Conserving Bird Habitat in Cities
Bird habitats are affected by population and urban growth, but there are many opportunities to design and manage urban landscapes for a variety of birds. However, there is no simple evaluation tool that translates empirical research into practical, usable information for developing green infrastructure in regards to bird habitat. Green infrastructure can include yards in neighborhoods, urban parks urban forest fragments, areas along roads and streets, and even areas around stormwater ponds. Dr. Mark Hostetler, UF/IFAS professor of wildlife ecology and conservation, tackles this issue by translating published research and creating an online bird habitat evaluation tool that essentially evaluates different development designs and impacts on forest birds.
Several different reviews were used to obtain a list of birds that could utilize urban habitats:
- Breeding articles that studied birds’ area-sensitivity to forest fragments during breeding season.
- Stopover articles that studied the use of forest fragments during spring and/or fall migration seasons.
- Built environment articles that studied a bird’s presence within residential neighborhoods (with trees) during breeding or migration season.
From the review of breeding studies in forest fragments, Hostetler and his graduate student, Jan Archer, were able to conclude that 75 different species breed in relatively small forest fragments ranging in size from one to 50 acres. They also identified fifteen bird species that will not breed in small fragments. These interior forests specialist species require large, contiguous forests to breed.
From the review of migration studies and stopover habitat in forest fragments, they found that 116 species could use forest fragments between one and 50 acres in size during migration seasons. These species were mostly long-distance/neotropical and even several interior-forest species used these small forest fragments as stopover habitat.
From the review of built environment studies, 109 species could use residential areas for breeding or as stopover habitat. 70 species could breed in residential areas and 82 species could use residential areas as stopover sites during migration seasons. Interestingly, several interior forest specialists used residential areas as stopover sites.
In summary, residential areas provide stopover and breeding habitat for over 100 forest bird species. Forest fragments provide stopover and breeding habitat for over 120 forest bird species and some interior-forest specialists use forest fragments and residential areas as stopover habitat.
Written by Alex Giang, CLUE Communications Intern
Watch the recording (Dr. Hostetler starts at 45:05)
Are you focusing on species that you would see only in Florida, the southeast, or throughout the US?
Dr. Hostetler: The synthesis was throughout the US. We did a synthesis of birds in the eastern part of the US, the western part of the US, and Canada, so any study that was done there we synthesized that, but for my current graduate students they’re all focused on Florida. In fact, they’re looking at Gainesville. With the COVID situation, as urban ecologists it’s been good that we can do things literally in our own backyard; we don’t have to travel so far. So, they are really doing some interesting stuff right now. Look for a couple of papers from my graduate student Ryan Buron that we’ll be publishing this year sometime.
Northern parula are in older residential neighborhoods with live oaks in Tallahassee.
Dr. Hostetler: The interesting thing about the northern parula is we see them in Gainesville in residential areas as well. Sometimes ecology is doing a lot of research for the obvious, but we have to do the research. Northern parulas nest up north in hanging moss. We have a lot of Spanish moss here in Gainesville and in Tallahassee, so particularly oaks, sweet gums, and other things that have Spanish moss is nesting material for the northern parula. That’s one of the studies that graduate student Natalie Pegg will be doing is trying to see what types of yards with trees within residential neighborhoods northern parulas are found on.
Were any human planted green spaces evaluated; not a forest?
Dr. Hostetler: Human planted… so, a lot of the forest patches within cities, particularly if you’re thinking about the eastern United States, have been cut down once, so it’s all secondary growth. Planted forests, depending on how they’re managed, can provide significant habitat; it’s all about the management, such as planted pines and hardwoods. So yes, they can provide habitat. The one thing I think is important to think about is the invasives. A forest patch is not a forest if it’s overrun with invasives like Melaleuca down south or Brazilian pepper down south; it’s not as good as more natural habitat that contains primarily native species. You really have to think about managing the invasives that occur in these patches, but yeah, managed forests can provide habitat for a variety of migrating species.
Moderator: So, the person who asked the question followed up and said, “planted trees in yards.”
Dr. Hostetler: Yes, so the built environment synthesis showed that many species use tree canopy cover within residential areas. Planted species in yards, particularly if they’re native, provide habitat for not only breeding species, but also migrating species and stop over habitat. For sure, planted species count in terms of habitat.
Does this mean that unmanaged forests are not the best for wildlife, maybe specifically birds?
Dr. Hostetler: It depends on where that forest is. A lot of unmanaged forest is really good habitat for wildlife because, for whatever reason, it’s away from cities; it’s not being inundated with invasives or fertilized water or air pollution, etc. So yeah, unmanaged, probably more wild is the best way to do it. However, a lot of the forest patches are kind of in the matrix of urban and rural, and so you have to manage those somewhat. Now, there is no way in the state we’re in, in terms of the anthropocene era, that were going to have truly all natural; there’s going to be a combination of exotics, invasive exotics, and natives. I think what is important to understand is that we’re not trying to go back to all native. We have what’s called recombinant ecosystems. There’s a whole host of literature out there that says we can’t go all the way back to totally native, but we can at least manage it to have more natives that would be there than if we didn’t manage it at all, so think of it in terms of recombinant ecosystems. I’m looking out at my yard right now and there’s sword fern, a plant that’s considered invasive; however, there’s lots of species that come in my yard that are native, both plant and animal. Don’t think of it as getting rid of all the invasives and all the exotics, think of it as just combining and thinking about managing more for the natives so it brings out more habitat for the species.
Moderator: So, is it accurate to say something’s better than nothing? You know, I’m thinking of central Florida, there’s no trees to start with and a development comes in, new houses, construction, and every house gets a tree. I mean, that’s not what you’re talking about with these forest tracks, but it’s something.
Dr. Hostetler: Well actually that is what I’m talking about because that built area with those individual trees are habitat, so for sure. I think a lot of people think, “well it’s urban, let’s just forget about it, let’s go outside the urban area.” But no, the combination of the urban and rural, and the natural and urban is critical for providing habitat and increasing biodiversity across the whole region, so I think urban areas are very important. A little bit is good, but if you plant an invasive that could be horrible and that can spread into the natural area. You want to minimize impacts from the urban area into the natural area, and part of that is realizing, “hey if we’re planting natives and not planting invasives were also improving the habitat within the city and minimizing the impact on nearby habitat.”
I was talking with a former extension agent a couple of years ago from an urban area in St. Pete, and she mentioned that the bird diversity had really been reduced in that area just because of the development there – it’s just so overbuilt. Is there any way to turn that around in these areas that are already built up to the extent that a place like St. Pete is built?
Dr. Hostetler: I think there is. There are ways to… again, for the forest birds, just planting a native tree and letting it grow over years. It might take decades, but yeah, you can definitely improve it. When I think of what I call controlled chaos; having sections of lawns that just go wild, and you can border it and make it look aesthetically pleasing, that can promote the diversity of birds and insects in the neighborhood. So yeah, I think you can retrofit almost any community, it just takes a little bit of emphasis, both from policy, developers, and individuals.
Are there any laws to protect particularly old trees in Gainesville?
Dr. Hostetler: Yes, there are. In fact, they have heritage tree laws, particularly for large live oaks and some other species that are protected, and if a tree becomes diseased and you have to take it down there’s a law that you have to replant it with trees. Gainesville is considered tree city USA, and that tries to cover more than 50% of our city in tree canopy.
Moderator: Are there laws like that elsewhere, most of Florida, or is it that Gainesville is an outlier in terms of the protection it gives.
Dr. Hostetler: There are other cities; Tampa has similar types of forest plans, so yeah, there are other cities that have those types of laws as well. But, Gainesville and Alachua county tends to be really trying to keep that tree canopy.
Do invasive birds like peafowl negatively impact native birds?
Dr. Hostetler: Well, it depends on the species, but the peafowl not really. Of course, you can imagine if you have hundreds of peafowl in one area, that’s going to really tear up the vegetation, so it just depends. Most likely it does not affect the native birds, particularly the forest ones. If you have trees and peafowl underneath is probably okay.
So, you developed this tool, now what are the next steps?
Dr. Hostetler: The next steps are putting it in the hands of people that make decisions. It really bolsters the tree laws because they say, “oh what are trees good for? They’re good for water, shading, energy…,” but they’re also good for biodiversity, so it helps bolster those laws and it’s a backdrop for that. Also, for decision makers like a developer they can say, “well it’s so difficult to put this road around these trees, why don’t I just cut the trees down and put it in there?” And this helps give them the impetus to say, “no, there’s a lot of species that use those individual trees.” So, we’re working with a few developers and using this tool to show that, “hey, those trees… keep that individual live oak that’s in that pasture right now and build around it.”