A recent column of mine in the Home and Garden section discussing how long birds live contained two errors. First, I said 7 grams, the weight of a particular bird species, was equivalent to half an ounce. Nope. An ounce is about 30 grams, so 7 is more like a quarter-ounce. Which, I suppose, makes survival of these tiny bird creatures for years even more impressive.

Also, discussing how long birds live, I failed to mention that about half of them never make it to their first birthday. Nature can't afford to let them all survive. Not enough food, not enough habitat. And, you don't want future generations of a species to be created by anything but the best breeding stock. So, disease, weather, lack of food, pesticides, other chemicals we spread in the environment, predators, cars, windows, and so on cull the population.

Actually, we make more than an effective contribution. Extract us – people – from the calculation, as was the world a long time ago, and you have true survival of the fittest, the evolutionary scheme that filters out the weak and vulnerable, ensuring continuation of the species.

Nature does the required job. Every bird, every animal killed under our hand is over-kill. That's why the lists of endangered and threatened species grow and grow and grow.