Each cluster of flowers, and then the fruit that follows, is arranged in a cyme. There are 5 cymes here. It was a broad, flat-topped flower cluster and is now a broad, flat fruit cluster.
Above: One of the cymes, outlined. Arrow points to the area that distinguishes a cyme from another broad, flat-topped flower form, the umbel.
Below: The center flower of a cyme, and the center fruit of a cyme, matures first. In an embel the center buds mature last.
Below: So the birds are plucking the center fruits from each viburnum cyme, first.
Not all of the Viburnum species have flowers in cymes, but many do. Below, Viburnum opulus, the European cranberrybush viburnum. Its fruits ripen from green to coral to red and hang on the plant through winter before the birds deem them ready to eat. Then, all are ready at the same time.