Do Monarchs Migrate at Night as Some Songbirds Do? Contributed by Dr. Bill Calvert Monarchs do not migrate at night. Basically I believe that it is too cold for them to fly at night. They have no source of warmth (radiation) to keep their muscles working. Here are three reasons why day time flight is advantageous to monarchs: 1) Cool Night-time Temperatures The monarch's flight threshold is about 13 degrees C (55F). They can't fly well until temperatures are in the 20's or even 30's. This is pretty close to the temperatures that warm blooded mammals maintain. (See related link: Why Do Monarchs Shiver?) During spring and fall migration, night time temperatures are typically below flight threshold. Day time temperatures are usually above the flight threshold for some period of time each day. If monarchs were to fly at night, they would have fewer--if any--hours of flight time in each 24 hour period. (Also, Monarchs are known to ride on the wind at high altitudes. It is even colder at higher altitudes than on the ground, thereby reducing their flight time further at night.) Monarchs often use thermals (rising columns of air) to soar to high altitudes. Thermals form during the day, due to uneven heating of the earth's surface by the sun, so would not be available to them at night. During fall migration, monarchs are often seen dropping down at the end of the day, and they spend the night in roosts. The next morning, they don't fly off until daytime temperatures rise to their flight threshold. 2) Wind Tail winds--winds blowing in the same direction as the monarchs are traveling-- are key to fast and efficient monarch migration. Winds are stronger during the day than at night. So, just as some songbirds fly at night to avoid strong winds, monarchs fly during the day to take advantage of strong winds. 3) Disorientation in the Dark Butterflies that attempt to fly in the dark show a lack of coordination. They appear to be disoriented and fall to the ground. Note: There are some observations that might suggest night flight, but there is no evidence that these monarchs were not blown out of control in these cases. Take the example of monarch butterflies appearing in the United Kingdom. They are apparently carried there during fall migration by strong, high altitude winds. The length of time needed to cross the Atlantic would be far longer than daylight of a single day, so the monarchs would be aloft at night. Presumably, however, these butterflies did not “intend” to go to Europe but were blown off course during their fall migration to Mexico. Copyright 2004-2007 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form