Estimating Greater Sage-grouse Juvenile Survival in Utah

Utah State UniversityDavid DahlgrenTerry MessmerDavid Koons

Introduction

Info Need

Study Area Parker Mountain

Methods

Methods – Burkepile et al. 2002

Methods Hen Behavior

Methods Monitoring

Methods Veg and Arthropod Sampling

Brood Mixing

Methods

Cause of mortality Handling Exposure Predation

Avian/Mammalian Unknown

Methods Modeling Manly and Schmutz 2001 - JWM

Maximum Likelihood Estimation (Version of the Mayfield Estimator)

Heterogeneity - D

Brood

ID

No. chicksstart

No. chicks

end

Age (days)

Start

Age (days)

End

Covariates

807 6 5 2 3 Year etc.

807 5 5 3 6 Year etc.

807 5 5 6 9 Year etc.

807 5 5 9 11 Year etc.

807 5 5 11 13 Year etc.

807 5 5 13 15 Year etc.

807 5 4 15 17 Year etc.

Methods

Modeling Survival First

Age Structure (weeks 1 to 6) Used to assess covariates AIC

Second Assess covariates

Temporal Brood hen characteristics Vegetation data Arthropod data

Methods

Modeling Survival Assumptions

Brood-mixing and right censoring Missing chicks Brood-mixing and missing chicks

Methods

Modeling Survival First Covariates

Year Brood Type Hen Behavior (restricted data set) Hen Age (restricted data set) Hatch Date

Methods

Modeling Survival Second – Vegetation Covariates (restricted data set)

Shrub cover and height Grass cover and height Forb cover and height

Third – Arthropod Covariates (2006, restricted data set) Hymenoptera (ants separate), Coleoptera, Lepidoptera,

Orthoptera, miscellaneous, and total arthropods

Results

Sample sizes Total

2005 n = 89 chicks in 21 broods (mean = 4.24) 2006 n = 61 chicks in 21 broods (mean = 2.91)

Handling Death (2.6%) 2005 n = 3 2006 n = 1

Excluded from the survival analysis

Results

Sample Sizes Chick mass

Mean = 29.5g (SE = 0.16) Transmitter averaged 5.1% (SE = 0.0003) of chick weight

Hen Behavior 43% Very protective (18/42) 38% Moderately protective (16/42) 19% Non-protective (8/42)

Results

Sample Sizes Brood Mixing

21% of marked chicks (31/146) 43% of marked broods (18/42) 45% of mixing events involved >1 chick (9/20)

Occurred weeks 1 to 6 70% (14/20) in weeks 2 and 3

Radio-marked hen mortality (n = 2)

Results

Sample Sizes Chick Mortality

n = 44 documented deaths n = 26 missing (assumed depredated) n = 6 exposure

Predation 91% (64/70) Unknown 75% (48/64) Mammalian 12.5% (8/64) Avian 12.5% (8/64)

Results Model K AIC wi

Age Specific Models (no covariates)

age = (week1)+(week2)+(week3)+(week4)+(weeks5-6) 6 345.89 0.00 0.99973

age = (weeks1-2)+(weeks3-4)+(weeks5-6) 4 362.47 16.58 0.00025

age = (week1)+(week2)+(week3)+(weeks4-6) 5 368.95 23.06 0.00000

age = (weeks1-2)+(weeks3-6) 3 372.67 26.78 0.00000

age = (week1)+(week2)+(weeks3-6) 4 374.64 28.75 0.00000

age = (week1)+(weeks2-6) 3 398.40 52.51 0.00000

age = (weeks1-2)+(weeks4-6) 3 400.48 54.59 0.00000

age = (weeks 1-6) 2 408.52 62.63 0.00000

Covariate Models

age* + brood type (regular or mixed) 7 253.60 0.00 0.99999

age* + hen age (yearling or adult) 7 279.42 25.82 0.00003

age* + year (2005 or 2006) 7 332.26 78.66 0.00000

age* + hen behavior (protectiveness) 8 335.07 81.47 0.00000

age* + hatch date (Julian days) 7 343.07 89.47 0.00000

i

First – Age parameterization

: AIC difference between a model (i.e., model i) and the best performing model (i.e., model with the lowest AIC among the set of models examined).wi: Akaike model weight.* The best model of age = (week1) + (week2) + (week3) + (week4) + (weeks5-6)

i

Second – Temporal and hencharacteristics

Results

Model K AIC wi

Age Specific Models (no covariates)

age = (week1)+(week2)+(week3)+(week4)+(weeks5-6) 6

345.89 0.00

0.99973

First – Age parameterization

i

Results

Model K AIC wi

Covariate Models

age* + brood type (regular or mixed) 7253.6

0 0.000.9999

9

i

Second – Temporal and hencharacteristics

Results

Survivorship Curve for Juvenile Sage-grouse, Parker Mountain, Utah, 2005-2006.

0.000

0.500

1.000

1 8 15 22 29 36

Days

P(s

urv

ival

)

Broods

Mixed Broods

Mean Survival to 42 days = 0.41 (SE =0.046)

Chick Survival in Regular broods = 0.38 Chick Survival in Mixed broods = 0.61

Results

Heterogeneity (D) Chicks/brood = 3.5 For best model

D = 1.10 (SE = 0.22)

Results

Model K AIC wi

age* (NULL) 6 -19.48 0.000.9999

9

i

Vegetation Covariates Null Model is best

Results

Model K AIC wi

age* + Ants 7-

115.16 0.000.5950

8

age* (NULL) 6-

114.39 0.770.4049

2

i

Arthropod Covariates Entire 42 days Ant model

Results

Model K AIC wi

age* + Orthoptera 5 -24.03 0.000.9999

9

i

Arthropod Covariates Early brood-rearing (day 1-21) Orthoptera (grasshopper) model

Estimates not significant

Take Home

Predation major cause of chick mortality However, survival was good (mean = 0.41) Our data suggested low dependence among brood

mates for sage-grouse chicks Brood-mixing may be important to survival, needs

further investigation There is evidence that Arthropods (especially

Orthoptera) may aid chick survival, needs further investigation (> sample size)

ThanksPARM USU Extension Parker Mtn. Grazing Association Jack H. Berryman Institute UDWR USFS BLM NRCS SITLA Farm Bureau County Commissioners

People Technicians Nathan Burkepile Jack Connelly Volunteers

Any Questions?