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,

Mockingbird

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)

Resources

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
http://www.illinoiswildflowers.info/trees/plants/hackberry.html
http://www.illinoiswildflowers.info/trees/tables/table153.html

USDA NRCS Plant Database
https://plants.usda.gov/core/profile?symbol=CEOC
https://plants.usda.gov/plantguide/pdf/pg_ceoc.pdf

USDA US Forest Service

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

 

 

 

Asters Yield A Treasure Trove!

Orange Sulphur on New England Aster (Symphyotrichum novae-angliae)

Orange Sulphur on New England Aster (Symphyotrichum novae-angliae)

A few days ago the weather was beautiful, with temperatures in the mid-60s, cloudless blue skies and a bit of a breeze, so we went for a walk at a wildlife management area in West Amwell, New Jersey.  We were looking for birds, fall fruit and foliage, and any other interesting critters that happened to present themselves.

We didn’t expect to see a lot in the way of butterflies because of the cool temperatures, and because it’s so late in the season.  We didn’t see many butterflies, but those we did see were pretty spectacular.  Orange Sulphurs were out and about, which was to be expected, since they are among the species that stay active as late as November in this area.  But the surprises were a Fiery Skipper and an American Snout, both of which are fairly rare in New Jersey, especially in late October.  All were nectaring on various species of asters, or other aster family members, the goldenrods.

American Snout

American Snout

Fiery Skipper on New England Aster (Symphyotrichum novae-angliae)

Fiery Skipper on New England Aster (Symphyotrichum novae-angliae)

Asters family members are the primary source of food for late season pollinators.  They are prolific in their long bloom period, often continuing into November.  Their flowering structure reflects a very clever strategy, and suggests this plant family’s alternate name, ‘composite’.  What looks to us like a single flower is actually a cluster of tiny flowers, potentially of two different types, ray flowers and disk flowers.

Blue Wood Aster (Symphyotrichum cordifolium)

Blue Wood Aster (Symphyotrichum cordifolium)

The photograph above of Blue Wood Aster (Symphyotrichum cordifolium) shows the classic flower heads of the Aster family:  a circle of ray flowers that look like petals, pale blue in this species, surrounding a cluster of tiny tubular disk flowers in the center of the head.  If you look carefully at the disk flowers in this photo, you can see that the outer rows are open and blooming, while those in the center of the cluster are still in bud.  This gradual bloom habit supports a long period of flowering, offering nectar to fall pollinators for many weeks.  The disk flowers of this plant are a pale yellow in bud and when they first open, then turning pink or magenta as they age.  This color change is thought to be a signal to pollinators, directing them to the receptive yellow flowers which are not yet pollinated and that will reward them with nectar, and steering them away from those blossoms that are already satisfactorily pollinated.  (Plants are so clever!)  Notice the pink and magenta disk flowers in some of the flower heads in this photo.

As soon as the temperature gets into the low 50s on these crisp late October mornings, the Bumble Bees begin foraging on billowing clouds of luminous Blue Wood Asters outside my windows, soon joined by other tiny bees and flies.  Large dense clusters of bright pale blue flowers top the heart-leaved covered stalks of this woodland beauty.  The shape of the leaves is reflected in the species name, cordifolium, and also gives this plant another commonly used name, Heart-leaved Aster.  Pair Blue Wood Aster with White Wood Aster (Eurybia divaricata) and Wreath (Bluestem) Goldenrod (Solidago caesia) or Zigzag Goldenrod (Solidago flexicaulis) for a spectacular late season shade garden display.

New England Aster (Symphyotrichum novae-angliae)

New England Aster (Symphyotrichum novae-angliae)

Favorites for a sunny garden or meadow include New England Aster (Symphyotrichum novae-angliae), which is also seen blooming in many spots along roadsides, and Aromatic Aster (Symphyotrichum oblongifolium), whose intense blue flowers are irresistible to insects and humans alike.

Following are more asters and their visitors.  You never know what treasures asters will yield!

Flower or Hover Fly, Helophilus sp, on Aromatic Aster (Symphyotrichum oblongifolium)

Flower or Hover Fly, Helophilus sp, on Aromatic Aster (Symphyotrichum oblongifolium)

Orange Sulphur on Aromatic Aster (Symphyotrichum oblongifolium)

Orange Sulphur on Aromatic Aster (Symphyotrichum oblongifolium)

Orange Sulphur on Awl Aster (Symphyotrichum pilosum)

Orange Sulphur on Awl Aster (Symphyotrichum pilosum)

Hover or Flower Fly, likely Toxomerus geminatus, on Aromatic Aster (Symphyotrichum oblongifolium)

Hover or Flower Fly, likely Toxomerus geminatus, on Aromatic Aster (Symphyotrichum oblongifolium)

Blue Wood Aster (Symphyotrichum cordifolium) with Bumble Bee

Blue Wood Aster (Symphyotrichum cordifolium) with Bumble Bee

Aromatic Aster (Symphyotrichum oblongifolium) with Common Buckeye

Aromatic Aster (Symphyotrichum oblongifolium) with Common Buckeye

Common Checkered Skipper on Aster

Common Checkered Skipper on Aster

Mating Bees on Aromatic Aster (Symphyotrichum oblongifolium)

Mating Bees on Aromatic Aster (Symphyotrichum oblongifolium)