America is, whether you want to admit it or not, a nation of immigrants. The country and culture that we have today was founded by immigrants, grew through immigration, and relies on the the hard work and innovation of immigrants to power our economy. My own father and brother-in-law are immigrants to this country from the Caribbean. It is fitting then, that some of our most beloved, beautiful, and brilliant birds are annual immigrants from the south. In this Creature Feature, we will explore a group of brightly colored little songbirds with a boisterous personality - the wood warblers.
Migration is a common strategy used by animals from insects to whales. Monarch butterflies make a multi-generational migration from Mexico to Canada, gray whales migrate up and down the pacific coast to reproduce in calm warm waters, elk in the Rocky Mountains migrate seasonally following food availability, and many deep ocean species make daily migrations up and down the water column.
When we think of bird migration in particular, we think of it in terms of "flying south for the winter." Just like we prefer to go on our Disney World Vacation in the middle of January when it is nice and warm in Orlando, but freezing cold here in New England, birds must migrate to escape the cold, right? Or maybe it is because the yummy insects and invertebrates the birds eat aren't out and about in the cold, so they fly further south to find food. Another excellent hypothesis. These ideas share the assumption that these birds belong here in the North, and only migrate South to escape unpleasant conditions here.
North-South, or, South-North?
Ornithologists have been debating this idea for more than 100 years now, and the matter still isn't settled. Migration has evolved in dozens of different families of birds many times, so the reasons are likely as diverse as the migrants themselves. In the end all migratory birds, the Parulids included, migrate for essentially the same reason most people leave their homes to make an immigrants journey - opportunity.
People don't pack up and leave their homes unless they are forced to. Warfare, political unrest, famine, and lack of jobs are just a few of the reasons that force people to leave their homes and risk it all to start anew somewhere else. Warblers aren't too different. The tropics, where most warblers spend their winters, are pretty crowded. There are a lot of birds there. Costa Rica, for example, has 918 recorded bird species, more than in all of the United States, despite the fact that it is smaller than West Virginia! The boreal and temperate forests of North America, are barren by comparison, especially in winter. So, when it comes time for these little birds to raise a family, warblers make the journey north where less competition for resources means they will have a better chance producing strong and healthy chicks. This is the hypothesis I tend to agree with - warblers are tropical birds that have evolved to migration for resources and opportunity during breeding.
The Beauty of Migrants
I think it is pretty neat. Our country has always been a place for immigrants, they've been coming for better opportunities and resources to raise a family longer than there have been humans on this continent! Plus, as someone who comes from a family of Latin American immigrants, I like thinking that these birds have their feet in both cultures, just like the Nuyoricans growing up in The States.
Plus, just look at these little guys! I think its a shame that so few people here in North America even know that these beautiful little songbirds are flitting about above their heads as they walk through the forest. They may be small, fast, and hard to see, but if you stop look and listen, you just might spot one. Now to close us out, here are a few pics I was lucky enough to get of some warblers, they aren't the best shots, but hey - they are quick little birds!