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Background
Some robins
can live up to 12 years, according to banding studies. These birds may have
built 20 or even 30 nests over their lifetimes! Robins don't need written
instructions for building their summer homes. They follow the "nest-building
blueprints" in their brains, and instinctively know how to build the
perfect structure to hold the eggs they're about to lay. Have you ever noticed
that robins' nests are always alike? But have you ever seen a robin teaching
another how to build a nest?
Imagine you
are a robin. You can make a robin nest yourself if you follow the instructions
below. In most places in North America, you will perform this nest-building
process two or three times a year. After a couple of years, you will be
a real building expert. Let's get started!
Nest-Building
Directions
1. Find
a suitable building site
- The site
should be protected from sun, wind and rain. It can be anywhere from
ground to treetop in height; the site must be on something sturdy enough
to anchor the nest securely in place. You don't want your nest to fall
off!
- Your nest
should also be very close to a good feeding spot so you can easily find
worms while keeping an eye on it, and it shouldn't be too far from water.
- Choose
a spot that is hard for predators to see. Remember, you and your eggs
and babies will be sitting here for the next 5 weeks, so be careful
to pick a spot that's safe, cool, and comfortable.
2. Gather
materials
- Grass
fibers: Collect about 350 dead grasses and twigs that are about 6 inches
long. (The pile should weigh about 135 grams.)
- Soft
mud: After a soaking rain, collect mouthfuls of mud in your beak and
travel back and forth to your nest site a few hundred times.
(If you happen to be a person rather than a robin, you might substitute
your hands for a beak to collect the mud, but don't forget that it takes
a pair of robins hundreds of visits to build the nest!)
3. Build!
- Weave
the grasses together, cementing them to each other and to the supporting
branch or windowsill with mud.
- Next,
use your tummy to shape the nest into a perfect baby cradle.
- Finally,
line the inside with the softest grasses and hairs you can find so the
eggs will stay warm and not get pierced by any twigs or sharp grass
edges. The nest must be tight and snug enough to cradle the eggs and
hold in your warmth, but large enough to hold four or even five BIG
nestlings.
When you are
finished, your nest should weigh about 205 grams when dry. (Of course it
will weigh more while the mud is wet!) This is a heavy nest. But four nestlings
together can weigh as much as 280 grams before they leave, so your nest
must be very strong!
Quiz
for Nest Builders
The perfect robin nest must serve as a snug baby cradle to keep the eggs
and babies warm, dry, and safe. . .with room for you (the mother robin)
to hunker down to incubate your young. You weigh about 77 grams. Each of
your eggs weighs about 6.3 grams when newly laid. Each baby weighs 5.5 grams
when it first hatches.
Q. Why are the babies lighter than the eggs?
During the
next 9-10 days, the babies will grow tremendously, weighing at least 70
grams before they start losing weight a few days before fledging. Fortunately,
by the end of the first week, you can sleep on a nearby branch rather
than with the babies so it won't get too crowded-- unless it rains. When
it rains, you have to sleep on top of the babies to keep them dry.
Q. Why do you suppose the nestlings lose weight while still in
the nest?
IMPORTANT NOTICE! You've done a lot of work to make this wonderful nest.
But after the babies leave, you often have to move out! Even the cleanest
robin family can't keep out mites, lice and flies. Once these critters
get a head start, they can really multiply fast, making an old nest unsafe
for a new batch of babies. You might raise later broods in the same remodeled
nest, or you (the female) may build a second nearby nest in 2 or 3 days.
Q.
What kind of site will you look for?
Try
This! Journaling Questions/Field Activities
- To encourage
robins to nest on your house and to make it easier to observe nesting
behavior, try building your
own robin nest box. See our handy instructions and tips for carrying
out your nest study:
- Print
a copy of our checklist to help and enjoy the robins in your yard! See:
National Science Education Standards
- An organism's
behavior patterns are related to the nature of that organism's environment,
including the kinds and number of other organisms present, the availability
of food and resources, and the physical characteristics of the environment.
- Behavior
is one kind of response an organism can make to an internal or environmental
stimulus.
- Plants
and animals have life cycles that include being born, developing into
adults, reproducing, and eventually dying.
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