Answers:
almost nothing!
If you are seeking "symbolism" in this song, you are either going to end up importing some that isn't really there, or be disappointed to discover that the song is NOT symbolic at all!
On the first point -- there have been some claims in recent years that the song was written as a "secret catechism" for Roman Catholics in England during a period when they were persecuted for openly practicing their faith. But the proponents of this view have shown NO historical evidence that it ever functioned this way (e.g. no written evidence from ANYONE that they understood it this way), and there are numerous problems with the very idea such as:
1) the disagreement among proponents about what several of the gifts are supposed to stand for
2) some to the interpretations are based on mistaken understanding of the lyrics (esp. "calling" birds standing for the four gospels, because the song originally had "colly" birds [i.e., BLACKbirds])
3) since the symbols are not at all obvious, the device would have been of little use for teaching children
4) the beliefs supposedly contained in the song --from Christ (supposedly the partridge) and the Trinity to the Ten Commandments-- would not have to be hidden because they are not distinctively Catholic... Protestants would agree with them
Also, it seems very likely that there was NO actual "pear tree" in the original version. The song seems to have some French roots or relatives. It turns out that the French for "a partridge" is "une perdrix", pronounced "oona pair-dree" which sounds very much like "in a pear tree".
For a further debunking see:
http://www.snopes.com/holidays/christmas...
No, this is just a simple childrens' counting song, and there need be no special/secrete/symbolic meaning in the individual items.
So why these particular items? When you take a look at the list of items they all make perfect sense in connection with the "12 days of Christmas". This celebration, culminating in "twelfth night" was a time of festivity, specifically of FEASTING, MUSIC and DANCING, and that's what the gifts describe.
http://en.wikipedia.org/wiki/twelve_days...
Thus:
#1-8 are all related to items at a feast, esp. to the meat --#1-7 are all BIRDS
- partridge, turtledoves, French hens, colly birds (=blackbirds)
- 'gold rings' refers to a pheasant with gold-colored rings on the neck
- geese, swans
These birds were often served at feasts (and several were considered delicacies)
http://www.medieval-weddings.net/wedding...
http://en.wikipedia.org/wiki/medieval_cu...
http://10000birds.com/birds-of-the-twelv...
#9-12 are all about music and dancing (two of each)
pipers, drummers
lords a-leaping, ladies dancing
http://en.wikipedia.org/wiki/the_twelve_...