The Conservany's lead scientist Sanjayan speaks about some of the world's greatest migrations.
It's spring, and that means the animals of the world are in motion again — flying, swimming, running and crawling to their summer homes and breeding grounds. The Nature Conservancy is celebrating this annual pageant of nature with a listing of the “Top Five Must-See Migrations” in Maryland and DC.
1. Blue Crabs
When people “migrate” to the shore for their summer vacations, a crab feast is often on the agenda. But did you know the crabs of the Chesapeake Bay also make their own migration?
Crabs are hatched after the pregnant female (called a “Jenny”) has traveled down to the southern tip of the Chesapeake Bay to release her eggs. In their first life stage the crabs are helpless larvae that float along the currents between the Bay and the Atlantic Ocean. But after 45 days they begin to earn their scientific name Callinectus sapidus (“beautiful swimmers”) by molting into their mobile crab stage and swimming higher into the Chesapeake Bay.
For a year and half they feed along the shores and tributaries of the upper Bay before the migration process starts all over again. The adult crabs mate, and the Jennys swim back down to the mouth of the Chesapeake to release their eggs.
The adult male crabs (called “Jimmies”) do their own migration — a vertical one. When winter comes they dig down into the mud where temperatures are more stable, and await the siren song of warmer temperatures and swimming Jennys to emerge.
The Nature Conservancy is working to conserve blue crabs by protecting the forests that filter water going into the Chesapeake Bay, and by working to protect the oyster beds that provide habitat for crabs.
In combination with science-based fisheries management, there is evidence these efforts are helping, with blue crab numbers doubling in the past two years!
2. Baltimore Orioles
Neotropical migratory songbirds herald the arrival of spring in Maryland and across North America, raising young and spending their summers here. In the fall, massive flocks hurtle into the night skies as they depart for their winter homes in Mexico, Central America, South America or the Caribbean.
Springtime also means baseball’s opening day. Maryland has a rich baseball heritage, as the birthplace of both Babe Ruth and thousands of Baltimore orioles — our state bird and Baltimore’s Major League Baseball mascot.
Much of Maryland lies within the southern range of the Baltimore orioles’ summer breeding grounds, with nests found along the edges of forests. Preserves where Baltimore orioles can be found during the summer include Nanjemoy Creek and Third Haven Woods.
Abundant food around the mouth of the Chesapeake Bay helps attract two of Maryland’s most majestic migratory animals. During the winter, humpback and fin whales feed along the Maryland coast as they head south to mate and calve in tropical waters. Humpbacks grow to 50 feet long, and their songs and spectacular leaps from the ocean thrill seafarers of all ages. Fin whales grow even longer; in fact, these powerful swimmers are the second-largest animal on Earth next to the blue whale.
From late December through mid March, the Assateague Island National Seashore provides a viewing point from the beach.
4. Great Blue Heron
These largest members of the heron family are nicknamed the “love birds” because around Valentine’s Day each year these tall, stately birds woo a mate and settle down to nest. Hundreds of great blue heron nests can be found together in rookeries around the Chesapeake Bay and its tributaries.
The raucous calls of the nestlings, squabbling between adults, and low swooping flights of the parents give these rookeries a near-prehistoric feel. In the summer the nestlings fly off, and the herons look to migrate south in the fall to ply the waters of the Carolinas, Georgia, and Florida for fish, crabs, and frogs.
You can see a great blue heron many places in Maryland, but you are almost guaranteed to see one if you visit Blackwater National Wildlife Refuge on the Eastern Shore in the summertime.
5. American Shad
A spring run of this “founding fish” was said to save General Washington’s Continental Army from starvation in 1778 at Valley Forge, along the Schuylkill River in Pennsylvania.
American shad spend the majority of their lives in the Atlantic Ocean. But with the coming of spring, the fish are cued by changes in water temperatures and salinity to move up the freshwater tributaries of the Chesapeake Bay to mate and lay eggs. Like a clock, the seasonal flows of these rivers tell the shad when to migrate.
The Susquehana River is the largest tributary of the Chesapeake River, and The Nature Conservancy is working with the federal government to improve conditions for migrating shad along the Susquehana’s four dams. Shad also migrate up the Potomac River, where people can be found fishing for shad within Potomac Gorge.