At this time of the year, both resident and migratory birds are feasting on a variety of colorful berries such as American beautyberry and pokeberries. However, have you noticed birds are not flocking to a native plant that produces one of the most colorful berries–the American Holly?
Nowadays if you peer into the foliage of an American holly, you will discover that the berries that are synonymous with winter and Christmas are still green. Even when they ripen, it will be a while before birds begin dining on these shiny red berries. In fact, in most years, American holly berries will remain on the tree well into winter and provide birds with a valuable source of food long after the last beautyberry or pokeberry has been gobbled up.
Among the reasons birds do not seek out holly berries when they first ripen is they are rock-hard and very bitter. It is only after the berries have been exposed to one or more frosts do they begin to soften up. Their exposure to cold weather also breaks down the chemicals that make the so bitter. Even then, they are not considered a choice food. American holly berries are not rich in many nutrients, although they are high in fats and oils.
However, when birds have little else to eat, they will dine on dine on holly berries. For birds that rely heavily on fruits and berries, holly berries can mean the difference between life and death. 
A woman in Walton County once told me that, in winter, she often decorates her window boxes with branches of American holly covered with its showy red berries. She went on the say that one-winter birds did not eat a single berry the entire winter. However, one extremely cold March day a flock of robins descended on her yard. Before the flock departed, the birds had eaten every single berry that had adorned the holly boughs placed in her window boxes.
In addition to the American robin, among the more than two dozen species of birds that eat American holly berries are the northern cardinal, eastern bluebird, northern mockingbird, wild turkey, and northern bobwhite.
This is just another example of the fact that we need to provide a wide variety of plants that provide food and cover for birds throughout the entire year.
This is so interesting — I have a number of Hollies in my yard, thinking this would feed birds, but over the 7 yrs I have lived here, I don’t recall seeing birds in the shrubs. Thanks for this info.
Martha,
I have had a similar experience. I see most use very late in the winter or even in the early spring. I have also heard of birds eating berries that fermented.