The above picture was taken a few days ago during the autumn migration season. It occurred to me that there are quite a few differences between spring and autumn migration in Ohio, so I figured now was a good time to post about it- thanks to Doug Overacker for discussing this topic with me and adding to whatever I knew about the subject.
To start with, here’s the characteristics of spring migration-
- It happens within a narrowly defined time period. Birds are anxious to get to their nesting grounds and start raising families. Males want to get the best nesting territory they can find to attract females and so they are in a hurry. The limiting factor is the availability of food. For instance, Warblers eat mostly insects, and as soon as the leaves start coming out on the trees they get ready to migrate because leaves are a great place to find insects. All of this makes spring migration a race against time, so it goes by fairly quickly. Spring migration lasts between March and late May (depending on the types of birds).
- Foliage is not completely mature when spring migration happens. Trees and bushes are often getting their leaves, but there are no tall ‘weeds’ in meadows yet, and undergrowth is still developing. This makes it easier to see spring birds since they are not totally obscured by vegetation.
- Birds are in their best plumage in spring migration, because they will immediately try to attract a mate when they get to where they like to nest. This makes male birds in particular easy to see because most have bright plumage.
- Birds are singing a lot in the spring. This is a way to attract a mate and to warn off other birds of their species. This is a big advantage to birders because you typically hear more birds than you see, and spring is the time of year when birdsong is prevalent.
Now, contrast this with autumn migration’s characteristics-
- Autumn migration is more drawn-out, taking longer because there is not the urgency to start a family that drives spring migration. Autumn migration can take place between late July and through November (depending on the types of birds).
- Foliage in autumn is much more developed than foliage in the spring. Trees and bushes are fully leaved (until late in the migration season), and there are plenty of tall ‘weeds’ such as Goldenrod, Horseweed and Greater Ragweed that fill fields, giving extra territory for migrants to utilize in search for food.
- Birds are usually in dull plumage during autumn migration. They’ve already raised a family, and they typically have just finished molting their feathers to replace them with new, more subdued feathers. There is no need for bright colors, and it probably is safer for birds to be harder to spot. This makes it harder to identify what birders see in the autumn.
- Autumn migration is significantly quieter than spring migration. Most birds aren’t singing because there is really no need to. If you are used to the riot of songs in spring and early summer, autumn comes as a shock it can be so quiet. You can hear the occasional song (and often those are by immature birds that sound a bit ‘off’ because they are still learning) and some calls, but by being rather quiet this season means less chances for identifying lots of birds.
- An additional factor comes into play in autumn- not only adult birds are migrating, but so are their offspring. Younger birds born that previous spring or summer are heading south, which means in autumn you have a significantly greater number of birds to see.
So, to summarize-
Spring migration is shorter, takes place with less foliage, and consists of brighly-plumaged birds that sing a lot.
Autumn migration is longer, takes place with more foliage and more widespread habitat, and consists of greater numbers of duller, quieter birds.
A rough guide to what migration months bring what birds:
March is spring waterfowl migration plus a handful of early land migrants such as Eastern Phoebes.
April is the big month for sparrows as well as many species such as orioles and thrushes.
May is warbler month, plus later arrivals such as flycatchers.
Then in the autumn-
July/August sees shorebirds migrating as well as some land birds.
September is the big month for warblers to head south.
October is sparrow month.
November sees waterfowl heading south.
Personally, I love the month of May in spring migration. Colorful birds can be seen and heard after the long winter months. Autumn migration is good too, after the hot summer. It’s more of a challenge seeing and identifying birds then, but it lasts longer.
The changing of the seasons means that year-round you can look for different conditions and different patterns of bird observation. This keeps everything interesting!