How effective are native, cavity-nesting birds at providing pest control on farms? Researchers with the Smithsonian's National Zoo and Conservation Biology Institute aim to find out. WMRA's Randi B. Hagi reports.
[birdsong, researchers walking through grass]
Through an open meadow near rows of cantaloupes and flowers, Research Fellow Allison Huysman leads a team of interns to check on baby birds. This produce farm, in the eastern foothills of the Blue Ridge in Rappahannock County, is one of nine properties in a study run by Virginia Working Landscapes – a Smithsonian program that promotes native biodiversity and sustainable land management.
We come upon a nest box with four eastern bluebird babies, about 11 days old.
ALLISON HUYSMAN: So what we'll do is we have fresh paper bags, kind of like craft paper bags, so we take them one at a time and they will poop in there … and then we collect that sample and I will use that in a genomics lab and I'll use a technique called DNA metabarcoding to see what they're eating.
Huysman, a doctoral student at the University of Maryland, is conducting a multi-year study to see what bugs eastern bluebirds and tree swallows eat on farms – and thus, how useful they are as natural pest control. Her team installed nest boxes on the farms to encourage these species to procreate here.
Intern James Rodriguez takes two babies out of the nest and plops them in paper bags.
JAMES RODRIGUEZ: You grab them, you gotta take aim, so if they poop, we gotta get it right in the bag.
HAGI: Does it happen pretty quickly once you grab them?
RODRIGUEZ: Usually, yeah, especially when they're bigger like this. [paper bag rustles]
But, sometimes, the baby birds wait until they're taken out of the bags to be weighed.
GROUP EXCLAIMS: Oh, no!
After returning all the chicks to the nest, the team conducts a "point count," watching and listening for the different bird species present within a 100-meter radius.
HUYSMAN: Common yellowthroat heard within 100. [birdsong] Yellow-breasted chat heard within 100, too.
RODRIGUEZ: Two black vultures seen within 100.
HAGI: Is it challenging at all for you guys to pick out the individual bird songs? Because to me it just sounds like a tapestry. [all laugh]
HUYSMAN: Yeah, it's definitely hard. It can be a little overwhelming. I find that just having the full 10 minutes allows you to just focus on each individual thing. … But you definitely have to train your ear to it.
[Cicadas buzzing, sheep bleating, researchers open gate]
At a beef, lamb, and pork farm up the road, nest boxes dot the livestock pastures. Intern Arzu Pahl opens one box and pulls out a bald, newly-hatched little bluebird.
RODRIGUEZ: How old?
ARZU PAHL: Like, two minutes! [laughs]
Huysman sets up a cardboard flap to trap the bluebird mom inside, so they can examine her. But it takes a few tries to get her.
PAHL: Yeah, they're divebombing her. They're not happy she's there.
This female has colored bands on her legs, so they know she's been caught before. They measure her weight and wing length, and look at her feather condition to determine age – and again, collect a poop sample for genomics testing.
[angry bird chirps]
PAHL: She's spicy!
Huysman's takeaways so far?
[dog barking in background]
HUYSMAN: The eastern bluebirds, they're eating a lot of different things. A lot of it is lepidoptera, which is butterflies and moths, and so that's kind of what we see, is caterpillars – they're bringing them back all the time to their nests. Also spiders and crickets and kind of anything you can imagine hopping around in the grasses. And then the tree swallows are eating – probably three-quarters of the diets that we've analyzed have been flies – and that is surprising. So, tree swallows are known to really rely on aquatic insects, and so we have gotten a little bit of that in there, but the amount of flies we've gotten is much more than we've expected. But that's really great for the farmers. We're hoping that they're going to help reduce the pest populations and that pest pressure on the animals.
She hopes the data will support the use of bluebirds and tree swallows as natural pest control to reduce the need for chemical pesticides.
HUYSMAN: The farms that we work on, they're all really interested in helping the larger ecosystem and they want to have that healthy environment. They all recognize the importance of regenerative agriculture, and taking care of their soils and plants and insects.
The nest boxes are crucial for these species that have to find cavities to nest in – they don't make their own. In the wild, that might be an old woodpecker hole in a tree. If they can't find a cavity, they won't breed that season.
HUYSMAN: It's really amazing – I mean, the farms that we added nest boxes to, at some of them, we put a nest box up, and in the time it took us to get back to our car, we would see birds checking out that nest box already. … It's kind of like that "Field of Dreams" quote: "if you build it, they will come."
