No sooner does the calendar show it is fall, and it really starts to feel like fall! The change in weather this past week has been remarkable. The rainstorm on Saturday was incredible. We received over two inches of rain at our home in the Prescott Heights area.
Shorter days, longer nights and cooler temperatures all combined together, give us a sense that the seasons are changing. This is true for wild birds as well especially the change in day length. Shorter days are one of the main triggers wild birds use to time their migration.
Interestingly, the reason for migration is not because wild birds cannot withstand cold temperatures. Most birds are sufficiently hardy to endure sub-freezing temperatures with their downy coat of feathers. If birds are capable of surviving freezing temperatures, what is their motivation to move south in the fall?
The major reason for migration is the issue of food availability. Most varieties of migrating birds migrate to ensure their access to food. Think about wild birds that eat insects. What happens to insects at the northern latitudes when these areas begin to experience freezing temperatures? The insects die. To stay alive, insect-eating birds migrate to temperate climates, oftentimes to Mexico and Central America, where insects are plentiful in the winter months.
A large majority of migratory songbirds in North America are insect-eaters. Examples of insect eaters include orioles, tanagers, warblers, vireos, flycatchers, hummingbirds, swallows and swifts. In contrast, most nut-and seed-eaters (but certainly not all) will usually spend the winter where they spent their summer. There are, of course, exceptions to the rule, such as the white-crowned sparrows and dark-eyed juncos that we see here in Prescott during the winter months. In spite of being seed-eaters, these birds migrate to southern latitudes. Since they are ground gleaners, it makes sense that they would migrate, as they spend their summers in areas that have deep snow cover in winter, making their food sources inaccessible in winter.
Another example of birds that need to migrate are species dependent on open sources of water in winter in order to find their preferred food sources. Food sources necessary for survival for species such as ducks, loons, grebes and shorebirds are found in open water. What happens when lakes and ponds freeze over? Their food sources are no longer available, forcing the birds to move south where bodies of water stay open in the winter months.
One thought to consider is how some bird species engage in elevational migration moving up or down in elevation seasonally, but moving perhaps only a few miles. This is a modified version of migration. In contrast, most migratory species engage in latitudinal migration, moving north and south hundreds, even thousands of miles each year between their summer breeding range and their winter range.
Providing seed throughout the winter months is a great way to support the wild birds that winter in the Prescott area. This is especially true when we get snow and their natural food sources are inaccessible. I personally feel it is more important to feed birds in the winter months. In the summer months, there is an abundance of natural food sources available to wild birds.