Migration is one of the many wonders of the animal world. Migration is defined as the seasonal movement from one region or area to another. Many different types of animals migrate, however migration is most famously associated with birds. Bird species of all types and sizes make migrations, some covering thousands of miles and even spanning continents. But when do birds migrate each year?
There are two main timeframes for migration: fall and spring. If you live in North America, you may have seen some of these mass migrations. Many people recognize (by sight and sound!) the V-formation of geese flying north or south, depending on the season.
It truly is a wonder how birds know when to begin their migrations. In this article, we will cover some of the cues that let birds know it is time to migrate and when these migrations tend to happen.
When do birds migrate?
As mentioned before, there are two main times of year when birds will make their migrations: fall and spring. Typically, birds will head south during the fall for the winter and north during the warmer spring months. Depending on the species, some birds will do their flights at night while others fly through the day. Some birds will fly through both the day and the night!
Fall
When temperatures start to cool down, many species of birds will gear up for a long trip down to where its warmer and travel south. During the winter, it can be very difficult for birds to find food and keep warm, so that is why birds will make the trip before winter arrives. Not all birds migrate though, in Northern North America there are several species that are well adapted for the cooler temps. These birds may have fluffy down winter feathers to keep warm.
It’s difficult to give a definitive time frame of when the migration south for the winter starts because fall starts a lot earlier up in cooler climates in the north. In places like Alaska or Canada, birds may start their fall migrations as early as late July-early August. States that are south of Canada and Alaska may start to see migrations anywhere between August and October at the latest.
Drops in temperature, changes in daylight hours, and the fact that there is less food available sends the signal for birds to start their migrations. The instinct to migrate is also partially ingrained in the genetic makeup of migratory birds.
Spring
With the coming of warm spring temps, many birds will start their long journey back up north where temperatures are mild and pleasant for the summer months. Birds that travel south during the fall partly do so to escape colder temps and get to an area where there is ample food to eat, so once things warm up again they are able to return.
Just as there are some species of birds that are native, year-round residents in northern climates, there are some species that are native residents to warmer climates in the south do not migrate during the spring.
In southern climates where temperatures are hotter, birds typically start to make their trip back up north earlier than those that have traveled to more central or mild climates. These trips back north may start as early as early March through May.
Environmental cues like temperatures rising and daylight hours getting longer let birds know that it is time to make the trip up north.
Why do birds migrate?
In the animal world, most behavior can be explained by motivators such as food and the instinctual drive to pass on ones’ genes through breeding. Bird migration is no different and is very much dependent on these two underlying motivators.
Food
For birds that are typically residents in cooler northern climates, food can become very scarce during the winter months. Typically, birds that eat nectar or insects can’t find the food they need once winter comes and need to travel south where insects to eat and plants to drink nectar from are abundant.
Then, when temperatures begin to rise, insect populations begin to boom up north, just in time for migratory birds to come back to feast. Warmer temperatures in the summer also means that plants will be flowering which is important for birds that depend on nectar for a food source.
Breeding
Passing on your genes through breeding and reproduction is absolutely an instinct in the animal world. Breeding requires resources- like food for energy and places to nest with optimal conditions. Most commonly, birds will migrate up north during the spring to breed. In the spring, things begin to heat up and food sources are more abundant. This is essential to make sure birds are healthy and fit enough to breed.