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Evaluating American Oystercatcher Productivity: Evaluating American Oystercatcher Productivity: A Comparison of Nest Success Estimation MethodsA Comparison of Nest Success Estimation Methods
Photo: www.birdsbykim.com
Tom Virzi, Ph.D. CandidateTom Virzi, Ph.D. Candidate
Department of Ecology, Evolution Department of Ecology, Evolution and Natural Resourcesand Natural Resources
Rutgers, The State University of NJRutgers, The State University of NJ
Research ObjectivesResearch Objectives
• Determine Breeding Habitat Requirements and Causes of Nest Failure
• Compare Reproductive Success Between Beach and Marsh Nesting Pairs
• Assess the Effects of Human Disturbance on Nest Success
Photo: www.birdsbykim.com
• Barrier Beach - Optimal Habitat• Salt Marsh - Sub-Optimal Habitat• Nest Success Lower in Sub-Optimal Habitat• Development/Disturbance on Beaches Pushes
Oystercatchers into Sub-Optimal Habitat
HypothesesHypotheses
Photo: www.birdsbykim.com
Methods
• Survey beaches, marsh and inlet islands for pairs/nests from March 1 - July 31
• GPS all pairs/nests found• Monitor nests every 3-4 days• Additional data recorded during nest checks:
– Point count of gulls– Presence/absence of mammal tracks– Human activity within 100m of nests/territories
MethodsMethods
Nest Success Nest Success Estimation MethodsEstimation Methods
• Apparent Nest Success– Biases High
• Mayfield Method– Daily Survival Probabilities
• Program MARK– Information Theoretic Approach (AIC)– Covariates
Nest Success TermsNest Success Terms
• Apparent Nest Success Measures– Hatch Success (# Nests Hatched / # Nests Found)– Nest Success (# Nests Fledged / # Nests Found)
• DSR – Daily Survival Rate– Nest DSR– Brood DSR
• Hatch Success (Nest DSR^28 Days)• Brood Success (Brood DSR^42 Days)• Nest Success (Hatch Success x Brood Success)
NJ AMOYs
North Coast – 8 Pairs
Central Coast – 25 Pairs
South Coast – 35 Pairs
Beach Breeding Beach Breeding Pairs in New JerseyPairs in New Jersey
Study Sites
Sites selected over a gradient of human
disturbance
Public Use
Beach Closures
ORV
Use
Island Beach
State Park
High Minimal Area
All Year
Forsythe NWR
Holgate Division
Low Entire Beach
Winter Only
Stone Harbor Point
Med Large Area
Winter Only
5
18
10
IB
HG
SH
Holgate
HolgateHolgate
Beach – 23 Pairs
Marsh – 3 Pairs
Island – 1 Pair
Total Pairs – 27
(Beach 2005 – 18)
Stone Harbor
Stone HarborStone Harbor
Beach – 19 Pairs
Marsh – 11 Pairs
Island – 8 Pairs
Total Pairs – 38(Beach 2005 – 20)
Island Beach
Island BeachIsland Beach
Beach – 5 Pairs
Marsh – 11 Pairs
Island – 25 Pairs
Total Pairs – 41(Beach 2005 – 5)
Comparison of Nest Success Estimation MethodsComparison of Nest Success Estimation Methods
Method 2004 2005 2006 Pooled
Apparent
- Hatch Success 15.0% 26.8% 25.9% 32.8%
- Nest Success 5.0% 15.5% 18.8% 17.9%
Mayfield
- Hatch Success 0.6% 20.0% 12.9% 18.4%
- Brood Success 0.3% 35.8% 57.1% 50.0%
- Nest Success 0.0% 7.2% 7.4% 9.2%
Program MARK
- Hatch Success 7.4% 20.0% 14.0% 16.7%
- Brood Success n/a 36.2% 57.3% 41.3%
- Nest Success n/a 7.2% 0.8% 6.9%
Comparison of Nest Success Estimation MethodsComparison of Nest Success Estimation Methods
Method 2004 2005 2006 Pooled
Apparent
- Hatch Success 15.0% 26.8% 25.9% 32.8%
- Nest Success 5.0% 15.5% 18.8% 17.9%
Mayfield
- Hatch Success 0.6% 20.0% 12.9% 18.4%
- Brood Success 0.3% 35.8% 57.1% 50.0%
- Nest Success 0.0% 7.2% 7.4% 9.2%
Program MARK
- Hatch Success 7.4% 20.0% 14.0% 16.7%
- Brood Success n/a 36.2% 57.3% 41.3%
- Nest Success n/a 7.2% 0.8% 6.9%
Hatch Success ModelsHatch Success ModelsProgram MARKProgram MARK
Delta AICc ModelModel AICc AICc Weights Likelihood #Par Dev{Year + Habitat + Mammal + Year.Habitat} 575.65 0.00 0.53 1.00 9 557.57{Year + Habitat + Mammal + Year.Habitat + Year.Mammal} 577.64 1.99 0.20 0.37 11 555.51{Year + Habitat + Mammal + Disturb + Year.Habitat} 577.64 1.99 0.20 0.37 10 557.54{Year + Habitat + Mammal + Disturb + Year.Habitat + Year.Mammal} 579.61 3.96 0.07 0.14 12 555.47{Year + Habitat + Mammal + Year.Mammal} 599.84 24.19 0.00 0.00 8 583.77{Year + Mammal + Disturb + Year.Mammal} 600.14 24.49 0.00 0.00 7 586.09{Mammal} 601.50 25.85 0.00 0.00 2 597.50{Year + Habitat + Mammal + Disturb + Year.Mammal} 601.85 26.20 0.00 0.00 9 583.77{Habitat + Mammal} 602.04 26.39 0.00 0.00 4 594.02{Mammal + Disturb} 602.55 26.90 0.00 0.00 3 596.54{Year + Mammal} 603.17 27.53 0.00 0.00 4 595.16{Year + Habitat + Mammal} 603.38 27.73 0.00 0.00 6 591.34{Habitat + Mammal + Disturb} 603.90 28.25 0.00 0.00 5 593.87{Year + Mammal + Disturb} 604.51 28.86 0.00 0.00 5 594.48{Year + Habitat + Mammal + Disturb} 605.36 29.71 0.00 0.00 7 591.31{Year + Habitat + Year.Habitat} 608.39 32.74 0.00 0.00 8 592.32{Year + Habitat + Disturb + Year.Habitat} 610.40 34.75 0.00 0.00 9 592.32{Habitat} 631.95 56.31 0.00 0.00 3 625.94{Habitat-Beach} 631.95 56.31 0.00 0.00 3 625.94{Habitat-Marsh} 631.95 56.31 0.00 0.00 3 625.94{Habitat-Island} 631.95 56.31 0.00 0.00 3 625.94
Brood Success ModelsBrood Success ModelsProgram MARKProgram MARK
Delta AICc ModelModel AICc AICc Weights Likelihood #Par Dev{Year + Habitat + Mammal + Year.Habitat} 187.33 0.00 0.22 1.00 7 173.26{Mammal} 189.35 2.02 0.08 0.36 2 185.34{Year + Habitat + Mammal + Year.Habitat + Year.Mammal} 189.36 2.02 0.08 0.36 8 173.26{Year + Habitat + Year.Habitat} 189.70 2.37 0.07 0.31 6 177.64{Year + Mammal} 190.43 3.09 0.05 0.21 3 184.41{Gull + Mammal} 190.63 3.30 0.04 0.19 3 184.61{Year} 190.82 3.49 0.04 0.18 2 186.81{Year-2005} 190.82 3.49 0.04 0.18 2 186.81{Year-2006} 190.82 3.49 0.04 0.18 2 186.81{Constant DSR} 191.03 3.70 0.03 0.16 1 189.03{Mammal + Disturb} 191.11 3.77 0.03 0.15 3 185.09{Year + Gull + Mammal} 191.67 4.33 0.03 0.11 4 183.64{Year + Mammal + Disturb} 192.27 4.93 0.02 0.08 4 184.24{Year + Mammal + Year.Mammal} 192.29 4.95 0.02 0.08 4 184.26{Gull + Mammal + Disturb} 192.63 5.30 0.02 0.07 4 184.60{Year + Gull} 192.65 5.31 0.02 0.07 3 186.63{Year + Disturb} 192.78 5.44 0.01 0.07 3 186.76{Habitat + Mammal} 192.91 5.57 0.01 0.06 4 184.88{Gull} 192.95 5.62 0.01 0.06 2 188.94{Disturb} 192.97 5.64 0.01 0.06 2 188.96{Habitat} 193.26 5.93 0.01 0.05 3 187.25
Nest Success Rates by HabitatNest Success Rates by HabitatPooled (2005 – 2006)Pooled (2005 – 2006)
Total Beach Marsh Islands
Hatch Success
16.3% 5.5% 20.1% 34.7%
Brood Success
51.3% 34.8% 53.8% 58.0%
Nest Success
8.4% 1.9% 10.8% 20.1%
Nest Success Rates by HabitatNest Success Rates by HabitatPooled (2005 – 2006)Pooled (2005 – 2006)
Total Beach Marsh Islands
Hatch Success
16.3% 5.5%(19.8% - 1.0%)
20.1%(18.8% - 21.6%)
34.7%(21.9% - 54.0%)
Brood Success
51.3% 34.8%(52.1% - 6.2%)
53.8%(26.9% - 63.3%)
58.0%(34.4% - 69.4%)
Nest Success
8.4% 1.9%(10.3% - 0.1%)
10.8%(5.1% - 13.7%)
20.1%(7.5% - 37.5%)
FindingsFindings
• Nest success influenced heavily by presence of mammalian predators
• Nestling survival may be correlated with interaction between hatch date and gull density
• High annual variability in nest success across habitats– Annual variability in flooding– Annual changes in mammal density
CART ModelingCART Modeling
• Site-level explanatory model– Habitat characteristics measured in field– GIS layers for development/land use
• Landscape-level predictive model– GIS layers only (surrogates)– Test model with statewide surveys on
barrier islands and in back bays
Future ResearchFuture Research
• Modeling Survival in MARK– Increase Banded Population
in NJ– Coordinate Band Resighting
Efforts with AMOY Working Group
• Modeling Nest Success in MARK– Refine Nest Monitoring
Methods– Datalogs
• Population Viability Analysis
Committee Members:• Julie Lockwood, Rutgers University• Rick Lathrop, Rutgers University• David Ehrenfeld, Rutgers University• David Drake, University of Wisconsin
Field Techs:• Mike Ferguson• Steve Grodsky• Patti Rendo• Sheryl Senczakiewicz
AcknowledgementsAcknowledgements
NJDFW - Endangered & Nongame Species Program:• Dave Jenkins• Todd Pover• Chris Kisiel• Kathy Clark
Larry Niles, Conserve WildlifeUSFWS - Forsythe National Wildlife RefugeNJ Division of Parks & Forestry – Island Beach State ParkThe American Oystercatcher Working GroupHumphrey Sitters, International Wader Study GroupJim Merritt, NJDFW - Program Director, Sedge Island
Natural Resource Education CenterDavid Lapuma, Rutgers University