Wild bird migration can take on many forms. In the northern hemisphere, it typically involves moving from south to north in the spring, and then reversing the pattern in the fall.
Another example of migration is called "elevational migration," where birds move relatively short distances, but experience a significant difference in elevation and get the same benefit of traveling great distances from north to south.
For example, an Anna's hummingbird that summers at 6,000 feet in the Bradshaws might migrate only 40 miles to the Phoenix area where it will spend a comfortable, warm winter at 1,000 feet.
Of course, there are some species that don't migrate at all. Birders often refer to these species as "permanent, year-round residents." Species fitting in this category are adapted to live either at higher elevations, or at latitudes farther north. In the Prescott area, we have a lot of non-migratory species such as Gambel's quail, spotted towhee, mourning dove, bushtits, etc.
The time of day when a bird migrates is an interesting topic for a column. For example, most song bird species, frequently referred to as passerines, migrate at night, while larger birds usually migrate during the day. You might wonder why different bird species migrate at different times of the day.
Song birds are typically small, and can fly only if they are continually flapping. If they stop flapping it would be a matter of only seconds before they would fall out of the sky. My analogy for song bird migration is to compare their long-distance flight to a marathon runner. Running a 26-mile race consumes a lot of energy and requires hydration. If it is a hot day, runners can get heat stroke.
Day time conditions in fall can be very windy and very warm. These are not favorable for a small song bird with a limited supply of fuel (body fat).
Think about small song birds, weighing somewhere between 10 and 15 grams. If they tried to fly for hours on end during the day, they could easily become overheated. They would also expend a tremendous amount of energy fighting windy conditions. However, flying at night provides much more favorable conditions - less wind, cooler temperatures, and an added benefit of predator avoidance at night.
In contrast, large bodied and broad-winged birds can fly for hours on end during the day without expending very much energy at all. During the day there are thermals, rising columns of warm air, and updrafts that provide lift for birds with the ability to soar.
If these birds tried to migrate during the night they would tire quickly as there would be neither thermals nor updrafts to keep them aloft. The only way they could fly would be by flapping their wings for hours upon hours, which would cause them to experience exhaustion.
The bottom line is the fact that each bird species is uniquely adapted to migrate in a specific way that minimizes exertion and maximizes efficiency. Nature truly is amazing!
This time of year many species of birds are migrating through the Prescott area such as warblers during the night and turkey vultures during the day. I suspect white-crowned sparrows will start showing up at backyard bird feeders this weekend. Be on the lookout!
Another quick reminder - the submission period for the 10th annual wild bird photography contest ends on Saturday, Sept. 29. For more information, stop by the store or visitwww.jaysbirdbarn.com.
Until next week, Happy Birding!