Fox Sparrows are medium-sized sparrows found across North America. They are quite variable in plumage across their range, with reddish-brown upperparts and gray underparts with bold streaking. Their diet consists primarily of seeds and insects. In this article, we will take an in-depth look at the diet of Fox Sparrows throughout the year.
Spring and Summer Diet
During the spring and summer breeding season, Fox Sparrows eat a variety of insects and other invertebrates. Some of the main insects consumed include:
- Caterpillars
- Beetles
- Grasshoppers
- Crickets
- Spiders
- Ants
- Aphids
- Fly larvae
Fox Sparrows forage for insects on the ground, flipping over leaves, debris, and bark with their bills. The protein rich insects are especially important for breeding birds and growing young. Seeds make up a smaller portion of their diet during this time. Some common seeds eaten include:
- Grasses
- Ragweed
- Dock
- Chickweed
Fox Sparrows will also occasionally eat small fruits and berries in the summer.
Fall and Winter Diet
In fall and winter, Fox Sparrows switch to eating primarily seeds and grains. They forage for seeds of grasses, sedges, chickweed, lamb’s quarters, knotweed, and other plants. A few of the main seeds consumed are:
- Panic grass
- Crabgrass
- Foxtail grass
- Pigweed
- Ragweed
- Goosefoot
Fox Sparrows use their conical bills to crack open and hull these small tough seeds. They will also eat waste grain in agricultural fields and even visit backyard bird feeders for offerings like millet and cracked corn.
Although seeds make up the bulk of the diet in winter, Fox Sparrows will still eat insects when available, including:
- Beetles
- Caterpillars
- Ants
They also supplement their diet with fruits and berries when present, such as:
- Sumac
- Virginia creeper
- Grapes
- Greenbrier
- Honeysuckle
- Dogwood
- Crabapple
Water and Grit
In addition to food, Fox Sparrows need access to water and grit. They get much of their water requirements from the foods they eat, but also drink water from streams, ponds, and puddles.
Grit is made up of small pebbles, sand, and gravel. Fox Sparrows swallow these grit particles, which grind and digest seeds in their muscular gizzards. Good sources of grit are often found along gravel roads or rocky streams.
Geographic and Individual Variation
The diet of Fox Sparrows can vary across their breeding and wintering range based on habitat and food availability. For example, those breeding in Alaska consume more insects like crane flies and moth larvae compared to southern breeders.
Wintering birds in the Appalachians eat a higher percentage of ragweed and panic grass seeds, while birds wintering in the West prefer goosefoot and pigweed. Agricultural grain becomes a bigger part of the diet for birds wintering near farms.
Individual Fox Sparrows also show preferences and flexibility in their eating habits. Some individuals or populations may become specialists at exploiting certain seed crops. Banding studies have shown that Fox Sparrows often return to the same wintering sites each year, presumably because they have learned reliable food sources.
Adaptations for Diet
Fox Sparrows have several key adaptations that allow them to consume their generalist diet:
- Conical bill – Thick conical shape allows them to crack tough seeds and hull them efficiently.
- Strong legs and feet – Allows them to kick back leaves and debris to uncover insects and seeds.
- Thick head feathers – Insulated skull protects them when hammering seeds open.
- Scratching feet – Can use feet to scrape and clear ground.
- Keen eyesight – Helps locate cryptic insects and seeds.
Foraging Behavior
Fox Sparrows use a variety of foraging techniques and behaviors to find their food:
- Scratching and kicking leaf litter – Uncovers insects and seeds.
- Flicking overturned leaves and debris – Reveals hidden invertebrates.
- Gleaning along branches – Plucks insects and berries.
- Probing crevices in bark – Finds insect larvae and pupae.
- Hammering seeds – Cracks hard seed coats on the ground.
- Digging in soil – Unearths insects and seeds.
- Visiting spilled grain – Forages at bird feeders or agricultural areas.
Fox Sparrows often forage in small flocks in winter for protection and to locate patchy food sources. They establish winter territories and feed together in loose groups.
Typical Foods Consumed by Season
Here is a table summarizing some of the typical foods consumed by Fox Sparrows during each season:
Season | Common Foods |
---|---|
Spring | Caterpillars, beetles, grasshoppers, leafhoppers, flies, spiders, ants, aphids, grasses, chickweed, dock, ragweed |
Summer | Caterpillars, beetles, ants, grasshoppers, grasses, forbs, grains, berries |
Fall | Grass and forb seeds, grains, berries, ants, beetles, grasshoppers |
Winter | Grass, forb and weed seeds, waste grains, berries, beetles, ants |
Young Fox Sparrow Diet
Fox Sparrow chicks are fed primarily insects for their first few weeks after hatching. The parents forage tirelessly to bring enough caterpillars, spiders, beetles and other soft-bodied insects to sustain their rapid growth.
As the chicks grow, the parents gradually start incorporating seeds into the food items brought back to the nest. By two weeks of age, Fox Sparrow chicks eat a mix of about 60% insects and 40% seeds. This helps them transition to the more seed and plant based adult diet.
Parent birds chew up the foods into an easy to digest paste to feed directly into the gaping mouths of begging chicks. This goes on for up to two weeks until the young leave the nest and start foraging on their own. The parents continue to supplement their diet for several more weeks as they improve their foraging skills.
Fox Sparrow Food Preferences
Although they are flexible generalist feeders, Fox Sparrows do exhibit some preferences and specializations in their diet:
- Often prefer panic grasses and weedy seeds in winter like ragweed and goosefoot.
- Favor caterpillars and grasshoppers to feed young in spring and summer.
- Will focus on abundant local seeds like thistle, amaranth, dock when available.
- Visit bird feeders with offerings like millet, corn, and hulled sunflower.
- Coastal birds forage along tide lines and eat marine invertebrates.
- West coast birds favor seeds of amaranth, saltbush, and chickweed.
These preferences help Fox Sparrows adapt and take advantage of readily available foods in their local and seasonal environments.
Unusual Foods
While Fox Sparrows are mostly seed and insect eaters, they have been observed consuming some unusual food items:
- Fat and suet – They are sometimes observed on suet feeders in winter.
- Sap – They occasionally feed on sap wells from sapsucker drill holes.
- Grains – They will eat newly planted rice and wheat grains in agricultural areas.
- Peanuts – They are drawn to peanut hearts set out for birds.
- Mealworms – They visit feeding stations stocked with live mealworms.
- Fruit – They may eat soft fruits like oranges and bananas on platform feeders.
These unusual foods likely provide needed calories and fat during harsh winters when natural foods are limited. Fox Sparrows remain flexible and opportunistic in trying new potential food sources.
Preferred Habitats for Foraging
Fox Sparrows use a variety of habitats when searching for food, but prefer certain conditions:
- Forest edges and openings – Provide access to seed plants and insects.
- Brushy thickets – Harbor good cover plus insect and fruit sources.
- Marsh edges – Supply insects, seeds from sedges and grasses.
- Streamsides – Offer damp conditions for many invertebrates.
- Trailsides – Provide seed from disturbance plants like goosefoot.
- Backyard feeders – Reliable source of grains, suet, and fruit.
Edge habitats with a mix of cover and access to seed sources tend to be most heavily used by foraging Fox Sparrows.
Impacts of Diet on Survival and Reproduction
The availability of food can directly impact the survival and nesting success of Fox Sparrows:
- Harsh winters with low seed crops may result in starvation.
- Dry conditions reducing insect abundance can lower reproductive rates.
- Nestlings depend on protein-rich insects for rapid growth and fledging.
- Abundant berries prior to winter are linked to overwinter survival.
- Breeding birds favor nesting areas with ample caterpillars.
Supplemental feeding and agriculture helping provide winter food can increase Fox Sparrow survival and condition. Milder winters with earlier insect hatches may also improve breeding success.
Comparison to Related Sparrow Diet
The Fox Sparrow diet is generally similar to that of related sparrow species, with a mix of seeds and insects. Some differences:
- American Tree Sparrow – More reliance on small weed and grass seeds in open areas.
- Song Sparrow – Greater consumption of insects like beetles and spiders year-round.
- White-throated Sparrow – Wider array of conifer seeds consumed including spruce, hemlock, and pine.
- White-crowned Sparrow – More specialized on panic grass seeds in winter.
- Dark-eyed Junco – Prefers small tree seeds like birch, alder and elm.
Compared to these other sparrows, the Fox Sparrow shows more flexibility across seasons, habitats, and food types. Their generalized diet contributes to their wide distribution across North America.
Conclusion
In summary, Fox Sparrows are adaptable feeders that consume a varied mix of seeds, plant matter, and insects. Their diet changes seasonally, focusing on insects in spring and summer during breeding, then switching to mostly seeds in fall and winter. Fox Sparrows forage on the ground, scratching through litter and hammering seeds. Their conical bill and strong legs help them exploit many food sources. Abundant food is linked to better survival and reproductive success. Although they eat a wide variety of items, Fox Sparrows prefer certain seeds, fruits, and insects when available. Their diverse diet allows them to thrive across a range of North American habitats. The flexible, opportunistic feeding behaviors of the Fox Sparrow exemplify how native birds are adapted to find nourishment throughout the year across different regions.