DOI: 10.5061/dryad.6djh9w179
title: Characterizing juvenile dispersal dynamics of invasive barred owls: implications for management

description: 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. 
description: # 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: &gt; Watson, Whitney and H. Anu Kramer (2023),
 Characterizing juvenile dispersal dynamics of invasive barred owls:
 implications for management, Dryad, Dataset, (DOI) * Corresponding
 publication: &gt; 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 &gt;70% and canopy height &gt;30 m * med: proportion of
 buffer with canopy cover &gt;40% and canopy height &gt;20 m,
 excluding areas with canopy cover &gt;70% AND canopy height &gt;30
 m * open: proportion of buffer with canopy cover &lt;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