Late winter and early spring are times when natural food sources are at their lowest and your feeders will still be used heavily. Gradually many of the birds will begin to lose interest as natural food sources become available and you can stop feeding entirely at this point if you wish. However, some people have actually begun feeding birds year round these days and have found that they can lure in additional varieties of birds during the warmer weather. With a constant food supply in your backyard, you may find more birds deciding to nest nearby. Suet and other perishable types of foods should not be offered in warm weather because they spoil too quickly.
Many folks get upset when they feed birds and suddenly begin to get visits from hungry squirrels.
Just about anything you put out for birds to eat, squirrels will like also. The problem with squirrels at your feeder is that they eat large quantities of food and often gnaw at the feeder when it is almost empty to get at the last remaining portions. People often go to extreme lengths to discourage squirrels from their feeders. Inverted metal cones are often placed above or below a feeder to try to foil a squirrel from gaining access. Some people, myself included, actually enjoy having squirrels at the feeder.