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Signs of Spring: May 11, 1998 Full Moon! Please report the unique sights and sounds of spring from your area. Tonight's full moon affects birds from the Atlantic to the Pacific--and everywhere in between. The full moon helps nocturnal hunters to see their prey, so owls can catch mice more easily and Whip-poor-wills and nighthawks can see more insects. Woodcock sometimes perform their spring dance all night long during a full moon. The bright moon also helps people to see migrants. In the 1950s, ornithologists named Lowery and Newman focused a telescope on the moon and saw hundreds of birds winging past, and learned many things about migration that ornithologists had never known for certain before. They found out that nighttime migrants start flying soon after dark, and that the numbers are greatest between 10 pm and 1 am, with the hugest numbers between 11 pm and midnight. By dawn virtually all nocturnal migrants land to rest and feed. They also found that herons, geese, and shorebirds migrate in close formation, but that virtually all small birds fly alone. When huge numbers of little birds like warblers are migrating at the same time, we can see lots of them in the sky, but they aren't really together--except by chance. They make little "seet" sounds in the sky, probably to keep track of each other to avoid mid- air collisions. If the moon helps us to see them sometimes, it can be a hindrance to the nighttime migrants themselves. Many scientists believe that the glare of a full moon probably makes it harder for night-time migrants to see the stars, and so their navigation may be at least sometimes a bit less accurate during full moon nights. Nevertheless, the middle of May is the peak of migration for many neotropical migrants, and no matter what phase the moon is in, they are on the move. The full moon also affects ocean tides, making them stronger than normal, which affects food supplies for many shorebirds. One ocean creature, the horseshoe crab, comes out of deep water to spawn on beaches during high tides, and spawning increases during the strong tides of full and new moons. Kathryn Reshetiloff, a scientist with the U.S. Fish & Wildlife Service's Chesapeake Bay Field Office in Annapolis, wrote that "the horseshoe crab (Limulus polyphemus) is found along the Atlantic Coast from Maine to the Yucatan peninsula. This fierce-looking yet harmless creature is valuable both ecologically and economically. Horseshoe crab eggs are an important food for shorebirds migrating along the Atlantic Coast. Horseshoe crabs are also used as bait in eel, whelk and catfish fisheries. Their importance doesn't end there. Horseshoe crabs are also used extensively for medical research." Right now, along the Atlantic coast, horseshoe crabs are starting to appear on the beaches, along with the shorebirds that depend on this food to fuel their migration. In Cape May, New Jersey, Red Knots, Ruddy Turnstones, and Sanderlings have been reported this week along with the season's first horseshoe crabs. The Cape May Bird Observatory is trying to protect the crabs from being overharvested, so that the shorebirds that depend on them can survive. Shorebird Crisis: The Horseshoe Crabs of Delaware Bay Natural Phenomena: Horseshoe Crabs and Shorebirds Try This! If you know anyone with a telescope or binoculars, see if you can see any migrants flying past the moon. Can you identify them? Tell us what you see! Now Think About This: Challenge Question # 7 "In many kinds of shorebirds, males do most, or even all, the work of raising the babies. In some species, like phalaropes, males even incubate the eggs. Why do you think the shorebird family has so many males working harder than females?" Discussion of Challenge Question # 6 Last week we asked you to consider this: Challenge Question # 6 "Why don't hawks gain and lose weight the way songbirds do while migrating" Most hawks catch their prey on the wing. Accipiters and falcons,--bird eating hawks like the Sharp-shinned Hawk and Merlin--fly about much of the day whether or not they're migrating. On non-migrating days they may fly many miles just going back and forth patrolling their woods trying to catch birds. When they're migrating, they're doing pretty much the same thing, only flying in a particular direction. So no matter whether they're migrating or not, they try to keep their bodies well-fueled and in top condition. Buteo hawks like the Red-tailed Hawk migrate on days when thermal air currents or updrafts will hold them high in the air without much flapping, so they conserve energy by flying high on a thermal, then cruising forward with wings set while searching out the next thermal. They can sometimes go over a mile without flapping once, so they don't need to build up a lot of fat either. Some migrating songbirds, such as swallows, also stay on the wing much of the day to find food. One ornithologist followed a Barn Swallow's day-to-day movements to calculate that it flew about 600 miles every day just going back and forth catching insects! But most songbirds simply flit from branch to branch like warblers, or spend most of their time running and resting like robins, and don't use up nearly as much energy in their everyday activities as they do when migrating. When these birds are flying hundreds of miles without rest during migration, they need an added fuel supply which they get from storing fat. When they migrate long distances, their bodies burn this fat. How to Respond to Today's Challenge Question 1. Address an e-mail message to: jn-challenge-spring@learner.org 2. In the Subject Line of your message write: Challenge Question # 7 3. In the body of your message, answer the question above. The FINAL Signs of Spring Update Will be Posted on May 25, 1998 Copyright 1998 Journey North. All Rights Reserved.