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Posts Tagged ‘songbird decline’

The property neighbouring ours doesn’t have a house on it. It is agricultural land used for growing corn and soybeans, with the exception of one odd little patch of forest. The few acres of trees form a little island in the midst of a sea of corn. The soybean crop has been harvested, but the corn is still standing.

A drainage system underlies the land and empties into a rather impressive ditch that borders the fields, eventually emptying into our little river. The water level in the river can change dramatically in heavy rain, no doubt in part due to the artificially accelerated rate of drainage of water from the soil. I took a walk along the ditch to take a look at the forest island, now that the soybeans have been harvested and a path along the edge of the field is clear.

It is composed mostly of impressive Red Pines (Pinus resinosa). They may have formed part of a plantation at one time, but if so, the straight-row pattern that is usually easy to see wasn’t evident. It seems strange that this one little patch of trees, a few acres worth, has been left untouched. I would like to think that they were saved for their majestic beauty, but it seems more likely that plans to harvest the timber will follow at some time in the future. Although the pines predominate, there is also a sprinkling of small maples and beech, now leafless. Around the edge of the forest fragment is a narrow ribbon of birch trees.

CORRECTION: Thanks to Tony for letting me know that the trees are actually Scots Pines (Pinus sylvestris)! They were planted about 35 years ago as a Christmas Tree plantation, but never harvested. As the trees were planted close together in anticipation of a harvest in 6 to 8 years, they grew to be rather spindly when they exceeded their “best before” date as Christmas trees. A number fell over and were otherwise lost, so the remaining stand represents the survivors. They appear to be doing very well.

If I had paid more attention to the cache of cones I came across, I might have done a better job of identifying these trees. Scots Pines are popular as Christmas trees because of their shape and good needle retention, while their fast growth habit and good response to shaping makes them popular with growers. They were one of the first tree species to be introduced to North America. John Laird Farrar notes in Trees in Canada that in Europe the Scots Pine is a tall, straight tree with wood of excellent quality. In North America, the trunks are seldom straight (although I would have to say most of the trees in this stand were pretty straight) and the wood quality is poor owing to the seed source chosen by early settlers. The trees can live in the range of 150 to 300 years, so this stand is still young.

Up until a couple of hundred years ago, most of eastern North America was covered in forest. Now, in eastern Ontario, in the Ottawa region, forest cover is only 13 percent in some areas, and the remaining forest is highly fragmented, a few acres here, a few acres there.

Fragments are not good habitat for birds. Forest fragmentation increases nest predation by a stunning list of predators. Skunks, opossums, and raccoons hunt at night. Snakes, chipmunks, even deer, are not averse to a tasty egg when the opportunity arises. Other birds such as blue jays and crows will rob nests of eggs and nestlings. Cats take a huge toll on the bird population. Cowbirds lay their eggs in the nests of other birds and their larger chicks often survive at the expense of the host’s own young. Predation is higher in forest fragments than in continuous forest. One study found in suburban woodlots, about 70% of nests suffer predation. In rural woodlots, it’s about 50%. Other studies have found different rates, but all found that nests in fragments suffer more predation than nests in continuous forest cover.

Fragments are population sinks. That is, more birds are killed over the breeding season than are replaced by new youngsters, resulting in a net loss to the population. The birds that nest in fragments are like a steady trickle of water going down the drain. Large forests are usually population sources because breeding success is relatively high. For example, the Great Smoky Mountains National Park, the largest national park in the eastern United States, has more than 200,000 hectares of continuous forest. Some 10,000 nesting pairs of wood thrush produce a surplus of almost three thousand females each year beyond the number required to replace the breeding females who have died.

Fragmentation of habitat is one of the reasons the songbird population is crashing. To read more about fragmentation and other songbird issues, check out Dr. Bridget Stutchbury’s book Silence of the Songbirds.

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Moey

Moey

While we cat owners like to think of our cats as warm, cuddly lap-sitters, the fact remains that cats are natural born killers. Inside that cute exterior is a very skilled hunter. In fact, cats are famous for their mousing abilities. However, mice aren’t their only victims. Any small creature is fair game to a cat, and that includes birds.

Cats are not a natural part of the North American ecosystem. They arrived with humans, and have been wreaking havoc on the bird population ever since. This might not have been too much of a problem when the cat population was small, but those days are long gone. Today, there are an estimated at 75 million cats in the United States alone. Studies of cat poop (ewwww!) have shown that the average cat kills and eats at least one bird a week. That includes cats whose owners have never seen their cat with a bird and are convinced that their pet doesn’t hunt. The instinct to hunt is strong. The fact that the cat is well-fed will not prevent it from hunting. Wearing a bell will not prevent these crafty hunters from successfully catching prey.

Capone

Capone

If you do the math, you will see that the toll cats inflict on the bird population is astronomical. Six hundred cats will kill 600 birds a week. Over a 10 week breeding period, those 600 cats will kill 6000 birds. Those figures are for house cats. Consider that half the cat population consists of free-roaming, homeless cats hunting for their livelihood. Cats kill millions and millions of songbirds every year. You can read more about cats and birds at the American Bird Conservancy site. Cat lovers and bird conservators agree. Cats belong indoors. The Great Outdoors is no place for a cat! For more on indoor cats, see Every Cat an Indoor Cat: Part One.

Arthur

Arthur

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silence

Silence of the Songbirds: How We Are Losing the World’s Songbirds and What We Can Do to Save Them, by Bridget Stutchbury. HarperCollins, 2007.

Every fall, we northern dwellers are accustomed to “our” birds leaving our cold, snowy winter behind and flying south. This seems like a very sensible thing to do, and if we think of them at all, it is probably to imagine the birds on vacation, soaking up the rays in the Neotropics. Far from being on holiday, birds that migrate south face a difficult season. They must compete with other birds for habitat that will keep them fed and allow them to build up the reserves they will need for the flight north and a new breeding season. Increasingly, their lives are imperiled by the destruction of the rainforest as more and more trees are replaced with agricultural fields. Other threats include the heavy use of pesticides that can result in mass poisonings. When they return north with the spring, life is no easier, with widespread habitat loss, cats, windows, lights, towers, and other disasters-in-waiting ready to take their toll.

Birds are amazing creatures, little more, it would seem, than sparks of life wrapped in feathers. What incredible lives they live! However, the ever-increasing challenges that songbirds must face, both in the north and the south, are causing a slow but steady decline in songbird populations across the continent. In the last 3 to 4 decades, the songbird population has fallen by a horrifying 20 to 30%. Songbirds are a vital part of the ecosystem. They perform irreplaceable services that we humans count on, from insect control to spreading plant seeds. The fading away of the songbird population is a symptom of the deep wound we have inflicted on the natural world. If they go, will we be next?

Bridget Stutchbury is a professor of biology at York University in Toronto, and a fellow and research associate at the Smithsonian Institute. She and her husband have devoted their careers to the study of songbirds. In Silence of the Songbirds, Stutchbury takes the reader with her as she looks at songbirds in their winter homes. She explains the science behind songbird studies and tools such as the Breeding Bird Survey. She examines the many threats that songbirds face. Finally, she offers the reader a list of solutions, how everyone can contribute to halting the decline of songbird populations. Anyone who has ever looked for the first robin of spring or enjoyed the sound of a bird singing in the yard will want to read this book. Understanding the problem is the first step in finding solutions.

How To Save A Songbird

Buy shade-grown coffee that is both organic and fairly-traded.

Buy organic produce

Avoid non-organic North American crops such as alfalfa, Brussel sprouts,blueberries, celery, corn, cotton, cranberries, potatoes and wheat.

Buy unbleached, recycled paper products

Turn off the lights at night in city buildings and homes during peak migration periods

Keep your cat indoors

For more on these issues, see these posts:

Every Cat an Indoor Cat

Natural Born Killers

Organic Food is For the Birds

Climate Change and the Boreal Forest

Shade the Coffee, Shelter the Birds

For more on the use of pesticides on potatoes in North America, see Michael Pollan’s book, The Botany of Desire, reviewed on November 23.

kingbirdhovering

Eastern Kingbird (Tyrannus tyrannus) catching insects on the wing.

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