Balancing act in the garde

Raising healthy youngsters is challenging for all parents, even for wildlife who choose to rear their young in our gardens. Parenting becomes a delicate balancing act among natural forces.

In late July a newly built bird nest setting five feet off the ground in a crotch of the river birch tree in my front yard caught my attention. The open cup was made of several layers. There was a platform of narrow weed stems and twigs. Atop the platform strips of birch bark, dead birch and oak leaves and pine straw were intertwined. This leaf layer also included pieces of cellophane. Fine rootlets lined the inner cup. To mold the cup, the female presses and rocks her body around the nest.

The open cup nest is a specialized container for eggs and nestlings. It functions as a microclimate for eggs, nestlings, and the incubating or brooding female. Nest temperature affects embryo development and the amount of energy expended by the female during incubation and brooding. This particular nest had clusters of leaves shading and fanning it.

Female cardinal Matching nest characteristics to descriptions in the

Peterson Field Guide to Birds'

Nests by Hal H. Harrison tentatively identified it as made by a northern cardinal. The identity was confirmed when an oval greenish- white egg with brown splotches appeared.

A female cardinal sat on the nest after the first egg was laid. Usually females wait until the full clutch is laid before incubating. One day after the first egg was laid, a second and final egg appeared. Daily inspection of the nest revealed eggs were in different positions, evidence the female had turned them to insure even heating and to prevent shell membranes from adhering to the shell.

For the next two weeks the female cardinal incubated the eggs continually. Her mate stayed in nearby tree tops warning her of danger by chipping loudly when I appeared with camera. Her short periods away from the nest were for feeding. The male was not observed at the nest. His bright plumage would be a signal to predators.

Fourteen days after the first egg was laid, the first nestling debuted. The next day the second nestling appeared. Both were born pink and naked, blind and wobbly. The egg tooth used to pip their way out of the shell was visible on top of the beak. Eventually, it was absorbed into the enlarging beak. Until nestling thermostats develop, the female broods the clutch.

Sideview of cardinal nest showing platform and leaf layers. Note birch bark in nest. Eggshells were not in the nest or on the ground. Adult birds either eat the shells or carry them far from the nest to thwart predators.

Nestlings slept and begged for food. Both parents feed nestlings soft- bodied insects at this stage of development. The growth of new cells and tissues requires the high protein diet insects provide. Begging nestlings reach their necks high into the nest and open their mouths wide. The beak closest to the parent is most likely to get fed first.

Nest sanitation is another parental task. Nestlings produce lots of waste. I observed a nestling expel a fecal sac, a diaper-like package of waste. Later the sac was gone. During the first few days of the nestling period, parents eat the fecal sacs to recycle the nutrients. Afterwards fecal sacs are carried far from the nest.

Male cardinal Six days after the first hatching, one nestling vanished from the nest. The nest was intact with no sign of an intruder. Parent birds were omnipresent with the surviving nestling but, despite their watchfulness, two days later the nest was empty. Again, the nest looked new. This time the parents were not around either.

Apparently, nest predation is high. Cardinals may attempt from two to five broods per nesting season but, at best, only one or two are likely to be successful. Since predation is rarely observed directly by humans, scientists use the condition of the nest as a clue to the predators. If a nest shows no signs of disturbance, the most likely predators are snakes like black racers, rat snakes, and corn snakes; birds such as crows, blue jays, owls and some hawks; and small mammals like eastern chipmunks, white- footed mice, and cats.

Cardinal eggs are greenish- white with brown splotches. After failure of a nest, parents usually move to a different location where the female begins building anew and the balancing act continues. The President's Orientation for the Garden Club Council

of Greater Columbia will meet August 24 at the Garden Council Building, 1605 Maxcy Gregg Park. The board will meet at 9 am, refreshemts will be served at 9:30, and the general orientation for club presidents, council officiers,

and committee chairs will begin at 10 am.

The red mouths with yellow rims of begging nestlings help parents get food in the right place. Grayish down appears in areas where feathers will emerge. Silhouette of male cardinal overseeing the nest. Six days after hatching one nestling vanished from the nest. Nest predation is high. Eight days after hatching two nestlings, the nest is em pty.