Nyjer (Thistle) Feeders
Nyjer seed is sometime refered to as thistle seed. It's a small seed that is high in oil content, making it high in energy and an ideal food for small birds. The bird most commonly attracted with a nyjer feeder is the goldfinch. The American goldfinch mainly eats grain (is granivorous) but it is diurnal, as it will also sometimes eat insects. In its natural setting it will feed on the seed of small annuals, mainly weeds, grass, and some trees. This includes thistle, dandelion, teasel, ragweed, sunflower, and more.
Nyjer feeders can also attract other small birds such as house finches, purple finches, and pine siskins.
The goldfinch is one of those birds that uses its feet while feeding, Some thistle feeder designs take advantage of this to put the feeder ports under the perch, making it harder for pests to encroach on the feeder.
These feeders have smaller ports to control the small thistle or nyjer seed. Some have slots for the feeder ports. Like any bird feeder you will want to mount it on a pole or a building in a place that is not accessable by sqirrels or cats. For a pole you may want to use a squirrel baffle as well. Some nyjer feeders have a cage to discourage large birds and squirrels. If you have a problem with squirrels a caged feeder is probably your best choice, as the baffles on the tops of many thistle feeders are made of plastic and won't do much to slow down the squirrels.