Bird Migration & the Changing Climate

It’s no news that climate change is impacting our natural environment, but what does this mean for birds, migration patterns, and lasting biodiversity? As winter tends to get warmer, why are birds still migrating? What makes them migrate in the first place?

Growing up, you may have learned about animal migration in your science classes. For many of us that has been quite a few years (myself included!) and much has changed about migration patterns since then.

What does migration mean and why do birds migrate?

Migration is the process of moving from an area with a lesser number of resources to an area with more plentiful resources. When talking about animals and birds more specifically, these resources are most commonly food and nesting locations. When the weather gets colder, resources for food and creating nests grow sparse, which encourages birds to migrate south to warmer weather and develop temporary homes with more accessible resources.

Birds migrate to reduce threats to their habitat. When resources are decreased, there becomes increased competition among all species for the same resources. During nesting season for birds, it becomes imperative for them to have access to plentiful resources so they can properly care for their hatchlings or chicks, and provide them a safe environment to be nurtured in. The increased competition in these colder areas would also mean that birds and their hatchlings would be easy targets for predators like cats, chipmunks, other birds, snakes, frogs, dogs, deer, coyotes, and many more.

Do all birds migrate?

Not all birds migrate. In fact, around 20% of all bird species migrate to find food and to breed. The most common pattern sees birds flying north in March and April to breed and returning to warmer regions in the south in September and October.

Some bird species don’t migrate because they can find sufficient food and nesting resources where they are currently located. There is a common misconception that birds cannot withstand cold temperatures, which is false. Many birds actually thrive in colder climates, typically those who are dependent on seeds as their primary food source. In North America, cardinals and sparrows, among others, are those that don’t migrate and are able to survive off the resources close to home.

How do birds know when to migrate?

Despite this question being studied by scientists for many years, there is no conclusive answer. However, scientists have found that migration can be triggered by a combination of changes in day length, lower temperatures, changes in food supplies, and genetic predisposition, all of which are dependent on the bird species and their needs.

How has climate change impacted bird migration?

There have been increasing threats to bird migration over the years and it only continues to increase. Bird migrations are some of the longest journeys taken by any animal, with many dangers on the way. From plastic pollution to climate change, they are increasingly threatened by human activity.

In a 2017 research study published in the journal Scientific Reports, the researchers analyzed 12 years of data looking at how the changing climate is impacting bird species. They found that “climate change is projected to drive hundreds of bird species to extinction and greatly reduce the ranges of others, and is already impacting species richness and composition.” Already, they were seeing that bird species couldn’t effectively sync up with the changing climate and there was a lack of adaptation to changing vegetation.

One impact that we can anticipate is increased competition for bird species, no matter if they are migratory or not. We have been seeing warmer winters in many traditionally cold winter weather locations. Birds residing in these places may begin their migratory process at a later date when the weather begins to get colder but in the meantime, the species in that area will be continuing to compete for resources. If they are arriving at their migration location late, they may also be experiencing some hardship finding enough food and nesting resources to properly care for their young, due to increased competition with other species.

What does this mean for bird populations and biodiversity?

A changing climate and habitat are threatening to bird species, and all species for that matter. We can anticipate increased competition among bird species, and possibly even extinction.

In the same research study, the author noted, “Although birds have had to adapt to climatic shifts and resulting asynchronies with resources throughout their evolutionary history, the current rate and magnitude of change have exceeded normal bounds, raising the question of whether migrant bird populations have been able to keep pace with key phenological events.” This means that birds have been adapting to changing climate since the beginning of time, but it has been changing drastically faster than previous, putting bird species at heightened risk of keeping up.

The author continued by saying that, “We found that a majority of migratory bird species adjusted the date of their arrival, usually in the direction (earlier or later) that vegetation green-up changed. Thus, it appears the phenology of migratory arrival is more often than not responding to climate change.” Which is great news! It means that many migratory bird species have been able to adapt to the changing climate and migrate at a time that makes sense for their survival.

It is certainly not all doom and gloom as birds are thankfully a very adaptable species. However, it is important to be prepared for anticipated changes incurred by the changing climate, and ultimately do everything you can to help reduce these drastic changes.

What can you do to help?

While any individual may not be able to save the entire bird population, you can have an impact! Here are a few ways that you can support bird species:

• Donate to WWF
• Birding watching and bird migrations can be enjoyed across several of our adventures from the penguins of Antarctica to a variety of songbirds in Yellowstone
• Buy or build a bird feeder. Filling a feeder with high-caloric snacks (sunflower seeds, oats, raisins, etc.) will be able to keep birds energized to continue their migration journey. Even if you don’t have a feeder, you can sprinkle these same snacks over your lawn or porch.