Migrating birds fly up from their wintering grounds in the south each year, beginning in late winter and continuing through the spring. Along their routes, they stop for food, water and rest. Important food sources for migrating birds include plant buds, as well as insects and other invertebrates. Without these foods, birds don't have the energy they need to continue their long journeys.

Once birds arrive at their final destinations, having adequate food is important not only for their own daily needs but also to provide the energy needed for nest building, mating, egg production, keeping nestlings warm and foraging for food to feed their young.

But what if the food they need isn't there when they need it? Over the years scientists and lay people who study birds and record their behavior have noticed that climate change may be affecting foods that birds rely on. Citizens who enjoyed keeping journals about the changing of the seasons, sometimes for many decades, noticed that certain plants were flowering a little earlier as time went on. In northern New Jersey and much of the northeast, warm spells earlier in the year have led to early blooms on flowering trees. Insects that don't usually emerge until March or April have been spotted in January and February. Scientists are concerned that warming trends worldwide are leading trees to bloom or leaf out earlier, and insects to emerge earlier.

How does this affect the birds? A migrating bird, on a journey that may be up to several thousand miles long, needs to be able to feed when it touches down at resting spots along the way. If buds have already opened or insects that the bird relies on have already emerged and dispersed before the bird arrives, it may weaken or die of starvation.

Some birds, particularly those who migrate shorter distances, appear to be adjusting their migratory schedules to catch up to changes in food source availability. A University of Edinburgh study looked at records kept by scientists and amateur naturalists, over the course of 300 years, in both Europe and the United States. They found that for each degree of increase in average temperature, migrating birds arrive one day earlier at their nesting grounds. The Field Museum, which has been monitoring migrating flocks of birds in Chicago for 30 years, has determined that some species are arriving about a week earlier than they used to. Birds that migrate long distances appear to be less able to adjust, and are therefore more likely to starve.

Milder winters due to warming trends also mean that birds that overwinter instead of migrating are more likely to survive, creating, in some cases, competition with migrants for limited habitats. Birds that arrive at their nesting grounds too early or too late to take advantage of food sources are less likely to successfully raise offspring. And if birds don't arrive early enough to eat insects that damage trees it can affect our forest habitats.

What can you do to help the birds? Scientists have determined that climate change involving warming trends is related to the production and use of energy derived from fossil fuels. Minimizing your use of fossil fuels can help slow down warming trends and give birds a better chance. Turn off lights when you are not in a room. Turn down the thermostat at night or when you are away from your home, and combine errands to reduce car use. Use public transportation when it is available. And talk with your friends and family about how they too can help our fine feathered friends.

By Jenny Aley, Volunteer Naturalist

March, 2017