May is known for flowers, picnics and warm sunny days, but in the animal world, May is a very busy month.
Along the coast, an ancient creature emerges along the shorelines briefly to spawn. For a short time, certain Atlantic Coast beaches are literally covered with the distinctive horseshoe crab.
Spawning begins in late April and runs through mid-August, although the peak spawning period is from late May to late June.
During high tide, horseshoe crabs migrate from deep water to beaches to spawn. The female digs a nest in the sand and deposits 4,000 to 30,000 eggs for the male to fertilize.
At low tide, adult crabs go back into the water but may return at the next high tide. Horseshoe crab spawning increases on nights with a full or new moon, when gravity is stronger and high tides are higher.
The world’s largest population of horseshoe crab is found in Delaware Bay. During the spawning season, wave action and the digging action of mating crabs exposes many eggs on the beach. Once an egg is exposed to air, it can dry out quickly, preventing it from hatching. It still plays a vital role in the ecosystem, though. These exposed eggs are the primary food source for migrating shorebirds making the journey from South America to the Arctic along the Atlantic Flyway.
Delaware Bay hosts the second largest population of migrating shorebirds in North America. The shorebirds in the Atlantic Flyway use only a few areas for feeding and rest on their migration. More than 1 million shorebirds fly nonstop from places as far away as Peru and Argentina—as much as 5,000 miles. More than half of the total flyway population of red knots, ruddy turnstones, and semipalmated sandpipers depend on the Delaware Bay’s horseshoe crab eggs as a rich and critically important food supply.
Shorebirds aren’t the only avian travelers. Birds are the nomads of the animal world, ceaselessly traveling with the change in season in search of food. It must be the burden they carry for the gift of flight.
In the fall as the climate gets cooler, birds who feed exclusively on insects, fruit or pollen must migrate to more temperate climates in South and Central America, Mexico and the Caribbean. As spring returns to North America, so do the birds as they follow their food sources back to their breeding grounds.
More than 360 species of birds make this annual migration including songbirds, such as warblers, thrushes, tanagers and vireos; some raptors, such as hawks, kites and vultures; and a few waterfowl, such as teal.
Some of these birds are common—the American robin, Eastern bluebird, ruby-throated hummingbird, gray catbird, purple martin, barn swallow and chimney swift. Others, such as the red-eyed vireo, scarlet tanager, wood thrush and Cape May warbler, may be familiar only to bird watchers.
A one-way migration can take anywhere from several weeks to four months. Typically, migration is accomplished in a series of flights lasting from several hours to several days. Between flights, birds stop to rest and refuel, which can take a day to a few weeks, giving birdwatchers an opportunity to see a great variety of birds.
To celebrate this annual event, the second Saturday in May is designated as International Migratory Bird Day. On this day and throughout May, bird-related activities and events are happening at National Wildlife Refuges, as well as local parks and nature centers. For information about events, contact Jennifer Wheeler at 703-358-2318 or e-mail IMBD@fws.gov
This May we’ll have a visitor that we haven’t seen in 17 years. The 17-year cicada will emerge and carpet the mid-Atlantic region from May through June. Known as a periodical cicada, the 17-year cicada is recognized for its shrill, almost deafening song, which males use to attract mates. A flying insect, this cicada is easily identified by its large size (about 1–2 inches long), protruding red eyes and large, clear wings.
As the soil warms, cicada nymphs crawl out of the ground and climb up tree trunks or other objects where they shed their skin and emerge as adults. Their purpose for the next four to six weeks is mating. The males’ song can be heard from early morning to late evening, until about July.
After mating, the female cicada cuts slits in small twigs to lays her eggs. Adults die soon after mating and egg laying. The eggs hatch and tiny nymphs fall to the ground where they burrow into the soil and spend the next 17 years below ground, starting the whole cycle again.
Cicadas will not significantly affect most large, healthy trees. Small trees, though, can be damaged by the female egg-laying. Damaged twigs may be pruned out after cicada activity.
Small shade and ornamental trees can be protected by covering them with cheesecloth or finely woven netting to prevent females from laying eggs in the twigs.
By emerging in such vast numbers, as many as 1.5 million insects per acre, cicadas overwhelm predators by their sheer volume. The mass emergence provides an unlimited feast for birds, snakes and mammals. Once the predators have eaten to capacity, there are still millions of cicadas left over to produce the next generation. Cicadas are not poisonous and do not bite or sting.