See the feeder in use by its intended customers :-)

https://youtu.be/Q_Fag1fDXCo

This is a lovely one-piece bird feeder (for smaller birds) that has a thread to accommodate a 2 litre soda bottle as the seed "hopper".

(after many requests, I made a liquid feeder version for hummingbirds and nectar eaters. It's at...
http://www.thingiverse.com/thing:260695

There's also a little "hook" you can glue/epoxy onto the base of the soda bottle to enable you to hang it in a tree.

Rev 04g is (hopefully) the final version of this model :-)

Tweet tweet enjoy :-)

UPDATE HISTORY (oldest at the bottom)

2014 03 30 ii
Couldn't resist two more little mods...
1) Holes allowing seed out made slightly larger and inside cone made a little steeper (I noticed coarser feed getting stuck often)
2) Put a taper between the narrow vertical cylinder and the thicker threaded portion to avoid the mess of overhanging print.

Sadly I am experiencing warping on the outer ring :-(
(ABS at 230 deg C, bed at 115 deg C) - any ideas to resolve/prevent are most welcome :-) Thx

2014 03 30 i
After much frustration at filling the PET bottle with feed through a too-narrow funnel, I made a double-headed-thread to simplify life. I now use a cut-off PET bottle as a funnel and screw both sides into the new piece. Easy :-)

2014 03 01 (318)
I got fed-up with un-tie-ing the string so often, made HOOK rev 3 with a gap :-) LOL (NB! - use support)

2014/02/23 (199)
Rev 04g

2014/02/21 (157)
Rev 4e

2014/02/9 (72)
Rev 3

2014/02/18 (68)
Rev 2
Thicker base, water escape holes, thinner walls,
re-worked interior for better seed flow.

2014/02/17
A less-hastily thrown-together hook uploaded.

2014/02/16 (15)
Apologies for up-loading beta version in error :-(
(I see about 15 people downloaded that version - sorry)