growth rate graphs can only be used to give you an approximation
of the growth of the baby bird you have found. This is because
of a number of things:
first is that the size of the same species of bird varies
a bit from one part of the United States to another. Birds
of the same species from the Upper Midwest and some mountain
states tend to be a bit larger than those from the Eastern
Seaboard and those from the Mexican border states and South
Florida tend to be a slightly smaller.
graphs do not divide the growth of male babies from female
baby birds – they give an average individual combined
nestling weight. In songbirds, males tend to gain weight faster
and end up heavier than female birds. The opposite is true
for the birds of prey.
third factor is that the baby bird's weight – from the
day of hatch – varies depending on the availability
of food to feed it. Some years provide better food supply
than others. These graphs were prepared from wild nestlings.
The baby bird you raise will have unlimited food available.
So it will often gain weight more rapidly than parent-fed
fourth factor is the number of babies in the nest. When only
a few chicks are in the nest, each chick has more food available
to it and will grow faster.
parent birds lay their eggs a few weeks early or a few weeks
late. When this happens, the parents may miss the time when
their favorite foods are most available, causing the chicks
to grow more slowly. The same thing occurs when rain or unusual
weather occurs during the breeding season.
see from these graphs that most baby bird’s growth follow
an “S” or sigmoid curve early on. The big difference
between small species of birds and large ones is not that
the large ones grow faster - large species of birds just keep
weight of your baby bird is not important. What is important
is that it stays on track, above, on or below its growth curve
graph. The best way to tell if your bird is developing normally
is to palpate its keel or breast bone. If it is convex –
like the chicken breasts sold at the supermarket – it
is fine. If it is V-shaped or concave, you have a problem.
Looking at the bird is not sufficient because you can be fooled
by fluffy feathers that hide a thin bird.
see from the graphs that some species of baby birds over-shoot
their adult body weights before they fledge. Others gain their
last few grams weeks or months after they are flying on their
also notice that there is often a small dip in body weight
near the time that the baby bird leaves its nest. This is
because it is not getting all the food it would eat. It is
hunger that gets the little bird airborne at an early age.
You should not see this fledging weight dip if you are supplying
all the food that your youngster desires. Perhaps the parent
birds were just exhausted and unable to keep up with the clutch’s
growing need for food. Perhaps it is the hormonal rush at
fledging that causes the baby birds to become antsy and hyperactive
at fledging time. Probably it is a combination of the two
that causes this dip.
not healthy to push the limits of a baby bird’s growth
potential by over-feeding. In some birds I have raised (penguins)
this led to chicks with muscle weight too heavy for their
bone structure to support - causing curved spines and foot
problems (bumblefoot). Bigger
is not necessarily better.
baby bird is going to learn to fly later than the feather
position on my graphs indicate. Have patience, some human
teenagers need encouragement to leave the nest - but they
all eventually do.
weight of baby birds is approximately their egg weight minus
the shell weight. It is slightly less once they have dried