Reflections in Nature: Some birds helpless at birth
The birds have been busy gathering supplies to build their nests. There are as many different types of nests as there are species of birds.
The location of where a bird decides to build its nest is very important. The nests of many songbirds need to be hidden from predators; therefore, the materials used must camouflage the nests. The nests also must be built in areas that will give protection from storms, extreme cold and excessive heat.
Birds that lay eggs that will hatch in a short period of time – usually two weeks – are called altricial, meaning that the young are born in a relatively helpless state.
In altricial birds, the nest is a protective nursery, where the young are provided with warmth and food by their parents.
At hatching, altricial birds are naked and their eyes are closed. An exception to this rule are the young of herons, hawks and owls, which are covered with down when hatched. However, of these birds mentioned, only the owls are hatched with their eyes open.
These altricial young nestlings usually spend about two weeks in the nest, where they are protected by the parents.
There are birds, such as hummingbirds, kingbirds and martins, known for their attacks on larger birds, such as hawks and crows. A crow simply flying too close to a nest soon will have the parents dive bombing in an effort to drive the crow away from their nest site. Different species of birds often will join in the chase to drive away the intruder.
Young birds that leave the nest shortly after being born are said to be precocial, which comes from the Latin word praecox, meaning “to ripen beforehand.” These young birds will develop inside the egg and won’t hatch for almost a month.
The young are called chicks and are able to move about soon after hatching and drying. They either are partly or not at all dependent on their parents for food. These chicks hatch with their eyes open and covered with down and will leave the nest within a few hours. An exception to this is that some gull and tern chicks will remain in the nest for a few days after hatching.
There is an interesting connection between the weight of the yolk of the egg and the condition of the young at hatching.
In altricial nestling, the egg yolk is 15 percent to 25 percent of the egg’s weight.
In a precocial chick, the yolk can be up to 50 percent of the egg’s weight. Due to the precocial chick being in the egg stage longer, the chick will need the extra food the egg provides.
Young birds that remain in or at the nest and cared for by the parents are said to be nidicolous, which comes from two Latin words: nidus meaning “a nest” and colere meaning “inhabit.”
Since the nestlings will spend time in the nest, a nest needs to be well constructed and camouflaged. Most nests are built in trees where they are fairly safe from ground predators.
The nests of precocial chicks usually are found on the ground. Their protection is that they have the ability to run, hide and feed themselves shortly after being hatched. These chicks are said to be nidifugous, which also comes from two Latin words: nidus meaning “nest” and fugere meaning “to flee.”
The number of eggs in a nest is called a clutch. As a rule the average number of eggs laid by songbirds tends to increase as the birds move north in latitude. Usually, a songbird will lay more eggs in their first nest of the season and a smaller number of eggs in their second or third nest.
Some birds are determinate egg-layers, laying only a certain amount of eggs and not replacing those eggs removed from their nest.
Other birds are indeterminate layers, meaning that they will continue to lay eggs to replace those removed from their nests. In one study done, a yellow-shafted flicker had 71 eggs removed in 73 days.
In late May, I found six eggs laid by a black-capped chickadee in a bird house in our backyard. A few days later, I found that the female had abandoned the eggs.
Several days later, I noticed a wasp flying around the bird house so I went to check and found the eggs gone but a new nest was being built on top of the old nest. This is very strange since last year a female chickadee laid her eggs in the same box and also abandoned them.
Bower retired after 34 years as a wildlife conservation officer for the state Game Commission. He has published several books about his experiences. Questions and comments may be sent to him at 153 Redington Ave., Troy PA 16947.