Lets
us start with Navagraha, you might have observed that the priest in the
temple does offering to Lord Shani and the vahanam on which rides
around the earth is through crow.
Lord Shani is the other name of Yaman who accepts all the rituals
done by us to our forefathers in other words pithur-dharpanam.As Yaman
is the executer of death to human's and he keeps an account.
There is a reason and story for this, till the period of Ramayana or
Thretha yuga everyone could offer their offering's or rituals to
forefathers directly on the day of their death every year and they
(forefathers) would come and collect them too , this a a method of
getting all the blessings from them directly , it is also said that
till then the human beings were able to know the correct and wrong
doings of last 1 years through their forefathers and correct their
mistakes if any committed.
What happened in Ramayana is that Bharathan done the last rituals to
King Dasharatha as Rama was in exile which as per Hindu system to be
done by the eldest son.It is also said that the exact star on which
King Dhasharatha died was properly known by Bharathan and on return
from exile Rama learned it and performed the ritual on the exact day
On completion of rituals Lord Rama awaited to see his father whom he
haven't saw on his death bed or the body. He awaited for hours long but
his father haven't appeared before the rituals, assuming that his
father is totally dissatisfied of him he was about to return to palace
to ask to saints and his guru's, the reason for his father not to
appear before him, as he started walking he heard a voice to stop and
it was King Dhasaratha before him, Lord Rama enquired him, does he done
any wrong to his father and all those stories of the reason of not
able to do these rituals properly and correctly and timely , hearing
this King Dasharathan said that nothing wrong is committed whereas he
was happy with the rituals, then the next question came from lord Rama
was why King haven't appeared as the rituals was completed , he
conveyed that whereas Bharathan who was also performing the same rituals
along these years was also performing it in the other side of the river
he had to visit him first and was discussing with him so the time went
off.
Hearing this Rama got angry and spelled that no father or forefathers
should appear before the children on the rituals or offerings
thereafter, he regretted for the spell he pronounced and discussed
with his father, what could be done, he called Yaman/Shani and asked for
the solution and it was said by Shani that as Lord himself has spelled
it can't he revoked so forefathers would not be able to come thereafter
directly to collect the offerings and rituals anymore and Shani could
come on their behalf as suggested by King Dasharatha, it was expressed
by Shani/Yaman a difficulty to be present and collect the offering by
the children to their forefather hence nominated its Vahanam - Crow to
be present.
Hence the Hindu's offer to crow and wait for them to take these offering to their fore fathers.