[Steve] So this project is a collaborative project
between the Vermont Center for Eco Studies, Audubon Vermont,
and the Rubenstein School here at UVM.
And I'm gonna be presenting on two years of data,
looking at sort of the bird community response
to structure and composition
of the vegetation in sugarbushes,
active sugarbushes in Vermont,
which is a fairly small part of the broader project
being carried out by the UVM team.
So I think we can all agree
that the best-tasting maple syrup
is made right here in Vermont,
(audience member cheering)
and Vermont sugarmakers also make the most.
And in addition,
the sugarmaking has really experienced a rapid growth,
both in terms of number of taps deployed
and the gallons produced,
yet relatively little is known
about how sugarbush management and practices
affect biodiversity and ecosystem services,
as well as the resilience of the sugarbush
to ecological stressors.
And what happened there?
Okay.
Traditional sugarbush management
occasionally or sometimes involves understory removal,
which eliminates forest regeneration
and often results in a closed canopy monoculture
of sugar maple with very little structural diversity,
which can have a variety of implications for biodiversity,
ranging from declines in understory species richness,
as well as presumably reduced abundance and diversity
of forest birds
as well as their primary prey, the arthropods.
So to address this issue,
Audubon Vermont initiated the Bird-Friendly Maple Project,
which recommends forest management techniques
that would strive to improve forest habitat value
as well as the diversity of native plants
and long-term productivity of the forest.
And specifically, Audubon's recommendations
manage for the diversity of tree species
with no more than 75% sugar maple,
structural diversity of the forest,
so there's a range of age classes and retention
of snags and cavity trees,
as well as of coarse woody material on the forest floor.
And in exchange, cooperating sugarmakers
who participate and follow Audubon's guidelines
and market their product with signage and labels
stating that they're bird-friendly
allows them to sort of stand out
in a pretty crowded marketplace.
And with the sort of the popularity
of the Bird-Friendly Maple Program
expanding into other states,
Steve Hagenbuch was interested in
some sort of empirical data
to look at whether the guidelines that he's recommending
really provide better habitat for birds.
And so in some discussions that we had,
this project was the result of that.
So some of our main project objectives
were first to quantify the forest breeding bird community
across the gradient of sugarbush production
and management intensities,
and look at how the differences in vegetation structure
and arthropod biomass influence breeding bird communities,
and finally use those results
to update Audubon's Bird-Friendly Maple guidelines
and provide some management policies
that would be relevant
across the entire Northern Forest region.
So in 2020 and 2021, we studied 14 different sugarbushes
across the northern part of Vermont, seven in each year,
and they ranged in size from just 37 acres to 1,400 acres.
Nine of those were enrolled
in Audubon's Bird-Friendly Maple Project.
And just being enrolled in the project
doesn't mean that the conditions on the ground
meet the Bird-Friendly Maple guidelines,
just means they have a forest management plan in place
that will over time result in those conditions.
So we established survey points on a 200-meter grid,
which resulted in 353 survey points.
161 of those were surveyed in 2020, 192 two in 2021.
So our bird surveys, we just did fixed radius point counts,
one visit at each point,
and during that one visit,
we did three independent four-minute point counts
for a total of 12 minutes at each point.
And again, those three four-minute counts were independent.
So you did one four-minute count followed by another one,
and then a a third, all independent.
We also assessed arthropod biomass
at just over a thousand surveyed plots.
At each of those 353 plots,
we had three subplots surrounding those
where we did our arthropod surveys.
We had two different techniques for surveying arthropods.
For litter-dwelling arthropods,
we used these small cardboard cover boards
that were placed on the ground,
visited twice a year,
and any organisms found on top or below were measured
and placed into taxonomic groups.
And then for foliage-dwelling arthropods,
we used a cordless shop vac
and literally cleaned the forest,
(audience laughing)
vacuumed the vegetation as high as we could reach,
which was maybe seven or eight feet,
so really just the understory.
And those samples were frozen and then analyzed in the lab,
sorted and analyzed and measured,
placed in the taxonomic groups,
and then biomass was estimated using parametric equations.
We did highly detailed vegetation surveys
at just over 1,400 plots.
We had a really detailed protocol
that Tony provided at the 353 center plots,
and then we had a more rapid assessment protocol
at the three surrounding subplots at each point.
Our analytical modeling, we used community models
to look at both occupancy, abundance,
as well as detection probabilities of the bird community,
and then we related those to the 17 covariates
on the right here,
which I've sort of broken up into five major groupings,
ground cover, canopy cover, understory diversity,
deadwood, and arthropods.
And then some of our results.
I really don't have time to go into all of our results.
I'm just gonna highlight a few.
At our point count surveys,
we had 10,332 observations of 72 species.
The vertical axis is the proportion of points
with at least one detection of one of those species,
one of those 72 species
which are listed on the horizontal axis.
So for example,
we had 57 species detected at less than 20% of our sites.
Or another way to look at it would be
we had 15 species detected at more than 20% of our sites.
By far, the two most common species, not unusually,
are were ovenbird and red-eyed vireo,
which were detected at 95% of our study plots,
followed by black-throated blue warbler at about 75%,
and black-throated green warbler at about 65% of our points.
We also detected six species of greatest conservation need
as listed in the Vermont Wildlife Action Plan.
So some of the community results for the occupancy,
the proportion, the probability of occupancy
for the bird community
increased as these three covariates increased,
the volume of coarse woody material,
the percent cover of the herbaceous plants,
and the litter depth, surprisingly.
And in the community N-mixture model,
similarly, these three covariates,
the percent cover of the high canopy,
and then again, herbaceous cover and litter depth
were significant positive relationships.
We also looked at just responsive individual species,
and these four species,
veery, black-throated blue warbler, mourning warbler,
and chestnut-sided warbler
had a significant response
to the richness of the small saplings
in both occupancy and the abundance model.
And then black-throated blue warbler and mourning warbler
also had a significant response to the percent cover
of the mid-story layer in both models.
So suggesting that not only is the mid-story cover
important for these species,
but the richness of that cover is also important.
And then in the occupancy, the probability of occupancy
for black-throated green warbler
and the abundance of chestnut-sided warbler both increased
as the cover of the mid-story layer increased.
So a few of the take-homes from these results.
We had four habitat covariates
that were important to the overall bird community,
the herbaceous cover, litter depth, coarse woody material,
and high canopy cover.
And at this point, only coarse woody material
is being addressed by the Bird-Friendly Maple guidelines.
And then we just came up
with some sort of straightforward management recommendations
to address these four different covariates
that can be implemented.
In addition to providing habitat
for forest interior species,
sugarbush management can also provide habitat
for early successional species,
particularly mourning warbler and chestnut-sided,
and as well as some forest species
that prefer a well-developed shrub layer,
like veery and black-throated blue warbler.
And again, we came up with some management recommendations.
Creating small canopy gaps
that will provide that habitat for these species
while retaining interior species.
Some of the future directions,
the UVM team, particularly Liza Morse, the PhD candidate
who will be looking at the bird community
and building on the work that that we've done
these two years.
She'll be adding additional years of data collection
as well as looking at the impacts of ecosystem services,
particularly carbon storage and sequestration
and the resilience of the forest
to disturbance under climate change.
And then another PhD candidate, Daniel Pratson,
will be looking at the human dimension side
of maple sugar production,
specifically sort of asking the question
whether incentivizing forest management
for a variety of ecosystem services
aligns with sugarbush landowner values.
And then Steve Hagenbuch at Audubon Vermont
is planning to update some of their guidelines
for the Bird-Friendly Maple programs
specifically to address some of our results
in promoting both understory
and the mid-story layer diversity of that vegetation,
and also developing some best management practices
to try to reduce the introduction of earthworms,
which can deplete the leaf litter layer.
And a few acknowledgements,
particularly to our participating sugarmakers
who provided us access to their lands,
as well as our small army of field staff and volunteers
who collected all the data,
and our funders.
So I have time, I can take a few questions.
[Audience Member 1] Do you have a guess for why
that leaf flitter is so important?
[Steve] Yeah, I don't.
I mean, it would certainly make sense for ovenbird
and other ground-foraging species, thrushes,
but that didn't seem to be the case
when we looked at individuals.
For some it did, but not all of them,
so I don't really have a good answer for that.
Daniel.
[Daniel] Curious if you were able to,
like if some of the mid-story and understory,
if you're able to parse out
whether it was non-native or invasive,
like if the presence of mid-story understory is important,
is there a difference between the non-native versus
like that, right?
[Steve] We didn't have much non-native
really in these sugarbushes.
Yeah, I don't remember any.
Liza, do you remember any you have any invasive?
(Liza speaking quietly)
[Steve] Yeah.
Yeah, Kate.
[Kate] I just had a question
regarding sort of the long-term plan.
Like since it seems like just sort of a snapshot
of the various sugarbushes now,
is there any plan to revisit this, say, in 20 years,
if they're still maple certified
to look at the change from current
to what it looks like in 20 years
and how birds might have changed over that time?
[Steve] Well, I won't be revisiting it.
(audience laughing)
[Liza] Someone can pay me to.
(audience speaking quietly)
[Steve] Yeah, but it's a good question,
and hopefully someone will.
[Kate] And I just had a thought
about the leaf litter thing.
I don't know if that would impact the arthropods,
which then impact the birds potentially?
[Steve] Yeah, well, I will mention
that the leaf litter arthropods
were not included in the model
because after we did the modeling,
we realized there was a problem
with one elementary equation that was incorrect.
So we didn't include that, so that would,
yeah, when Liza's done.
Come back next year.
Liza will have that information.
Yeah.
[Audience Member 2] So for your desired condition
for the certification, it was not more than 75% sugar maple
and then one of the take-homes
was related to downwood material?
Do you see whether that's best
if it's sort of equally dispersed throughout the plot,
or is it best in clusters?
You know, if you were trying to target
those sorts of things,
would you wanna make little islands
or just make sure it's available
throughout the entire parcel?
[Steve] Yeah, I don't have
a good recommendation for that.
I don't know if it matters whether it's clustered
or dispersed throughout, yeah.
And yeah, even though only nine of these sites
were participating in the Bird-Friendly Maple Program,
all of our sites had less than 75% sugar maple
as an average,
as a mean for the sites.
Great.
Additional questions?
Alright.
Alright, well, Dan.
Alright.
[Dan] I'm curious about herbaceous variable
and the mid and overstory canopy cover.
So I'm not quite sure if it's a positive or negative
relationship to the birds,
but you know, I would think with increasing canopy cover,
you have less light that might reduce the herbaceous layer.
So is, I mean, can you...
[Steve] Yeah, presumably the herbaceous layer
was coming into some of those small canopy gaps
where those early successional species were responding to.
But yeah, it's a kind of a dichotomy to have,
closed canopy and herbaceous layer being important.
Great.
I don't want to keep everybody from the break,
but thank you, Steve.