Deciphering a troubled hatch

The
good news is: our second hatch turned out 16 happy, healthy
chicks.  The bad news is: my hatch
rate was a rather
abysmal
73%.  What happened?



With a troubled hatch, I
like to rule out the obvious factors
first.  I gathered the eggs for this hatch during a wet week, so
about half of them had minor dirt smears.  Could dirt be the
problem?  It definitely didn’t help, but since only half of the
non-hatching eggs were dirty, versus 45% of all eggs that went into the
incubator, dirt doesn’t seem to have been the deciding factor.

How about mother of the
eggs?  Two-thirds of the dead-in-the-shell
chicks were laid by our Rhode Island Reds…but half of all the eggs
that went into the incubator were from Rhode Island Red mothers. 
While it’s possible the mother was the problem, it seemed much less
likely once I cracked the dud eggs open and discovered that all except
one were fully formed but hadn’t pipped.



Two symptoms caught my
eye as being more likely to be tied to the root
cause of my low hatch rate.  First, this hatch was long and strung
out — the first chick came out of its shell on Sunday morning, with
the last one popping out nearly four days later on Wednesday
night.  A good hatch will have nearly all chicks unzipping within
24 hours, so this elongated hatch was definitely a warning sign.

The other thing I
noticed was that all of the dead chicks were in the
top half of the tray, and eggs in that area also hatched later. 
(Average hatch order for the bottom half of the tray was 4.5, with a
100% hatch rate; average hatch order for the top half of the tray was
7.8 with a 45% hatch rate.)  Combining the elongated hatch with
the irregularities within the incubator, my analysis is that the
temperature in the top half of the incubator was cool or irregular.



I’ve noticed minor
temperature irregularities within the incubator
before, but they seemed more problematic this time around.  I did
notice a bit of fuzz up in the part of the incubator you’re not really
able to clean, and I could see how dirt up there might mess with the
unit’s operation.  Maybe I’ll store up some bravery and take the
unit apart before our next incubation run and do a wholesale
cleaning.  At the least, I’ll do a test run with thermometers in
different parts of the incubator to make sure that temperature really
is the problem.



All of that said, a
hatch rate of 73% is still pretty good, so for now I’m rest on my
laurels and enjoy the antics of our miniature flock.