Hackberry, Butterflies and Birds

Common Hackberry (Celtis occidentalis) is a tree whose ridged, warty bark makes it easy to recognize in any season.  It may be easiest to spot in winter, since there are fewer leaves to distract from Hackberry’s distinctive outerwear.

Common Hackberry (Celtis occidentalis)

Look for Hackberry on a winter day that’s a little warmer than normal, and you might be rewarded with a glimpse of one of the butterflies that are among Hackberry’s known associates, the Mourning Cloak and the Question Mark.

Mourning Cloak butterfly

Question Mark butterfly. It is named for the white markings on its wing.

Both of these butterflies survive the winter as adults, spending most of the time sheltering in dry accommodations such as under loose bark, in a woodpile, or in a crevice or hole in a tree.  The butterflies are able to produce an anti-freeze-like substance that keeps them from succumbing to the winter cold.  They are mostly inactive during the winter; they rarely eat and don’t reproduce.  But they may venture out on a warmish winter day to look for a snack of minerals from rotting fruit, dung, sap or mud puddles.  When you are a butterfly that wakes up from a winter nap in northern latitudes, you have to have a flexible diet.  Not many flowers are blooming to offer nectar during the cold winter months.

While these butterflies may be found anywhere in the woods, in the warmer months when reproduction is on their mind, they are known to associate with Hackberry trees because they are one of the species whose leaves the caterpillars of both these butterflies can eat.  In addition to Hackberries, Mourning Cloak caterpillars use the leaves of a variety of trees, including willows, elms, birch, cottonwoods and aspen.  Question Mark caterpillars can also eat elm tree and nettle leaves.

Question Mark caterpillar on Hackberry leaves

In the spring and summer months, you may see additional butterflies whose caterpillars specialize on Hackberry leaves.  These species depend solely on Hackberries for their survival.  They include the curious looking and aptly named American Snout, the Tawny Emperor, and Hackberry Emperor.

American Snout butterfly drinking nectar from Short-toothed Mountain Mint (Pycnanthemum muticum)

The American Snout drinks nectar in addition to seeking out minerals.  Its long ‘nose’ is thought to have evolved to look like the stem of a leaf, which together with the cryptic coloration of its wings helps this butterfly to hide in plain sight, disguised as a dead leaf.

Tawny Emperor

Hackberry Emperor

Because Tawny and Hackberry Emperors rarely nectar, you are most likely to encounter them in or near wooded areas where their caterpillar food is present.  Their diet of minerals from mud, sap, and rotting materials such as fruit and dung is similar to that of the Mourning Cloak and Question Mark.  Hackberry Emperors also find human sweat to be a good nutritional source.  It is the species of butterfly I have most often seen landing on people to get a quick snack!

Hackberry Emperor getting minerals from soil and rocks.

Hackberry Emperor getting minerals from the sweat on someone’s shirt!

Hackberry Emperor getting minerals from the hood of a car. Is it the paint or the dirt?

Not every caterpillar will live to become an adult butterfly, since there are many predators to elude first.  The Hackberry Emperor caterpillar in the photo below has fallen victim to a parasitic wasp. Her larva will develop inside the caterpillar, consuming its insides until the wasp is mature enough to emerge.  As you might expect, the caterpillar is unlikely to survive.

Hackberry Emperor caterpillar, with a predatory wasp.

Several moth species including the IO Moth, and White-marked and Banded Tussock Moths also use Hackberries, among other woody species, as food for their caterpillars.

White-marked Tussock Moth

Banded Tussock Moth

The round growths on the leaves in the photo below are galls called Hackberry Nipple Galls.  They are caused by a type of true bug in a group called psyllids, or less appealingly, jumping plant lice.  The insects develop inside the galls and emerge when they mature.

Common Hackberry with ripening fruit and Hackberry Nipple Galls, caused by Pachypsylla celtidismamma.

Many of these insects are a potential bounty of food for birds.  I watched the young Tufted Titmouse below and its nest mates forage for food and play among the branches of a mature Hackberry.

Tufted Titmouse in Hackberry

Hackberry’s somewhat inconspicuous flowers are pollinated by the wind, blooming at the same time that the leaves are beginning to emerge.  Hackberries are monoecious; they have some flowers with just male reproductive parts, others with just female flowers, with both types of flowers on the same trees.  In the photo below, both male and female flowers are present.  The female flowers have two stigma-tipped styles that are spread in a ‘v’ shape projecting from the flower. (They look like forceps, or they also remind me of the arcade games where you have to use a similar looking tool to retrieve a toy from a glass enclosure.)  The male flowers have five or six anther-tipped stamens that barely project beyond the enclosing sepals.  A tree may even have some flowers with both male and female parts.  Pollen is carried by the wind from the anthers and deposited on the stigmas.

Common Hackberry (Celtis occidentalis) flowers. The female flowers have 2 styles spread in a ‘v’ shape. The male flowers each have 5-6 dark-colored anthers.

If the flowers are pollinated, a fruit called a drupe is produced.  A drupe is a fleshy fruit that has a stony enclosure around the seed inside, like a peach.  The fruit ripens in fall, but may persist into winter. Birds as diverse as Mockingbirds,


Pileated Woodpeckers,

Pileated Woodpecker

and Wood Ducks eat Hackberry fruit.

A pair of Wood Ducks

Raccoons and squirrels are among the small mammals who eat the fruit.

A raccoon peaking out from its home.

Common Hackberry’s natural habitat includes wooded floodplains and hillsides, and can grow to a height of about 115 feet (35 meters).  It is native in Manitoba, Ontario and Quebec provinces in Canada and most of the United States, from New Hampshire to Montana in the north, south through Utah, New Mexico and east to Florida, except Louisiana, although it is less common in the southern part of its range.   It is also often used as a street tree.

There is a related species, Sugarberry (C. laevigata) that is native in the southern half of the United States and in the western states.  Dwarf Hackberry (Celtis pumila) is native in Ontario, Michigan, and from New Jersey west to Kansas, and south from Texas to Florida.  The butterflies that specialize on Hackberries use these species, too!

Common Hackberry (Celtis occidentalis)


Allen, Thomas J.; Brock, Jim P.; Glassberg, Jeffrey. Caterpillars in the Field and Garden. 2005.

Cech, Rick; Tudor, Guy.  Butterflies of the East Coast.  2005.

Eastman, John.  The Book of Forest and Thicket.  1992.

Eaton, Eric R.; Kauffman, Ken.  Kaufman Field Guide to Insects of North America.  2007.

Eiseman, Charley; Charney, Noah.  Tracks & Sign of Insects and Other Invertebrates.  2010.

Martin, Alexander C.;  Zim, Herbert S.; Nelson, Arnold L.  American Wildlife & Plants A Guide to Wildlife Food Habits.  1951.

Rhoads, Ann Fowler; Block, Timothy A.  The Plants of Pennsylvania.  2007

Tallamy, Douglas W.  Bringing Nature Home.  2007

Wagner, David L.;  Caterpillars of Eastern North America, 2005.

Illinois Wildflowers

USDA NRCS Plant Database

USDA US Forest Service

Oregon State University College of Agricultural Sciences Department of Horticulture Landscape Plants




A Butterfly Garden that Embraces the Shade

Winter doesn't want to quit!

Winter doesn’t want to quit!

Feeling like spring will never arrive? Let’s fantasize a little. Let’s think about gardens in bloom.  And butterflies.  We’ll soon be seeing them.  Really!

When you think about a butterfly garden, shade may not be the first attribute that comes to mind.  But really, maybe it should be. Or at least it should be one of the first.

Ok, maybe not shade for shade’s sake, but for the food plants that cast it.

When you think about it, many butterflies rely on woody species – trees or shrubs – as food plants for their caterpillars.  For example, of the six species of swallowtail butterflies that are possible where I live in New Jersey, four require trees or shrubs as food plants, and one uses a shade tolerant vine.  Most of the hairstreaks, many of the azure and brushfoot species, and the Hackberry and Tawny Emperor all require trees or shrubs as their caterpillar food plants.

Hackberry Emperor

Hackberry Emperor

Other butterflies have evolved to use shade tolerant herbaceous species like violets, Black Cohosh, and Golden Alexanders as food plants.  So a shade garden can be a really valuable asset to the butterflies in the neighborhood.



My husband and I chose our house because we like the natural woods that surround us on two sides, preserved 24 years ago by the developer.  Even though we live in a townhouse community at the edge of a small town, the woods give us the illusion of living in the country.  We love the trees for their own beauty as it evolves through the seasons. And we love the birds they bring to feast on the fruits and insect protein that are abundant here.

Tufted Titmouse in Blackhaw Viburnum (Viburnum prunifolium)

Tufted Titmouse in Blackhaw Viburnum (Viburnum prunifolium)

Carolina Wren

Carolina Wren

Somewhat to our surprise, we found we also had butterflies. As we learned more about them, we realized we had some very desirable territory for butterflies, and other critters, too. Finally, I understood when I saw an Eastern Tiger Swallowtail flitting high up in the White Ash or Tuliptrees, that it was a female laying her eggs on their leaves.

Tuliptree (Liriodendron tulipifera) blossom

Tuliptree (Liriodendron tulipifera) blossom

Eastern Tiger Swallowtail

Eastern Tiger Swallowtail

The Mourning Cloak may have been drawn here because of the elm trees in the woods behind the house.

Mourning Cloak nectaring at Red Maple (Acer rubrum) blossoms

Mourning Cloak nectaring at Red Maple (Acer rubrum) blossoms

Why were Spicebush Swallowtails visiting our woodland garden? It’s the food plants, silly; their namesake Spicebush is present here, and so are Sassafras trees, which they are also willing to use.

Spicebush Swallowtail with Purple Giant Hyssop (Agastache scrophulariifolia)

Spicebush Swallowtail with Purple Giant Hyssop (Agastache scrophulariifolia)

The birds and butterflies have a somewhat mutually beneficial relationship. It’s true that the birds may be interested in eating the butterflies sometime during their lives, but on the plus side, birds keep insect predators of butterflies in check.  As a bonus, birds also provide dietary supplements for butterflies that are inclined to dine on mineral sources.  The Silver-spotted Skipper pictured here is sipping the nutritious offerings conveniently left by one of the local birds in the form of its droppings.

Silver-spotted Skipper getting minerals from bird droppings

Silver-spotted Skipper getting minerals from bird droppings

After stoking up, this little butterfly was off, maybe in search of an appropriate place to lay her eggs, like a near-by Black Locust tree.

Red Maple, White Ash, Sassafras, Flowering Dogwood, Blackhaw Viburnum, and a Crab Apple all grow in the common area along side our house.  As the trees grew over the years, they shaded out the lawn surrounding them.

Before the shade garden

Before the shade garden

Moss developed where grass once grew.  Chickadees plucked the moss until their beaks were full, gathering the soft lush material to line their nests. This was great!

Chickadee in Blackhaw Viburnum (Viburnum prunifolium)

Chickadee in Blackhaw Viburnum (Viburnum prunifolium)

So we decided to embrace the shade. It was futile trying to maintain a lawn that disappeared by July every year.  We got permission from our homeowners’ association to plant a shade garden under the trees and in place of the lawn that once grew next to them. This was a win for our association, since money would no longer have to be spent fruitlessly reseeding, fertilizing and mowing the lawn, or more accurately, the mud.

Now we have a constantly changing display of blossoms, ferns, sedges, foliage, and fruits. We took advantage of the moss, encouraging it to cover a winding path through the garden. There is always something blooming from about mid-April to the end of November; sometimes longer if the Witch-hazel is especially happy.  After that, the fruits offer visual appeal for us, and food for our local residents.  The birds love the new habitat, and we have more butterflies than ever, enjoying nectar and other food sources, and looking for a place to start the next generation.

Our wildlife-friendly shade garden

Our wildlife-friendly shade garden

I have my desk facing a second floor window so I can be easily distracted by birds, or watch a female Spicebush Swallowtail pause on a Sassafras leaf to lay an egg, then float down to lay another on the Spicebush that entices her below.

In future episodes, I’ll tell you more about the plants here and the critters we see enjoying them.

Note:  This is part one of a 3 part series.  For part 2, click here, A Butterfly Garden that Embraces the Shade – Spring.  For part 3, click here,  Embracing the Shade:  Summer and Fall

This article was adapted from one that was published in the Winter 2012 issue of Butterfly Gardener, a publication of the North American Butterfly Association.

Life in Dead Wood

‘Getting rid of dead wood’ or ‘Cutting out the dead wood’ are phrases that are so commonly used that they have become ubiquitous when referring to a ‘reduction in force’ in the corporate world. These phrases have their origin in advice for maintaining landscaping. In a formal setting where neatness is desired, or where a dead tree or branch poses a threat to people, property or power lines (why don’t they bury those power lines, anyway?), removing dead wood is certainly a prudent thing to do.

But is ‘getting rid of dead wood’ always a good idea? Does dead wood have any function or benefit in a less formal or a natural setting?

Well, let’s think about it. On the plus side, dead wood does provide a home for many species of fungi, some of which are eaten by insects, mammals (including people!) and other critters.

Mushrooms on dead wood

Mushrooms on dead wood

Some insects even develop inside mushrooms, like the puffballs pictured below.



At first glance these snails seem to be using the mushrooms as a sun deck, but a closer look shows that they are feeding here.

Snails feeding on mushrooms

Snails feeding on mushrooms

The young edges of the colorful Chicken of the Woods mushroom are edible, and taste like, well, chicken.

Chicken of the Woods

Chicken of the Woods

Many insect species, including ants, wasps, bees, beetles and even butterflies make dead wood their home for at least part of their life cycle.

Eastern Commas, Question Marks and Mourning Cloaks survive the cold northern winter as adults, often taking shelter in a woodpile or underneath loose bark.

Eastern Comma

Eastern Comma

Mourning Cloak

Mourning Cloak

Some species of solitary bees may make their nests in dead wood, like the sweat bee pictured below sipping nectar in the company of a Gray Hairstreak butterfly. This little sweat bee and other solitary bees are important pollinators, many providing free pollination services for food crops. Some of our native bees are more efficient pollinators than Honey Bees, because the native bees are a better anatomical match for the plants with which they evolved.  Providing habitat for native bees can reduce the need to pay to truck in Honey Bees, the migrant workers of the insect world.  It may also increase pollination rates and crop yield.

Sweat Bee and Gray Hairstreak on Indian Hemp (Apocynum cannabinum)

Sweat Bee and Gray Hairstreak on Indian Hemp (Apocynum cannabinum)

Most wasps are predators of other insects, helping to keep their populations in balance. Mason wasps, for example, provision their nests with caterpillars on which their larvae feed as they develop. They usually nest in borings made in dead wood by other insects like beetles or bees.

Mason Wasp (Monobia quadridens) on Hoary Mountain Mint (Pycnanthemum incanum)

Mason Wasp (Monobia quadridens) on Hoary Mountain Mint (Pycnanthemum incanum)

There are ant species that make their homes in rotting wood. Ants don’t cause wood to rot, and they don’t eat the wood. They excavate spaces for their nests in wood that is already soft, moist, and decaying. Ants are important seed dispersers for many plants, including violets, trilliums, Dutchman’s Breeches, Spring Beauty, and many more.

Ant with Canada Violet (Viola canadensis)

Ant with Canada Violet (Viola canadensis)

Ants and wood boring beetle larvae are favorite foods of many woodpeckers. Among them are the largest woodpeckers in North America, the Pileated Woodpecker. Have you have ever had a Pileated Woodpecker attack the siding of your home? If so, it’s because the bird has detected the presence of a delectable meal of carpenter ants there, which would only be present if you had rotting wood. So think of it as a free consultation, courtesy of nature, to let you know that you have some maintenance to do. Replace, paint or otherwise seal the wood to prevent moisture from getting in, and your problems with ants and woodpeckers will go away. They’ll go back to feeding on insects in the naturally rotting wood found in nature.

Pileated Woodpecker feeding on insects in dead tree

Pileated Woodpecker feeding on insects in dead tree

In the photo below a Pileated Woodpecker is peeking out from his nest hole. Can you tell what type of tree this is?

Pileated Woodpecker looking out of nest hole

Pileated Woodpecker looking out of nest hole

If you said ‘dead’, you’re correct! In addition to providing a bountiful source of insect protein, dead wood offers real estate for homes for many birds, including Downy, Hairy, and Red-bellied Woodpeckers, and Flickers. Even Chickadees excavate holes in very soft, rotting wood for their nests. Titmice, White- and Red-breasted Nuthatches, Carolina and House Wrens all nest in holes in dead or living trees, sometimes using abandoned woodpecker holes. All of these birds also forage for insect protein, a bounty of which is available in or on dead wood.

Carolina Chickadee

Carolina Chickadee

Eastern Gray Squirrels are among the small mammals that may make their homes in hollows in dead or living wood. Their diet depends heavily on tree nuts, but it also includes insects and fungi, as does that of Eastern Chipmunks.

Eastern Gray Squirrel

Eastern Gray Squirrel

Chipmunks often dig underground burrows, but they also use tree cavities for shelter. Larger mammals, like Red Fox or even Black Bear may use fallen or hollowed out trees as a shelter.

Eastern Chipmunk peeking out of tree stump

Eastern Chipmunk peeking out of tree stump

The chipmunks and squirrels may become a meal for a Red Fox …

Red Fox, hunting

Red Fox, hunting

or a Red-tailed Hawk …

Red-Tailed Hawk

Red-Tailed Hawk

… or a Great Horned Owl. Dead broken trees, called snags, are a favorite nesting place for these large predators.

Great Horned Owl in snag

Great Horned Owl in snag

All of this activity contributes to the breakdown and decomposition of the wood, which provides valuable nutrients to the soil. This makes a new generation of plants possible, keeping the cycle of life going.

Tree stump with mushrooms, mosses, ferns and Canada Mayflower (Maianthemum canadense)

Tree stump with mushrooms, mosses, ferns and Canada Mayflower (Maianthemum canadense)

Dead wood provides shelter and food for insects and other arthropods, birds, and large and small mammals, including people. With the assistance of all of the inhabitants who avail themselves of these services, dead wood gradually breaks down, enhancing the soil for a new generation of plants.

Dead wood also helps to divert and slow the flow of water in heavy rainstorms, allowing the water to slowly penetrate into the soil where it falls, rather than rapidly running off into creeks, rivers, streams and storm sewer systems, contributing to flash flooding along the way.

So, what do you think, should we ‘get rid of the dead wood’?




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