biodiversity climate change migration

Blackburnian Warblers in Costa Rica- Will They Always be Here?

Fall passerine migration has reached Costa Rica. Unlike the woods and fields of Niagara, it doesn’t happen in waves of birds that shake the pollen from the Goldenrod. The subtle movements and gentle colors of warblers, vireos, and Least Flycatchers in early autumn foliage aren’t a part of our fall landscape but that’s alright; every place has its avian charm. In Costa Rica, our fall migration charms start with flocks of Swallow-tailed and Mississippi Kites, group after group of Eastern Kingbird, an abundance of Red-eyed Vireos and wood-pewees. As in the north, the ancient annual movement of birds also happens in Costa Rica, it just takes on different flavors and shades of bird.

An Eastern Kingbird migrating through Costa Rica.

Other birds that paint a Central American autumn are thousands (likely millions) of Cliff, Barn, and Bank Swallows, Purple Martins, and many Scarlet Tanagers. Although we don’t see the full array of classic, confusing fall warblers, a fair number still move into and through Costa Rica. You see, our fall migration is a combination of birds coming back to their winter homes and others heading further south, straight to the bird continent that begins with Colombia. The Blackburnian Warbler is one of those passage migrants and these days, it can be the most common warbler in town.

The other day, we had our first fall taste of Blackburnians while visiting some friends for some morning birding in higher habitats. Although our birding destination was still heavily influenced by an urban component, there were enough gardens and green space to connect us with a healthy number of birds. For folks from North America, this will surely sound odd but the best bird on our morning list was actually a Tree Swallow. A species that doesn’t need to travel this far south, we don’t get too many in Costa Rica and most sightings take place in later months. Nevertheless, we were surprised and pleased to be looking at a juvenile Tree Swallow flying around with a feeding swarm of resident Blue-and-white Swallows.

Blue-and-white Swallow

The rest of the morning gave us more typical migrant species; a Western Wood-Pewee that sallied from a garden post, a couple of Wilson’s Warblers at higher elevations, and our first Black-and-white Warbler of the fall. More groups of swallows also moved through, mostly in the form of Cliff and I do enjoy watching those but our main quarry, our most hoped for birds were wood-warblers. This being the height of Cerulean Warbler migration in Costa Rica, I have to admit that this special beauty was the number one bird on my mind. We weren’t looking in the best of places but at this time of transience, it can happen anywhere, even in the riparian zone out back.

We might not have seen a Cerulean on that day but checking each and any warbler still rewarded us with numerous looks at another favorite beauty, the Blackburnian.

We must have seen at least 8 of this popular species on that morning, maybe more, and on subsequent days, I saw some while walking near home. Unlike the male warblers of May, the birds that boast their presence with bright colors and song, these Blackburnians were in fall stealth migration mode. They didn’t chip, they didn’t respond to pishing or pygmy-owl or screech-owl calls. They were too busy feeding for any of that nonsense, too intent on bulking up to head back into the night skies and move to their Andean wintering grounds.

Given their quiet focused ways, the warblers almost went unnoticed, even as they steadily moved through the foliage, hopping here, picking something off a leaf there. Given that effective unobtrusive behavior, I wonder how many more were out there in Costa Rica? Hundreds? Probably thousands, all spread across green space, feeding to fill up and keep moving.

Blackburnian Warbler in stealth mode.

The tropical foliage where they forage and spend the winter is a far cry from their breeding grounds. It’s hard to imagine both types of forest in the same frame of thought but the connection is made with Blackburnian Warblers and other birds. They form a bridge between fantastic humid biodense forests of the Andes with fantastic mixed forests of the north. Those breeding grounds are forests of Maple, Oak, and Spruce, places where I have been serenaded to near sleep by the steady toots of Northern Saw-whet Owl, places where one awakes to the ethereal song of Wood Thrushes, places where I made my first birding steps.

Hemlock and pine and June in such places is an incredible show of birdsong. At least it should be. It still is in many places but given the massive decline in birds, I am sure it’s not as loud as it warrants. Nor are the trees as massive and tall as they should be even though much forest has grown back.

Naturally speaking, it’s extremely important to know how things should naturally be because how else can we know if an ecosystem is working as it should? How else can we know if the vegetation is growing as it should to provide people hundreds of years from now with carbon sequestration, food, and other essential benefits? How else can we know if there are enough Blackburnian and other warblers to act as natural pest killers? How else can we know if we are working with our natural surroundings and not breaking down the essential connections, wiping away a safety net that would keep us thriving for the long run?

The Blackburnians that are moving through Costa Rica didn’t have to deal with the conflagrations out west. The Olive-sided Flycatchers and Western Wood-Pewees I saw today are the lucky ones, they made it here in time. The other countless number of birds that died in those flames and that may have been erased by the subsequent smoke weren’t so lucky. Terribly, many people also lost their lives, countless more people survived but lost their homes along with everything inside.

Olive-sided Flycatcher
Western Wood-Pewee

Having gone through the devastation of a home fire (and not even one where the house was destroyed), I can’t begin to tell you how terrible that is but if you can imagine one moment to the next being homeless and having nothing, and maybe also losing a loved one or family pet, that gives a fair idea. If there’s any way anyone can help, check out these possibilities, these people need it now.

On the bird side of things, the fires make me wonder if there will be fewer Wilson’s Warblers in Costa Rica this winter. The fires may have been partly responsible for the large number of bird deaths from New Mexico. For the Wilson’s that winter in Costa Rica, it all depends on where they are coming from but if we as a species can’t make major changes in time, eventually, it won’t much matter where that species, Blackburnians or many other birds live. Whether they survive drastic changes brought on by human-caused climate change or not will be one more sick gamble of the Anthropocene.

We can put the odds in their favor and keep seeing Blackburnian Warbler in Costa Rica, on the Texas Coast, and Magee Marsh but only if we make major changes now in our collective behavior. We CAN make changes to limit the fires and other major disasters that have the ability to eventually disrupt food production and other basic aspects of life to the point of causing suffering for huge numbers of people. Let’s make the change, the time to do it has already been now.