You can witness the amazing annual convergence of spawning horseshoe crabs and migratory shorebirds along the Delaware Bayshore every spring. DNREC’s DuPont Nature Center at Mispillion Harbor is one of the best places to observe this wonder of nature.
Each spring, with warming water temperatures, hundreds of thousands of horseshoe crabs leave the depths to spawn on Delaware Bay beaches.
The Mispillion Harbor is a prime location to view these prehistoric creatures as they gather during late April through June along the shoreline and shallows. Peak spawning occurs during the month of May.
The Mispillion Harbor provides the perfect habitat for horseshoe crabs to safely spawn. The harbor is shallow, warming up quickly in the spring. The harbor’s jetty provides protection from wave action, making for calmer waters especially during spring storm events. And finally, the Mispillion Harbor has gently sloping sandy beaches that are perfect for the crabs to lay their eggs.
During this same time of the year (May through early June), thousands of migratory shorebirds make their way to the Delaware Bay looking for a stopover as they journey north to nest in the arctic.
These shorebirds are tired and hungry when they arrive and are looking for coastal wetlands and open beaches for foraging and roosting.
For many species, horseshoe crab eggs — packed full of protein and fatty acids — are a critically important food source for shorebirds to build up their energy reserves quickly. Hungry shorebirds, like the federally-threatened red knot, will gorge on the eggs and double their body weight in about two weeks, improving their physical condition.
Once full and rested, they will resume their migration north to begin nesting.
The best time to view horseshoe crabs is from May through early June during any high tide. Peak spawning typically occurs during the new and full moon high tides in the month of May.
Note: Please follow all beach access rules and policies when visiting Delaware Bay beaches. Check each community’s policies before you go.
The best time to view shorebirds is from the middle of May until the beginning of June, right after a high tide.
Note: Please always observe shorebirds from a distance to avoid disturbing them and disrupting their feeding.
Learn more about horseshoe crabs from the Ecological Research Development Group
How to Report Banded Birds