Biology Reference
In-Depth Information
Q What part of the egg turns into the chick?
A
The yolk is a single giant cell that divides to form the chick. Of course, the whole yolk
doesn't split in half — the cells that divide from it are very tiny and grow to surround the
yolk as it shrinks, providing the nourishment for the growing chick.
Q My Cockatiel lays eggs all the time, but there isn't a male in sight. I thought you
needed two parents to make a baby.
A
You do need two parents to make a baby bird. But during the breeding season (which
for Cockatiels is much of the year), females ovulate whether or not they mate. Unfertil-
ized eggs, like store-bought chicken eggs, have a yolk and albumen but can't produce a
chick.
It may be a good idea to let her build a nest and lay the eggs in there. Once she has
a full clutch, she'll start incubating them and will stop ovulating. If you remove the egg
every day, she'll keep laying eggs. Producing eggs requires calcium, so if she's continu-
ally laying eggs, she may suffer from calcium deficiency.
Q While at our family cabin in Michigan, I found a Cooper's Hawk egg on the
ground, about a hundred yards from where the nest was. It was cold to the touch,
but I picked it up and kept it warm, just in case. I'd like to know if there's a way to
find out if the chick inside is still alive.
A
Toseethechickinside,peoplecandleeggs;thatis,theyholdthemupsothey'rebacklit
by a bright light. But please don't try to hatch this egg. If it was dropped, it's very likely
the embryo was killed. It's even likely that the parents tossed it out when it didn't hatch
after other nestlings did hatch. If something else happened and a live egg was dropped
by a predator or fell out of the nest in a storm or accident, its chances of hatching into a
healthy chick are low. Being shaken, the impact of falling, and being significantly cooled
after the onset of incubation could each be problematic.
LET SLEEPING BIRDS LIE
Water birds sometimes sleep in the water.
Some sleep on tree branches or in cavit-
ies, too. Some birds can be literally half asleep — they close one eye and allow one half
of their brain to sleep while the other eye and half of the brain are engaged in watching
for predators.
