Excel 2007 : generating "absence data"

I have a dataset describing the number of birds of different species observed at a number of sites:

site_id, species, number_present
1, a, 2
1, b, 1
1, c, 1
2, x, 2
2, y, 2
3, z, 1

What i'd like to do is create additional rows for each site indicating absence - i.e. that 0 of species x, y and z were observed at site 1.

Is there a quick and easy way to do this (relative to manually creating rows..)?

Thanks in advance for your help on my first post to this forum

One way (probably not the most efficient) Add a column in front that you can hide if you want. And a column for total birds seen (2 species A were observed, 10 total birds observed)
a b c d e
new column site species number total number of birds observed

Assuming there is a header row (row1)
a2 : =COUNTA($E$2:$E2)
A3: =COUNTA($E$2:$E3) - you can drag to copy down the column

Then you could set up the other rows using vlookups. If there are 3 sites:
=if(countif($a$2:$a$100,1),vlookup(1,$A$2:$E$100,1,False),"")

This would return the first Site that no birds showed - the next cell would read:
=if(countif($a$2:$a$100,2),vlookup(2,$A$2:$E$100,1,False),"")
This would return the second site that no birds showed.
AS LONG AS there is one entry for that site i.e.:
1,none,0,0
2,a,5,10
2,b,1,10
2,v,4,10
3,nane,0,0

with the hidden column shown:
1,1,none,0,0
0,2,a,5,10
0,2,b,1,10
0,2,v,4,10
2,3,none,0,0