Ask A Scientist Zoology Archive

name         Jim S.
status       other
age          40s

Question -        We visit a lake near the Kalamazoo river every
year.  Every year we see at least one pair of swans, every year they
start off with six to ten young, and every year they lose several or all
of their young.
This year we had one pair with seven cygnets, soon to be six.  One
 night two disappeared, one of which we found washed up on a sand
 bar.  The next day the parents were obviously driving away or trying to
 kill one of the cygnets.  It was very dark and difficult to observe the
 exact behavior but they had obviously separated the one from the other
 three, he (she) was screaming either in pain or bewilderment, and the
 adults appeared to be trying to drown it.  The next morning the cygnet
 was alone on the shore and as I understand from my in-laws it dead.  They
 found it with a severed foot and broken wing.
Do you have any idea what is behind this behavior?
-----------------
Jim,

As a former field biologist, the first thing you need to think about is exactly what 
did you see?   Predators are the number one problem with geese and swan success in 
rearing young.  What you may have witnessed is the parents attempting to protect a 
cygnet.  Of course, I do not know for I was not there.  Snapping turtles, owls, hawks, 
snakes, raccoons, etc. are always looking at young birds as meals.  The missing foot 
may have been the work of a snapping turtle.  Common!  It is a hard life out there on 
the pond and you may not have seen the entire picture.  As for parent behavior toward 
their young, usually the adults gradually abandon their broods, but only after a point 
that they can survive on their own.  At this point in time, chasing away offspring may 
be observed.

Steve Sample 
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