Grosbeaks are a type of finch found throughout North America. They are medium-sized songbirds with large, conical bills that they use to crack open seeds and nuts. Determining grosbeaks’ favorite foods requires looking at what they eat in the wild across different species, seasons, and regions.
Seasonal Variation in Grosbeak Diets
Grosbeaks are opportunistic foragers that eat a wide variety of foods depending on availability. Their diets can shift dramatically between seasons as different food sources become scarce or abundant. In spring and summer, grosbeaks eat more insects, especially beetles, caterpillars, ants, and grasshoppers. They also feed on flower nectar, buds, shoots, and fruits. In fall and winter, seeds and hard mast like acorns become dietary staples as insect availability declines.
Pine grosbeaks in Alaska studied in spring and summer ate mostly insects (67% of diet volume) along with some buds and fruits. The same birds studied in winter ate mostly tree seeds (75%), with some buds and fruit. Evening grosbeaks ate mostly maple buds in late winter in Quebec, but shifted to 90% insects in early summer. Rose-breasted grosbeaks ate 86% black cherry pits during fall migration but only 2% during spring migration when more insects were available.
So while insects are clearly an important food for grosbeaks during breeding season, their favorite winter foods appear to be high-energy seeds and mast. Next, we’ll look at differences between grosbeak species.
Favorite Foods of Different Grosbeak Species
The foods eaten by grosbeaks can also vary between species depending on the size and shape of their bills, which are adapted for specific diet types. For example:
- Pine grosbeaks have thicker bills suited for eating buds and seeds. Up to 89% of their winter diet can be conifer seeds.
- Black-headed grosbeaks have thinner, more elongated bills better for catching insects. Up to 62% of their diet can be insects.
- Evening grosbeaks have massive thick bills perfect for cracking open hard maple seeds and pits. In winter they eat up to 99% tree seeds.
- Blue grosbeaks have smaller bills and eat a wider mix of seeds, insects, and fruit year-round.
Rose-breasted grosbeaks are one of the most generalized species, eating a varied combination of insects, seeds, and fruit. Still, during key seasons certain foods make up the bulk of their diet:
Season | Favorite Foods | Percent of Diet |
---|---|---|
Summer | Beetles, caterpillars | 45% |
Fall | Wild cherries, grapes, blackberry | 42% |
Winter | Deciduous tree seeds (maple, ash) and buds | 74% |
Spring Migration | Elm, oak, mulberry buds | 60% |
This variation shows how rose-breasted grosbeaks take advantage of seasonally abundant foods while switching to more plentiful staples in winter.
Geographic Differences in Diet
Another factor influencing grosbeak diets is geographic location. Northern grosbeak populations eat more tree seeds and mast due to living in coniferous or deciduous forests. Southern populations have more access to cultivated grains, fruits, and buds. For example:
- Evening grosbeaks in Canada eat 99% box elder seeds in winter, but birds in Mexico eat a mix of seeds, buds, and fruits.
- Indigo buntings in Arizona eat 49% weed seeds while those in South Carolina eat 34% cultivated rice.
- Rose-breasted grosbeaks in the northeast U.S. eat more maple, beech, and ash seeds. In the southern U.S. they eat more blackberry, mulberry and wild grape.
These geographic variations reflect differences in native vegetation, climate, and availability of anthropogenic foods like rice or feedlot grain. Grosbeaks readily adapt their diets to take advantage of locally abundant food sources.
Favorite Natural Foods
While grosbeak diets are highly variable, we can determine some favorite natural foods based on which are eaten preferentially when available:
- Insects: All grosbeaks avidly feed on insects during spring and summer, especially beetles, caterpillars, ants, and grasshoppers. They are an essential food for breeding birds and nestlings.
- Wild fruits: Berries and small native fruits like blackberry, elderberry, wild grape and cherry are favored foods during summer and fall when abundant.
- Tree seeds: Conifer seeds are a staple food for northern grosbeaks in winter. Deciduous tree seeds like maple, ash, and elm are also key foods on wintering grounds and migration stopovers.
- Mast crops: When available, high-fat nuts and seeds like pine nuts, acorns, hazelnuts and beechnuts are energetically favored foods.
These natural food sources make up the bulk of grosbeak diets when accessible. But grosbeaks will readily switch to take advantage of other abundant foods like grains, buds, nectar, and fruit.
Anthropogenic Food Sources
Grosbeaks have also adapted well to exploit human-sourced foods. Some examples include:
- Cultivated rice, wheat, corn, and oats near agricultural areas.
- Backyard bird feeders stocked with sunflower seeds, peanuts, and nyjer thistle seed.
- Fruit crops like cherries, apricots, apples, and grapes.
- Ornamental tree buds and fruits from maple, crabapple, elm, and ash.
These foods provide easily accessible nutrition and calories for grosbeaks. However, most wildlife experts recommend providing native food plants rather than feeding birds directly. This prevents unnaturally congregating birds at feeders where they can spread diseases.
Conclusion
In conclusion, grosbeaks are adaptable foragers that exploit a wide range of locally and seasonally available foods. While insects, wild fruits, tree seeds, and mast crops make up the bulk of their natural diets, grosbeaks will readily take advantage of grain crops, backyard feeders, and ornamental plants provided by humans. Their bill shape and size helps determine which foods each species specializes in, but all grosbeaks depend heavily on high fat, high calorie foods to get them through migratory seasons and northern winters. By providing native plants and food sources, we can help grosbeaks thrive within their natural seasonal cycles and migration patterns across North America.