Just as the hummingbirds are beginning their long migrations, so too are other bird species vanishing from backyard feeders, but not all for the same reasons. During the fall, seed heads, fruits, and other food sources ripen, offering greater natural abundance in addition to the helping hands of humans. Because of this, it may seem that birds are less plentiful, but the truth is that they are exploring more culinary options than just mixed seeds and other treats offered at feeders. While some do take to the skies and won't return for months, others are merely expanding their epicurian tastes.
It is crucial that backyard birders do not abandon their feeding efforts at this juncture. Many of the birds who are still visiting feeders are storing seed -- either in caches or through layers of body fat -- for the coming cold, and others are eager to get quick energy sources as they pass through on their way to warmer winter homes. In preparation for winter, it is suitable for birders to slowly reduce the supplies of seed they offer as feeders are not emptied as quickly, but maintaining a good supply will give birds a reference and the knowledge that they can rely on these resources. If they know that, they will be welcome friends when winter's need strikes.
My own feeders are less frequented of late, though the lesser goldfinches, house finches, sparrows, and Eurasian collared doves are still steady guests, though perhaps in lesser numbers than weeks past. For however long they remain -- and I know a good few of them will not leave -- they will be welcome, as will be any friends who might be passing through our skies.