Download the 2003 Results

City of New York Parks & Recreation
2003 Avian Monitoring Report
For The Bronx Forest Restoration at Bronx Park
Last Updated: May 25, 2005
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 2003 we conducted seven site visits between May 14 and July 16. 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
2003 Avian Monitoring Report
For The Bronx Forest Restoration at Bronx Park
Last Updated: May 25, 2005
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, Common yellow-throat, and Song sparrow, five 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
2003 Avian Monitoring Report
For The Bronx Forest Restoration at Bronx Park
Last Updated: May 25, 2005
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
2003 Avian Monitoring Report
For The Bronx Forest Restoration at Bronx Park
Last Updated: May 25, 2005
RESULTS
We found 27 possible, probable, or confirmed breeding avian species in the Bronx Park study area
during the 2003 breeding season. Of these, we confirmed the breeding of twelve 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 restoration area, the upland areas, and the study site as a whole. We found 20 species in the swamp
forest, 19 in the skunk cabbage area, 16 in Parkway 1, 10 on the island, and 6 in Parkway 2.
SPECIES
REPRODUCTIVE PHASE
OBSERVATION
CONFIRMED
American robin
Young fledged
Fledgling
Gray catbird
Young fledged
Fledgling
Red-winged blackbird
Young fledged
Fledgling
Mallard
Courtship / Pair bond established
Pair
Northern cardinal
Young fledged
Fledgling
Northern flicker
Young fledged
Fledgling
Blue jay
Nest established
Active nest
Brown headed cowbird
Courtship / Pair bond established
Pair
House sparrow
Young fledged
Fledgling
Mourning dove
Young fledged
Fledgling
Northern oriole
Young hatched
Adult carrying food
Red bellied woodpecker
Young fledged
Fledgling
Warbling vireo
Nest established
Active nest
Wood duck
Courtship / Pair bond established
Pair
Yellow warbler
Young hatched
Adult carrying food; alarm calls
Chestnut sided warbler
Male chase
European starling
Alarm calls
Table 1. Latest phase of reproduction confirmed for avian species during 2003 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
2003 Avian Monitoring Report
For The Bronx Forest Restoration at Bronx Park
SPECIES
Status
Swamp
Parkway2
Last Updated: May 25, 2005
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
American Robin
0
4
6
1
3
3
0
0
0
2
0
2
2
2
7
5
9 18
Blue Jay
1
0
0
2
0
0
0
0
0
0
0
0
1
0
1
4
0
1
5
Blackburnian warbler
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
1
0
0
1
Black and white warbler
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
1
0
0
1
Brown headed cowbird
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
1
Canada goose
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
1
Carolina Wren
1
0
0
0
0
0
0
0
0
0
0
0
1
0
0
2
0
0
2
Chestnut-sided Warbler
0
1
0
3
0
0
0
0
0
0
0
0
1
0
0
4
1
0
5
Common Yellowthroat
1
0
0
1
0
0
0
0
0
0
0
0
0
1
0
2
1
0
3
European Starling
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
1
0
1
Gray Catbird
2
7
3
0
2
2
0
1
1
0
1
0
0
5
1
2 16
7
25
House Sparrow
1
0
0
0
0
0
0
0
1
0
0
0
0
0
0
1
0
1
2
Mallard
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
1
0
1
Mourning Dove
0
0
0
1
0
0
0
0
0
0
1
0
0
0
1
1
1
1
3
Northern Cardinal
3
0
0
0
1
0
0
0
0
0
1
1
0
2
0
3
4
1
8
Northern Flicker
1
0
0
2
0
0
0
0
0
0
1
1
2
2
0
5
3
1
9
Northern Oriole
1
0
2
1
0
0
1
0
0
2
0
0
3
3
4
8
3
6
17
Northern parula
2
0
0
1
0
0
0
0
0
0
0
0
0
0
0
3
0
0
3
Prairie warbler
1
0
0
1
0
0
0
0
0
0
0
0
1
0
0
3
0
0
3
Red-bellied Woodpecker
0
0
0
0
1
0
0
0
0
0
0
0
0
0
2
0
1
2
3
Red-winged Blackbird
1
0
0
2
1
1
0
0
0
4
0
3
2
2
2
9
3
6
18
Scarlet tanager
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
1
Song Sparrow
1
0
0
1
0
0
1
0
0
0
1
0
3
0
0
6
1
0
7
Tufted titmouse
1
0
0
0
0
0
1
0
0
0
0
0
0
0
0
2
0
0
2
Warbling Vireo
0
0
1
0
0
0
1
1
0
0
0
0
1
1
0
2
2
1
5
Wood duck
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
1
0
1
Yellow Warbler
0
0
1
0
1
0
0
0
0
2
0
1
3
1
1
5
2
3
10
Totals
32
71 51 48 170
Table 2. Avian species breeding at Bronx Park, Bronx in 2003. 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 H’s (Shannon-Weiner indeces) for all probable and confirmed territories each subdivision of
the site are: Swamp, 1.31; Parkway2, 1.67; Parkway1, 1.04; Skunk, 2.25; and Island, 2.11. The H’ for the
entire census area was 2.27 The percentage of probable and confirmed territories held by Gray catbird,
Red-winged blackbird, Yellow warbler and Common yellow-throat, and Song sparrow is 39.4%.
City of New York Parks & Recreation
2003 Avian Monitoring Report
For The Bronx Forest Restoration at Bronx Park
DISCUSSION
Last Updated: May 25, 2005
The species richness at the Bronx Park study site in 2003 (27) compares favorably with what was
found in the 2002 and 2004 breeding bird surveys at Riverdale and Seton Falls Parks. Riverdale had 27
species in 2002 and 24 in 2004, while Seton Falls had 30 species in 2002 and 28 in 2004. The overall H’
for the Bronx Park (2.27) was somewhat lower than that found at Riverdale or Seton Falls in either year. In
Riverdale the H’ was 2.69 in both years, and at Seton Falls the H’ was 2.75 in 2002 and 2.42 in 2004.
The least disturbed areas of the Bronx Park study site, the Swamp and the skunk cabbage area, had
the highest numbers of species reported. The skunk cabbage area had 13 probable or confirmed breeding
species, whereas the Swamp had only seven, which contributes to the lower H’ in the Swamp. 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 two other species (Northern oriole and Red-winged blackbird) also held more than two
territories.
The island, despite having only 10 species reported, had an H’ only slightly lower than that of
Skunk. No one species was dominant in terms of total number of territories. The island is also the probable
site of nesting by the pair of Wood ducks. Parkway 2 had a substantial number of species (16), but, as in
the Swamp, was heavily dominated by the American robin and Gray catbird. Parkway 1 had the fewest
species and territories (4). This is not surprising, given that it is area of the site with the thinnest border of
trees.
Several species less common in New York City were found during this survey. A male Scarlet
tanager was heard singing in the Swamp on one occasion, but most likely did not remain to breed. This
species requires large continguous areas of mature forest, and is a species that NRG would like to attract to
the Bronx Park restoration area. We confirmed nesting of Warbling vireo in the Swamp, and recorded an
additional two probable nesting pairs, one each in Island and Skunk. We sighted a pair of wood ducks on
one occasion, and a single individual on two other occasions. This species has been seen in previous years
on the island, and we believe they may breed there. To encourage them to return after the restoration, a
wood duck nest box has been placed on the island.
Species that were heard singing only once, early in the season, and which are almost certainly
migrants in this site were the Blackburnian, Black and white, and Prairie warblers. The Northern parula was
heard singing on two occasions from two different locations, and we believe it was also a migrant. These
migrants were found primarily in the Swamp and Skunk sections.