After the rain is a good time to feed birds

THE NATURAL VIEWPOINT

When a powerful storm moves through, as one did recently, I wonder

what the birds do to keep dry or warm. Rain makes their wings too

heavy to fly well, so they go under cover in heavy rain. During a

recent downpour, I watched our local House Wren seek shelter under

the car.

Winter storms are necessary for the shrubs which are the base of

the birds’ food chain. Rain encourages new vegetation, more

plant-eating bugs, spiders to eat them, etc., and flowers, berries

and seeds -- all potential food sources for the birds. Rainy weather

is part of their lives and the birds must be able to survive.

Right after the rain lets up, there’s suddenly a lot of activity

in the shrubbery, as the birds pop up to forage from wherever they

took cover. It’s a great time to bird watch, but at a distance;

they’re hungry. Food is the driver of a bird’s life; avoidance of

cold or wet is not as important as filling its crop by nightfall.

Do they suffer in harsh weather? Of course; it’s a tough time for

all animals exposed to the elements, and the fittest survive best.

One particular storm gave us a peek at the usually invisible

workings of natural selection for the most fit. This unusually severe

snow, rain and sleet storm in Rhode Island in 1898 became famous

because a biologist named Herman Bumpus collected a lot of dead and

stunned House Sparrows after the storm. He took them back to his lab,

where some recovered. He then made a series of measurements on each

bird, such as length, wingspread, weight, beak size, head size, etc.

Comparing survivors and non-survivors, he noted that birds with

average measurements survived better than those with more extreme

measurements. Birds that deviated from the norm were not as “fit.”

The long- or short-winged birds, the heavier or lighter birds, were

not as well adapted as the “average” birds living in these

conditions.

House Sparrows are the Downtown “Zinc” birds: chestnut-backed,

gray bellied, the males with black bibs around their beaks. They

chirp incessantly and hop around looking for seeds (or croissant

crumbs). In 1851 and 1852, 100 birds were brought from Europe and

released in Brooklyn. They survived by eating seeds found in

then-plentiful horse feed and manure.

Nowadays, seed in bird feeders provides a large part of their diet

in urban areas, and an estimated 150 million of them live in the U.S.

and Canada.

Bumpus’ measurements were taken about 50 years after their

introduction, at a time when the birds were still adapting to their

new continent.