What to plant - plants for fruits and seeds

A significant number of plants rely on birds to act as dispersal agents for their seeds. As an incentive, the plants often offer nutritious fleshy fruits to attract birds to take the seeds, hidden inside, and ingest them. The seeds have tough external coats that protect them from the digestive systems of birds, allowing them to be deposited elsewhere once they have passed through the bird’s gut.

Different fruits become available at particular times of the year, with some ‘available’ on the plant for a substantial period – perhaps because they are longlasting or because they are only taken after more popular fruits are exhausted. Holly, in particular, has a long fruiting season. The first berries become available during September and the long-lasting fruits may remain on the tree through until the following July. Although one reason for this is the durability of the fruits, another is the fact that many Holly
trees are defended by Mistle Thrushes, which prevents other birds from feeding on the fruits.

Fruiting season can vary across even closely-related plants. While Sorbus aria ripens in September, Sorbus torminalis ripens in November and Sorbus aucuparia ripens from late July. However, it is worth noting that Sorbus aucuparia has a more northerly range than the other two species and that plants in the northerly part of their British range tend to have fruit that ripens earlier than seen in their southern counterparts. The nutritional characteristics of fruits may also vary with season, notably with water content of the pulp declining and average lipid content increasing as the season progresses.

Species preferences

A series of studies by Barbara & David Snow have highlighted the preferences of a number of familiar
species. Blackbird was found to be rather catholic in its tastes, typically taking a range of fruits (including haws, rosehips, sloes, Dogwood, Buckthorn, Elder, Yew and Holly), though haws seemed to
be the preferred fruit when choice was available. Song Thrush showed a clear preference for Yew, sloes, Elder and Guelder Rose and apparent avoidance of rosehips. The larger Mistle Thrush showed a strong preference for sloes over haws, while Redwing found sloes too large to tackle, preferring instead to feed on haws, a preference also shown by Fieldfare. Only Blackbird, Fieldfare and Mistle Thrush were able to handle rosehips effectively, the hips being too large for the smaller Song Thrush and Redwing. Late
in the fruiting season, when the choice is limited to Holly and Ivy, preference seems to be strongly towards Ivy, suggesting another reason why Holly berries may remain untouched until very late in the
season.

Aliens and cultivars

There has been a fair amount of debate over the different cultivars of some berry-producing shrubs (including those in the genus Sorbus) and how attractive they might be to birds. Since birds have been shown to use berry colour as an indicator of nutritive rewards, it seems sensible to assume that the differentlycoloured varieties of these shrubs will differ in their attractiveness to birds. Ornamental fruits whose colours are not widely replicated within native fruits (for example white – seen only on Mistletoe)
may prove less attractive to birds. This could explain why white-berried forms of Sorbus remain on the tree for so long.

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