Be
Mine!
Robins and Their Mates
One scientific study showed that about 75% of all fledgling robins die
before November their first year. Of those that survive that long, about
half die before the next November. About half of all 2-year-old robins
die each year, and about half of all robins of every other age die each
year, too.
Q. "If
200 robins were fledged in a town one year, how many of the fledglings
would be alive in November?
ANSWER: 75% of 200 is 150,
so 150 robins would die and 50 would survive.
Q. "How
many would be alive the following November?
ANSWER: 25
Q. "How many would be alive the following November?
ANSWER: 12 or 13.
Q. "How many years would it be before all these fledglings had probably
died?
ANSWER: 6 or 7.
Q. Does it
make sense that half of all 6-year-old robins die every year, and half
of all 1-year-old robins die every year? Birds that are old have the same
chance of surviving from one year to the next as birds that are young.
Can you explain why?
ANSWER: The older
a robin becomes, the more experienced he or she is, and the more able
to survive a large number of dangers than less experienced robins.
Based on
that data, how much of a chance does a robin have that his or her mate
will return to their territory the next spring?
ANSWER: About half.
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