Anatomy of Preservation

Here's a neat time-lapse video produced by the University of Michigan's Museum of Zoology, filmed in the Mammal Division – it shows the preparation of a bat specimen, from a body in fluid preservation to a mounted, articulated skeleton. Take a watch, and prepare to be impressed by the quick work of the bug room's dermestid beetles! You might also recognize some of the mounts on the wall...

Feed the Birds!

It's November – and in the northwoods, that means less sunlight, colder temperatures, and an influx of winter birds visiting the bird feeders. If you too have a bird feeder, you might notice the vast amounts of chickadees, nuthatches, and woodpeckers that visit immediately before a particularly chilly or snowy day. These incredible birds don't migrate south for the winter: they remain year-round, even through the coldest and darkest months. To keep their tiny bodies warm, they must eat constantly, and though there are plenty of natural food sources, you can help!

Suet cakes, usually made from bird seed and rendered beef fat, are a product designed for feeding woodpeckers and other winter birds. At first glance, beef fat might seem like a strange component to bird food – and in a way, it is. Many birds, however – including chickadees and woodpeckers – do scavenge the meat and fat from animal carcasses, especially in the colder months. Deer remains are an especially important source of wintertime protein; in cities and subdivisions, though, where there are few or no deer, cow fat – a waste product of the beef farming industry – becomes the alternative.

But before you go out and buy suet cakes for your winter birds, let's skip the rendered beef fat and talk about a little DIY project!

You'll need a medium- to large-sized, freshly-dead mammal, a few suet cake molds, a small amount of birdseed, and some peanut butter, if you really want to get fancy.

In the spirit of this blog, I used the fat from a medium-sized raccoon, found dead on the road. (During this time of year, many mammals – raccoons included – are bulked up for the winter, and the amount of fat they accumulate is really quite impressive.) After skinning the raccoon, I set aside about a half-pound of fat – enough to make two suet cakes.

Step One: Melt the Fat!

Stick the animal fat in a saucepan – ideally, one you won't be cooking your own meals in!

 

When the fat is first harvested, it's slimy, pink, and opaque. As it's heated, however, it turns a creamy color, becoming translucent before melting to a clear liquid.

It takes very high temperatures for fat to melt, so proceed with caution! It also takes time – be patient, and allow for the fat to melt almost completely before removing it from the heat. When there are only a few small globs of unmelted fat remaining, turn off the heat, and let the saucepan cool for at least 15 minutes before proceeding to the next step.

Step Two: Extra Goodies!

Though a solid block of animal fat is perfectly edible to birds, it doesn't hurt to add in some other tasty treats, as well. Before you mix anything into the melted fat, however, make sure it's not too hot. Drop a small amount of water into the saucepan: if it sizzles, the fat is still too hot! If not, you're ready for this next step.

Mix in a few tablespoons of peanut butter, if you'd like, then add in the goodies: sunflower seeds, peanuts, and even dried cranberries are a great addition to the diet of your backyard winter birds.

Step Three: Cool It!

Once all your ingredients are incorporated, it's time to pour the mixture into suet cake molds. I used the leftover packaging from store-bought suet cakes, but other homemade or impromptu molds will work, too – so long as they fit into a standard suet feeder.

Allow the suet cakes to cool in your freezer for several hours. They'll be ready to put outside the next morning!

Step Four: Feed the Birds!

Once it's completely solidified, place your homemade suet cake into a suet feeder and hang it up with the rest of your bird feeders. Don't be dismayed if the birds don't immediately flock in to eat!

Though I hung up the suet cake on Sunday, it wasn't until today that we observed birds feeding from it. This morning, Steph saw a female hairy woodpecker (Picoides villosus) eating the suet and took some photographs for me.

Whether you're a hunter with some leftover fat from your kill, or you have a habit of picking up roadkill from the curb, making homemade suet cakes is a rewarding experience, and one that your backyard winter birds are sure to enjoy!

Bones Beneath the Window

In autumn, when the foliage starts to die back, summertime deaths are revealed. When the obstructing plants wither, we see several months' worth of decomposition and scavenging; often, there's a brief window of opportunity to find these skeletons, when the flora of the forest floor has senesced but the trees have not yet shed their leaves. Roadside ditches, choked with invasive weeds and shrubs in the warmer months, lay bare the year's roadkill; our garden, full of broad-leafed hostas and colorful daylilies, becomes dry and dormant for the winter.

At some point over the summer, a warbler collided with our window, fell beneath the hostas, and died. Like most animal deaths, it went unnoticed — at least, by humans. In the months that followed, decomposers and scavengers consumed the carcass, eating flesh, organs, connective tissues, and even the smaller, softer feathers. Left behind was a skeleton, tiny and fragile, primary feathers still clinging to the bones.

Some months after the warbler's death, it was finally discovered by human eyes. Fallen needles from a nearby red pine had already concealed much of the carcass.

 

I was struck by the fragility of the skeleton, and the fact that it had weathered several months in the same spot, undisturbed and intact. The skull of the bird still pointed to the sky, in a seeming act of defiance of being reabsorbed into the earth. 

 

How many animal deaths go unnoticed by human eyes? How many birds have struck our windows? How many reptiles and amphibians are hit on the road, unseen at high speed? How many organisms are fed by these deaths? As the autumn landscape turns to a palette of browns and grays, look for those that have passed during the summer months. Discover their bones, ask questions, and learn something from them.

A Final Journey

Every year, sexually mature salmon travel upstream to reproduce. It's an amazing journey, and it's been well-documented in places such as the wilds of Alaska, where the salmon swim inland from the Pacific Ocean in astounding quantities, so numerous that their shiny bodies nearly spill from the rivers. Along the way, many are consumed – by grizzly bears, by bald eagles – until at last, they reach their final destination: for once they spawn, the salmon die.

What some may not know is that this same journey takes place elsewhere – in my backyard, for example, along the Chocolay River. In the autumn, the coho salmon (Oncorhynchus kisutch) begin to leave Lake Superior, swimming upstream to spawn. Other species in the salmon family join, as well: rainbow trout (Oncorhynchus mykiss; more commonly known as steelheads here) and chinook salmon (Oncorhynchus tshawytscha), both of which, along with coho salmon, were stocked in the Great Lakes some years ago.

As they make their spawning run, the behavior and physical appearance of salmon undergo some dramatic changes. They stop feeding; the snout of the male salmon becomes large and hooked, and the body of the female salmon swells with roe. By the time they spawn, as Bernd Heinrich notes in his book Life Everlasting, the flesh of the living fish has already begun to deteriorate. They die soon after, and their corpses help to feed the ecosystem in which their offspring will soon hatch.

The bodies of these large fish are eaten by many animals, including raccoons (which likely dragged this deceased salmon from the Carp River)...

 

... and by people. I caught my first-ever coho salmon today, from the Chocolay River. After filleting it, I left the rest in the backyard. The neighborhood foxes and raccoons will finish what I didn't take.

Sorry

A few days ago, Steph heard the impact of a bird hitting one of our windows. Despite looking, she couldn't locate it; yesterday, I finally found the bird, camouflaged amongst fallen leaves and pine needles. It was a hermit thrush.

 

 

The hermit thrush (Catharus guttatus) has, in my opinion, one of the most beautiful songs. In the spring and summer months, they are a common sound in the northwoods; I have heard the flutelike call lilt through an otherwise silent jackpine forest, and it's an experience I won't soon forget.

Now, however, is not the time for birdsong: it's migration season, when our summer birds head south for the winter. This hermit thrush was likely passing through, on its way to warmer places; perhaps it flew all the way from a boreal forest north of Lake Superior. It saddens me to know that its life and journey were cut short by our window – a window that has never caused trouble for birds before, but now has decals to keep this from happening again.

See also: Moving Closer, from September 11, 2010.