Download (Charadrius melodus) in Southern New Jersey - SUNY-ESF

2016 Sussman Internship Report
Michelle Stantial
Factors Limiting Abundance and Productivity of Piping Plovers (Charadrius melodus) in Southern New Jersey
Michelle L. Stantial
SUNY College of Environmental Science and Forestry, Dept. Environmental and Forest Biology, Syracuse, NY
Summary
During the 2016 breeding season a total of 591 hours were spent in the field from April 15 - August 15 at seven study
sites in New Jersey: Barnegat Lighthouse State Park, Edwin B. Forsythe NWR (Holgate Unit), North Brigantine Natural
Area, Malibu Wildlife Management Area, Avalon-Dunes, Stone Harbor Point, North Wildwood, and Cape May Point
State Park (Fig. 1). Activities included trapping, banding, and radio-tagging adult and hatchling piping plovers, weekly
resighting surveys, weekly chick captures, and bi-monthly predator occupancy surveys. Our goals of this study are to
provide recommendations for predator management and restoration to land managers within the state of New Jersey that
will simultaneously reduce predation pressures and create suitable habitat to begin recovery in the state.
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Introduction
Successful recovery of endangered species requires an understanding of factors that limit population size and growth rate.
Population dynamics typically vary depending on the reproductive success of individuals, which can be influenced by a
number of factors including environmental impacts, habitat loss and predation. High reproductive success can lead to
increases in abundance and dispersal rates, influencing regional population growth. The Atlantic coast population of
piping plovers (Charadrius melodus) was listed as threatened under the U.S. Endangered Species Act (ESA) in 1986.
Since listing, the population has increased from 790 pairs in 1986 to more than 1,898 pairs in 2012 (USFWS 2013), a 140
percent increase. Although conservation of this species has seen great recovery success through protection and
management, recovery units within the Atlantic coast population have seen fluctuations in growth in recent years. From
2007 to 2010, the total Atlantic Coast population experienced a 6% decline; the Eastern Canada and New York-New
Jersey recovery unit populations decreased 15% and the Southern recovery unit population experienced an 8% decrease,
however, the New England recovery unit grew 7% during the same time period (USFWS 2011). Major causes of decline
and continued threats to the recovery of the Atlantic coast piping plover population include degradation of breeding and
foraging habitat, anthropogenic disturbances, and increased rates of predation compared to pre-settlement times (Wilcox
1959, Burger 1994, USFWS 1996, Maslo et al. 2012).
Population monitoring is an integral part of recovery efforts for Atlantic Coast Piping Plovers (USFWS 1996, Hecht and
Melvin 2009). Monitoring allows wildlife managers to identify limiting factors of survival and productivity, assess
effects of management actions and regulatory protection, and track progress toward recovery. A coast-wide effort to
summarize data on abundance, distribution, and reproductive success of piping plovers has continued since the species’
ESA listing. Recovery actions include procedures to reduce the amount of habitat loss due to human development and
management techniques to protect adults, eggs, and chicks from predators and disturbance (Hecht and Melvin 2009).
Management techniques include extensive monitoring of breeding pairs from the time of arrival on the nesting grounds
until the time of departure, symbolic fencing to provide buffers around nesting areas preventing human disturbance,
predator management including the use of exclosures to protect nests (Melvin et al. 1992), and off-road vehicle
restrictions to allow broods to forage without the threat of being crushed by a vehicle. Removal of a species from
protections of the ESA requires both increases in abundance, distribution and reproductive success as well as
improvements in factors that led to listing of the species (Hecht and Melvin 2009). Despite intensive management that
aligns with recovery plan guidelines, the population of piping plovers nesting in New Jersey has seen no increase in
abundance since the species listing.
The goal of this study is to understand the roles of predators and foraging habitat in piping plover population dynamics in
New Jersey piping plovers. Our results will lead to more comprehensive recommendations for predator management and
restoration in regards to chick foraging to land managers within the state of New Jersey that will simultaneously reduce
predation pressures and create suitable habitat to begin recovery in the state.
Methods
Monitoring, Nest, and Chick Survival
In collaboration with NJESP, CWFNJ and the Wetlands Institute, a total of 53 nests from 40 pairs of piping plovers were
monitored at a total of seven study sites from Barnegat Light State Park to Stone Harbor Point. Field crews attempted to
assess nest fate (i.e., active, hatched, depredated, overwashed, abandoned, weather loss, unknown cause of loss, or
unknown fate [nest not present, unsure of hatch or nest loss]) every 1-3 days. For nests that hatched, we attempted to
determine brood fate within established territories or proximity of banded parents, every 1-3 days until all chicks had
fledged or were assumed dead based on the absence of the chicks and parents.
We used logistic exposure models (Shaffer 2004) to compare daily nest survival at each of our study sites using data from
2012-2016. We included random slopes and coefficients by site for the linear predictor in our nest survival models
because baseline probabilities of nest predation may depend on site-specific factors such as predator communities. We
also included an effect of nest exclosure.
We used Young survival models (Lukacs et al. 2004) to compare daily chick survival between broods at each of our study
sites using data from 2012-2016. We included random slopes and coefficients by site for our Young survival model
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because baseline probabilities of chick survival may depend on site-specific factors such. We also included a random
effect of site on detection probability because visit frequency varied among sites.
We used continuous feed cameras at a subset of nests to verify causes of nest loss and document predator visits when the
nest was not lost. We recorded more than 5000 hours of video footage from the 2015 and 2016 field seasons which will
continue to be analyzed during the winter of 2016-2017.
Adult Nest Trapping and Chick Captures
We spent a total of 55.4 hours trapping piping plover adults and 100.0 hours capturing piping plover chicks during the
2016 field season. A total of 33 piping plovers adults were trapped and newly banded in New Jersey during the 2016 field
season, and a total of 25 piping plover adults were equipped with radio-tags. A total of 100 piping plover chicks were
banded and 21 were equipped with radio-transmitters (Table 1). Chicks were recaptured and weighed every 5-7 days. No
injuries occurred as a result of handling. No injuries occurred as a result of transmitter attachment, all birds receiving
radio-tags appeared to incubate nests, tend broods, and otherwise behave normally.
Resighting Surveys
We spent a total of 325.2 hours resighting individually marked piping plover adults and chicks during the 2016 field
season. Resighting surveys were conducted once a week and all areas of potential nesting and foraging habitat at each
study site were searched for banded adults and chicks.
Habitat Use
We spent a total of 42.0 hours conducting behavioral observations of banded adults and chicks to assess habitat use across
a variety of different nesting and foraging habitat configurations and varying levels of recreational beach use. Behavioral
observations were 10 min periods where every 10 seconds the behavior of the adult or chick was recorded as either
foraging, resting, courting, territorial, incubating, brood tending or disturbed. Additionally, each time an adult or chick
actively pecked at the substrate to capture a prey item, this action was recorded. We used Multi-Response Permutation
Procedure (MRPP) (Talbert and Cade 2013) to test for differences in activity budgets and time spent in various habitat
types for chicks and adults amongst all of our study sites.
Predator Occupancy Surveys
We spent a total of 144.5 hours conducting predator surveys at piping plover breeding sites during the 2016 field season.
Predator surveys were conducted once every two weeks (twice per month). We conducted bi-weekly mammalian predator
track surveys and avian point count surveys at randomly located plots at each of our study sites. During each survey, we
counted the number of track trails present in each plot by predator species and identify all avian species present within
100 m of the center of the plot. We recorded plot-specific covariates that may affect occupancy such as the distance to the
dune, distance to the forest, and distance to human development, survey-specific covariates that may affect occupancy
such as the distance to human recreation, the number of humans present, the distance to the nearest American
oystercatcher nest, and the distance to the nearest least tern nest, and survey specific covariates that may affect detection
rate, such as the saturation of the substrate, weather conditions, and tracking conditions. We used dynamic occupancy
models (MacKenzie et al. 2005, Kéry and Schaub 2012) to estimate the probability of habitat use by red foxes and track
how of predator habitat use changes throughout the course of the nesting season.
Radio Telemetry
Two automated telemetry units were placed in the field to monitor the daily activity patterns of radio-tagged piping
plovers. One tower was placed at the Holgate unit of EB. Forsythe NWR and was in operation for a total of 75 days
during the breeding season. A second tower was located at North Brigantine Natural Area and was in operation for a total
of 69 days.
Results
Monitoring, Nest, and Chick Survival
For the 2016 season, 62 piping plover chicks were fledged from the monitored study sites, representing a fledge rate of
1.62 chicks/pair, exceeding the minimum requirement of 1.21 chicks/pair as required to maintain a stable population.
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This region has observed an increase in reproductive success since 2012 when only 0.33 chicks/pair fledged from the
same seven study sites. Nest loss due to predators such as red foxes, fish crows, and large gulls has been cited as the
primary cause of poor hatch success, yet the causes of chick loss are largely unknown. During 2016, the primary causes
of nest loss in the study region was due to flooding (n=5). Other causes of nest loss included unknown predation (n=2),
Virginia opossum (n=2), raccoon (n=2), abandonment (n=2), fox (n=1), skunk (n=1), American oystercatcher (n=1),
buried by sand (n=1), and hatching failure (n=1). Daily nest survival was similar across all study sites but lowest at Stone
Harbor point for both exclosed and unexclosed nests, and exclosures had a significant effect on daily nest survival (Fig.
2). Chick survival was found to vary among study sites (Fig. 3). We documented incidents of fish crow, herring gull,
laughing gull, red fox, and mink removing eggs from nests in 2015 video footage and skunks removing eggs in 2016
video footage.
Habitat Use
We found no differences in activity budgets for adults and chicks at all of our study sites. However, we did find
differences in the amount of time that adults and chicks spent in various habitat types at each of our study sites (Figs. 4
and 5).
Predator Occupancy Surveys
Distance to dune was the only significant covariate. As the distance to the dune increased, the probability of habitat use
by red foxes decreased (Fig 6).
Ongoing analysis includes occupancy of all other predator species to each of our study sites, chick growth rates, weekly
survival of adults and chicks, review of automated telemetry data, and review of nest camera video footage.
Acknowledgments
This project was funded by the Edna Bailey Sussman Foundation, U.S. Fish and Wildlife Service, National Fish and
Wildlife Foundation, and the New Jersey Division of Wildlife. C. Davis, and T. Pover provided logistical support. R.
Linhart, A. Bonk, B. Giblin, A. Damminger, K. Dudgeon, D. Tattoni, J. Freeman, and Z. Bailey collected and entered the
data.
Literature Cited
Burger, J. (1994). The effect of human disturbance on foraging behavior and habitat use in piping plover (Charadrius
melodus). Estuaries 17:695–701.
Hecht, A., and S. M. Melvin (2009). Expenditures and Effort Associated With Recovery of Breeding Atlantic Coast
Piping Plovers. The Journal of Wildlife Management 73:1099–1107.
Kéry, M., and M. Schaub (2012). Bayesian population analysis using WinBUGS: a hierarchical perspective. In. 1st ed.
Academic Press, Boston.
Lukacs, P. M., V. J. Dreitz, F. L. Knopf, and K. P. Burnham (2004). Estimating survival probabilities of unmarked
dependent young when detection is imperfect. The Condor 106:926–931.
MacKenzie, D., J. Nichols, A. Royle, K. Pollock, L. Bailey, and J. Hines (2005). Occupancy Estimation and Modeling:
Inferring Patterns and Dynmaics of Species Occurence. In. 1st edition. Academic Press.
Maslo, B., J. Burger, and S. N. Handel (2012). Modeling Foraging Behavior of Piping Plovers to Evaluate Habitat
Restoration Success. The Journal of Wildlife Management 76:181–188.
Melvin, S. M., L. H. MacIvor, and C. R. Griffin (1992). Predator Exclosures: A Technique to Reduce Predation at Piping
Plover Nests. Wildlife Society Bulletin (1973-2006) 20:143–148.
Shaffer, T. L. (2004). A unified approach to analyzing nest success. The Auk 121:526–540.
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Talbert, M. K., and B. S. Cade (2013). User Manual for Blossom Statistical Package for R. [Online.] Available at
http://pubs.usgs.gov/of/2005/1353/.
USFWS (1996). Piping Plover (Charadrius melodus) Atlantic Coast Population Revised Recovery Plan.
USFWS (2011). Abundance and productivity estimates – 2010 update: Atlantic Coast piping plover population.
USFWS (2013). Preliminary 2012 Atlantic Coast Piping Plover Abundance and Productivity Estimates.
Wilcox, L. R. (1959). A Twenty Year Banding Study of the Piping Plover. The Auk 76:129–152.
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Table 1. Sample sizes of banded and radio-tagged piping plovers in NJ, 2016. All radio-tagged birds were also banded, and are therefore included in both
categories
Adults
Chicks
Newly
Previously Total
Site
Pairs Banded
Banded
Banded
Avalon-Dunes (AVDU)
1
1
1
2
Barnegat Lighthouse State Park (BALI)
3
3
3
6
Cape May Point State Park (CMPSP)
0
0
0
0
E. B. Forsythe NWR – Holgate (HOLG)
25
24
25
49
a
Island Beach State Park (IBSP)
1
0
0
0
Malibu Wildlife Management Area (MWMA) 0
0
0
0
North Brigantine Natural Area (NBNA)
5
0
10
10
North Wildwood (NOWI)
0
0
0
0
Stone Harbor Point (SHPT)
5
5
5
10
Total
40
33
44
77
a
Island Beach State Park was not a study site, but two chicks were banded in 2016 for monitoring purposes.
Radio
Tagged
1
2
0
17
0
0
3
0
2
25
Newly
Banded
3
8
0
62
2
0
16
0
9
100
Radio
Tagged
1
3
0
12
0
0
3
0
2
21
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Figure 1. Map of 2016 study sites in southern New Jersey.
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Figure 3. Daily survival probability of chicks at each study site, 2012-2016.
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Figure 2. Daily survival probability of unexclosed and exclosed nests at each study site, 2012-2016.
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Figure 4. Amount of time adults spent within in each habitat type at each study site, 2016(MRPP, P < 0.01).
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Figure 5. Amount of time chicks spent within each habitat type at each study site, 2016 (MRPP, P < 0.01).
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Figure 6. Relationship between probability of fox habitat use and the distance to the nearest dune to the predator track survey plot.
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