Birds prepare to leave the nest

This time of year, the young undergo rites of passage from one life stage to another. Parents watch with a mixture of relief and regret as their offspring prepare to leave the nest and become independent. Not just human offspring, of course. Birds do it, too.

Sunday was a busy day for the house wrens that have again nested in our hanging birdhouse. All day, the parents made trips to the nest with beaks full of insects, encouraged by a steadily increasing chorus of chirps from their nestlings.

Suddenly there was a great commotion, and a black phoebe followed by two young ones flew into the yard. That family was in the next stage of development.

Black phoebes are also called tuxedo birds, as the adults have black heads, chests and backs, and a bright white belly. Only one of the phoebes was dressed like that. The others were all black, had downy feathers on their heads and bodies, and bright yellow on their beaks ? fledglings, just out of the nest.

Birds grow their flight feathers early, and most can fly when they leave the nest. But the rest of their feathers are fluffy down, good only for insulation; body-covering feathers for waterproofing and smoother aerodynamics grow in later.

Ground-nesting birds like quail and ducks are born with down feathers, and they walk away from the nest like little balls of fluff within a few hours of hatching. Birds in nests hidden in trees hatch helpless and naked.

Nestlings that rely on their parents to bring them food have bright red or yellow on their beaks. These colors are behavioral “releasers,” and they encourage the parents to feed the young. In experiments, birds peck preferentially at bright colors. The yellow on the beak of a fledgling reminds the parents that the youngster still needs to be fed.

The phoebe parent returned with food for the two chicks several times in the next hour. This whole process is known as “branching.” The parents park just-fledged offspring on a branch and fly off to find food. The young become more capable over time ? days or weeks, depending on the bird species ? and start following the parents around.

As the beak color fades and the young improve their flying skills, parents become reluctant to feed them. That is when you can see young birds chasing their parents from branch to branch, calling and using begging behavior.

A begging bird opens its beak, holds its wings down by its sides and shakes them.

On Monday, the wren nestlings were chirping loudly most of the time, and the parents were feeding them almost nonstop. They were clearly going to fledge very soon. I made sure there was space on my camera’s memory card.

Alas, it was not to be. On Tuesday morning, the bird house was quiet by the time I got up. The early wren escapes the photographer! We had missed graduation day.

But there are other birds in the air, and yesterday a very loud trio of crows were flying around outside the house; two young ones pursuing a reluctant parent.