[ ♪ INTRO] Deforestation is killing tropical  birds, but not in the way that you might think.

They’re starving to death because  they can’t get an Uber Eats driver. The birds are relying on an  important service provided by ants.

And that service requires  large, intact forested areas. In other words, it’s a tale of  dominoes falling one after the other. When we think about deforestation,   we normally think that loss of habitat is  what causes animal populations to decline.

After all, animals lose their  homes and sources of food. But the way a forest is cleared matters, as well. Forest fragmentation occurs when a large forested  area is broken into small, isolated patches.

It can mean that species don’t have enough  space to search for sufficient food,   or can’t easily travel into other forested areas. For the various species of birds  collectively called antbirds,   fragmentation like this is especially deadly. And not because their trees or food source is gone,  really, but because their dining buddies are.

See, antbirds have that name  not because they eat ants,   but because they follow after ants to get food. In this case army ants, specifically. Army ants are found in tropical rainforests in Africa and South and Central  America, such as the Amazon.

They hunt by going on raids that can be  many hundreds of thousands of ants strong,   and their colonies are much larger  than those of other kinds of ants. I’m talking a million workers  alone making up a raiding party. Instead of foraging individually for crumbs  of food to bring home like a typical ant, army ants hunt together to catch live prey,   including other animals  way bigger than themselves.

Of course, that’s usually still other  insects, including their favorite: other ants. Larger individual insects, though,  like grasshoppers and cockroaches,   will scatter from approaching army ant raids, and then get snapped up by the  hungry antbirds who are lying in wait. It’s a pretty smart tactic, and makes  for easy meals for the antbirds.

A set up like this means antbirds don’t  need to work much to get their food, especially when their home  range is full of a reliable   army ant species that raids nearly every morning. Some species of really committed ant-following  birds get upwards of 50 to 70% of their  total diet from following these raids. And it’s those committed species  that are most at risk.

Because they’ve foraged and fed  with ant support for so long, these antbirds can no longer  hunt by themselves effectively,   and can’t feed themselves well any other way. After generations of adaptation,  these specialist species may just   not have the right behavioral skills  for hunting independently any more. And while researchers continue to  untangle antbird ant-preferences and behavior, we also keep cutting down  rainforests and fragmenting their homes.

Naturally, fragmentation  harms the army ants first. For as small as they are, they need large,   continuous space for their raids, and quantity  is more important than quality of space. And I do mean large.

For a single army colony of  10,000 to 10,000,000 ants to   meet its energy demands and survive,  it requires up to 30 hectares of land. That’s 300,000 square meters,  or almost 100 football fields. A colony doesn’t stay put, either.

It goes through periods of low activity,  active raiding, and home relocation. Raids usually spread out from home in a fan shape,   and a new home is usually selected  along the same compass direction. This helps a colony avoid re-raiding food  sources that they’ve already cleared out.

You know, keeps things fresh. It also means a single antbird needs to seek out   multiple army ant colonies in  their range to stay well fed.   So when we cut down trees and make smaller  pockets of forest where there used to be   larger continuous forested area, army  ant colonies start to die out first. Without enough ant colonies conducting  regular raids, the poor antbirds go hungry.

Not because their preferred food has died out,   but because their Uber Eats driver is gone and  they don’t know how to find their own food. Now, not all army ant species are quite  this sensitive to fragmented forests, which means a savvy antbird could just go  find another swarm for their dinner date. Unfortunately, other army ant  species often have different plans.

Some species just have the wrong schedule. Antbirds like to follow ants that raid through  most of the day and afternoon, but not at night. And some species don’t raid so frequently,  or not at all during the dry season,   leaving whole chunks of the year  for the antbirds to be on their own.

So that’s a no-go. And some army ant species  hunt their prey underground,   which isn’t going to work for a bird either. The best solution is simply preserving intact  forest to help protect the ants and the birds.

But because of the role of fragmentation,  it isn’t enough to simply maintain a certain   total amount of green space  left behind by deforestation. We also need to consider maintaining  contiguous green space to ensure army ants have enough room to raid and thrive . To be fair, army ants are not  the most charismatic species.

So if you aren’t moved to protect the  forests for them, then do it for the birds. Or maybe for the butterflies that eat fresh antbird poop in order to get nutrients important for laying their eggs. Or the tropical lizards and frogs  that also eat the escaping insects.

Or the raptors that follow the  raids in order to eat the antbirds. Or really any number of other animals in  this big, connected, forest food web. And we of course are all connected by this here World Wide Web   Which is very helpful because we couldn’t have made this  video without help from our Patrons.

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