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posted on August 4, 2009 | Science and Nature
On the Diaper-changing Behaviour of Robins

On the Diaper-changing Behaviour
of Robins

What is going on in this picture?

One of the
great truths of physics is
that what goes up must come
down again. 
A truth as great in life
is that, barring upchucking, what goes
in one end must stay inside
or come out
the other end.
It is parents’ lot in life to
put enough of the right kind of food
in one end then deal with what
comes out the other. 
ain’t no other way.


At least for altricial
species that take time in the
nest to develop. 
Precocial species are
right out of the eggshell. 
some jays, whole family groups tend young
and species
like cuckoos and cowbirds
don’t tend
at all but lay eggs in other species’ nests and let the
hosts do all the work.  B
ut in general, parents do the
dirty work both coming and going. 
In the first year
or two of life, human babies progress in several
stages from defecating in diapers, which their
parents later change, to using the toilet as
their elders do and
the same applies to
robins, Turdus migratorius.

For two weeks from
hatching to fledging from the
robin parents are engaged similarly,
as I observed at a nest in my studio,
and just as in
the case of humans, robin nestlings are increasingly
cooperative as they age.  This eases and speeds parents’
tasks, lets parents bring more food, allowing babies to
grow faster, the nest to stay cleaner and freer from
and is an all-around good thing for
everyone concerned. Including
sculptors in the area.


When I say
robin babies grow more
cooperative as they age I don’t mean
to say they cooperate with each other.  Not
that at all; they cooperate with the hand that feeds
Except for an exception I’ll tell you about later,
it was tooth and claw for the babies.
The biggest baby
has the biggest mouth, longest neck, strongest wings, and
can push its siblings down and step on them best.  It takes
all the advantage it can get. 
Fortunately for the rest of
its sibs. parents do as well as they can to even things
out but
big still gets bigger faster. If each chick
had its way,
it would get all the food and
its sibs would get none of it.

What happens to the
poop?  As the chicks grew more
and more able to make the task easier
for their parents, they did.
Please forgive
me for being interested in things like this, but I
noted several stages in the development of their
diaper-changing routine. 
Also forgive the
graphic detail below –  as a biologist
I feel obliged to share
it with you.

It isn’t that
biologists are particularly
obsessed with poop, you understand,
ot that at all. We’re no more obsessed with
poop than we are with sex or any of a thousand
other things.  W
e’re just obsessed, that’s all.  We’re
obsessed with how things work, inside and outside
our skins.
It’s like I said at the start.  Some of what
goes in one end must come out the other and
there’s no getting out of that fact.
That in
itself makes it interesting from
biological and parental

At the earliest
stage of development,
were dead to the world whenever their
weren’t actually feeding them.  Asleep,
no movement, no sound,
little to observe, especi-
ally given their small size at the time.
saw parents carrying away
but didn’t see how
they got them.

Later, chicks
heard parents coming
and prepared
before they arrived,
necks stretched,
mouths wide open, eyes
closed, beginning to beg. 
At that stage parents
chose which mouth to feed on that trip, fed it,
then searched for fecal sacs
carried them away, one each
trip from the nest.


wonderful happen-
a little later and I had
no way to expect it. A
fter feeding
one or more
chicks, the parent flew to a
nearby perch and
waited for a minute or two,
then flew back to the nest.  It perched on the rim,
head cocked sideways like listening for worms
on a lawn,
then plunged its beak behind
one chick,
came up with a fecal
sac and was gone,
as a wink. 

I couldn’t
see details at that stage
well enough to tell,
but parents
probably either picked fecal sacs
as they emerged
or actively
pulled them from
the vent.

What happened
was even more amazing
and surprising   than what I’d just seen.
It was incredible.  Chicks actively extended
their vents in the air,
aimed straight up, which
allowed their parents to pull large fecal sacs straight
from their bums.
Here a parent perches over a chick,
its nearly naked bum pink and proud, and pulls
up on its fecal sac,
which is just emerging.
That’s service. That’s efficiency. That’s
cooperation. And
two adjacent
chicks have their
heads up.

second later, the same
chick’s bum still in the air, pink and
pleasant as you please
and rimmed like a
friar’s pate with a ruffling of feathers
and bare north of there. 
Note that
the parent is still in place.  S
its giant foot and breast.


Here, when the
chicks are larger, more alert
and  much more feathery a day later,
a parent leaves the nest with a fecal
and will return with a
crop of food.


Imagine the
amount of food
two parents delivered
in the
same 24 hours
and the amount of
they hauled away! Robin
poop is part of a whole

Think about the
sensitivity of the cooperation.
During and before feeding visits to the
chicks are mean and nasty to each other
in scrambling to be the one, meanness and nastiness
depending on age and capability: competition. But
only one chick at a time stuck its bum in the air
begged for food
during diaper-changing visits.
hat showed discrimination and
remarkable restraint.

Carrying poop away,
one parent usually bombed

the driveway to my studio with sacs,
beginning about 60 feet from the nest, flying
at cruising speed by then,
and the other usually
missed the road
on the far side, toward the
creek, but at about the same range of
distances from the nest and
at the same velocity.

By then, every
chick was awake and alert,
feathers coming in fast and showing
great interest in events
outside the nest
like my movements,
insects flying past and
the like.  
Parents kept bringing food, chicks
kept eating, growing, pooping fecal
sacs until they fledged.

Then, robins being
robins and predation on robins
being what it is
in North America, largely
due to house cats,
they turned around and did
it again
the same summer, but on the other
side of the building
where I didn’t bother
them so much. 
Parents bombed poop
approximately where they’d
bombed it
the first
time around.

Species handle nestling waste differently.

Eagle chicks
energetically poop
their own waste over the edge
of the nest.  A goshawk nest I climbed
up to once was unbelievably filthy, smelly,
and overrun by ants.
If the mother hadn’t
returned and threatened to tear me limb from
limb, as goshawks are known to do, I would
have left anyway. 
It’s as easy to understand
the ecological and evolutionary value of
keeping bird nests clean as it is to
understand us keeping our
own homes clean.

For one thing,
odor free nests should be
harder for mammalian predators
to find,
and robins often nest on and
around human structures, where cats
tend to abound. 
Clean nest environs
are also more likely to be tolerated
by human hosts, whether or
not robins are aware
of that fact.

Robins clearly
take waste “away” from
their nests.  But where in the world
do they take it? 
At first thought, you
might think, as we used to think of
ourselves, that “away” should
be good enough – just
throw it away.

But is it good
enough, even for robins?
How far, what directions, what
kinds of places? Does it matter?  Predators
can be amazingly sensitive to patterns of relevance
to finding food for themselves and they might vector in
on nests using patterns of fecal sacs too obviously
organized in any way with respect to the nest
site and find and eat the babies.
I wondered.


Then, as I
walked up from the
house toward the studio one
an adult robin flew out of my
outside studio
with a fecal sac in its bill,
white, shining,  and clearly a burden,
out over
 my stoneyard, accelerated down the road
toward me and passed nearly exactly over my head
at full speed. 
With nearly perfect timing, far enough
ahead that I could
watch it happen, the robin dropped
the bomb.  B
omb curved down, robin curved up and
in slow motion like in a war movie or a
and it splatted to the ground only
inches from my foot,
still mostly
contained in the sac but
spread out a bit.

It was a close call.

about all I have to
say about the defecation
strategies and  diaper-changing
behaviour of Turdus migratorius,
at least for now,
but check out that
other story about the same nest:
The Deep Meaning of Creativity.

If you’re
interested or have a
dirty mind, robins’ scientific
name Turdus has nothing to do
with the subject of this story, poop
and what to do about it.   Robins are
thrushes, turdus is a Latin word
for thrush, and there are

65 species of robins,
all in the genus

First published in the Vancouver Observer.

Edited March 2021

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