Complete Guide to What Bluebirds Eat -Seasonality & Feeding Best-Practices

Bluebirds eat insects, larva, other arthropods, and berries. Their diet changes with seasonality and temperature. Nestlings eat the same food as their parents. Planting certain plants and learning feeding best-practices can help your bluebirds thrive.

You might also wonder, which is better to feed bluebirds – live or freeze-dried mealworms?

In this article, you’ll learn all about eating and feeding behavior of bluebirds, as well as things to consider when supplementing their food with seedcakes and mealworms. Finally, we’ll talk about the kind of plant life that will help attract better food sources and even provide year-round food bluebirds depend on.

What adult bluebirds eat in the wild

Bluebirds are both insectivores and frugivores, meaning they eat insects, and fruit and fruit seeds.

What is interesting about the insectivorous nature of bluebirds is that the classification is a little narrow compared to what bluebirds really eat. Weather permitting and when available, bluebirds feast on arthropods and even other animals.

In the animal kingdom, arthropods make up the largest phylum, and it includes classes such as insects, crustaceans, arachnids, and millipedes and centipedes.

Though, of the arthropod phylum, researchers found that larva and insects make up the largest portion of the bluebird diet during spring and summer.

Table 1 lists examples of different arthropods that would make fairly common prey for bluebirds.

Table 1. Families within the arthropod phylum and examples

In case it’s been a while since you’ve seen the terms phylum and class and order – these terms relate to the hierarchy of how scientists classify organisms.

Figure 1 shows the taxonomic hierarchy starting with domain (bacteria, archaea and eukarya) and ending with genus and species.

Ultimately, in the wild, bluebirds are going to forage for arthropods, fruits and seeds from fruits.

When talking about fruit, we’re really talking more about berries or very small fruits.

Examples of fruits and the seeds from fruits that bluebirds will eat include (Beal, 1915; Weinkam, Janos, & Brown, 2017):

• Juniper
• Currants
• Honeysuckle berries
• Mulberry
• Bayberry
• Hackberry
• Flowering dogwood
• Pokeberries
• Blackberries and raspberries
• Ink berry
• Elderberries

Rather than eating berries in the summer when some of the cultivated types (blueberries, raspberries, etc.) are eaten, berries and berry seeds become the primary food source during winter months when insects are harder to find.

How bluebird diets change seasonally

Spring and summer bluebird diet

During the spring and summer months, arthropods of all sorts and other small animals are plentiful.

While many of us who host bluebirds still like to supplement feeding with mealworms, lawns with even moderate plant diversity give way to a fantastic buffet of cutworms, moths, beetles, crickets and other insects.

In fact, hosting bluebirds is a great benefit since they can help control insect populations, and eat garden pests.

In figure 2 are two examples of bluebirds having caught an insect and caterpillar. Both food items were fed to their young, and if you consider the demands of 4-6 nestlings in addition to the dietary needs of parent bluebirds in the spring and summer, there is considerable insect foraging happening that can benefit your gardens.

While bugs and grub are plentiful during the spring and summer, that doesn’t mean bluebirds won’t eat fruit and seed.

In fact, many bluebird landlords have discovered what appears to be blood in a nest box, but the deep red stains against the wood interior are just berry juice.

Really, when it comes down to it, bluebirds will hunt and forage for whatever they can, insects being a more prevalent source of food, and fruit usually being more of a very secondary option.

Fall and Winter Bluebird Diet

During the late fall and winter seasons when the temperatures are colder and there is less daily sunlight, bluebirds may shift their diet to exclusively or mostly fruits and seed (berries). The dietary shift is largely due to the lack of availability of insects during colder months.

When it comes to what types of berries bluebirds eat, researchers found preferences to be all over the place.

Some berry and seed preference have to do with availability, wind and weather, foraging technique, and seed handling (Beal, 1915; Weinkam, Janos, & Brown, 2017; Pinkowski, 1977).

Researchers in various study locations have found different fruit preferences. One study observing a population of mountain bluebirds in New Mexico recorded bluebirds mostly eating One-seed Juniper (Burnett & Fair, 2008), which was a more available fruit option during the months of December through February.

In other locations, researchers found bluebirds eat winterberry, other juniper species, honeysuckle berries, as well as other types of winter fruits.

Click to learn more about bluebird diet during wintertime in our article about bluebird migration.

Unusual food bluebirds eat

Researcher Benedict Pinkowski wrote extensively about what bluebirds eat, documenting what adults and nestlings eat and summarizing observations from other researchers.

In 1974, he published a small article in the Wilson Bulletin detailing his observation of a male eastern bluebird preying on a shrew.

What is admirable about Pinkowski’s observation is that he not only recorded how the bluebird stunned the shrew, but the lethargy and regained health of the bluebird after eating it.

Another researcher documented their observation of a female eastern bluebird preying on a small, 8 inch snake.

The female stunned the snake first, and then ingested only part of it before taking a small break while some of the snake still dangled from her beak. Afterward, she finished eating the snake (Flanigan, 1971).

What this ultimately shows is how versatile bluebirds can be, and how food items selected can depend on what they happen to find and can successfully hunt.

What nestling, fledgling and juvenile bluebird eat

The diet of nestling, fledgling and juvenile bluebirds is pretty much the same as adult bluebirds. Young bluebirds eat what their parents bring to the nest box, which includes small insects, larva, other arthropods, small animals, and occasionally some berries.

When young bluebirds hatch, both male and female bluebirds split the duty of finding food and bringing it to the nest box.

If you watch, you’ll see your bluebirds bringing all sorts of items – moths, caterpillars, beetles and a large variety of other bugs.

For those hosting bluebirds who supplement your bluebirds’ food with live mealworms, you may wonder sometimes why the don’t visit the mealworm feeder as much during late spring and into mid summer.

This can happen when other bugs are extremely plentiful within your bluebirds’ territory, and they enjoy the variety.

Benedict Pinkowski published another paper where he observed several nest boxes with the goal of documenting feeding rates and types of food brought to the nestlings (1978).

The most common order of insects brought to nestlings were from Lepidoptera – these are your butterflies, skippers and moths. And bluebirds mostly brought larva versus adult moths, skippers and butterflies.

The next most common order was Orthoptera – these are your grasshoppers and crickets, followed by species in the Arachnid class (spiders).

While these were Pinkowski’s observations, trail monitors and other bluebird hosts may observe a different distribution of insect types and food items brought to the nest box.

For instance, some bluebird parents will also feed berries to nestlings. This can also leave a mess and a bit of staining from the juice.

Don’t be immediately alarmed if you open a box and see what looks like blood while all your nestlings appear healthy. In this case, closely inspect the nestlings to ensure there is no true injury, and look around to see if there is evidence of berries (seed, fruit flesh, etc.).

Insects and berries are also the water source for nestlings

A very interesting, and important point about nestling bluebird diet is that the bugs they eat or the berries they’re provided is their sole source of hydration.

On hot days, do not attempt to give nestlings droplets of water. The same is true if you find an abandoned nestling.

Providing water to baby birds can actually destabilize their electrolytes and put them in biochemical danger.

Juicy, squishy larva and berries are the best means of hydration for baby bluebirds.

Dangers of poor parental food choices

While adult bluebirds generally know how to take care of their young and what food they should give them, there are occasional mishaps.

For instance, during years where cicada emergence is heavy, bluebirds may select them as a food choice. But some bluebird monitors have seen the horror of these types of insects obstructing breathing (this doesn’t always happen, but it can).

On one occasion, a trail monitor found one of his females dead while incubating her eggs. Her mate brought her a cicada and it cause her to choke.

Large earthworms can also cause problems, potentially obstructing the airway.

The challenge you face as a monitor is the legal aspect of intervening when you observe a food item that could be a choking hazard.

For instance, if you discover a large earthworm that is mostly dangling out of a baby bluebird’s beak – do you take it out so he doesn’t choke?

Instinctively, our answer would be yes, but this is a legal gray area, because beyond general monitoring, bluebirds are protected and interference with an active nest would be against the law.

That said, it’s hard for the humanity within us not to want to do something.

Odd items brought into nest boxes

Though larva, insects and spiders are some of the most common items brought to the nest boxes, bluebird monitors and some researchers have recorded bluebirds taking in other unusual animals into nest boxes.

Lizards, especially skinks, are one example of an uncommon animal type being fed to nestling bluebirds. Small frogs, like tree frogs have also been recorded being brought by parents to nestlings.

Feeding bluebirds – Mealworms (live or dried) & Seedcakes

One way to attract bluebirds to your yard is by making food extremely easy to find and accessible. This is why so many bluebirders provide mealworms.

A question that comes up when providing mealworms is whether to put out live or freeze-dried mealworms.

It is probably no surprise that bluebirds are going to be more attracted to live, juicy mealworms. The downside is the cost. And this is why freeze-dried mealworms have become a helpful second option for many bluebirders.

Do you need to separate mealworms from bran when giving it to bluebirds?

Another common question that comes up when serving bluebirds live mealworms is if mealworms should be plucked out from the bran.

When giving bluebirds live mealworms, they do not need to be separated from bran; however, leaving them in the bran can lead to mold in your feeders, rot and because it is a grain, it could attract house sparrows.

Therefore, while it is not required, it is a helpful precaution. The downside is that it can take some time to separate them, and it is not a perfect process.

If you don’t like touching mealworms, use gloves or tweezers to separate them from the substrate.

Do bluebirds eat birdseed?

In the wild, especially during wintertime, bluebirds will eat fruit flesh and often the seed that comes with it.

When it comes to feeders, bluebirds don’t usually visit typical feeders, nor will they usually eat birdseed that is still in its shell.

However, when wintertime comes and bugs are scarce and there aren’t a lot of other food options, you may observe bluebirds trying to access your feeders.

We have found that square seedcakes are a great options, and you can put them in regular suet cages. We suggest seedcakes instead of suet because suet cake and nuggets tend to attract more starlings (an invasive bird known to kill native birds including bluebirds for nest cavities).

Seedcakes with berries, exposed nuts (no shell) are a great choice. Hot pepper seedcake options with the same material are another good choice because they may minimize squirrels from hogging the feeder.

Important considerations when feeding bluebirds

Caring for and feeding bluebirds is a big responsibility. It might not seem like feeding can be a big deal, but food not only attracts bluebirds, but other animals as well.

For other native songbirds, attracting them with food is not a real issue. In fact, this is a wonderful thing, especially if we are trying to be good hobby conservationists.

However, food can also attract invasive species and predators.

Therefore, here are some important best-practices to follow when feeding bluebirds, especially during the nesting season:

1. Use starling resistant bluebird feeders when putting out live mealworms. Attracting starlings to your yard is a great hazard, especially during the nesting season. Covered mealworm feeders, caged feeders and Gilbertson mealworm feeders are great options.
2. Choose seedcakes instead of suet cakes. Though suet also provides a good fat source, the nuts within seedcakes will also have a good amount of fat and protein. By avoiding suet (fat-based) cakes, you may reduce the risk of starling invasion.
3. Choose seedcakes that have nuts fully exposed (out of the shell) and berry options as well.
4. Emphasize feeding more in the winter than during the nesting season.
5. Providing seed also attracts nocturnal predators, raccoons for example, and that can put your nest boxes at more risk. Do not put seed out during nesting season. Instead, stick to live mealworms, if you must feed at all.
6. During the nesting season, yards with a lot of plant variety including gardens that attract diverse bugs may have less need for supplemental feeding. Yards with only a grass lawn and little plant diversity and water sources may benefit their bluebirds by providing live mealworms.
7. Should you observe invasive birds at your feeders during the nesting season, take them down. They pose significant risk to the livelihood of your cavity nesting birds.
8. If your budget is tight, save live mealworms for times of extreme heat. This will help parent bluebirds conserve energy by having easier access to food, and supply nestlings with plenty of fluid.
9. If one of your parent bluebirds perished while eggs or nestlings are still in the nest, supplemental feeding with live mealworms can dramatically improve the success of that nest.
10. If a cowbird egg (native and protected) was laid in your bluebird nest box among bluebird eggs, supplementing food with live mealworms may allow bluebird young to survive.

Click to learn more about bluebird predators and how to protect nesting bluebirds.

The importance of perches in bluebird habitats

Researcher Benedict Pinkowski spent time recording the foraging techniques of eastern bluebirds, and made an interesting observation (1977).

After analyzing his data, he found the most common method of finding food is by the drop method, where bluebirds sit on a perch, look for food and then drop down from the perch to seize it.

Because this is the most common foraging technique, and perhaps extremely efficient, he hypothesized that available perches may also help contribute to bluebird success during the nesting period.

Small trees and shrubs make great perches in your yard, as well as repurposing fallen boughs or branches, staking them into the ground near the bluebird nest box for helpful bug scouting.

You can also use shepherds hooks of varying sizes as nearby perches.

Learn about how to attract bluebirds to your yard by clicking here.

The importance of calcium during nesting season

When female bluebirds lay eggs, they lose a considerable amount of calcium. Calcium deficiencies can lead to thin eggshells, breakage or cause the female to become eggbound.

Unfortunately, mealworms are pretty deficient in calcium. So when relying on them and providing them as food for your bluebirds, you will also want to supplement their food with calcium.

Click to learn more about female bluebirds, incubation and calcium needs.

You can do so by putting live mealworms in a dish, with just a little bit of pulverized, baked chicken eggshells, and swishing them around a bit so the eggshell powder dusts the mealworms. Then set them out.

All you have to do is save your eggshells. When you’re ready to pulverize or make them into powder, heat your oven to 200 F. Bake the broken up eggshells for 30 minutes to sterilize them. Then use a heavy mortar and pestle to grind them into a powder.

Important: Eggshell dust could be hazardous to your lungs. We really recommend you use a mask while grinding them or pouring them.

Planting bluebird food

Planting food for bluebirds is not limited to plants with fruit they’ll eat. You can also use plants that will attract other insects and larva for bluebirds to glean food from.

However, we do have a helpful table of some plants that produce berries in the late fall and winter when bluebirds and other songbirds depend on berries.

Though not on the list, fruiting species of juniper, especially native juniper are great options that bluebirds, robins and cedar waxwings, to name a few, depend on during the late fall.

Learn about caring for migrating bluebirds by clicking here.

How you can observe what bluebirds eat in the wild

The easiest way to learn what bluebirds eat in the wild for yourself is to spend time observing. Looking out your window is one option, or visiting sites known to have bluebirds interacting with the habitat is another great way to watch how they find food and what they eat during different periods of the year.

Keeping a bluebird nest box, regularly monitoring it, or even installing a nest box camera are other great ways to actively learn more about what bluebirds eat.

Ultimately, bluebirds have a variable diet that shifts with the season and availability. Bluebirds are savvy hunters, eating many different types of animals and arthropods. Nestling and young bluebirds eat the same thing as their parents. Their diets comprise larva, bugs, arthropods, other small animals and fruits.

References

Beal, F. E. L. (1915). Food of the robins and bluebirds of the United States (No. 171). US Department of Agriculture.

CK-12 Foundation. (2016, August 17). Arthropod Classification – Advanced. Retrieved March 10, 2023, from https://www.ck12.org/book/ck-12-biology-advanced-concepts/section/15.33/

Flanigan AB. 1971. Predation on snakes by Eastern Bluebird
and Brown Thrasher. The Wilson Bulletin 83: 441.

Pinkowski, Benedict C. “Predation on a shrew by an Eastern Bluebird.” The Wilson Bulletin 86, no. 1 (1974): 83-83.

Pinkowski, B. C. (1977). Foraging behavior of the Eastern Bluebird. The Wilson Bulletin, 404-414.

Pinkowski, B. C. (1978). Feeding of nestling and fledgling Eastern Bluebirds. The Wilson Bulletin, 84-98.