Bronx River Forest and Floodplain Restoration - Bond Act Project
1-Year Post Project Monitoring and Status Report
Prepared for New York State Department of Protection
by
City of Department of Parks & Recreation, Natural Resources Group
DRAFT July 2006
Authors
Marielle Anzelone, Vegetation Monitoring
Marit Larson, Fluvial Geomorphologist and Project Manager
Ellen Pehek, Bird Monitoring
CONTENTS
1. INTRODUCTION
2. SITE DESCRIPTION
3. PROJECT STATUS
3.1 Floodplain and channel
3.2 Upland Forest
4. MONITORING
4.1. Vegetation
4.2. Birds
4.3. Channel Morphology
4.4. In-stream Habitat
5. RESULTS AND DISCUSSION
TABLES AND MAPS
Table 1. Plants installed and observed mortality
Table 2. Bird Species, Reproductive Phase, Observation
Table 3. Bird Species and Location
Table 4. Channel cross-sections
MAPS
- Project area and schematic design
- Vegetation Monitoring Plots
- Pre- and Post Channel Cross-section locations
- Extent of Knotweed: 1999 and 2005 entitation
- Bronx River Forest Natural Areas Entitation
- Planting Sites
Bronx River Forest and Floodplain Restoration - Bond Act Project
As-Built Monitoring and Status Report
1. INTRODUCTION
In 2004, construction began on the Bronx River Forest floodplain and river channel rehabilitation
project funded by The New York State Clean Air/Clean Water Bond Act. This project was a
pivotal component of on-going efforts by the City of New York/Parks & Recreation’s Natural
Resource Group, the Bronx River Alliance, and other community groups to restore the Bronx
River and its floodplain in the northern end of Bronx Park. The project was designed to help
address the reduced resource and habitat value in the Park resulting from the impacts of urban
development and neglect.
One of the consequences of urban disturbance in the Bronx Forest is the prevalence of exotic
herbs, trees and vines that out-compete the native vegetation. One of the most aggressive exotic
plant species is Japanese knotweed (Polygonum cuspidatum). It dominates the floodplain as well
as the banks of the river, hindering regeneration of native woody riparian trees and shrubs that
grow lower on the riverbank and provide bank protection and aquatic cover. Japanese knotweed
also frequently grows in dense stands over eight feet tall, and accelerates the natural accretion of
sediment that forms berms along the river banks, thus limiting access to the river and visibility.
Other results of disturbed urban landscape and conflicting management interests in the Park are
flashy flows, high sedimentation, the disconnection of the channel and floodplain, and reduced
in-stream habitat. Trails and ball fields were difficult to maintain due to flooding in some
locations, and in other locations, high flow waters that could have been stored on the floodplains
were trapped in the channel due to fill or excessive sedimentation on the banks. The sandbedded channel was homogenous and contained few in-stream habitat features, such as pools or
structural cover. The low flow channel was excessively wide and shallow.
To combat these problems of diminished resource value, the project goals were to:
 Re-establish more diverse, native species-dominated riparian and river bank vegetation that
could improve habitat and provide soil stability
 Reconnect the channel to the floodplain where possible by reclaiming filled lands and
creating over-flow opportunities
 Convert a playing field in the floodplain to a floodplain forest
 Enhance in-stream habitat
 Provide more opportunities for access, passive recreation, and education along the river.
The monitoring described in this report is aimed at evaluating the success of the native plantings
and invasive species control measures, and the impact of the rehabilitation work on the
vegetation community, breeding birds, and the channel configuration and stability.
2. SITE DESCRIPTION
The Bronx River Forest Bond Act Restoration Project is located in the in Bronx Forest
Floodplain, at the north end of Bronx Park, and is bordered by ball fields and the Metro North
railroad to the west, the Bronx River Parkway to east, and Kazimiroff Blvd to the south. The
total Bronx Forest Floodplain area is about 30 acres and included a section of the historic Bronx
River Parkway and bridge, an under-utilized playing field, an asphalt trail along the east side of
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the river, a forested island and about 6 acres of upland, some of which was fill. The floodplain
area was largely forested, and had a varied topography resulting in some areas being more
frequently flooded than others. The capital construction project discussed here occurred on
about eight acres of the floodplain, and the NRG forester’s additional invasive plant control work
is occurring on approximately six acres.
3. PROJECT STATUS
Floodplain and channel
The environmental analysis and design for the Capital Project was conducted from 2002-2003
and included a characterization of channel sedimentation, vegetation, hydraulic and hydrologic
conditions, floodplain soils, and channel geomorphology. A combination of strategies were
proposed to achieve these objectives, including:
- clearing and grubbing riparian areas invaded by Japanese knotweed
- excavating high-flow channels to better connect the channel and floodplain
- installing boulder and large wood in-stream habitat structures
- grubbing and grading river banks to establish more appropriate planting slopes
- planting native trees and shrubs in containers and using bioengineering techniques
- installing filter fabric to deter invasive species re-growth
Construction was initiated in August 2004, and began with the installation of erosion and
sediment control at the toe of the riverbanks, using coir logs. Riverbanks were then cleared,
grubbed, and graded to remove invasive plant rhizomes and establish slopes more suitable for
planting, particularly of inundation tolerant woody species. Banks were then seeded and covered
with coir webbing for erosion control. This fabric was either cut to allow installation of
containerized plants in the early fall. In the winter, the fabric was lifted back to allow installation
of bioengineering materials, or cuttings from dormant woody shrubs). These were installed in the
form of brush fascines (bundles of cuttings) along the toe of the banks, or as brush layers
installed perpendicular to the bank to form a brush mattress.
As the bank reconstruction progressed from downstream to upstream along the channel, habitat
features were installed. A four-foot diameter oak tree that fell during a storm in the first week of
construction was used to create an overhang at a tight outer channel bend. Boulders were used to
bin this, and other pieces of large woody debris, and to deflect flow towards the center of the
channel. These boulder obstructions in the channel were intended to promote sedimentation
towards the banks and scour or deepening towards the center of the channel. We worked with
the Bronx River Alliance and their conservation crew to cable LWD to the toe of the bank to
provide additional cover where possible.
The existing asphalt trail along the river was re-graded to better convey flows to swales and
depressions in the floodplain. At two locations, elevated vehicular boardwalks were constructed
over excavated sections of the highly sedimented channel banks to try to allow more frequent
flooding to the back areas of the floodplain while permitting the vehicular access that the Parks
Department required. Several pedestrian boardwalk sections and an overlook were also installed
to allow greater access on the floodplain. The boardwalks were completed for use in April 2005.
The largest area of floodplain reconnection to the channel was at the former Cricket Pitch. Here,
over 500 cubic yards of fill were removed and an overflow channel was excavated in the fall of
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2004, and thousands of floodplain forest trees, shrubs, herbs and graminoids were installed in the
fall of 2004 and spring 2005. Part of the former parkway was also converted to forest when the
concrete was removed and converted to a narrower bikeway through the forest.
Finally, an interpretive sign was installed to help explain the project and floodplain processes in
the forest on top of the Burke Ave Bridge. In total:
- Over 6 acres of floodplain forest were cleared, grubbed
- Over 8 acres were planted with native trees and shrubs either in containers or using
bioengineering techniques
- Approximately four acres of riverbank were grubbed and graded for planting (approx. 4
acres)
- Over 16,000 native trees and shrubs and over 7800 herbs and grasses were installed
- Over 2000 ft of riverbank were planted with native woody plants and
- Excavating high-flow channels to better connect the channel and floodplain (approx. 1000
square yards)
- Ten boulder and large wood in-stream habitat structures were installed.
- Over 8500 square yards of filter fabric were installed to deter invasive species re-growth
Planting sites were irrigated as needed, particularly at the Cricket Pitch, in the summer 2005.
Invasive Japanese knotweed was removed mechanically throughout the planting areas in 2005,
and is still being removed throughout the planted area, as it re-grows, by the contractor in 2006.
Beginning in 2007, Parks will have responsibility for invasive species control in the planting
areas.
The project received a design award by the Connecticut chapter of the American Society of
Landscape Architects.
Upland Forest
On the upland slopes surrounding the Bronx River floodplain, NRG foresters have worked to
reduce exotic invasive trees, shrubs and herbs such as cork tree (Phellodendron amurense), treeof-heaven (Ailanthus altissima), tartarian honey suckle (Lonicera tartarica), mugwort (Artemisia
vulgaris), Japanese honeysuckle (Lonicera japonica), garlic mustard (Alliaria petiolata), and
Japanese knotweed (Polygonum cuspidatum) through chemical and mechanical means. They
have combated exotic invasive herbaceous understory vegetation through mechanical removal,
and restored the slopes by placing seed, mulch, and erosion control fabric. In 2002, Foresters
planted hundreds of native herbaceous and graminoid species, such as white snakeroot
(Eupatorium rugosum) and Pennsylvania sedge (Carex pensylvanica) in containers through the
erosion control fabric. Invasive species control work in these areas continues as needed and as
staffing allows. Several monitoring plots were installed in the upland hillslope restoration sites,
but were not re-sampled this year.
4. MONITORING
4.1. Vegetation
Vegetation monitoring was conducted to evaluate the success of the plantings (percent survival)
and impact of the plantings on plant species diversity, cover, and invasive plant dominance in the
forest floodplain.
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Methods Planting Success
Due to the large numbers of plants installed, a complete post-project count was not conducted.
Instead, installed plants were counted in a sub-set of all the planting areas, dead plants were
counted, and visual assessments were made of plant loss.
Methods for Cover and Species Richness
Eleven plots were established in 2002, each measured 3m x 3m: one reference wetland planting
area plot (number 14); two control plots (numbers 19 and 20); and two reference plots (numbers
24 and 30). Six new floodplain plots were established in 2005 (number 40-43, 50, 51). The
location of all plots was marked with wooden or rebar stakes, drawn on a map and GPSed.
During sampling, temporary stakes were used to mark all corners of the 3m x 3m plots and the
meter tape was be strung around the plot. A 1m x 1m plot for herbaceous layer sampling was
temporarily demarcated in the NE corner of the 3m x 3m plot. Relative percent cover was
estimated at three distinct levels: herbaceous, shrub, and tree canopy. Percent cover at each level
was visually estimated for each species found in the plot. At each level all species present as
well as dominant species were noted.
Methods for Vegetation Communities
An inventory of the vegetation community that has been was conducted using entitation, a
process of identifying and describing ecologically distinct plant communities, or entities.
Entitation results in a map and database that can be used to identify where certain species are
dominant or present, and to help prioritize areas that may be threatened, should be protected, or
should be restored. This mapping can serve as a baseline for assessing change. The methods
used will be available shortly to download from the City of New York Department of Parks and
Recreation’s Natural Resources Group website.
4.2. Breeding birds
To assess changes occurring to the breeding bird population over the course of the Bronx Forest
restoration, a breeding bird census was conducted, using spot-mapping techniques based on those
employed by the Cornell Laboratory of Ornithology and the National Audubon Society
(Robbins, 1970) (see Figure 1). No pre-project monitoring was conducted.
Methods
In 2005 we conducted an abbreviated breeding bird survey due to ongoing construction of
boardwalks on the site. We performed three site visits between June 9 and July 6. Each visit
began within an half an hour of sunrise, when bird vocalization peaks (Ralph et al. 1993) and
lasted 1.5 to 3 hours.
To ensure birds were detectable, we did not conduct visits during moderate to severe
precipitation or winds. During each visit, as we walked the census route, we recorded birds seen
or heard on a survey map of the site. Species was indicated using the four letter USGS Bird
Banding Codes. We also recorded breeding-related behaviors using symbols established by the
British Trust for Ornithology (Bibby et al. 1992). We used these behavior registrations to
delineate territories and to classify the breeding status of these territories as outlined below. We
always walked the same census route, although we varied starting points to avoid surveying the
same areas at the same time each morning. We did not actively search for nests during census
visits.
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We used the territory classification system formulated by the Natural Resources Group Salt
Marsh Restoration (Brown & Alderson, 2001), which fuses the National Audubon Society
system (Robbins, 1970) with the system developed by the New York Federation of Bird Clubs
for the NYS Breeding Bird Atlas. Any “mapped territory” as defined by the Audubon Society
constitutes a “Confirmed Breeding” status under the Breeding Bird Atlas system.
We classified each territory as a “Confirmed”, “Probable”, or “Possible” breeding territory
according to the following guidelines.
CONFIRMED: To classify a territory as confirmed, we made at least one of the following
observations for the species in question:
 Singing bird within the territory area on at least three consecutive site visits
(criterion for a “mapped territory” according to Robbins, 1970)
 Active nest
 Bird carrying fecal sac
 Bird carrying food
 Unfledged or recently fledged young
 Distraction display or injury-feigning
PROBABLE: To classify a territory as probable, we made at least one of the following
observations for the species in question:
 Singing bird within the territory on more than one site visit
 Pair in suitable breeding habitat
 Chasing of conspecifics, agitated behavior or anxiety calls
 Bird carrying nesting material or excavation of a nesting hole
 Courtship and display
POSSIBLE: To classify a territory as possible, we made the following observation for the
species in question:
 Singing bird within suitable habitat on at least one site visit
For the purposes of data analysis, we divided the study site into five sections. See Figure 1 for
delineations of these five sections. The thin strip of forest between the Bronx River and the
Bronx River Parkway was divided into Parkway 1on the North and Parkway 2 to the South. The
other three sections are the swamp forest (Swamp), the strip of mature forest with skunk
cabbage, mayapple, and trout lily in the herbaceous layer that lies between the Bronx River and
the ballfields (Skunk). and the island. For each section, we tallied the number of species holding
possible, probable, and confirmed breeding territories. In addition, for the site as a whole, we
calculated the percentage of breeding territories that were held by Red-winged blackbird, Gray
catbird, Yellow warbler, and Song sparrow, four of the most common breeding species at
disturbed wetland sites. For this calculation, we included only territories and species that
qualified as probable or confirmed for breeding. We also calculated breeding species diversity
using the Shannon-Weiner index (H’), for all probable and confirmed breeding territories. We
calculated H’ for the restoration area and upland areas individually and also for the study site as
a whole.
4.3 Channel morphology
Although historically the Bronx River was a naturally meandering channel, it has largely been
straightened and confined and anchored in place by bridges, highways, railroads, and rock
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revetment. Channel morphology monitoring allows us to determine if significant bank erosion,
bank deposition, pool deepening, or pool in-filling is occurring.
Methods
In the spring of 2006, one year after project completion, six permanent cross-sections were
established in the Bronx Forest at locations where pre-project cross-sections had been surveyed
for the purpose of developing a hydraulic model (HECRAS) for the design phase of the
restoration project. The pre-project surveys were not permanently marked in the field, so
approximate locations were used and the pre-and post-project cross-sections were qualitatively
compared to assess whether significant differences in channel geometry could be detected. With
the installation of permanent cross-section, we will be able to be accurately re-survey in
consequent years to assess the degree of change in channel geometry, whether from erosion or
sediment.
The cross-section survey included:
- identifying the approximate location of the pre-project cross-section in the field
- establishing permanent end points for the new cross-sections by using 8” railroad tie nails
and flagging which was later be replaced by 1” x 2’ diameter metal pipe.
- surveying locations that could be identified on the pre-project survey, such as the trail,
greenway, and corner of bridge that could be used as reference elevations to locate our crosssection on a survey.
4.4. In-stream habitat
The decades of straightening and channel clearing, together with flashy high urban storm flows
and high sediment deposition lead to a relatively homogenous channel bed with in-stream cover
and or high flow refuge for aquatic organisms in the Bronx Forest. Several parameters were
considered that impact habitat and could be effected by local in-stream structures and improved
management. These include:
 Large woody debris (LWD) - provides stream structure by creating pools, providing refuge
and cover for fish and providing quality macroinvertebrate colonization habitat.
 Instream Cover - provides important resting, rearing and hiding habitat for aquatic fauna.
The abundance and diversity of cover is important to determine the diversity and abundance
of fish and macroinvertebrates the system is capable of supporting. Further, abundance and
diversity in cover types allows for increased disturbance recovery.
 Pool - provide resting places and cover for fish species. Pool substrates and sizes are
evaluated to determine the diversity of pool types, which impacts the diversity of aquatic
organisms supported within present channel pools.
 Bank Condition - bank angle, height and vegetation serve as predictors of erosion potential.
Bank vegetation provides macroinvertebrate habitat and fish cover.
 Riparian Zone/Canopy - provide shade and canopy cover to the stream helping to keep water
temperatures low, filter out contaminants and serve as a source of LWD recruitment.
Methods
Habitat characteristics within the project area were surveyed using a modified visual assessment
adapted from the level II Habitat Assessment in EPA’s Rapid Bioassessment Protocols for Use in
Streams and Wadeable Rivers: Periphyton, Benthic Macroinvertebrates, and Fish (Barbour et al
1999).
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The entire reaches was evaluated via a stream walks and canoe trip in July and August 2005 and
via a visual assessment by planting area in April and May 2006. LWD was counted and the
residual pool depth (or net pool depth, independent of current water depth at the time of
measurement) was measured by measuring the maximum pool depth and the minimum channel
depth downstream of the pool. In 2005, representative transects were surveyed to better quantify
stream and riparian conditions spaced according to judgment to be representative of sampled
reaches (Meador et al 1993). These transect measurements consisted of substrate, aquatic cover,
bank condition and riparian canopy cover measurements. All ocular estimations were
periodically calibrated with a survey tape. All transect data was collected in the cross channel
corridor that extends 5m upstream and downstream of the transect location. Representative
transect data was then weighted according to length of similar stream subreaches to determine
overall average habitat cover with stream areas. In 2006, aquatic cover, bank condition, and
riparian cover estimates were made visually by planting area.
5. MONITORING RESULTS AND DISCUSSION
5.1. Vegetation
Planting Success
The table below shows the subset of planting areas that were re-counted in June 2006. On
average, in the planting areas with a known number of plants in January 2005 (Areas 1,2,3,6) ,
the total number plants counted was in total only 64% of the total number of plants counted upon
installation. This is probably because the plants could not be relocated, or were planted slightly
outside the planting area, since very few dead installed plants were found (at most 2% of total
counted). Other plants that had died may no longer have been visible to count and some may
have been vandalized (although the small heavily vandalized area near the Burke Ave Bridge
was not re-counted here). Most importantly, however, no significant numbers of dead plants
were observed after the plant installations. Overall, the qualitative observations suggest that in
most planting areas, at least 85% of the installed plants survived.
Table 1. Plants installed and observed mortality
Planting
Area
Area 1
Area 2
Area 3
Area 4
Area 5
Area 6
Area 7
Area 15a
Number of plants
installed by January
2005
354
189
829
190
689
528
786
107
Additional plants
Number of
installed spring
Installed plants
2005?
dead by June 2006
0
3
6
yes
1
yes
2
0
yes
16
yes
7
% Survival
100%
98%
99%
Known
vandalism
yes
100%
yes
Plant cover and species richness
The relative percent covers were entered into a spreadsheet (Appendix A) and used to estimate
the percentage of the plot covered by each plant species present. Also calculated for each
species were the average percent cover if present, number of plots present, and relative
frequency. Calculations per plot included total percent cover of all plants, percent cover of plant
groups (woodies, graminoids), species richness, the average and standard deviation for each.
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Nineteen new species were found in 2005, bringing the total number of species to 148. These
new additions included plants installed for the restoration, such as sweet pepperbush (Clethra
alnifolia) and steeplebush (Spiraea tomentosa) and spontaneously occurring species such as
creeping yellow cress (Rorippa sylvestris) and nodding smartweed (Polygonum lapathifolium).
One significant new entry is the noxious weed purple loosestrife (Lythrum salicaria), found
growing in plots 50 and 51 in the area formerly used as a cricket pitch (See vegetation
monitoring plot map).
These additional species brought the number of plant families represented in the monitoring plots
up from 39 in 2004 to 52 for 2005. The family with the most representatives was Asteraceae
(Aster family) with 18 species. Poaceae (Grass family) and Rosaceae (Rose family) both had 11
species.
The family with the greatest number of new species was the Grass family, with seven new
species. Some of these were planted, such as Virginia wild rye (Elymus virginicus) and rice cutgrass (Leersia oryzoides). Both of these species are native wetland grasses, installed with the
hope they maintain permanent residency. The exotic annual rye (Secale cereale) was also
brought in with the purpose of acting as a temporary erosion control. Over time perennials will
shade this plant out. Volunteer species included crabgrass (Digitaria sanguinalis), barnyard
grass (Echinochloa crus-galli), goose grass (Eleusine indica), all of which are exotic and
common in open, disturbed sites. One native volunteer was fall panic grass (Panicum
dichotomiflorum), a native species and found in disturbed, open wet areas.
Of all the plants encountered, 38% (56 species) were exotic, 11% (17 species) were invasive,
14% (21 species) were considered native and uncommon in New York City, 1% (1 species –
river birch {Betula nigra}) was rare in New York State, and 22% (32 species) were installed
(Appendix A).
Total percent cover for all 11 plots was greater than 100% (range from 108-198), average 146%.
Percent cover was not correlated to species richness. The number of species in a plot varied
from 10-27, with an average of 18.3, out of 84 species. There were no significant trends in
species richness with regard to restoration, control, or reference plots.
Reference plot 24 had the highest percentage of woody cover, with 165%. Average cover was
101.2%. Plots established in areas where there was significant existing canopy tree cover had
higher woody coverage than those plots in more open areas. Five of the six newly established
plots fall into the latter category (plot 40 being the sole exception). Reference plot 30 had the
highest number of woody species, with 12 (average 5.7). These were all native species. Plot 42
had only one species, black willow (Salix nigra), but this one tree covered 50% of the plot.
Graminoid percent cover had a wide range, from 0-104%, average 9.7%. Plot 50 in the former
cricket pitch had the high percentage with large concentrations of native species such as Virginia
wild rye, rice cut-grass and fall panic grass. The number of graminoid species ranged from 0-6,
with 2.3 average. Herbaceous cover ranged from 1-82, with 34.5% average. Four plots all had
15 herbaceous species, one was reference plot 24, the other 3 were newly established plots 40,
41, 42. The plot with the least amount of herbaceous cover was control plot 20, with only 1%
cover for five herbaceous species present.
The woody species with the highest percent cover was green ash (Fraxinus pensylvanica) with
17.3% (95% average in the two plots where it was recorded). The most frequently recorded
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woody species was sycamore (Platanus occidentalis), found in 6 of 11 plots (.54 frequency), but
only 3.8% cover. This percent cover will be greater in following years, as these planted saplings
grow and expand. Only two woody vine species were recorded, Oriental bittersweet (Celastrus
orbiculatus) and Virginia creeper (Parthenocissus quinquifolia). Each was present in only one
plot, with little percent cover. The graminoid with the most percent cover was the installed
native rice cut-grass (Leersia oryzoides), with average cover of 30% for the two plots where it
was recorded. The most frequently found grass was also native, but not planted, fall panic grass
(Panicum dichotomiflorum), recorded for six plots with 8.6% cover in those. The herb with the
most percent cover was the exotic invasive common mugwort (Artemisia vulgaris), with average
cover of 17.9% for the seven plots where it was recorded. This is more than twice the cover of
the next most abundant species, the native nodding smartweed (Polygonum lapathifolium) with
6.7% cover from 3 plots. The most frequently found herb was also native, but not planted, the
weedy common wood sorrel (Oxalis stricta), with 1.7% cover for nine plots. Overall there were
many herbaceous species present (12) but little representation with regard to aboveground
biomass. Much of this may be attributed to the small size of the recently installed plants. We
expect the percent cover of the herbaceous layer to increase dramatically in 2006.
Japanese knotweed was found in 7 plots. In two of these plots its percent cover was less than 1,
and so was noted as “present” with zero percent cover. Where present, average cover was 7.8%.
Thus this invasive was not a significant presence in any of the plots, except for one. Control plot
20 had 25% knotweed cover, more than double the 10% found in two other plots, and despite
128% woody cover by 7 different species. The strategy of shading out Japanese knotweed takes
several years to work, as the plant stores energy reserves in its extensive rhizome system.
Knotweed’s presence in this plot should decrease over time.
Vegetation Communities
The entitation in the Bronx River Forest showed that much of the forest has some exotic invasive
plant present or dominant in the understory. The recently planted areas, however, have either no
significant Japanese knotweed, or only present but not dominant.
5.2. Breeding birds
We found 23 possible, probable, or confirmed breeding avian species in the Bronx Park study
area during the 2005 breeding season. Of these, we confirmed the breeding of 9 species
according to New York Federation of Bird Clubs protocols. Table 2 shows the observations used
to confirm breeding for each species for which we observed behaviors more indicative than
territorial singing. See Table 2 for a list of all possible, probable, and confirmed breeding species
with the numbers of territories each species held in the subsections of the site as well as the site
as a whole. We found 12 species in the swamp forest, 17 in the skunk cabbage area, 8 in
Parkway 1, 9 on the island, and 11 in Parkway 2.
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Table 2. Bird Species, Reproductive Phase, Observation
SPECIES
REPRODUCTIVE PHASE
OBSERVATION
CONFIRMED
American robin
Young fledged
Fledgling
Cedar waxwing
Courtship / Pair bond established
Pair
Common grackle
Young fledged
Fledgling
Downy woodpecker
Young fledged
Fledgling
European starling
Nest established
Active nest
Gray catbird
Young fledged
Fledgling
House sparrow
Courtship / Pair bond established
Pair
Mallard
Young fledged
Fledgling
Northern flicker
Courtship / Pair bond established
Pair; alarm calls
Northern oriole
Young fledged
Fledgling
Red bellied woodpecker
Nest established
Active nest
Red-winged blackbird
Young fledged
Fledgling
Warbling vireo
Courtship / Pair bond established
Pair; alarm calls
Yellow warbler
Territory established
Male chasing conspecific
Table 2. Latest phase of reproduction confirmed for avian species during 2004 spot-mapping census of a section of Bronx Park
in the Bronx, NY. All species for which we made observation(s) more strongly confirming breeding than territorial singing are
included. The table shows the reproductive phase attained by each species as well as the observation used to confirm that phase.
New York City Parks & Recreation / Natural Resources Group.
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Table 3. Bird Species and Location
SPECIES
Status
Swamp
Parkway2
Parkway1
Island
Skunk
Entire Census
Area
Ps Pr Cf Ps Pr Cf Ps Pr Cf Ps Pr Cf Ps Pr Cf Ps Pr Cf All
Acadian Flycatcher
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
1
0
1
American Robin
1
5
6
0
2
2
0
2
2
0
1
3
0
3
4
1 13 17
31
Black-crowned Night Heron
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
1
0
0
1
Blue Jay
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Brown headed cowbird
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
1
0
0
1
Cedar Waxwing
1
2
0
0
0
0
0
0
0
0
0
0
0
0
0
1
2
0
3
Cerulean Warbler
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
1
0
0
1
Chestnut-sided Warbler
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
1
0
0
1
Common Grackle
0
0
0
0
0
0
0
0
1
0
1
0
0
0
1
0
1
2
3
Downy Woodpecker
0
0
1
0
0
0
2
0
0
0
0
0
0
0
2
2
0
3
5
European Starling
0
0
1
0
0
0
2
0
0
0
0
0
0
0
2
2
0
3
5
Gray Catbird
2
4
0
0
1
1
2
3
0
1
1
0
1
2
2
6 11
3
20
House Sparrow
1
0
0
3
0
0
0
1
0
0
0
0
0
0
0
4
1
0
5
Mallard
0
1
1
0
0
0
0
0
0
0
2
0
0
0
0
0
3
1
4
Northern Flicker
0
0
0
0
1
0
0
0
0
0
0
0
0
1
0
0
2
0
2
Northern Oriole
1
0
1
1
1
1
1
0
1
2
0
0
1
0
1
6
1
4
11
Northern parula
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
1
0
0
1
Red-bellied Woodpecker
1
0
0
1
1
0
0
0
0
0
0
0
0
0
1
2
1
1
4
Red-eyed Vireo
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
1
0
0
1
Red-winged Blackbird
0
2
1
1
1
0
3
0
1
2
1
2
1
1
0
7
5
4
16
Song Sparrow
0
0
0
0
0
0
0
0
0
1
0
0
1
0
0
2
0
0
2
Warbling Vireo
4
1
0
1
0
0
0
0
0
1
1
0
3
3
0
9
5
0
14
3
0
0
2
0
0
0
0
0
0
2
0
1
0
0
6
2
0
8
14 15 11 11
7
4 10
6
5
7
9
5 13 10 13 55 47 38 140
Yellow Warbler
Totals
0
Table 3. Avian species breeding at Bronx Park, Bronx in 2005. Territories were classified as confirmed (CF),
probable (PR), or possible (PS) according to the following criteria: an observation of an active nest, a bird carrying
food or a fecal sac, or unfledged or recently fledged young, or three observations of a singing bird on separate study
visits during the species’ breeding season confirmed a territory; an observation of a bird carrying nesting material, of
a male-female pair, of an aggressive encounter between conspecifics, or two observations of a singing bird on
separate study visits during the species’ breeding season qualified a territory as a probable breeding territory; finally,
an observation of a singing bird during the species’ breeding season classified a territory as a possible breeding
territory. The far right column shows total numbers of breeding territories (confirmed, probable, and possible) for
each species. Birds are listed in the taxonomic order established by the American Ornithologist’s Union (AOU).
New York City Parks & Recreation / Natural Resources Group.
The skunk cabbage area had 10 probable or confirmed breeding species and the Swamp had 9. In
addition, two species (American robin and Gray Catbird) dominated the number of probable and
confirmed territories in the Swamp. No other species held more than 2 territories. Skunk was
also dominated by these two species, but Warbling vireos held 3 territories. The island had 7
species with probable or confirmed territories, dominated by the American robin and Redwinged blackbird. The two Parkway sites each had 6 species. Parkway 1was dominated by
American robin and Gray catbird, and Parkway 2 by American robin and Red-winged blackbird.
Overall, 68% of all territories were held by the American Robin and 32% by the Gray catbird.
The percentage of probable and confirmed territories held by the species typical of disturbed
wetlands was 29.4%.
The H’s (Shannon-Weiner indeces) for all probable and confirmed territories each subdivision of
the site are: Swamp, 1.8; Parkway2, 1.64; Parkway1, 1.59; Skunk, 2.04; and Island, 1.81. The H’
for the entire census area was 2.
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The species richness at the Bronx Park study site in 2005 (23) compares favorably with what was
found in the 2003 breeding bird surveys at Bronx Park (27 species). Considering that the 2005
survey consisted of only 3 visits, the species richness also compares favorably with that at
Riverdale and Seton Falls Parks. Riverdale had 27 species in 2002, 24 in 2004, and 38 in 2005,
while Seton Falls had 30 species in 2002 and 28 in 2004. The overall H’ for the Bronx Park in
2005 (2.14) was somewhat lower than that found at the same site in 2003, and was still lower
than those from Riverdale or Seton Falls. In Riverdale the H’ was 2.69 in 2002 and 2004 and
2.73 in 2005, and at Seton Falls the H’ was 2.75 in 2002 and 2.42 in 2004.
Whereas in 2003 American robins and Gray catbirds were co-dominant in terms of number of
territories, in 2005 the American robin held more than twice the number of territories as did the
Gray catbird. The reduction in Gray catbird territories relative to American robins may be a
result of the removal of Japanese knotweed, a species providing the dense cover preferred by the
Gray catbird for nesting. Species typical of disturbed wetlands comprised only 29 percent of
territories this year, as opposed to 39 percent in 2003. The removal of Japanese knotweed may
also have reduced nesting sites for these species.
As in 2003, the least disturbed areas of the Bronx Park study site, the skunk cabbage area and the
swamp, had the highest numbers of species with territories and higher H’ values. The island
again had an intermediate number of species with territories and H’, with the two Parkway sites,
areas contiguous with the Bronx River and/or Mosholu Parkways, being the least diverse.
Although we sighted wood ducks on two occasions (two males on June 9 and a single female on
July 6), we did not confirm breeding in our three visits. The continued presence of this species at
the Bronx Forest despite extensive excavation and ongoing construction is encouraging. This
species has been seen in previous years on the island, and we believe they may breed there.
Hopefully, the wood duck nest box that has been placed on the island will increase the chances
of successful breeding by this species.
Several species less common in New York City were found during this survey. One male each of
Acadian flycatcher, Cerulean warbler, Chestnut-seded warbler, and Northern parula were heard
singing in the skunk cabbage area on June 20, but most likely did not remain to breed. The Redeyed vireo, heard singing on one occasion in the Skunk area, is a rare nester in New York City.
We found probable nesting of Warbling vireo, and uncommon nester in New York City, in the
Swamp, skunk cabbage area, and Island. The Red-bellied woodpecker, another uncommon nester
in the City, was confirmed in Skunk and probable across the river in Parkway 2.
The above conclusions are tentative, considering that they are based on only three site visits,
with disturbance created by ongoing construction. A more comprehensive survey planned for
2006 should help clarify these results.
5.3. Channel morphology and in-stream habitat
The comparison of newly established, permanent post project channel cross-sections in 2006 at
the approximate location of the pre-project cross-sections surveyed in 2006 allowed a qualitative
assessment of the degree of channel change in the as-built condition. Overall, the cross-sections
show that channel dimension was not significantly altered, though at several sites the riverbank
levy was excavated, specifically at cross-sections E & F (Appendix E). The cross-sections also
demonstrate the degree of deposition that characterizes the sites. At cross-section A, on the
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inside bent, the position of the coir log shows that about 10 ft of sand and silt was deposited
channel-ward and up to 2 ft deep after the final excavation and placement of the coir log. The
survey in 2007 will show how much sediment has deposited at the sites where the berms were
excavated, and give an indication of the sustainability of those high overflow areas.
Table 4. Channel Cross-section Description
Bond River-morph
Act Name (2006)
XS
A
XS65
HEC-RAS
Station
Equivalent*
Interfluve 437
River Mile
(feet)**
Location
4.62
(24387’)
XS at tight bend in east channel around island, approx 450
ft upstream of Kazimiroff Brdg
B
XS72
Interfluve 1020,
MMI 24970
4.73
(24970’)
XS at south end of long vehicular boardwalk, approx 1000
ft upstream of Kazimiroff Brdg
C
XS75
Interfluve 1250;
MMI 25200
4.77
(25200’)
XS at south end of long vehicular boardwalk, approx 1000
ft upstream of Kazimiroff Brdg.
D
XS78
Interfluve 1552,
MMI 25487
4.83
(25502’)
XS upstream of long vehicular boardwalk, at small boulder
vane approx 1550 ft upstream of Kazimiroff Brdg.
E
XS90
Interfluve 2310;
MMI 26260
4.97
(26260’)
XS at high flow entrance to cricket pitch, approx 2300 ft
upstream of Kazimiroff Brdg.
F
XS93
Interfluve 2650;
MMI 26600
5.04
(26600’)
XS upstream of long vehicular boardwalk, at small boulder
vane approx 2650 ft upstream of Kazimiroff Brdg.
* Cross-sections were surveyed to run a HEC-RAS model developed by Interfluve, Inc in 2002. These were
incorporated in the model developed for the whole river by Milone and MacBroom, Inc. in 2005.
** distance upstream of river mouth as identified by FEMA+A19
Cross-section A: The post-project XS shows that the outer bank was stabilized with boulders and a
4’x25’ oak tree. The bank was not built out to the degree suggested by the 2002 comparison. Rather the
2006 XS was situated near a tree and not at the furthest outer point in the bend. The cross-section with the
lower point bar indicates the as-built condition where coir logs were placed at the toe of the point bar after
excavation, clearing and grubbing. The point bar has accumulated 10 ft laterally into the channel and two
ft vertically from the toe of the bank.
Cross-section B: The 2006 XS shows where the boardwalk was constructed and a boulder toe of bank
was constructed. Again, the post-project XS was not located precisely on the pre-project XS. The left
bank was not filled as suggested in the photo, but rather was probably located closer downstream next to
the red maple on the bank than the pre-project XS. The post-XS shows a pronounced pool, which may be
being maintained by the upstream boulder vane. The residual pool depth of this pool is not very high,
however, since the entire section of channel is relatively deep, probably due to the backwater from the
downstream log jam where the channel splits and flows around the island.
Cross-section C: Very little change is apparent from this XS, although on the east bank, a scour around a
cabled piece of LWD that was lifted up on the bank during high flow may have caused the hole in the
bank in 2006.
Cross-section D: Here the pre- and post-project XS’s are very similar, since no significant grading was
done on the banks. The lower trail elevation on the left bank, or east side of the river is apparent.
The post-XS appears not to have the deep pool on the right bank that the pre-XS has. However, a pool,
with a residual pool depth of 1.7 ft is still present at this location on the outside of the bend on the right
bank.
Cross-section E: Although these pre- and post-XS are not well-aligned, and thus show different widths,
the excavation of the bank into the former cricket pitch is obvious on the right bank
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Cross-section F: The post-XS shows how the riverbank levy on the levy bank was excavated between
the trail and the river. The post-XS also has a distinct pool on the outer right bank unlike the pool on the
left side of the channel in the pre-XS. This difference may be more a matter of the XS’s being located in
different positions rather than a shift in thalweg position.
Bank erosion and sedimentation were observed qualitatively at other sections of riverbank. At
the upstream end of the island on the west channel, downstream of the debris jam and exposed,
bank erosion cause the excavation of about 60 ft of coir log. This site will be protected with
cabled LWD and replanted in the summer and late fall. The opposite bank at this site received
over 6” of sand deposition. Sand deposition was also at least 6” deep upstream in Area 5
upstream of the island on the east bank, in Area 7 on the east bank, and in Area 15 upstream of
the Burke Ave Bridge on the west bank.
5.4. In-stream Habitat
In-stream and riparian habitat was modified after the project according to several measures,
below. Although several of these changes we expect to be permanent (boulders) or long term
(cabled LWD), other increases in cover, from pools or woody vegetation (in the future) may not
be maintained or reach their potential if high sediment loads persist or invasive species become
dominant again.
LWD
The number of pieces of LWD found in channel increased from approximately 18, in 2004, to 35
in 2005, and 38 in 2006. At least six pieces of LWD were cabled into place. (Appendix F)
Pools
The number of pools has increased from 11 to 13. Residual pool depth probably did not change
significantly (Appendix G). Total pool area probably also increased, but this was not quantified.
One boulder vane just north of the longest boardwalk was not associated with a (by forcing or
maintaining it) but the others boulder vanes did. Sediment transport in this reach is high, as
evidenced by the predominantly sand substrate and sand deposition on the banks. Other
evidence is the variability of sand deposits: after some storm events, just downstream of the
Burke Ave Bridge, sand can be found to entirely blanket the bed; after other storm events, cobble
and rubble are visible through the sand.
Riparian and Bank conditions
As the cross-section surveys showed, bank angels were not dramatically altered throughout the
reach. In some locations, where banks were grubbed and graded bank, high rates of sand
deposition have increase the heights and angles to their original position. The length of bank that
has native understory shrubs rather than only invasive plants has increased (Appendix H). This
is evidenced by the rapid habitat assessment that documented non-invasive herbaceous and
understory plants. Prior to the rehabilitation project, Japanese knotweed would have been the
only species present on the riverbank for long sections. The Extent of Knotweed Map shows
more knotweed dominant on the riverbank in 1999 than in 2005. The did not change significantly
before or after the project, and is not expected for decades, until the woody bank vegetation
matures.
In-stream Habitat
The area of the channel with cover increased after the project, primarily as a result of the
placement of LWD and large boulders in the banks and on the channel. This is evidenced by the
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observation that much of the aquatic cover was associated with substrate (boulders) and wood
that was not as abundant in the reach prior to the restoration project (Appendix I). A more
detailed mapping of channel topography before and after the project would have been necessary
to quantify the change in in-stream habitat. In-stream habitat may have improved more
significantly had more in-stream bars and boulder vanes been constructed in the reach during the
project. One of the project objectives was to increase the number of native woody riparian
species growing at the toe of the riverbanks. If these trees and shrubs establish successfully,
there should be an increase in overhanging vegetation and woody roots providing in-stream
cover over time. Continued LWD management involving cabling LWD to the banks will also
help increase in-stream habitat.
ATTACHMENTS
APPENDIX A. Bronx River Bond Act Vegetation Monitoring Data
APPENDIX B. Bronx River Forest Floodplain Bond Act Flora, May 2006
APPENDIX C. Bronx River Bond Act Capital Project Plant Quantities
APPENDIX D Distribution of plant by Area as of January 2005
APPENDIX E. Pre- and Post Channel Cross-section figures
APPENDIX F. Large Woody Debris counts
APPENDIX G. Pools
APPENDI X H. Riparian Conditions
APPENDIX I. In-stream Cover
Photos
- Construction
- Cricket Pitch Sequence
- Before and After
- Vegetation monitoring photos
NYC Parks NRG
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