I have been re-reading the new book “Songbird Journeys” by Miyoko Chu. Since I read it the first time and mostly late at night, I didn’t retain some of its wonderful information.
So I am finding it most informative the second time around. Many of you have written or called me with questions about bird migration, so I had planned to write such an article for some time.
Our spring migration starts locally in early March with the arrival of birds that winter nearby in the border states such as Arizona and New Mexico, the mountain bluebirds and red-winged blackbirds. Later arrivals usually winter farther south in Mexico, Central America and South America. The flow of these birds continues northward with the peak being reached in the first two weeks of May.
Man has always wondered how birds found their way on such journeys of thousands of miles often over routes they have never taken before if they are young birds. It has long been presumed they used the sun, moon and stars for orientation, and this has proven to be true. They also use land masses such as the Rocky Mountains, patterns of polarized light and the Earth’s magnetic field.
We have also wondered if the birds flew across the Gulf of Mexico or if they stayed overland and flew around the west end of the Gulf of Mexico. This book explains that they do both. Some birds take the much longer land route but the greater numbers fly across the Gulf. In the spring, they wait along the shore until they have a warm southeasterly wind, then they leave at night.
With a warm tailwind, they make the trip before daylight. However, their fat supplies are nearly gone, and they usually spend a day or two in the same area to feed before they continue northward.
If the weather changes in mid-flight with a rainy cold front coming in from the north, thousands of birds die for there is no place for them to land, and they cannot buck the north wind and cold rain for most of their body fat has been used.
In fall, it is just reversed, with the goal being the Yucatan Peninsula and South America, and a tailwind out of the north. If caught by a change in the weather when halfway across the Gulf, they will land on ships, bits of driftwood, but mostly they have no choice to do anything but keep flying. They drop down closer to the surface of the water where supposedly the wind force is diminished. But the majority of them never make it.
Some of the other amazing facts I gleaned from this book are that thrushes clocked by Cochran and Wikelski averaged 840 heartbeats per minute during migration, and their wings beat between 600 and 780 times per minute.
The most amazing fact was that a bird’s stored body fat, which is used for this and all migration flights, is so rich that they burn it at a rate that would be equivalent to 720,000 miles per gallon if they were flying on gasoline. This is incredible, and I will be amazed if other research in this area is not going on already to see what kind of fuel they can create out of the chicken fat that everyone throws away. Maybe the Kentucky Fried Chicken colonel will produce a new fuel that will do even more for the economy than his chicken.
The birds that do not die in the Gulf due to a weather change are still nearly exhausted when they finally land. There are places that stick out into the water that seem to attract these birds like magnets.
On the first sight of land, they literally seem to fall out of the sky, landing on the beach or in shrubs along the shore or farther inland where there are woods and trees.
There is one such place, call High Island, Texas, which has recently been made a nature sanctuary for this reason. Such “fallouts” occur there with enough regularity that people now go there in “bad” weather in hopes of witnessing such an event.
Locally, I have had a few migrants passing through my yard all during the month of May and even into the first few weeks of June. On Monday, June 13, a yellow warbler was singing in a ponderosa pine and a vesper sparrow was eating millet at my feeder. On Tuesday, June 14, the violet-green swallows that nest in one of my boxes every year  arrived to find the boxes they have used in the past already are occupied by a pair of house wrens, a pair of white-breasted nuthatches and a pair of mountain chickadees.
Another box used in the past is now being used by a fox squirrel family. The swallows did a lot of swooping around, and I hoped they would use one of the other houses that are still empty, but they seemed to have moved on. I shall miss their graceful evening flights.
If you haven’t read “Songbird Journeys” by Miyoko Chu, do get a copy from the library. It is published by Walker & Co., New York.