Traveling across the nation this winter, I was astounded by the amount of movement—thousands of people driving or flying hundreds of miles from their homes and back again. I pondered why. Was it to visit family, see new places, take a break from the norm? Each person had their own reasons, and, likewise, each person was putting up with any number of difficulties: plane maintenance, changing weather, traffic, bad food, parking. Yet every winter people persevere and continue long migrations from home.

Wandering around Malibu Lagoon and the chaparral, I was equally astounded by the number of visiting birds in addition to our year-round residents.

Unusual ducks, yellowrumped warblers and Canada geese made temporary homes in the relative warmth of the Santa Monica Mountains. But I wondered, did these birds migrate for the same reasons as the thousands of human travelers? Did they long for the waters of Malibu the way some people long for their mother's cooking? Were they compelled by a need to get away? Why did they migrate? And how did they know where to go?

Migration in general refers to a regular seasonal journey. While often it refers to birds, many species partake in an annual expedition—deer migrate to lower elevations each winter; amphibians hop a few hundred yards from dry land to nearby water to lay eggs; butterflies journey to breeding grounds. These cyclic migrations are in contrast to animals changing locations due to abrupt habitat shifts. These animal movements are usually only one way, rather than the round-trip nature of migration.

Many species migrate, but birds are one of the world's foremost migrators, and they do it in a number of ways. While flying is the most common method, penguins swim for hundreds of miles, and the blue grouse walks to lower altitudes in the winter for better foraging.

Regardless of the mode of migration, seasonal journeys are ancient and beneficial.

The bad with the good

Most birds traveling in the northern hemisphere take flight to northern breeding grounds and return to southern wintering sites. Long summer days in the north provide the birds with more opportunities to feed their young before winter sets in.

In addition, it has been found that birds breeding in the north, with extended daylight hours, lay larger successful clutches than their counterparts in tropical climes, where the day length does not change significantly. This allows for greater proliferation of the species.

This proliferation is balanced by the enormous cost of migrating. Beyond the huge energy expenditures, hazards are numerous.

One example is increased predation. As birds are flying to wintering sites, predatory birds take advantage of traditional patterns and wait for flocks of exhausted prey to pass. I have seen this in Big Sur, with a peregrine falcon picking off migrating hummingbirds along the coast.

Another danger is the increased risk of encountering pathogens and parasites at crowded stopover sites. Other perils are lack of food, climatic changes and human impact.

Mitigating migration

To mitigate these threats, birds have evolved many strategies to ensure that migration is beneficial.

One strategy is to fly at night. By traveling at night, birds reduce predation, decrease overheating and increase food intake by eating during day. Nevertheless, night fliers must contend with a tremendous loss of sleep.

Another strategy reducing the perils of migration is the avoidance of barriers. Interestingly, barriers to one species are not necessarily the same for other species. For instance, water birds avoid huge expanses of land devoid of watering holes, but perching birds will shun large areas of open water, while coastal birds steer clear of the open ocean. In order to support their physiological and behavioral adaptations, migratory routes reflect the necessities of each species.

It is important that humans realize that the brief instant we observe a bird in our home range is only a small glimpse of the bird's entire life.

Birds' breeding grounds, stopover sites, wintering ranges and migratory routes are each equally important to their health and maintenance. Factors such as hunting, power lines, wind farms, offshore oil rigs, climate change and loss of wetlands can destroy one or all of these important locations.

Therefore national and international cooperation is essential for the survival of many bird species. Luckily, individuals have understood that birds are not aware of our political boundaries and established the Migratory Bird Treaty Act of 1918 and others like it.

Perhaps the only understanding that we need is a quick reflection on our own winter travels. As each of us endures the stresses of airports, highways, crowded stores and family gatherings, maybe we can have a little more empathy for the trials and triumphs of migrating birds.

Meghan Walla-Murphy can be reached at the following e-mail: mwallamurphy@yahoo.com.