Characterizing juvenile dispersal dynamics of invasive barred owls: implications for management
Data files
Nov 13, 2023 version files 16.41 MB
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bdowdispersal_rand.csv
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distancebysex_input.csv
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distancebysex_over30day_input.csv
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distancebysex_step_input.csv
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juvdispersaldata_habitatselection.xlsx
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README.md
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RSF_input.csv
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SSF_input.csv
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survival_input_censor.xlsx
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survival_input_mort.xlsx
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survival_input_surv.xlsx
Abstract
Characterizing natal dispersal can help manage the spread of invasive species expanding their ranges in response to land use and climate change. The Barred Owl (Strix varia) is a prominent example of an apex predator undergoing a rapid range expansion, having spread from eastern to western North America where it is now hyperabundant—threatening the Northern Spotted Owl (S. occidentalis caurina) with extinction and potentially endangering many other native species. We attached satellite tags to 31 Barred Owl juveniles at the southern leading edge of the Barred Owl’s expanding range in California to characterize natal dispersal patterns and inform management. Juveniles traveled up to 100km from natal territories and experienced high mortality (annual survival = 0.204). At landscape scales, juveniles preferentially used forests, shrublands, and lower elevations during dispersal and avoided grasslands and burned areas. At finer scales, juveniles preferred shorter (younger) forests, lower elevations, and drainages, and avoided unforested areas. Our results suggest the Barred Owl range expansion is being driven primarily by high reproductive rates and densities despite low juvenile survival rates and dispersal through putatively suboptimal younger forests as a result of exclusion from high-quality habitat by territorial individuals. These findings also point to several strategies for conserving Spotted Owls and other native species in the Barred Owl’s expanded range, including: (1) creating and maintaining Barred Owl-free reserves bounded by open or high-elevation areas; (2) creating reserves large enough to reduce immigration by long distance dispersers; and (3) removing Barred Owls from large riparian corridors.
README: Characterizing juvenile dispersal dynamics of invasive barred owls: implications for management
- Persistent Identifier: (DOI)
- Creators: Whitney A. Watson and H. Anu Kramer
- Suggested Citations:
- Dataset citation: > Watson, Whitney and H. Anu Kramer (2023), Characterizing juvenile dispersal dynamics of invasive barred owls: implications for management, Dryad, Dataset, (DOI)
- Corresponding publication: > Watson, W. A., D. F. Hofstadter, G. M. Jones,c, H. A. Kramer, N. F. Kryshak, C. J. Zulla, S. A. Whitmore, V. O'Rourke, J. J. Keanee, R. J. Gutiérrez, and M. Z. Peery (2023). Characterizing juvenile dispersal dynamics of invasive barred owls: implications for management. Ornithological Applications. Accepted. (DOI)
Contact Information
- Name: Whitney A. Watson
- Affiliations: Department of Fish, Wildlife, and Conservation Ecology, New Mexico State University; Department of Forest and Wildlife Ecology, University of Wisconsin - Madison
- ORCID ID: https://orcid.org/0009-0003-3465-5945
- Email: wwatson@nmsu.edu
Alternative Contact: graduate PI
- Name: M. Zachariah Peery
- Affiliations: Department of Forest and Wildlife Ecology, University of Wisconsin - Madison
- ORCID ID: https://orcid.org/0000-0002-2545-9470
- Email: mpeery@wisc.edu
Additional Dataset Metadata
Acknowledgements
* Funding sources: California Department of Fish and Wildlife
(Q1910801) and Save the Redwoods League (157)
Dates and Locations
- Dates of data collection: Field data collected between March 2020 and September 2022
- Geographic locations of data collection: Fieldwork conducted in Mendocino and Sonoma Counties, California, USA. Additional data collected remotely via satellite-GPS tags deployed on owls from Humboldt, Trinity, Glenn, and Lake Counties, California, USA.
Methodological Information
- Methods of data collection/generation: see manuscript for details
Data and File Overview
Summary Metrics
- File count: 15
- Range of individual file sizes: 2 KB - 23,367 KB
- File formats: .R, .csv, .xlsx, .dbf
Table of Contents
R code files:
- RSF_code.R
- SSF_code.R
- survival_code.R
- distance_code.R
- generate_available_points.R
Data files:
- rsf_input.csv
- ssf_input.csv
- survival_input_censor.xlsx
- survival_input_mort.xlsx
- survival_input_surv.xlsx
- distancebysex_input.csv
- distancebysex_over30day_input.csv
- distancebysex_step_input.csv
- juvdispersaldata_habitatselection.xlsx
- bdowdispersal_rand.csv
Setup
- Recommended software/tools: R version 4.1.2, RMark version 3.0.0 (requires program Mark version 9.0)
Contents:
R code files:
RSF_code.R
- Description: code for generating, comparing, and visualizaing RSF models for coarse scale juvenile barred owl habitat selection analysis
- Format(s): R script
- Size(s): 14 KB
SSF_code.R
- Description: code for generating, comparing, and visualizing SSF models for fine scale juvenile barred owl habitat selection analysis
- Format(s): R script
- Size(s): 36 KB
survival_code.R
- Description: code for running juvenile barred owl survival analyses
- Format(s): R script
- Size(s): 10 KB
distance_code.R
- Description: code for comparing dispersal distance and direction between juvenile barred owl sexes
- Format(s): R script
- Size(s): 9 KB
generate_available_points.R
- Description: code for generating available locations for use in both coarse-scale (RSF) and fine-scale (SSF) habitat selection analyses
- Format(s): R script
- Size(s): 14 KB
Data files:
rsf_input.csv
- Description: data input for RSF analysis with information on buffered areas (radius 399 m) around 486 locations "used" by dispersing juvenile barred owls based on satellite-GPS tag data as well as 4860 "available" locations randomly generated within overall dispersal area for comparison
- Format(s): csv
- Size(s): 478 KB
- Dimensions: 5347 rows x 15 columns
- Variables:
- Index: unique number assigned to each location observation
- used: whether the location was used (1) or available (0)
- Long_WGS84: longitude of the location in WGS84
- Lat_WGS84: latitude of the location in WGS84
- Fire_period: whether the location was occupied by a juvenile barred owl while August Complex fire was actively burning (mid-fire) or after burning had stopped (post-fire)
- Owl_ID: for "used" locations, unique USGS band ID assigned to owl which location is associated; "0" for "available" locations
- Sex: sex of the dispersing owl, if location was "used"
- GMT_Date: date of the collected owl location on GMT time, if the location was "used"
- pNLCDforest: proportion of location buffer classified as "evergreen forest" or "mixed forest" according to NLCD
- pNLCDshrub: proportion of location buffer classified as "shrub/scrub" according to NLCD
- pNLCDgrass: proportion of location buffer classified as "herbaceous/grassland" according to NLCD
- pBurn: proportion of location buffer with any fire 2011-2020 according to MTBS
- pHiSev: proportion of location buffer with "high-severity" fire 2011-2020 according to MTBS
- elev: elevation (in meters) of the location averaged across the buffered area
- hydro: binary value indicating whether a perennial stream, river, lake, or reservoir was present within the location buffer
ssf_input.csv
- Description: data input for SSF analysis with information on buffered areas (radius 399 m) around 320 locations "used" by dispersing juvenile barred owls based on satellite-GPS tag data as well as 3200 "available" locations randomly generated within constraints of each used step (10 available for each 1 used) for comparison
- Format(s): csv
- Size(s): 305 KB
- Dimensions: 3521 rows x 14 columns
- Variables:
- used: whether the location was used (1) or available (0)
- Step_ID: unique ID assigned to each location stratum (a used location plus 10 associated available locations)
- Point_ID: unique ID assigned to each point (Step_ID plus unique point ID within stratum between 0 and 10, with 0 indicating used location)
- Owl_ID: unique USGS band ID assigned to owl which location is associated with
- Sex: sex of the dispersing owl, if location was "used"
- tall: proportion of buffer with canopy cover >70% and canopy height >30 m
- med: proportion of buffer with canopy cover >40% and canopy height >20 m, excluding areas with canopy cover >70% AND canopy height >30 m
- open: proportion of buffer with canopy cover <40%
- burn: proportion of location buffer with any fire 2011-2020 according to MTBS
- hiSev: proportion of location buffer with "high-severity" fire 2011-2020 according to MTBS
- elev: elevation (in meters) of the location averaged across the buffered area
- ridge: the proportion of ridge topographic position class within buffer around location
- drain: the proportion of canyon/drainage bottom topographic position class within buffer around location
- hydro: binary value indicating whether a perennial stream, river, lake, or reservoir was present within the location buffer
survival_input_censor.xlsx
- Description: data input for known-fate survival analysis in which juvenile barred owls with unknown fates were censored from the analysis beginning at the month interval in which last known location occurred
- Format(s): xlsx
- Size(s): 10 KB
- Dimensions: 27 rows x 7 columns
- Variables:
- ID: unique ID associated with each satellite-GPS tag deployed on a juvenile barred owl
- ch: capture history of individual juvenile barred owl in the form LDLDLDLDLDLDLDLDLDLDLDLD representing 12 1-month-long intervals in which owl either survived the duration of the interval (10), was censored from the analysis (00), or died during the interval (11)
- year: year in which individual was tagged (2020 or 2021)
- cohort: dispersal cohort of individual, with "1" representing owls which left natal territories between 4 August and 4 September of a given year, and "2" representing individuals which left natal territories between 5 September and 5 October of a given year
- sex: sex of the individual
- weight: mass of the individual in grams as recorded at capture
- brood_size: total number of young in brood individual owl came from
survival_input_mort.xlsx
- Description: data input for known-fate survival analysis in which juvenile barred owls with unknown fates were considered to have died during the month interval in which last known location occurred
- Format(s): xlsx
- Size(s): 12 KB
- Dimensions: 32 rows x 7 columns
- Variables:
- ID: unique ID associated with each satellite-GPS tag deployed on a juvenile barred owl
- ch: capture history of individual juvenile barred owl in the form LDLDLDLDLDLDLDLDLDLDLDLD representing 12 1-month-long intervals in which owl either survived the duration of the interval (10), was censored from the analysis (00), or died during the interval (11)
- year: year in which individual was tagged (2020 or 2021)
- cohort: dispersal cohort of individual, with "1" representing owls which left natal territories between 4 August and 4 September of a given year, and "2" representing individuals which left natal territories between 5 September and 5 October of a given year
- sex: sex of the individual
- weight: mass of the individual in grams as recorded at capture
- brood_size: total number of young in brood individual owl came from
survival_input_surv.xlsx
- Description: data input for known-fate survival analysis in which juvenile barred owls with unknown fates were considered to have survived through the end of the study period
- Format(s): xlsx
- Size(s): 12 KB
- Dimensions: 32 rows x 7 columns
- Variables:
- ID: unique ID associated with each satellite-GPS tag deployed on a juvenile barred owl
- ch: capture history of individual juvenile barred owl in the form LDLDLDLDLDLDLDLDLDLDLDLD representing 12 1-month-long intervals in which owl either survived the duration of the interval (10), was censored from the analysis (00), or died during the interval (11)
- year: year in which individual was tagged (2020 or 2021)
- cohort: dispersal cohort of individual, with "1" representing owls which left natal territories between 4 August and 4 September of a given year, and "2" representing individuals which left natal territories between 5 September and 5 October of a given year
- sex: sex of the individual
- weight: mass of the individual in grams as recorded at capture
- brood_size: total number of young in brood individual owl came from
distancebysex_input.csv
- Description: input for analysis of dispersal distance and direction between sexes including all 31 individual juvenile barred owls tagged in study
- Format(s): csv
- Size(s): 3 KB
- Dimensions: 32 rows x 8 columns
- Variables:
- ID: unique ID associated with each satellite-GPS tag deployed on a juvenile barred owl
- sex: sex of the individual
- year: year in which individual was tagged (2020 or 2021)
- final: the Euclidean distance from an individual's dispersal origin to their final settlement location, mortality location, or final transmission location
- max: the Euclidean distance from an individual's dispersal origin to their farthest GPS location collected during dispersal
- total: the sum of all steps between satellite-transmitted GPS locations of an individual during dispersal
- mean5day: the Euclidean distance between two successive GPS locations collected five days apart or, if step interval other than five days, the one-day dispersal distance (step length divided by the step interval) multiplied by five
- azimuth: the direction (0--360°) of an individual's final settlement location, mortality location, or final transmission location in relation to its dispersal origin
distancebysex_over30day_input.csv
- Description: input for analysis of mean dispersal distance and direction between sexes including only individual juvenile barred owls tagged in study whose tags remained active at least 30 days beyond dispersal initiation
- Format(s): csv
- Size(s): 2 KB
- Dimensions: 20 rows x 8 columns
- Variables:
- ID: unique ID associated with each satellite-GPS tag deployed on a juvenile barred owl
- sex: sex of the individual
- year: year in which individual was tagged (2020 or 2021)
- final: the Euclidean distance from an individual's dispersal origin to their final settlement location, mortality location, or final transmission location
- max: the Euclidean distance from an individual's dispersal origin to their farthest GPS location collected during dispersal
- total: the sum of all steps between satellite-transmitted GPS locations of an individual during dispersal
- mean5day: the Euclidean distance between two successive GPS locations collected five days apart or, if step interval other than five days, the one-day dispersal distance (step length divided by the step interval) multiplied by five
- azimuth: the direction (0--360°) of an individual's final settlement location, mortality location, or final transmission location in relation to its dispersal origin
distancebysex_step_input.csv
- Description: input for analysis of length of dispersal steps (standardized to 5-day steps) between sexes
- Format(s): csv
- Size(s): 21 KB
- Dimensions: 593 rows x 6 columns
- Variables:
- ID: unique ID associated with each satellite-GPS tag deployed on a juvenile barred owl
- sex: sex of the individual
- step_length: number of days elapsed between two successive satellite-GPS dispersal locations of an individual
- dist_step: Euclidean distance traveled by an individual between two successive satellite-GPS dispersal locations
- dist_1day: dist_step divided by step_length
- dist5day: dist_1day multiplied by five
juvdispersaldata_habitatselection.xlsx
- Description: input for analysis of length of dispersal steps (standardized to 5-day steps) between sexes
- Format(s): csv
- Size(s): 78 KB
Sheets:
Guide:
- Description: descriptions of behavioral states and fire periods assigned to each juvenile barred owl dispersal location observation in "Nocturnal_RSF" and "Nocturnal_SSF" sheets
- Dimensions: 15 rows x 3 columns
Nocturnal_RSF:
- Description: location data collected from dispersing juvenile barred owls for assignment of available points for coarse-scale RSF habitat selection analysis
- Dimensions: 496 rows x 11 columns
- Variables:
- Record_ID: unique number assigned to each observation
- Owl_ID: unique USGS band ID assigned to owl which location is associated with
- Sex: sex of individual
- Lat_WGS84: latitude of the location in WGS84
- Long_WGS84: longitude of the location in WGS84
- GMT_Date: date of the collected owl location on GMT time
- Year: year of the collected owl location on GMT time
- Month: month of the collected owl location on GMT time
- Day: day of the collected owl location on GMT time
- Behavioral_state: see "Guide" sheet in excel file
- Fire_period: see "Guide" sheet in excel file
Nocturnal_SSF:
- Description: location data collected from dispersing juvenile barred owls for assignment of available points for fine-scale SSF habitat selection analysis
- Dimensions: 352 rows x 13 columns
- Variables:
- Record_ID: unique number assigned to each observation
- Owl_ID: unique USGS band ID assigned to owl which location is associated with
- Sex: sex of individual
- Lat_WGS84: latitude of the location in WGS84
- Long_WGS84: longitude of the location in WGS84
- GMT_Date: date of the collected owl location on GMT time
- Year: year of the collected owl location on GMT time
- Month: month of the collected owl location on GMT time
- Day: day of the collected owl location on GMT time
- Previous_date: GMT date of most recent preceding step collected from same individual
- Time_step: time elapsed between "Previous_date" and "GMT_date"
- Behavioral_state: see "Guide" sheet in excel file
- Fire_period: see "Guide" sheet in excel file
bdowdispersal_rand.csv
- Description: file containing information on randomly-generated points within juvenile barred owl dispersal area (minimum convex polygon of all dispersal locations plus buffer of 30k) with locations overlapping water removed
- Format(s): csv
- Size(s): 15,050 KB
- Dimensions: 405,546 rows x 4 columns
- Variables:
- CID: NULL
- NLCD_2019: land cover class of point according to NLCD 2019 (see https://www.mrlc.gov/data/legends/national-land-cover-database-class-legend-and-description)
- Long_WGS84: longitude of the location in WGS84
- Lat_WGS84: latitude of the location in WGS84