Because many species of wading and swimming birds are able to feed at all hours, they migrate either by day or night and are not accustomed to seek safety in concealment. Some diving birds, including ducks that submerge when in danger, often travel over water by day and over land at night. Strong fliers like the snow geese can make the entire trip from their staging area in James Bay, Canada, to the wintering grounds on the Louisiana Gulf coast in one continuous flight. These birds are seldom shot by hunters en route between these two points but are often observed, when migrating, by aircraft pilots. Graham Cooch of the Canadian Wildlife Service tracked a flight of the blue phase of this species in 1955. The birds left James Bay on October 17 and arrived on the Gulf coast 60 hours later after an apparent continuous flight over the 1,700-mile route at an average speed of 28 miles per hour. Golden plovers, likewise, probably make the southward flight from the Arctic to the South American coast in one giant leap. Other Arctic species on their northward flight in the spring might prefer to fly at night in lower altitudes, but must necessarily fly during the day at higher altitudes because of the length of the days. Many warblers that normally fly at night may find themselves over water at daybreak and be forced to keep flying during the day until landfall is made. [Illustration: _Figure 3. Migration of the blackpoll warbler. As the birds move northward, the isochronal lines become farther apart, which indicates that the warblers move faster with the advance of spring. From April 30 to May 1 the average speed is about 30 miles per day, while from May 25 to May 30 it increases to more than 200 miles._]