Nectar bird feeders are largely meant to cater to hummingbirds, which makes it a little easier to prioritize when looking for specific benefits. As a general rule, you want to look for a product that is equipped with some sort of brightly colored design. Bright colors, particularly red, are known for attracting hummingbirds from great distances, so make sure that your feeder has some sort of bright aspect to it.
Depending on your area, it can also be beneficial to look for a product that offers guards against other kinds of pests. Bees, wasps, and ants are all known to have an interest in the nectar used in feeders, so if you have plenty of them in your area, you might want to look for bee guards and ant moats. Some rely on the color yellow to repel bees and wasps as well.
The next consideration should always be the amount of nectar that it can hold. These feeders can hold anywhere from 8 ounces to well over 50 ounces instead. Depending on the amount of birds in your area and the frequency with which you want to refill the feeder, size might be a major factor for you.
Based on how much traffic you have, you might be interested in feeders with different numbers of ports. Ports are where the birds will be able to access the nectar, so take the time to decide how many birds that you want to feed at once. Generally, the more ports there are the better.
Another thing to look for when you are deciding on a nectar feeder is the materials involved. These products come in a variety of different materials, and each one has its benefits and drawbacks. Plastic is light and easy to clean but can break down over time. Glass will withstand the ages but might be prone to breaking. Consider your needs and act accordingly.