[music]

Brian Lehrer: Brian Lehrer on WNYC. Now for our month of may check in with BL Trees, our year-long once a month project to follow the life of a tree through the four seasons and the 12 months looking at and learning about the trees around us, what they do for and to us and what we do for and to them. New York City has millions of trees. We hope you pick one out to follow this year. Maybe even tweeted us a photo using the hashtag #BLTrees as we're inviting you to do once a month as you follow your tree through the year anywhere in our listening area.

Today, we're going to talk about birds and trees. It's the spring migration season. Birding Twitter is full of tweeting birds photos at least of the many birds passing through town on their way back North and stopping off to hang out in the trees around the area. Turns out the relationship between bird and tree is more involved than just a branch to nest on. Let's learn how and why. Back with us is our guide for this year-long adventure, urban ecologist Marielle Anzelone, founder of New York City Wildflower Week who proposed this project and is offering her expertise in putting it together month by month. Hello again, Marielle.

Marielle Anzelone: Hi, Brian. It's good to be back.

Brian Lehrer: Today, she is joined by Desiree Narango, a conservation scientist at the University of Massachusetts, and working in collaboration with the US Forest Service researching this link between tree and bird conservation. Welcome to WNYC, Desiree. Thank you for joining us.

Desiree Narango: Hi, Brian. Thanks for having me. I'm glad to be here.

Brian Lehrer: Marielle, we invite everybody to pick their tree to follow this year, one outside their window or in their backyard or a tree that's on their block or caught their attention just walking around their neighborhood and get to know it and then, remind us, do what?

Marielle Anzelone: Then we want people to share what they find, to post their photos on Twitter using the hashtag #BLTrees. We formed a little community of people who are really interested to see how people's trees are doing. It's been about six months so far. We've seen a lot going on with our trees lately.

Brian Lehrer: Remind everybody what your tree is and how it's doing this May.

Marielle Anzelone: My tree is a pin oak which is a tree that's native to New York City. It typically grows in wild areas but mine is planted on a corner in Kensington in Brooklyn. It's near where I live. Since it's an oak, oaks are a little slow to leaf out. Other trees were flowering, had these big beautiful flowers and they're still waiting, but oaks are interesting because they are wind-pollinated. The flowers are very small. I posted a picture of what some of the male flowers look like.

They dangle, they hold pollen and then they fall on the ground and get caught up in cigarette butts and other things. Those are flowers and floral parts. Of course, the

female flowers stay on the tree and eventually become acorns.

Brian Lehrer: I think a lot of people don't think about flowers having gender. That's a good lesson right there. Some new way to look at some of our trees. Desiree, the early bird might get the worm but what it really wants is the caterpillar. Caterpillars are picky when it comes to which trees they live on.

Desiree Narango: Absolutely. We see across lots of songbirds that, even among all the insects, that they especially prefer to eat those delicious caterpillars which are the larva that turn into butterflies and moths. The caterpillars are plant eaters and they're very picky and very specialized to use particular host plants. They are evolved to use mostly native plants. We need to have those native plants to support the caterpillars so that the birds can find them so they can eat and feed their young.

Brian Lehrer: When we plant non-native species of trees, we don't bring their ecosystems with them. We might like the way the tree looks and it might grow here but it's not necessarily fully participating as it were because it's not always providing the same amount of food for the birds in the area?

Desiree Narango: Exactly. Our native insects have adapted to the chemical compounds that are found in tree leaves. They also have adapted to the timing of the leaves, like Marielle said about the timing of when a tree leaves out and they've adapted to how they look as well. It turns out that when we introduce these non-native trees from other ecosystems across the world, that our native insects don't recognize them. They don't use them. They're not providing the food for the birds to eat. The birds aren't really using them to find food as well.

Brian Lehrer: A question that a lot of our listeners have probably never thought about, how many caterpillars does it take-- Sounds like the beginning of a joke. How many caterpillars does it take to support a bird or a bird family?

Desiree Narango: Oh, takes a lot of caterpillars. For example, for the chickadee, which is a bird that I studied for a research project of mine when they're feeding their baby birds in the nest, they need from 6,000 to 9,000 individual caterpillars just to feed one nest of baby chickadees. That's just a little bird that weighs 10 grams. It's about 10 paper clips in your hand.

If we think about bigger birds cardinals or woodpeckers, it's taking thousands and thousands of caterpillars to allow those birds to breed and to thrive. Even on top of that, these birds really need these insects very quickly, these caterpillars, especially, very quickly when they're making these grand migratory movements as well. The birds are really doing a great job at taking care of those caterpillars and keeping our plants healthy too.

Brian Lehrer: All right, listeners. Who has a story or a question about the relationship between birds and trees? 212-433-WNYC 212-433-9692, or you can tweet your question about birds and trees @BrianLehrer for Marielle Anzelone, founder of New York City Wildflower Week who proposed this, once a month, following a tree through the year series that we're doing that started in November.

We're doing the may episode right now.

Joined today by Desiree Narango, a conservation scientist at the University of Massachusetts Amherst, working in collaboration with the US Forest Service researching this link between trees and bird conservation. Lisa and Forest Hills, you're on WNYC. Hi, Lisa.

Lisa: Hi. I love your show.

Brian Lehrer: Thank you. Now, we have Lisa. Hi there. Now we have you.

Lisa: Oh, sorry. Hi, thank you so much for taking my call. I really love your show. This story's more about a bird than a tree. This week, I noticed this pile of old branches, old leaves, even little pieces of plastic on the back of my air conditioner. I thought, "Oh, it is some bird collecting things to make a nest." I was worried they would make a nest on the back of my air conditioner, then when I have to start using it that would be really bad for the nest.

I swept everything off the back of my air conditioner. Within 12 hours the whole pile was back. Then I started noticing, I think it was a mourning dove, was coming and picking little things individually and flying away with them. It was as if this bird was using the back of my air conditioner as a loading dock for their nest-building project. I have a video of it. It's the cutest thing. The spur must have been back 20 times picking. You could see it was like deciding, "Do I want to take the plastic or the leaf?" It was the cutest thing. I should probably share that.

Brian Lehrer: What a great story. The air conditioner as a loading dock. Lisa, thank you for sharing that. Mary on Staten Island, you're on WNYC. Hi, Mary.

Mary: Good morning. I had a non-bird question, I'm afraid.

Brian Lehrer: That's okay. It is a tree question, right?

Mary: It's a tree question. Recently the trees on Staten Island are starting to drop these golden threads, thicker threads but not as thick as a rope. I don't know which tree does this. I don't know what the little threads do if there's some seed or what have you. Because of the recent weather, they clumped up on the street, they got rained on and then the wind dried them into great big bundles and it looks like sidewalk seaweed.

Can someone tell me what tree this is and whether it's really something you'd be allergic to or what is going on?

Brian Lehrer: Marielle, is this ringing a bell?

Marielle Anzelone: Yes, it's ringing a bell. It's exactly what I was talking about earlier. These are the male flowers from oak trees. Oaks are just starting to finish up releasing their pollen and flowers are all-- Different kinds of plants all have different flower structures. For oaks, the male and the female flower parts are in different

flowers entirely, as opposed to being in the same flower, as you might find in a rose or other things.

The males are only useful for pollen. They dangle from the tree and you don't see it. They're very hidden behind-- as the leaves are emerging, you see it, but we don't recognize them also as flowers, because they don't have the sterile parts like the petals that are beautiful and big and are attractants to bees, "Here I am. Come pollinate me."

Because oaks are wind-pollinated, petals, in fact, would be an obstacle to wind pollination because you're blocking the places where the pollen needs to go. Those are the male flowers of oak trees. They're dropping now and it's just, as you say, they collect on the ground and they almost look a little bit like urban tumbleweed. You can touch it, it won't bother you, but they do have pollen.

The pollen in oaks is one of the things that causes spring allergies. Wind-pollinated plants are sticky and airborne and they stick to your eyes, they stick inside your nasal passage and that's what causes allergies. Plants that we would recognize as being a flower, those don't cause the allergy, it's the wind-borne, grasses and oaks among others.

Brian Lehrer: Mary, there you go, thanks for asking a great question. Kevin in Belmar, you're on WNYC. Hi Kevin?

Kevin: Good morning. Question is how delicate is the balance between the caterpillars that are basically destructors of foliage and the butterflies that then become the pollinators and how unique is that relationship in nature?

Brian Lehrer: Desiree, can you take that one?

Desiree Narango: Sure. Across all of the caterpillars that turn into butterflies and moths, we know that more than 90% of them are plant specialists. Just like the monarch butterfly feeds exclusively on milkweed, all of those butterflies and moths, or almost all of them are feeding on just a handful of different plants. It's a very delicate balance. If you don't have those plants, those caterpillars won't be there and then they won't grow up to become those butterflies and moths.

We also know that there are some trees and shrubs that do the lion share of supporting most of that diversity. For example, those oak trees that are dropping those flowers all over the neighborhoods, they are supporting over at least 526 different species of butterflies and moths in the state of New York. That compares to a different tree, like a tulip tree or a black gum that's only supporting about a dozen or so.

Some of these trees are really, really important to have in our ecosystems, in our neighborhoods, so that we can support most of that diversity.

Brian Lehrer: Raj in Edison, you're on WNYC. Hi, Raj?

Raj: Hi. How are you? Thanks for having me. I have a quick question. My wife

noticed that birds that look like robins always come back to the same little tree in our backyard and seem to build a nest each time new in spring and then, of course, in winter, everything goes away, and then again next spring, we see similar kinds of birds. The question we have is, is it the exact same birds that come back to the same tree, or is it just different birds that might or be others?

Desiree Narango: Oh, that's a great question. It could be the exact same bird. For some of the birds that I studied for my research, we actually put little bands on their legs so that we can identify individuals. I had chickadees that came back to the exact same nest box for five years in a row, which is really exciting.

Brian Lehrer: How do you even know?

Desiree Narango: I have a robin on my back porch that nests on the same trellis every single year. It could definitely be the same birds.

Brian Lehrer: How long do they live?

Desiree Narango: It depends on the species. The small birds will live 2 to 5 years or so, but the bigger birds like cardinals and robins some birds have been recorded to live 12 or more years.

Brian Lehrer: How do you know it's the same individual bird without having tagged it or something?

Desiree Narango: Unfortunately, you can't, unless they have some unique behavior or a unique mark on their plumage, but otherwise it's going to look like every other bird that's out there.

Brian Lehrer: Brian in Westchester you're on WNYC. Hi, Brian?

Brian: Hi. How are you? Love the show. This is the first time I've ever called because this is a subject it's close to my heart. I feed my birds a lot and they seem to know that I feed them a lot. Clearly the same chickadees, pair of cardinals, 10 mourning doves, they all come back. My question is really is it okay to feed them that much?

Because they seem to be like, "Hey Brian, you haven't fed us like in a day or two, where's that food?" It's a constant thing about a $70 a month investment. They're always in my backyard. I love it and I see the same Chickadees year after year. That's my question.

Brian Lehrer: Great question. I bet a lot of people wonder about that. Desiree, should they feed the birds? Is a bird feeder good or bad or neutral for birds or humans feeding the birds in our midst in any other way?

Desiree Narango: That's a great question. If you have a feeder in your yard that you're keeping clean and free of disease and you're keeping your cats inside so that they're not preying on the birds, then that feeder is a really good thing for you,

especially, because now it's bringing the birds closer to you so that you can see them and appreciate them. In terms of survival and reproduction, those bird feeders aren't bad, but they're not necessarily good either.

The birds don't need them in order to survive. They're mostly eating insects, especially right now during the breeding period. Most of our birds are relying exclusively on insects and just coming to your feeder occasionally to get some of that seed. The best thing that you can do is plant native plants around your yard so that you can provide lots of insect food for the birds to eat and to feed their young. Then you can also keep that feeder nearby too, so you can see who's visiting as well.

Brian Lehrer: There's a 2019 study that found there were 3 billion fewer birds in the US and Canada than in 1970, 3 billion fewer. Desiree, where'd all the birds go, do we know?

Desiree Narango: Unfortunately, we lost them. We lost them because of lots of disturbance that we have affected our ecosystems with, especially in terms of habitat loss and climate change, invasive species. We have lost lots of those individual birds and we have much fewer numbers than we used to have.

It's a really unfortunate and depressing number, but I want to emphasize that there's really something that we can do. In terms of habitat loss, planting trees in these areas where we've taken away all the green space can be a really great opportunity to start to bring those birds back by providing the habitat that they need to survive.

Brian Lehrer: In our last 30 seconds or so, Marielle, to the thought from earlier in the segment, choosing a native tree like a red maple, an oak, certain kinds of elm trees, sweetgum, choosing a native tree when planting new ones makes a difference?

Marielle Anzelone: It does, it makes a really big difference. Also, some of Desiree's research shows a lot of birds will nest in a tree and not forage very far. If they don't have native trees within their foraging range, they won't find enough with the caterpillars that they need to feed their young in order to fledge the nest and survive. Yes, having lots of native trees everywhere is really critical.

Brian Lehrer: Marielle Anzelone, founder of New York City Wildflower Week who proposed this project of picking out a tree and following it once a month on the show for a year. We started in November, so we're halfway through. Thank you so much as always. And Desiree Narango who joined us for this month's May addition of #BLTrees, a conservation scientist at the University of Massachusetts Amherst. Thank you so much, Desiree.

Desiree Narango: Thanks, Brian. This was really fun.

Copyright © 2022 New York Public Radio. All rights reserved. Visit our website terms of use at www.wnyc.org for further information.

New York Public Radio transcripts are created on a rush deadline, often by contractors. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of New York Public Radio’s programming is the audio record.