggers-air-quality-alert-in-parts-of-maine/

Its official—the first half of this year is the warmest on record (world wide) http://www.weather.com/news/climate/news/earth-record-warmest-january-june-2015

Cold water in the north Atlantic: http://www.realclimate.org/index.php/archives/2015/03/whats-going-on-in-the-north-atlantic/

Images of temperature anomalies (variations from average) from NOAA: https://www.ncdc.noaa.gov/sotc/global/201506

Wow, words can hardly express my delight in finding this parody site: http://arcticready.com/ #failbetter

On Shell’s permit http://finance.yahoo.com/news/u-s--throws-shell-a-lifeline-with-arctic-drilling-permit-152427071.html#

Arctic sea ice current conditions: http://nsidc.org/arcticseaicenews/

Why did Shell get a permit? Democracy Now interview: http://www.democracynow.org/2015/8/18/obama_gives_shell_final_approval_to

Will Ferrell in Zoolander: https://www.youtube.com/watch?v=llgY3VBwTAo

Tick Seasonal Patterns

Note: This program first aired on August 8, 2015.

Ticks, though nearly universally reviled for their parasitic eating strategy and disease carrying potential, have a pretty amazing life history. A little knowledge about their seasonal cycles can even help you understand why they show up when they do, why they seemingly disappear for a while and when you need to be most concerned about having them around.

Here in Maine, the ticks we are most worked up about belong to the genus Ixodes. There are several species, only one of which carries the most common tick borne illness in this area, Lyme Disease. Ixodes scapulara is the deer tick or black legged tick, and that is the one to keep track of, so it’s the one we will use as our example of tick life history.

In Maine the deer tick’s life can take upwards of 2 years to complete. It starts as an egg, hatching in August or September, essentially the end of the growing season. What emerges from the egg is called the larval stage; they are tiny, very hard to see, but because they are larval, you don’t need to fly into a panic if you some how notice you have been bitten by one. Larval tick hatch from eggs in a pure state—meaning, even if their mother was carrying the bacteria that causes Lyme disease, the bacteria does NOT carry over into the eggs. Newly hatched larval ticks don’t have the bacteria in them yet. So if you get bitten by one a. you probably won’t notice because they are so small, and b. it doesn’t matter for Lyme disease, since they can’t transmit it to you anyway. In late summer/early fall these larval ticks are primarily feeding on rodents like white footed mice, shrews and chipmunks, and it is from these animals that they first contract the Lyme causing bacteria. White footed mice are the primary reservoir for the disease, not deer like so many people think. After the larval ticks have fed in the fall, they over winter engorged in the leaf litter and eventually molt.

The next spring the ticks emerge as newly molted nymphs. The nymphs need to eat in the spring, and when everyone freaks out about the sudden flush of ticks as soon as things warm up, these are the ticks they are freaking out about. As we just learned, these nymphs could have acquired the Lyme causing bacteria from their first meal the fall before as larvae, and it is from getting bitten by these nymph stage ticks that most humans pick up the Lyme causing bacteria. After these nymphs feed in the spring, they molt into adults.

Adult females need to eat again before they can lay eggs, and it is typically fall before they do their biting. They over winter fully engorged, and emerge in the spring to lay their eggs, thus completing their life’s work. So to recap: larval ticks feed in the late summer, nymphs in the spring/early summer, adult females later in the fall. Only the nymphs and adults can transmit disease, with nymphs doing the lions share of infecting. The other commonly encountered ticks here in Maine are wood ticks, the adults of which are the ones you might find trying to bite you in late spring or early summer. Now that it is August, I hardly see any of these. Now I am just waiting for fall and the emergence of the adult deer ticks. It seems strange to mark the passage of the seasons by the different life stages of a creature so despised, but knowing the rhythm of the ticks not only empowers me but adds yet another layer of understanding, another layer of connection between myself and the rest of nature.

References:

Comprehensive list of ticks in Maine from Maine Medical Center Research Institute: http://www.mmcri.org/home/webSubContent.php?list=webcontentlive&id=108&catID=4&subCatID=19

Clear graphic of deer tick life cycle: http://www.tickencounter.org/tick_identification/deer_tick_life_cycle

Wood ticks: http://entnemdept.ufl.edu/creatures/urban/medical/american_dog_tick.htm

The Sophistication of Ticks

Note: This program first aired August 1, 2015.

Ticks seem to be everywhere this season, in the woods where I walk, on my dogs and cats, crawling up my pant legs, and this past spring, all over Facebook-everyone was posting about the spring emergence of the ticks. And I get it, Lyme (not to mention all the other tick borne diseases) is sometimes difficult to treat and can be life altering for some of sufferers. But this isn’t a program about health or disease, it’s about the natural world, and for better or worse, ticks are part of that world.

Ticks are arthropods, a group of animals that is characterized by having a chitinous exoskeleton and jointed legs. Insects and crustaceans are classes of arthropods we are all familiar with. Ticks are in the class Arachnida with spiders and mites, a sub group of arthropds that typically have 8 legs and specialized mouth appendages. In reading up on ticks I learned some things that are fascinating, and so even though they are one of the most hated groups of animals around, I want to share what I found out.

Ticks, like many insects, undergo incomplete metamorphism, which means that they hatch from an egg into a form that is similar to the adult, usually just smaller and sometimes with less well developed appendages or body parts. For example the deer ticks we worry about so much here in Maine have only 6 legs in this newly hatched stage. Typically this stage is called larval, though you shouldn’t confuse it with the larval stage of an insect like a butterfly that undergoes complete metamorphism. In those organisms “larva” means caterpillar or grub or maggot, something that looks nothing like the adult. Baby or larval ticks look like tiny ticks, and they feed on the same thing as adults; blood. Tiny larval ticks require a blood meal before they can grow into the next stage of life, once they have eaten, they molt their exoskeleton and emerge as a nymph. Nymph ticks often look just like adults, only smaller. They also need a blood meal in order to molt and grow into the last stage of life, the adult. The job of the adult tick is to mate, and only the female needs a blood meal, so that she can lay her eggs, and the cycle starts over. So, egg hatches, larvae, feeding, nymph, feeding, adult, feeding; they eat three times (and only three times) during their lives which can last over a year here in Maine.

Three times in a year and a half, that isn’t much food, for that much time. Each time they bite they have to get enough food for months. How they do it is really interesting. We all know that ticks embed themselves into the skin of their victim, staying attached for days while they suck out the blood they need to further their life cycle. Ticks have specialized mouth parts that work in tandem, one part ratchets while the other part drives deeper into the skin. These parts are lined with reversed direction barbs, so they can’t simply slide back out. Once the mouth parts are fully embedded, no energy is required for the tick to stay there and feed.

Ticks are very small animals, yet they need to get enough food to sustain them for months from just one feeding. If you have ever seen an engorged tick on your dog or cat, all shiny and gray and swollen, you know that ticks have an abdomen that can stretch to hold a large volume of blood. Even more remarkable though is the level of sophistication the ticks have when feeding. As the ingest blood from their host, it is immediately digested and separated out. Ticks keep the red blood cells, apparently the most nutritious fraction of blood. All the rest, the plasma fluid, salts, other blood cells, gets excreted back into the host’s body. So the ticks suck your blood, take only the best parts, and spit the rest back out, thus concentrating their meal. That is how they are able to feed once and live for many months on that one meal. And that is why, for animals that have a high tick burden, anemia can become a real problem.

Detested, persecuted, hated; ticks get a bad rap in the animal world. They are only doing what we all are though, living the only life they know how to lead, fulfilling their biological destiny along the way.

References: 

About ticks and climate change http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2582486/

Tree of Life site for Arachnids http://tolweb.org/Arachnida

Comprehensive list of ticks in Maine from Maine Medical Center Research Institute: http://www.mmcri.org/home/webSubContent.php?list=webcontentlive&id=108&catID=4&subCatID=19

A Maine based company with lots of info on their website: http://www.mainelyticks.com/familysafety-lifecycle.html

Tick mouthparts: http://www.nytimes.com/2013/10/30/science/earth/how-does-a-tick-do-its-dirty-work-research-video-offers-a-clue.html?_r=0

Thank you Ed Yong for citing this article (though no one seems to have looked at how they detatch themselves and get those amazing barbed mouthparts out of your skin): http://rspb.royalsocietypublishing.org/content/280/1773/20131758

Moose, ticks and anemia http://www.nwf.org/Wildlife/Threats-to-Wildlife/Global-Warming/Effects-on-Wildlife-and-Habitat/Moose.aspx

The Principles of Natural Selection as they apply to Baby Birds

Note: This show first aired July 25, 2015.

Natural selection is the mechanism by which evolution takes place, and by evolution, I mean the change in genetic material in a population over time. That change over time is thought to make populations more robust, more “fit”, fitness meaning more successful reproductively; and successful reproduction is the name of the game when it comes to life on Earth.

Darwin’s theory of evolution by natural selection is based on three simple premises: that more individuals are produced than can survive, that there is variation in the traits of those individuals, and that the individuals with the traits best suited for survival and reproduction in the environment will survive. The genes that code for the successful traits get passed on. Genes that code for less successful traits get passed on far less frequently, and eventually disappear from the gene pool. That is how over time, the genetic makeup of a population changes.

We’ve been talking the last couple of weeks about an ill fated pair of baby birds, they were discovered tumbled out of a nest that was blown out of a tree, and birds and nest were replaced into said tree as best an anxious adult and curious child could do. Upon first check up, the baby birds were discovered to be out of said nest again, and replaced a second time. Upon second check up, both babies were gone, as were the parents. In some ways the experience feels like failure, but as I talked about last week, the odds for those babies were never very good even in the best circumstances, which brings us to that first tenet of Darwinian evolution: more individuals are produced each generation than can survive. So why didn’t these birds survive? 

The second tenet of natural selection states that there is variation in traits among individuals in a population. Among all of the chipping sparrows in the northeast, some make very strong well protected nests, others make flimsier ones. Some choose nest sites out of the prevailing wind, others choose more exposed shrubbery. Nest building is a very instinctual behavior in birds (though there are studies that show that as some birds practice, their nests get better, indicating that there is a significant learning component to nest construction as well). The instinctual part of nest building results from genetics, some birds have genes that code for proteins that end up directing cells to do X, other birds may have genes that code for proteins that direct cells to do Y. If X causes the nest to be built in a very secure location, and Y causes the nest to be built in a more exposed location the genes have significant implications for the fitness of the individuals. Those birds may survive, but where they locate their nests impacts the survivorship of their young, and whether or not the genes of the parents get passed on into the chipping sparrow gene pool or not. If they can’t successfully reproduce because they keep building their nest in an unsuitable place, they are a genetic dead end, which brings us to Darwin’s third tenet of natural selection. Genes that code for successful traits get passed on, genes that code for less successful traits eventually die out.

There is one more factor beyond how successful or not the traits your genes code for are, and that factor is simple bad luck. Sometimes organisms are doing all the right things, have robust traits, and high survivorship, when bad luck strikes. In the case of birds, they could be in a tree that gets cut down, or in a tree that gets damaged by lightening or a falling nearby tree, things that don’t have anything to do with their nest location and building skills. And that is the other hard truth about natural selection, there is a large and strong random component to it. Just as the mutations that give the gene pool variation are random, so are the incidents of “bad luck” that can change the distribution of genes in a population without respect to their impact on fitness. These shifts in gene frequency due to bad luck (or being in the wrong place at the wrong time) are called genetic drift, and the smaller the population size, the bigger an impact it can have. 

The mechanism of natural selection cuts a broad and unforgiving swath through populations every reproductive cycle, and while there can be bad luck, there is rarely good luck. The modern human experience of the world is so different from this that it is hard for us to remember. In nature, the default is failure. Keep this in mind as you look around you and recognize what you see for what they are-the chosen few, the rare success stories amidst nearly infinite attempts at life.

References:

The basics of Darwinian evolution: https://www.ndsu.edu/pubweb/~mcclean/plsc431/popgen/popgen5.htm

On birds, nests, instinct and learning—this well publicized study came out in 2011 and challenged the long held assumption that bird nest building is entirely instinctual http://www.sciencedaily.com/releases/2011/09/110925192704.htm

More about those chipping sparrow nests: http://www.allaboutbirds.org/guide/Chipping_Sparrow/lifehistory#at_nesting

Genetic drift: http://evolution.berkeley.edu/evolibrary/article/evo_24

First Year Bird Mortality

Note: This program first aired on July 18, 2015.

Today I have an update to the story I told last week. If you missed it, my niece and I recalled the experience of finding a bird nest that had been blown out of a tree. It was on the ground, and around it were the baby birds that had been in it. We put the birds back in the nest and put the nest back in the tree the best we could, hoping the parents, who were anxiously flitting around the tree chirping, would be able to resume their parenting duties. We realized that this was the right thing to do, even though emotionally it was really hard, our nurturing drive kicked into over drive and we just wanted to take the babies home to “save” them.  And I wish I could give you a happy ending to last week’s story, but the fact is, I can’t. When I went back the next day, the nest was empty, the babies gone, and the parents, if they were around, were silent. When my niece called later for an update, I had to tell her the truth. I was anticipating some melodrama, but instead she said so matter of factly “I kind of knew that was going to happen”, and that was the end of it.

You may wonder, as I have, if putting the babies back into the nest and leaving them was indeed the “right thing to do”. After all, even though we did the right thing, we left them with their parents, it didn’t work out. The reality is that even though they had the best chance of surviving under the care of their natural parents, that doesn’t mean that chance was very high to begin with. This is another one of those dirty secrets of nature that most of us never think about. Most things that are born don’t make it out of childhood. The average mortality for first year birds can be as high as 90%. For typical passerines or perching birds, juvenile mortality in the nest is around 50%, that is before the young even fledge. Nest predation and weather related accidents account for most of this mortality. Once the young fledge and eventually learn to take care of themselves, mortality pressure doesn’t let up but it changes form some what. Young birds aren’t as successful at feeding themselves, so starvation gets added to predation as another factor in first year bird mortality. Most of us, watching our back yard bird feeders, never have any idea the odds are so poor.

But what is the alternative? If a pair of robins in your yard has two successful broods a year (Robins are thrushes and will have a second and even occasionally a third brood in a single season if time allows), and each brood consists of 4 young, at the end of the season where there were 2 robins we now have 10. An environment that easily supported 2 robins may not so easily support 10. And what of next season, if all 10 of those robins were to survive and reproduce? The world would soon be flooded with robins, the environment denuded of all appropriate robin forage. It isn’t even a realistic scenario, and we all understand that. But in order to have the realistic scenario, a relatively steady state of robin population in our back yards, young robins die. Old ones do too, but robins are adapted to have more babies hatch than old birds dying, because the young are such easy prey. If you have many offspring, hopefully one will make it to old age.

Humans used to live this way too. When child mortality was much higher than it is now, women gave birth to many more children. As health care has improved and child mortality has dropped dramatically in most parts of the world, the number of children a woman gives birth to has dropped as well. We no longer have to hedge our bets like the birds do.

Most birds will try again and renest when they experience a nest failure, like those chipping sparrows at my neighbor’s house. There’s still a chance that we will see their young flying this summer, just not the young from that ill fated nest. And when I see an adult bird, I’ll see all of its nestmates now as well, the ones who pulled nature’s short straws, enabling life as we know it, to go on.

References:

Uncited but with interesting math: http://www.countrysideinfo.co.uk/bird_lifespan.htm

Uncited but good ideas (personal blog of a bird researcher) http://toughlittlebirds.com/2013/07/10/the-fledgling-problem/

Check out her entire blog, really nice stuff: http://toughlittlebirds.com/2014/05/30/helping-baby-wild-animals/#more-2653

http://toughlittlebirds.com/

The Junco study: http://www.jstor.org/stable/5000?seq=1#page_scan_tab_contents

The free shelf at my local academic library yielded a 1975 copy of Wallace and Mahan’s An Introduction to Ornithology 3^rd Ed, which has been a great source of foundational material!