Delaware Bay is an outlet of the Delaware River within the U.S. Northeast. With the Bay’s contemporary water mixing for a lot of miles with the salt water of the Atlantic Ocean, it’s some of the vital habitats for shorebirds on this planet. EarthSky’s Shireen Gonzaga visited Delaware Bay in Could 2024 on the top of spring migration. She mentioned many birds fly right here from alongside the Atlantic shoreline, stopping to feed and relaxation earlier than making their strategy to their breeding grounds within the Arctic. See Shireen’s video of shorebirds in Delaware Bay, above.
Shorebirds want quite a lot of habitats
Most shorebird species are extremely migratory. Within the Americas, they journey northward in spring, speeding to breeding grounds within the Canadian Arctic tundra. That’s a principally treeless habitat with low-growing vegetation like grasses and mosses. There, they elevate their chicks in early summer season.
Shorebirds head south beginning in mid-summer, this time at a slower tempo. First, the adults depart, adopted by juveniles in late summer season. Many spend the Northern Hemisphere fall and winter months over a large geographic vary, from the southern U.S. all the best way to the tip of South America.
Throughout migration and at their wintering websites, shorebirds forage in quite a lot of habitats. You’ll see them feeding on invertebrates, like worms on tidal mudflats and bugs in shallow freshwater marshlands. Or you may even see them on a seashore, plucking prey like small crustaceans from the sand.
Horseshoe crab eggs are a worthwhile meals supply
Why do the birds cease in Delaware Bay? It’s partly as a result of Delaware Bay hosts the most important inhabitants of breeding horseshoe crabs on this planet. In Could and June, these marine arthropods spawn on the seashores throughout spring tides. A lot of their little inexperienced eggs find yourself on the seashore floor, a bounty to ravenous shorebirds.
Ruddy turnstones and red knots rely closely on the eggs of horseshoe crabs. That’s as a result of these eggs are wealthy in proteins and fat, important for constructing muscle and fats reserves wanted for long-distance migrations.
Delaware Bay is a vital cease for pink knots
Purple knots are robin-sized shorebirds. A lot of them undertake epic migrations. Some pink knot populations stay as far south as Tierra del Fuego, on the tip of South America, about 10,000 km (roughly 6,000 miles) from Delaware. Different populations winter on the coasts of Brazil and the southern U.S.
A major variety of pink knots cease at Delaware Bay on their strategy to Arctic tundra breeding grounds in Canada, so far as 3,000 km away (about 2,000 miles). These long-distance migrants arrive at Delaware Bay seashores round early Could. They’re emaciated once they get there, having drained fats reserves gathered at their earlier foraging web site.
Purple knots spend about two to a few weeks at Delaware Bay seashores, largely gorging on horseshoe crab eggs. Once they arrive, the birds weigh about 100 grams (3.5 oz). By the point they depart, they’ve doubled in weight, in fats that can gas their northward migration.
The pink knot subspecies (Calidris canutus rufa) discovered within the Americas is classed as threatened below the Endangered Species Act. Their numbers have plummeted up to now few many years, about 70% for the reason that Eighties.
Shorebirds in decline
Migration could be very bodily demanding. Shorebirds want locations the place they’ll feed and relaxation undisturbed, to recuperate and construct up fats reserves that gas the following leg of their journeys.
Locations for them to feed and relaxation have dwindled. Local weather change additionally affects these birds. In consequence, shorebird populations are in decline.
The Western Hemisphere Shorebird Analysis Community (WHSRN) mentioned on their website:
Shorebirds are amongst a number of teams of birds displaying essentially the most dramatic declines. Species that undertake hemispheric migrations depend on particular habitats and meals sources to outlive, however these sources are more and more below risk from human disturbance, habitat loss and degradation, over-harvesting, growing predation, and local weather change.
The group additionally wrote:
Local weather change is going on now. With shorebirds’ reliance on coastal wetlands, the Arctic tundra, saline lakes in arid areas, and extremely specified meals sources throughout migration, they’re extraordinarily weak to the modifications which can be occurring, corresponding to:
– Lack of habitat on account of rising tides
– Hotter and drier circumstances in some areas
– Shrub encroachment on nesting habitat in a warming Arctic
– Mismatched timing of migration and meals sources
At Delaware Bay, shorebirds that depend on horseshoe crab eggs face a further downside: a shortage of eggs. Horseshoe crabs have been closely harvested to be used as bait in eel and conch fisheries. In consequence, fewer eggs can be found on the seashore for birds. Regardless of harvesting restrictions, horseshoe crab numbers stay at historic lows.
State and federal wildlife companies are monitoring shorebird populations carefully in Delaware Bay. They’ve offered habitat by preserving vital areas the place the birds can feed and relaxation undisturbed. Lately, there have been some steps to scale back harvesting of horseshoe crabs. However will these steps be sufficient to assist the shorebirds? Time will inform.
The place to see shorebirds in Delaware Bay
For spring shorebird migration, Could is the most effective time to go to the Delaware Bay space. Should you’re new to shorebirds, it’s greatest to affix a birding area journey so a information may help you determine the birds. Deliver a pair of binoculars and, when you’ve got one, a recognizing scope.
Some seashores in New Jersey have designated viewing areas the place you possibly can watch the birds. On the Delaware aspect, Bombay Hook National Wildlife Refuge is a superb place to view shorebirds in wetland habitats. For seashore shorebirds, a superb place to begin is the Dupont Nature Center close to Slaughter Seashore.
Backside line: The Delaware Bay coastal area is likely one of the most vital shorebird habitats on this planet. In spring, some shorebirds rely closely on the eggs of horseshoe crabs to gas their northward migration.
