Dance of the BumblebeesApr 12th, 2012 | Category: Bee Science
Tracking the season in a patch of Staten Island forest.
Trout lily has won the battle for the forest floor. Last Friday, its leaves filled every inch of our site in Corson’s Brook Woods. There was nowhere safe to step without leaving shoe-shaped indentations behind.
This ubiquity is subtle in our main photograph. Trout lily’s muted, muddy tones recede into the background. Most of these leaves are single, sterile and flowerless. Typically only 1 percent of the population has the ability to bloom.
The reason is youth. Flowers are metabolically expensive for plants to produce. Roots must first amass enough girth, which can take several years. When the plants are finally ready to flower, underground tubers also send up a second leaf, helping to pay the price of floristic beauty with additional photosynthates.
Spreading via sterile clones is a common woodland strategy. Flowers, the means of sexual reproduction, present an opportunity to diversify. As if to illustrate the principle of genetic variability, a few of the many golden trout lily blooms have distinctive brick-red anthers.
I lie on the ground to get a better view of foraging bees — honeybees, miner bees, bumblebees. As they move from blossom to blossom, gathering nectar, their pollen-dusted bellies rub against the flowers’ female parts, facilitating floral sex. One bee makes a getaway with its stash gathered neatly in the pollen baskets, called corbiculae, on its hind legs. This pollen is now unavailable for pollination, bound for hungry bee larvae back in the nest.
An efficient bee may collect as much as half of a flower’s available pollen in a single visit. Trout lily’s guard against such sudden depletion by opening its anthers — its male parts — over two consecutive days. This rationing means each flower has more opportunities for its pollen to find a mate.
Trout lily’s pendulous flowers discourage visits from ants. Instead, these insects are drawn to the more accessible wildflower spring beauty. We find tiny, honey-hued acorn ants happily sipping spring beauty nectar while providing no pollination. By now the forest floor is awash with the blossoms, like the foamy caps of foliar waves.
On the ground among them is a downy feather, white with black spots. Later, I hear a trembling quirrr sound coming from the hollow of a standing dead tree: the call of a red-bellied woodpecker. I remain still for several minutes, but never see the bird.
Walking through the woodland, I take stock of available surface water. Small pocket wetlands are characteristic of our site, but this year many are merely patches of mud. Winter provided no melting snows, and March was exceptionally dry. These conditions have contributed to brush fires on other parts of Staten Island.
At the edge of one droughty vernal pool is a single, eager bloom of wild geranium. Nearby is a small patch of wild ginger. Discarded plastic bags are prevalent, drifting in from the college campus nearby. Above our heads are eastern phoebes — five, six, more — and the songbirds’ razzy peeps fill the air along the forest’s edge. A mourning cloak butterfly appears and then slips behind a tree.
Emerging leaves of woody plants expand in a colorful array like unfolding fans. Chartreuse tulip trees, gingered white oaks, plummy blackhaws appear as the rites of autumn writ small. Luckily we are close enough to watch it happen.
Marielle Anzelone — botanist, urban ecologist, founder of NYC Wildflower Week and author of last year’s Autumn Unfolds series on City Room — is tracking spring’s progress in a forest on Staten Island each week. Go to her Flickr page to see more photos.