The U.S. Fish and Wildlife Service published a 1980 landmark study by Aelred D. Geis on bird food preferences. The information below is based on the results of that study, referred to as the 'Geis Study.' The majority of the species tested in the study preferred the following food types:
The sunflower seed is attractive to so many species because of its high oil content that provides energy for feather replacement, migration, and survival in winter months. The various sunflower seed sizes can be manipulated and hulled by most species. Although other high oil content seeds such as peanuts, flaxseed, rapeseed and safflower (in a later study) were provided as choices, it is apparent from the study results that most species simply do not like these alternative oilseeds. It may be a matter of the seed coats of these alternative oilseeds that are difficult to remove.
- Oil-Type Sunflower Seeds -- Preferred by most species in the study. This is the small black seed that has a thin shell and is easy for most species to hull. Most of the commercial packages include some black oilseed sunflower. The only species that did not have a preference for this seed was the starling and the tree sparrow.
- Gray Striped Sunflower -- Tends to be a larger seed with a heavier hull. In the Geis Study most species preferred the smaller, black sunflower seeds. However, in today's market, this type of seed is sized in processing plants with the larger seed targeted for human consumption and the smaller seeds directed to the bird food market.
- Hulled Pieces and Kernels -- Preferred by the smaller species such as the American Goldfinch, House finch, and white-throated sparrow. This high-energy ready to eat food can be used to attract particular species. One advantage of this product is minimal waste and no sunflower hulls to clean up.
OTHER FOOD TYPES
White and Red Proso Millet -- Millet is another preferred food. The following species had a higher preference for millets compared to the sunflower types in the Geis Study: Brown-headed cowbird, Dark-eyed junco, House sparrow, Mourning dove, Song Sparrow, Starling and Tree sparrow.
Other food sources that can be found in wild bird food mixes may have an attraction or a preference for one or two bird species only. Common products are buckwheat, canary seed, corn, flax, milo, oats, peanut hearts and kernels, rapeseed or canola, rice, hulled oats, Nyjer, and wheat. The Geis Study calls most of these food types "Commonly used but essentially unattractive foods."
Source: Geis, Aelred D. "Relative Attractiveness of Different Foods at Wild Bird Feeders". U.S. Fish & Wildlife Service Special Scientific Report No. 233. 1980.