![]() ![]() That means, on a good migration day, we most likely WON’T see monarchs as they fly far overhead. NEXRAD (Doppler) radar has shown that monarchs travel most of the time within the planetary boundary layer, at around 800-1200 feet high. We can’t see monarchs with the naked eye when they fly more than 300 feet high. Since monarchs cannot fly when their flight muscles are below 55✯, cold air temperatures will limit how high they can fly (See ). Air cools as you move higher into the atmosphere. ![]() How high can monarchs fly? Wind speed and air temperature affect the height of monarch flight. Clearly, conservation efforts in the central flyway are key to the monarchs’ survival. This conclusion was further supported by tagging data, which showed monarchs traveling the eastern flyway are far less likely to reach Mexico than their counterparts traveling the central flyway (see. The eastern flyway lagged behind the central flyway roosts in timing, suggesting that monarchs traveling the eastern flyway have a reduced chance of making it to Mexico. Two distinct flyways emerged: an “eastern flyway” and a “central flyway.” The central flyway appears to lead directly to Mexico. Three years of data were analyzed to determine the monarchs fall migration pathways. ” Since 2002, Journey North has collected sightings of fall roosts. Davis published a paper entitled, “ The Fall Migration Flyways of Monarch Butterflies in Eastern North America Revealed by Citizen Scientists. What pathways do the monarchs follow? Elizabeth Howard of Journey North and Andrew K. If they have favorable tail or quartering winds, monarchs can flap their wings once every 20-30 feet and maintain altitude. Monarchs can glide forward 3-4 feet for every foot they drop in altitude. To see what a typical monarch’s flight pattern might look like, see Migrating monarchs use a combination of powered flight and gliding flight, maximizing gliding flight to conserve energy and reduce wear and tear on flight muscles. It glides until it finds another thermal, and rides that column of rising air upwards again. At that point, the monarch glides forward in a S/SW direction with the aid of the wind. Monarchs spiral upwards in the thermal until they reach the limit/top of the thermal (where the rising air has cooled to the same temperature as the air around it). The rising air in the thermal carries them upward, and their overall movement ends up being an upward spiral. In order to stay in the air, they must move forward while also staying within the thermal. Monarchs are so light that they can easily be lifted by the rising air. Monarchs use thermals in the same way that hawks do. Thermals often form wherever large patches of dark ground are adjacent to lighter-colored ground, such as over parking lots, above farm fields, highways, next to rivers and lakes, and above mountains. They form wherever the air is just a few degrees warmer than the air next to it. Why do monarchs ride thermals? Thermals are columns of rising air, caused by uneven heating of the earth. By mid-morning, on a clear day, thermals will form and monarchs will ride these thermals. As the arc of the sun rises, and the air mass above ground begins to heat up, monarchs will fly at 1-2m high. Early in the morning, they will fly almost at ground level. They may fly just over the top of your windshield as they cross the road in front of you! These monarchs are staying low to the ground, picking up radiant heat from the earth to help warm them. If you drive on east-west roadways during migration time, you may see monarchs in directional flight flying at car-level. On 50-60✯ days in the fall, you may notice monarchs flying very low to the ground. But on a cloudy day, they generally don’t fly if it is below 60✯. On a sunny day, these muscles in their thorax can warm to above air temperature when they bask (the black scales on their bodies help absorb heat), so they can actually fly if it is 50✯ and sunny. Monarchs cannot fly unless their flight muscles reach 55✯. They usually fly for 4-6 hours during the day, coming down from the skies to feed in the afternoon and then find roosting sites for the night. First, how do monarchs migrate? Monarchs begin leaving the northern US and Canada in mid-August. Many people have questions about the dynamics of fall migration. Learn more here:, and to find out when migrating monarchs will be moving through your area, enter your latitude here. These monarchs will survive on stored fat all winter, so they need to build up fat reserves by nectaring along their migration route. Get your gardens ready for migrating monarchs to fuel up on nectar sources. It has been a promising summer, Monarch Larva Monitoring Project ( data show that monarchs are reproducing well and we should see a modest increase in the overwintering population this year. ![]()
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