Monday, May 28, 2007

Nest success

This is the time of year when birds are building and using nests. But as parents, birds are often unsuccessful, both at building nests and at protecting their occupants.

Bad weather and faulty construction can lead to nest failure. But most bird nests are also subject to predators. Various studies of nest predation have found that between a third and a half of nests are attacked by other birds, small mammals, and reptiles such as snakes.

Percentages of predation can vary widely. A study of Hermit Thrushes in Arizona found that predators attacked 83% of the nests. A study in the same state of Black-headed Grosbeaks found predators attacked only 23% of the nests.

Dr. Steven W. Kress reported a study that found that of 100 Song Sparrow eggs, 74 hatched successfully and 52 eventually fledged. That’s a loss of nearly 50%.

Years ago, Dr. Arthur Allen of Cornell University estimated that less than 20% of all nests succeed in producing a complete set of new, mature birds. But as Allan and Helen Cruickshank point out, that’s nature’s checks and balances. “Should all of the birds’ eggs laid in North America in a single season not only hatch but the young mature,” they said, “the continent itself would be so crowded with birds that man himself would suffer acutely.”

Tuesday, May 22, 2007

Frozen out

Tulip Trees bloom in May – you can see their petals being discarded to the ground below by squirrels eating parts of the sweet, green-orange flowers. These members of the magnolia family are our tallest trees, averaging 120 feet, often reaching 150 feet, and known as tall as 190 feet.

Tulip Trees were once circumboreal – found in North America, Europe and Asia. They now live only in China and eastern North America. The European Tulip Trees were wiped out, not by man but nature, in the last ice age. On our continent, as the ice moved south, the Tulip Tree seeded its way southward ahead of the shelf. In Europe, however, the Mediterranean to the south and mountains to the east trapped the species and none survived.

Because our trees could “escape” down the north-south coastal plains, ridges and valleys, our part of the world is home to many more species than Europe has.

Thursday, May 10, 2007

Alien invasion

A new invasion of alien plants is looming, but the invaders are not from the east or west, but the south.

For centuries, aliens have been arriving from Europe and Asia, imported as garden flowers, herbal flavorings or medicines, or just hitching a ride with crop seeds. They came from climates similar to ours and, finding no enemies, the likes of Garlic Mustard, Purple Loosestrife, Japanese Knotweed, and Japanese Barberry thrived to become pests.

Enter global warming. As the New England winters weaken, both plants and animals that could not survive here are moving northward. While white birches and other species are dying off because of the warmth, palms are already surviving in southern New Jersey and Pennsylvania, and kudzu, which has been called “the plant that ate the South,” has crossed the Mason-Dixon and is already in Connecticut.

How to deal with so complex a problem befuddles even the experts, but it can’t hurt for us to leave a smaller footprint on our Earth, while at the same time, stomping invasives when we spot them.

Wednesday, May 02, 2007

Killer cats

Few scenes are as peaceful and domestic as the family cat, curled up and purring in your lap, on a cool spring evening. But for uncountable millions of creatures, house cats are not so warm and fuzzy, and feline fangs are the last thing they see before they die.

Conservation officials say that of the 90 million pet cats in the U.S., only 35% are kept indoors. The rest are let loose to hunt, killing “hundreds of millions of birds, and more than a billion small mammals, such as rabbits, squirrels, and chipmunks each year,” says the Connecticut Department of Environmental Protection.

Habitat destruction is the leading cause of declining bird populations, but right up in second place are cats, both domestic and feral.

The killer is becoming the killed, however, as house cats are now prey themselves. Increasing numbers of coyotes and now fishers – a large carnivorous marten that has been reintroduced into our woods – are catching and eating many house cats.

The answer to both deadly problems is simple: Keep kitty indoors.