LEAF-OUT!

Phenology: The first third of May

Chuck Tague

    May is nature at full throttle!  I am already overwhelmed.  I ask myself, “What am I doing at the computer?  There’s a Nashville Warbler singing outside my window.”  What else am I missing as I sit here typing?

    For a start, I’m missing:

migrating birds

nesting birds

amphibians mating

reptile activity

wildflowers, spectacular (yet ephemeral)

mushrooms

butterflies

dragonflies

flowering shrubs

colorful moths

shiny beetles

    The excitement of early May revolves around leaf-out, the new foliage on the deciduous trees.  There is rain in the forecast.  Today, tomorrow, very soon, the trees in southwestern Pennsylvania will explode with green.

    So much of life revolves around leaf-out in the eastern United States.  One day the trees are bare.  The sunlight warms the forest floor.  Winds move, unimpeded, through the branches.  Then, after the warm days of late April or early May, followed by rain, the canopy is thick, lush and fresh.

    Many western Pennsylvania trees are wind-pollinated.  On wind-pollinated plants, pollen-producing flower parts dangle from branches.  Some, the catkins, resemble suspended sausages.  Others hang from thread-like stems.  The pollen receivers are harder to find.  On oaks, look on the tips of twigs that face away from the trunk, a position that protects the tree from self-pollination.

    For wind-pollination to work effectively:

1.  the trees must produce huge quantities of pollen;

2.  they must coordinate the production with others of its species;

3.  pollen must be released when the winds move most effectively through the forest -- before or simultaneously with, leaf-out.

Sugar Maple flowers

A partial list of wind-pollinated trees in western Pennsylvania

Box Elder    Acer negundo

Sugar Maple    Acer saccharum

Black Alder    Alnus glutinosa

Yellow Birch     Betula Alleghaninsis

Black Birch    Betula lenta

Ironwood    Carpinus caroliniana

Hop Hornbeam    Ostrya caroliniana

American Hazelnut    Corylus americana

American Chestnut    Castanea dentata

American Beech    Fagus amaericana

White Oak    Quercus alba

Swamp White Oak    Quercus bicolor

Scarlet Oak    Quercus coccinea

Scrub Oak    Quercus illicifolia

Bur Oak    Quercus macrocapus

Chestnut Oak    Quercus montana

Yellow Oak    Quercus Mulenbergii

Northern Red Oak    Quercus rubra

Black Oak    Quercus velutina

Shingle Oak    Querus imbriaca

Pignut Hickory    Carya glabra

Shagbark Hickory    Carya ovata

Butternut    Juglans cinerea

Bitternut Hickory    Carya cordiformis

Mockernut Hickory    Caya tomentosa

Black Walnut    Juglans nigra

White Ash    Fraxinus americana

Green Ash    Fraxinus pensylvanica

Pitch Pine    Pinus rigida

White Pine    Pinus strobis

Eastern Hemlock    Tsuga canadensis

Big-toothed Aspen    Poplus grandidentata

Eastern Cottonwood  Populus deltoides

Quaking Aspen    Populus tremuloides

    In addition, a few tree species produce wind-dispersed seeds, called a “samara” in the spring.  Look for the disk-like seeds of American and Slippery Elms and the twin-bladed twirlies of Red and Silver Maple.

Silver Maple samara

    When will the pollen fly?  Sneezing and irritated eyes tell many people the oaks and hickories are now in bloom.  I know from the color of my vehicle.  Normally silver-gray, this morning it had a deep yellow luster.  See Kate St. John’s insightful blog from April 28. (a curious case of circuitous “blog-miration”)

    Many caterpillars take advantage of the fresh leaves.  The most conspicuous are the Eastern Tent Caterpillars.  These colonial moth larvae hatch from a crusty, foam egg-case on cherry twigs.  Triangular silk tents appear a week or so before the cherry leaves emerge.  Each evening the tiny caterpillars venture out and munch on leaves or buds.  They spin a silk life-line that leads them back to their shelter.  View the life-cycle of the Eastern tent Caterpillar in the Nature Observer photo gallery.

    It’s not just the tent caterpillars.  Hordes of inchworms hatch with the emerging leaves of their specific host plant.  Migrating songbirds time their northbound journey with leaf-out to take advantage of this abundant source of caterpillar protein.

    Birder’s Hint:  Keep an eye on flowering oak trees for waves of warblers, flycatchers, grosbeaks and vireos.  It’s not just the caterpillars that attract the birds, but flies, wasps and beetles that come for the oak’s pollen

    Jewelweed leaves are popping up.  Look for a dime-sized day-flying moth, the White-striped Black Moth.  These flutter low to the ground in damp forests or sip from the edge of mud puddles.  Females lay eggs on the fresh jewelweed leaves.

    Snowberry Clearwings, day-flying moths that hover over flowers like hummingbirds will be out soon.  Look for Rosy Maple Moths at lights at night.

   

Butterfly activity will pick up in the next week.  Eastern Tiger Swallowtails are out.  Black, Pipevine and Spicebush Swallowtails will be flying soon.  Zebra Swallowtails are not common in southwestern Pennsylvania, but keep an eye out, especially around patches of Pawpaw.  There have already been reports of early Monarch in western Pennsylvania this spring.  Look for sprouting milkweeds -- and Monarch eggs.

Rosy Maple Moth

    Flowering Dogwood will be at its peak this weekend.  Shrub dogwoods are just starting to bud.  Spring Azures, tiny blue butterflies, are flitting through the forest.  The females are ovipositing on the dogwood blossoms.  On April 27, my Nature Journal group watched this azure female lay an egg at Moraine State Park.

    Bladdernut shrubs will bloom soon, as will Choke Cherry, Wild Plum, and other insect pollinated woody plants.  Bumblebees will be very busy.

Drooping Trillium

    Forest wildflowers are at their peak but with leaf-out, their source of sunlight will be obliterated.  On April 28, around 7:30 a.m., I walked the short trail to Frankfurt Mineral Springs in Raccoon Creek State Park.  It is a narrow gorge and the sunlight shines on the north slope for a short time in the morning, at least until leaf-out.  The display of trillium was breathtaking.  There were Large-flowered Trillium, Drooping Trillium and Wake Robin, and a tremendous variety of colors: whites, pinks, maroons and intermediate shades.  There were also Miterwort, Wild Ginger, Wild Blue Phlox and several violet species.  This display should continue for another week or so.

Blue eyed Mary

    Look for Blue-eyed Mary at Enlow Fork, Cedar Creek Gorge in Westmoreland County (along the bike trail bank on the forest side of the entrance) and along Little Traverse Creek In Raccoon.  (From the park office go east toward the lake.  Cross the first bridge over the creek and walk to a bridge over a small tributary.  The Blue-eyed Mary are just up the steam.)

Baltimore Oriole eating Serviceberry blossoms

    Serviceberry blossoms will soon drop but the apple blossoms are just beginning.  I always look for the first Baltimore Oriole to arrive with the apple blossoms.  I saw my first this year on April 24.  In the grasslands, the Bobolinks should be back this weekend.  Henslow’s Sparrows were singing in Imperial last weekend.  Grasshopper Sparrows should be singing now.  In wetlands look for the first Green Herons.  I saw my first Eastern Kingbird on April 26.  What songbirds should you look for?  In the next two or three weeks, all of western Pennsylvania’s warblers, vireos, flycatchers, tanagers and more should return.  Waves will pass through.  Many will stay and nest.  On Tuesday at Raccoon Creek State Park, my nature journal group watched this Yellow Warbler build a nest.

Yellow Warbler nest-building

    White-throated Sparrows are singing in the woods near my house.  White-crowned Sparrows will join them in the next day or two.  Soon they will both disappear.  How long will the Dark-eyed Juncos stick around?

    In the next week expect to see Virginia Rail, Sora, Common Moorhen, Solitary Sandpiper, Least Sandpiper, Least Flycatcher, Great Crested Flycatcher, Eastern Kingbird,  Veery, Warbling Vireo, Blue-winged Warbler, Nashville Warbler, Northern Parula, Magnolia Warbler, Black-throated Blue Warbler, Blackburnian Warbler, Cerulean Warbler, American Redstart, Worm-eating Warbler, Ovenbird, Hooded Warbler, Indigo Bunting, Lincoln's Sparrow, and Orchard Oriole.

    Wood Thrush, Gray Catbird, White-eyed Vireo, Yellow Warbler, Yellow-throated Vireo, Scarlet Tanager and Rose-breasted Grosbeak are already here.  I saw my first Swainson’s Warbler on April 28, a very early sighting.

    The first babies will soon be moving about. Young Great Horned Owls are climbing clumsily through the trees.  Screech owl babies have hatched and are growing fast.  In heronries scattered throughout western Pennsylvania, long necks and dagger-like beaks twist like snakes from huge stick nests high in trees, squawking impatiently when adult Great Blue Herons return with food.  On April 23, a Killdeer was on eggs at Moraine State Park.  View a photo essay on Killdeer.

   In the mountains, the Common Raven nestlings will soon fledge.

    Miniature cottontails will soon be feeding along grassy edges.  Fox kits will remain safe in the den until they are three months old, probably in July or August.

    Susanne Varley saw her first Ruby-throated Hummingbird on April 28. 

   I found a Dryad Saddle on a tree stump in Raccoon Creek State park.  Rustle through the leaves below dead or dying Slippery Elms.  After the rain the morels should be out.

Yellow Morel

    Whatever you do, get out.  There are only so many springs in a lifetime. None are ever the same.

Long-spurred Violet, Viola rostrata

McConnell’s Mill State Park, May 8, 2008