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City of New York Parks & Recreation
2005 Avian Monitoring Report
For The Bronx Forest Restoration at Bronx Park
Last Updated: February 23, 2006
INTRODUCTION
Bronx Park is a 718.1 acre park consisting of woodland, playing fields, and horticultural
landscapes, bordering the Bronx River in the Bronx, NY. City of New York Parks & Recreation (DPR) /
Natural Resources Group (NRG) is conducting a multi-faceted ecological restoration in a 70 acre forested
section of the park. Located just north of the New York Botanical Garden in Bronx Park, the site consists of
a thin border of forest along each side of the Bronx River, a larger portion of swamp forest, and a forested
island. All of these areas have been invaded by Japanese knotweed (Polygonum cuspidatum) and various
invasive tree species. Ongoing forest restoration work, involving NRG, the Bronx River Alliance, and
other community groups, includes removal of Japanese knotweed and re-planting with native tree, shrub,
and herbaceous species. The Bond Act Restoration at the Bronx Forest included excavation and
recontouring of areas invaded by Japanese knotweed, re-establishment of the connection between the
Bronx River and the swamp forest, and re-establishment of native trees and shrubs.
In order to assess changes occurring to the breeding bird population over the course of the Bronx
Forest restoration, NRG is conducting a breeding bird census, using spot-mapping techniques.
MATERIALS & METHODS
To assess the breeding bird population at our study site (see Figure 1), we used spot-mapping
techniques based on those employed by the Cornell Laboratory of Ornithology and the National Audubon
Society (Robbins, 1970).
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 bird detectability, 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.
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
City of New York Parks & Recreation
2005 Avian Monitoring Report
For The Bronx Forest Restoration at Bronx Park
Last Updated: February 23, 2006
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 Redwinged 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.
City of New York Parks & Recreation
2005 Avian Monitoring Report
For The Bronx Forest Restoration at Bronx Park
Last Updated: February 23, 2006
Figure 1
Swamp
Parkway1
Skunk
Parkway2
Island
N
Figure 1. Bronx Park restoration area, showing the five sections used in analyzing data from the
breeding bird survey in 2003.
City of New York Parks & Recreation
2005 Avian Monitoring Report
For The Bronx Forest Restoration at Bronx Park
Last Updated: February 23, 2006
RESULTS
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 1 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.
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 1. 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.
City of New York Parks & Recreation
2005 Avian Monitoring Report
For The Bronx Forest Restoration at Bronx Park
SPECIES
Status
Swamp
Parkway2
Last Updated: February 23, 2006
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
Yellow Warbler
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
Totals
0
Table 2. 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 Red-winged 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 percent of all territories were held by the American Robin and 32 percent by the Gray
catbird. The percentage of probable and confirmed territories held by the species typical of disturbed
wetlands was 29.4%.
City of New York Parks & Recreation
2005 Avian Monitoring Report
For The Bronx Forest Restoration at Bronx Park
Last Updated: February 23, 2006
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.
DISCUSSION
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 Red-eyed 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.