DOI: 10.5061/dryad.0000000ff
title: Data from: Breeding Sternula antillarum (Least Terns) disturbance distances and duration of escape behaviors: pedestrians necessitate larger conservation buffers than do passing vehicles

description: We tested the behavioral responses of breeding Sternula antillarum(Least
 Terns) to pedestrians and off-road vehicles and show that disturbance
 source, intra-colony characteristics, and environmental factors all
 influenced the distance, at which the birds were disturbed, as well as the
 duration of their response. Our goal was to inform wildlife buffer
 distances used to protect breeding S. antillarum at Cape Hatteras National
 Seashore, North Carolina and beyond. We measured breeding S. antillarum
 behavioral responses to pedestrians and vehicles during routine activities
 at eight colonies and during experimental activities at three colonies.
 Pedestrians caused the highest flush probability when walking directly
 towards a nest (Cox proportional hazard models: cumulative risk = 1 at
 both 100 m and 50 m) and lowest when walking past a nest (cumulative risk
 = 0.14 at 100 m and cumulative risk = 0.54 at 50 m). Passing vehicles had
 the lowest probability of causing birds to flush, cumulative risk = 0.02
 at all measured distances, up to 25 m from the nest. We also applied
 generalized linear models to model the duration of responses and found
 that it was affected by the number of nests in a colony, the density of
 nests in a colony, nest life stage, nest clustering, date, degree of pivot
 of a disturbance source along its route, and nest distance from colony
 edge. These results suggest that conservation managers can reduce S.
 antillarum buffers in locations where there are less disturbing human
 activities or less reactive S. antillarum colonies.
description: # Breeding Sternula antillarum (Least Terns) disturbance distances and
 duration of escape behaviors: pedestrians necessitate larger conservation
 buffers than do passing vehicles Dataset DOI:
 [10.5061/dryad.0000000ff](10.5061/dryad.0000000ff) ## Description of the
 data and file structure We collected data on breeding Least Tern escape
 behaviors in response to human-related disturbances on Cape Hatteras
 National Seashore. Disturbance data collection protocols followed routine
 human activities, and experimental human activities. We tested
 experimental human activities with four categories: pedestrian approaches,
 off-road vehicle approaches, pedestrian passes, and off-road vehicle
 passes. We analyzed these data using Cox proportional hazard analyses to
 determine the distance at which Least Terns responded to each disturbance
 protocol and we used generalized linear mixed models to determine which
 factors influenced the likelihood of a Least Tern disturbance response and
 the duration of their response (i.e., flush duration and time off nest).
 ### Files and variables #### File: extra.off.nest.obs2022.csv
 **Description:** data including flush duration and time off nest used to
 supplement analyses related to the comparison of flush duration and time
 off nest during pre-treatment control periods and treatment periods. #####
 Variables * Date: the date at which a treatment was completed (mm/dd/yyyy)
 * Nest.Number: a unique nest identifier * Flush.Dur: duration of flushing
 behavior (i.e. time spent off substrate) in seconds * Off.Nest: duration
 of time off nest, could include time spent off nest but not in flight
 (i.e., duration of nest exposure) in seconds * Trial: each approach or
 pass within a day's experimental period (app = approach trial, pass =
 pass trial) * Descript: the disturbance source description (Truck =
 off-road vehicle, Ped = pedestrian) #### File: OPPORTUNISTIC\_R\_DATA.csv
 **Description:** data collected during routine activities during the 2021
 season. "NAs" denote that data was not collected because it was
 not applicable and are missing because those values could not be collected
 based on a given bird's behavior or limitations of our equipment.
 ##### Variables * Date: the date when the disturbance response was
 observed (mm/dd/yyyy) * Time: the time at which the disturbance response
 was observed in EST timezone (HH:MM:SS) * RPA: resource protection area, a
 unit of defined management area used by Cape Hatteras National Seashore to
 often delineate between overlapping protected species breeding
 grounds resource protection area. Names based on closest landmark (e.g.
 Ramp 29) or a cardinal direction and a beach (e.g., South Beach). *
 Colony: a specific unique number given to a colony of breeding Least Terns
 * V.Point: denotes the sequence of vantage points at which data were
 collected during a protocol that followed routine human activities *
 Nest.Number: a unique identifier for each nest * Type: a delineation
 between human-related and non-human-related sources of disturbance (A =
 human-related, N = non-human-related, X = unknown) * Descript: a
 description of the disturbance source (pred bird = predatory bird, UTV =
 side-by-side two person off-road vehicle, nest switch = the
 incubating/brooding bird switched incubation or brooding duties with its
 mate) * Number: the amount of individual sources of a specific type of
 disturbance at one time (e.g., five pedestrians) * Habitat: the part of
 the beach in which the disturbance sources were within when they caused,
 or had the potential to cause, disturbance * Speed: the speed of the
 disturbance source in m/s * Trajectory: the angle in compass coordinates
 at which a disturbance source move towards a nest * Turn.angle: the degree
 of pivot within a circle that a disturbance source turned between the last
 moment and the next moment along its path * Closest.act: the closest a
 disturbance source approached a nest as measured by a Garmin etrex unit
 and interpolated through the "move" package in R and ArcGIS
 Online (in meters) * Closest.est: the closest a disturbance source
 approached a nest as estimated by the researchers in the field (in meters)
 * Behavior: the specific disturbance or agitation behavior exhibited by a
 target Least Tern. Approximate distances included are an estimate of the
 closest the source approached the nest in meters. * AID.est: the estimated
 agitation initiation distance (in meters) * FID.est: the estimated flight
 initiation distance (in meters) * Amt.birds: the number of individual
 birds of the target species exhibiting the same response behavior at a
 given time * Flush.Dur: duration of flushing behavior (i.e. time spent off
 substrate) in seconds * Off.Nest: duration of time off nest, could include
 time spent off nest but not in flight (i.e., duration of nest exposure) in
 seconds * Bird.per.sect: the number of birds within a section of beach as
 in which the researcher could reasonably observe and collect data *
 AID.act: the agitation initiation distance (in meters) as measured by a
 Garmin etrex GPS unit and determined by interpolating the location of a
 disturbance source using the "move" package in R * FID.act: the
 flight initiation distance (in meters) as measured by a Garmin etrex GPS
 unit and determined by interpolating the location of a disturbance source
 using the "move" package in R * Enter.Colony: the time (to the
 second) in which a disturbance source entered a colony (HH:MM:SS) *
 Enter.RPA: the time (to the second) in which a disturbance source entered
 a RPA (HH:MM:SS) * Exit.Colony: the time (to the second) in which a
 disturbance source exited a colony (HH:MM:SS) * Exit.RPA: the time (to the
 second) in which a disturbance source exited a RPA (HH:MM:SS) * Col.Dur:
 the duration of time that a disturbance source spent within a colony (in
 seconds) * RPA.Dur: the duration of time that a disturbance source spent
 within a RPA (in seconds) * Density: the density of Least Tern nests
 within a colony (number of nests divided by the area of the mininum convex
 polygon of a colony) * PSOD: the number of potential sources of
 disturbance within ~150 meters of the edge of a colony * Size: the number
 of active Least Tern nests in a colony at a given time * Center: the
 distance (in meters) between a nest and the closest edge of the
 colony's minimum convex polygon * Temp: the air temperature at a
 given time (in Fahrenheit) * TempC: the air temperature at a given time
 (in Celsius) #### File: approach\_logs.csv **Description:** all
 disturbance response data collected in 2022 during during experimental
 approach trials. "NAs" denote that data was not collected
 because it was not applicable and are missing because those values could
 not be collected based on a given bird's behavior or limitations of
 our equipment. ##### Variables * Treatment: the sequential order showing
 the number of treatments completed up to that given day * Date: the date
 at which the disturbance response was observed (mm/dd/yyyy) * Time: the
 time at which the disturbance response was observed in EST timezone
 (HH:MM:SS) * UTM.time: the time at which the disturbance response was
 observed in UTM timezone (HH:MM:SS) * Walker/Driver: initials of the
 person who was walking or driving, used to keep track of who had last
 walked or driven for that colony to change the walker or driver and keep
 the Least Terns from getting used to a single person * Cloth.color: the
 general color of the clothing worn by a pedestrian or the general color of
 the vehicle, included to ensure a color wasn't worn more than once in
 a row at the same colony to ensure Least Terns did not get used to a
 single person * Morning/evening: demarcates if observations were completed
 in the morning or evening hours (i.e. 6 am to 12 pm)  or evening hours (3
 pm to 6 pm) * RPA: resource protection area, a unit of defined management
 area used by Cape Hatteras National Seashore to often delineate between
 overlapping protected species breeding grounds. Names based on closest
 landmark (e.g. Ramp 29) or a cardinal direction and a beach (e.g., South
 Beach). * Colony: a specific unique number given to a colony of breeding
 Least Terns (as categorical) * Colony.: a specific unique number given to
 a colony of breeding Least Terns (as numeric) * NestNumber: a unique
 identifier for each nest (as categorical). Any data that provide a
 distance and a cardinal direction are to denote observations of a loafing
 Least Tern in relation to the closest nest point. Loafing birds were used
 as data points if there were not enough Least Tern nests available for
 data collection at a given time. * Nest.Number: a unique identifier for
 each nest (as numeric) * Long: longitude of a nest in decimal degrees *
 Lat: latitude of a nest in decimal degrees * Facing: the approximate
 cardinal direction a target Least Tern was facing during a specific trial
 (e.g., N = north, SE = southeast) * Eggs.Chicks: denotes if eggs or chicks
 are present in a nest. So long as one chick was present, this variable
 would say "chicks". "Loaf" denotes observations of an
 adult bird that was assumed to not be attached to a nest. * NestAge: the
 approximate number of days since the first egg was laid in the nest *
 Descript: a description of the disturbance source (e.g., PED = pedestrian,
 ORV = off-road vehicle) * Depth.colony: the distance into the colony a
 disturbance source moved (in meter) * Observe.type: whether the
 observations were collected by spotting scope or video camera
 ("spot" = spotting scope, "cam ()" = camera (type of
 camera)) * Pseudorep: the trial within a treatment period (ctl = control,
 1 = first trial, 2 = second trial, etc.) * FID: the flight initiation
 distance (in meters) as measured by a Garmin etrex GPS unit and determined
 by interpolating the location of a disturbance source using the
 "move" package in R * Behavior: the type of behavior exhibited
 when agitated (e.g., head up, head twitching) (UNK = unknown cause of
 disturbance response, inc = incubating, loafer = a bird that is standing
 around but not attached to a nest, territorial ghost crab = bird was
 territorial with a ghost crab, mob TUVU = bird mobbed a turkey vulture,
 mob LAGU = bird mobbed a laughing gull, intraspecific = reacted to another
 Least Tern) * AID:  the agitation initiation distance (in meters) as
 measured by a Garmin etrex GPS unit and determined by interpolating the
 location of a disturbance source using the "move" package in R *
 AID.dur: the duration of the agitation behavior (in seconds) *
 AID.time.ref: the time (to the second) at which the agitation behavior
 occurred in EST time zone (HH:MM:SS) * UTM.time.ref: the time (to the
 second) at which the agitation behavior occurred in UTM time zone
 (HH:MM:SS) * Flush.Dur: duration of flushing behavior (i.e. time spent off
 substrate) in seconds * Off.Nest: duration of time off nest, could include
 time spent off nest but not in flight (i.e., duration of nest exposure) in
 seconds * Amt.birds: the number of individual birds that exhibited that
 behavioral response at a given time * Closest: the closest a disturbance
 source approached a nest as measured by a Garmin etrex unit and
 interpolated through the "move" package in R and ArcGIS Online
 (in meters) * Resettle.dist: the distance (in meters) between a
 disturbance source and a nest at the moment which the bird returned to
 incubation or brooding posture on its nest * Speed: the speed of the
 disturbance source in m/s * Trajectory: the angle in compass coordinates
 at which a disturbance source move towards a nest * Turn.angle: the degree
 of pivot within a circle that a disturbance source turned between the last
 moment and the next moment along its path * Density: the density of Least
 Tern nests within a colony (number of nests divided by the area of the
 mininum convex polygon of a colony) * Size: the number of active Least
 Tern nests in a colony at a given time * NNI: nearest neighbor index, an
 index representing the clustering or dispersion of nests in a colony
 (&lt;1 is clustered, &gt;1 is dispersed, =1 is random) * PSOD: the number
 of potential sources of disturbance within ~150 meters of the edge of a
 colony * Noise: a binary variable denoting if a vehicle or pedestrian was
 playing a podcast aloud on their phone as a facsimile of human
 conversation during a trial (Y = noise was incorporated, N = noise was not
 incorporated) * Alt.ve: denotes if a different vehicle than the base white
 pickup truck was used for an off-road vehicle trial (Y = alternate vehicle
 was used, N = alternate vehicle was not used) * Center: the distance a
 nest was from the outer edge of the minimum convex polygon of the current
 colony (in meters) * Temp: air temperature in Fahrenheit degrees * TempC:
 air temperature in Celsius degrees * File reference: the type of video
 file collected, if observations were collected with a video camera *
 Comments: relevant comments that do not fit within the bounds of the data
 collection expectations to provide further context to a given situation
 #### File: pass\_logs.csv **Description:** all disturbance response data
 collected in 2022 during during experimental pass trials. "NAs"
 denote that data was not collected because it was not applicable and are
 missing because those values could not be collected based on a given
 bird's behavior or limitations of our equipment. ##### Variables *
 Treatment: the sequential order showing the number of treatments completed
 up to that given day * Date: the date at which the disturbance response
 was observed (mm/dd/yyyy) * Time: the time at which the disturbance
 response was observed in EST timezone (HH:MM:SS) * UTM.time: the time at
 which the disturbance response was observed in UTM timezone (HH:MM:SS) *
 Walker/Driver: initials of the person who was walking or driving, used to
 keep track of who had last walked or driven for that colony to change the
 walker or driver and keep the Least Terns from getting used to a single
 person * Cloth.color: the general color of the clothing worn by a
 pedestrian or the general color of the vehicle, included to ensure a color
 wasn't worn more than once in a row at the same colony to ensure
 Least Terns did not get used to a single person *
 Morning/evening: demarcates if observations were completed in the morning
 or evening hours (i.e. 6 am to 12 pm)  or evening hours (3 pm to 6 pm) *
 RPA: resource protection area, a unit of defined management area used by
 Cape Hatteras National Seashore to often delineate between overlapping
 protected species breeding grounds. Names based on closest landmark (e.g.
 Ramp 29) or a cardinal direction and a beach (e.g., South Beach). *
 Colony: a specific unique number given to a colony of breeding Least Terns
 (as categorical) * Colony.: a specific unique number given to a colony of
 breeding Least Terns (as numeric) * NestNumber: a unique identifier for
 each nest (as categorical). Any data that provide a distance and a
 cardinal direction are to denote observations of a loafing Least Tern in
 relation to the closest nest point. Loafing birds were used as data points
 if there were not enough Least Tern nests available for data collection at
 a given time. * Nest.Number: a unique identifier for each nest (as
 numeric) * Long: longitude of a nest in decimal degrees * Lat: latitude of
 a nest in decimal degrees * Facing: the approximate cardinal direction a
 target Least Tern was facing during a specific trial (e.g., N = north, SE
 = southeast) * Eggs.Chicks: denotes if eggs or chicks are present in a
 nest. So long as one chick was present, this variable would say
 "chicks". "Loaf" denotes observations of an adult bird
 that was assumed to not be attached to a nest. * NestAge: the approximate
 number of days since the first egg was laid in the nest * Descript: the
 type of disturbance source used in a trial (PED = pedestrian, ORV =
 off-road vehicle) * Behavior: the type of behavior exhibited when agitated
 (e.g., head up, head twitching) (UNK = unknown cause of disturbance
 response, inc = incubating, loafer = a bird that is standing around but
 not attached to a nest, territorial ghost crab = bird was territorial with
 a ghost crab, mob TUVU = bird mobbed a turkey vulture, mob LAGU = bird
 mobbed a laughing gull, intraspecific = reacted to another Least Tern) *
 Depth.colony: the distance into the colony a disturbance source moved (in
 meters) * Observe.type: whether the observations were collected by
 spotting scope or video camera ("spot" = spotting scope,
 "cam ()" = video camera) * Pseudorep: the trial within a
 treatment period  * FID: the flight initiation distance (in meters) as
 measured by a Garmin etrex GPS unit and determined by interpolating the
 location of a disturbance source using the "move" package in R *
 AID: the agitation initiation distance (in meters) as measured by a Garmin
 etrex GPS unit and determined by interpolating the location of a
 disturbance source using the "move" package in R * AID.dur: the
 duration of the agitation behavior (in seconds) * AID.time.ref: the time
 (to the second) at which the agitation behavior occurred in EST time zone
 (HH:MM:SS) * UTM.time.ref: the time (to the second) at which the agitation
 behavior occurred in UTM time zone (HH:MM:SS) * Flush.Dur: the duration of
 the agitation behavior (in seconds) * Off.Nest: duration of time off nest,
 could include time spent off nest but not in flight (i.e., duration of
 nest exposure) in seconds * Amt.birds: the number of individual birds that
 exhibited that behavioral response at a given time * Closest: the closest
 a disturbance source approached a nest as measured by a Garmin etrex unit
 and interpolated through the "move" package in R and ArcGIS
 Online (in meters) * Resettle.dist: the distance (in meters) between a
 disturbance source and a nest at the moment which the bird returned to
 incubation or brooding posture on its nest  * Speed: the speed of the
 disturbance source in m/s * Trajectory: the angle in compass coordinates
 at which a disturbance source move towards a nest * Turn.angle: the angle
 in compass coordinates at which a disturbance source move towards a nest *
 Density: the density of Least Tern nests within a colony (number of nests
 divided by the area of the minimum convex polygon of a colony) * Size: the
 number of active Least Tern nests in a colony at a given time *
 NNI: nearest neighbor index, an index representing the clustering or
 dispersion of nests in a colony (&lt;1 is clustered, &gt;1 is dispersed,
 =1 is random) * PSOD: the number of potential sources of disturbance
 within ~150 meters of the edge of a colony * Noise: a binary variable
 denoting if a vehicle or pedestrian was playing a podcast aloud on their
 phone as a facsimile of human conversation during a trial (Y = noise was
 incorporated, N = noise was not incorporated) * Alt.ve: denotes if a
 different vehicle than the base white pickup truck was used for an
 off-road vehicle trial (Y = alternate vehicle was used, N = alternate
 vehicle was not used) * Center: the distance a nest was from the outer
 edge of the minimum convex polygon of the current colony (in meters) *
 Temp: air temperature in Fahrenheit degrees * TempC: air temperature in
 Celsius degrees * File reference: the type of video file collected, if
 observations were collected with a video camera * Comments: relevant
 comments that do not fit within the bounds of the data collection
 expectations to provide further context to a given situation #### File:
 PDP\_logs.csv **Description:** all disturbance response data collected in
 2022 during during routine human activities. "NAs" denote that
 data was not collected because it was not applicable and are missing
 because those values could not be collected based on a given bird's
 behavior or limitations of our equipment. ##### Variables * Treatment: the
 sequential order showing the number of treatments completed up to that
 given day * Date: the date at which the disturbance response was observed
 (mm/dd/yyyy) * Morning/evening: demarcates if observations were completed
 in the morning (i.e. 6 am to 12 pm)  or evening hours (3 pm to 6 pm) *
 Time: the time at which the disturbance response was observed in EST
 timezone (HH:MM:SS) * UTM.time: the time at which the disturbance response
 was observed in UTM timezone (HH:MM:SS) * RPA: resource protection area, a
 unit of defined management area used by Cape Hatteras National Seashore to
 often delineate between overlapping protected species breeding grounds.
 Names based on closest landmark (e.g. Ramp 29) or a cardinal direction and
 a beach (e.g., South Beach). * Colony: a specific unique number given to a
 colony of breeding Least Terns (as categorical) * Colony.: a specific
 unique number given to a colony of breeding Least Terns (as numeric) *
 NestNumber: a unique identifier for each nest (as categorical).  Any data
 that provide a distance and a cardinal direction are to denote
 observations of a loafing Least Tern in relation to the closest nest
 point. Loafing birds were used as data points if there were not enough
 Least Tern nests available for data collection at a given time. *
 Nest.Number: a unique identifier for each nest (as numeric) * Long:
 longitude of a nest in decimal degrees * Lat: latitude of a nest in
 decimal degrees * Facing: the approximate cardinal direction a target
 Least Tern was facing during a specific trial (e.g., N = north, SE =
 southeast) * Eggs.Chicks: denotes if eggs or chicks are present in a nest.
 So long as one chick was present, this variable would say
 "chicks". "Loaf" denotes observations of an adult bird
 that was assumed to not be attached to a nest. * NestAge: the approximate
 number of days since the first egg was laid in the nest * Descript: a
 description of the source of disturbance (UTV = two person side-by-side
 off-road vehicle, pred bird = a predatory bird, intraspecific = another
 least tern, ped = pedestrian, GBBG = great black-backed gull, nest switch
 = the incubating/brooding bird switched incubation or brooding duties with
 its mate) * Behavior: the type of behavior exhibited when agitated (e.g.,
 head up, head twitching) (inc = incubating, loafer = a bird that is
 standing around but not attached to a nest, UNK = unknown cause of
 disturbance response) * Pseudorep: the trial within a treatment period
 (ctl = control, 1 = first trial, 2 = second trial, etc.) * FID: the flight
 initiation distance (in meters) as measured by a Garmin etrex GPS unit and
 determined by interpolating the location of a disturbance source using the
 "move" package in R * AID: the agitation initiation distance (in
 meters) as measured by a Garmin etrex GPS unit and determined by
 interpolating the location of a disturbance source using the
 "move" package in R * AID.dur: the duration of the agitation
 behavior (in seconds) * Flush.Dur: the duration of the agitation behavior
 (in seconds) * Off.Nest: duration of time off nest, could include time
 spent off nest but not in flight (i.e., duration of nest exposure) in
 seconds * Amt.birds: the number of individual birds that exhibited that
 behavioral response at a given time * Closest: the closest a disturbance
 source approached a nest as measured by a Garmin etrex unit and
 interpolated through the "move" package in R and ArcGIS Online
 (in meters) * Resettle.dist: the distance (in meters) between a
 disturbance source and a nest at the moment which the bird returned to
 incubation or brooding posture on its nest * Speed: the speed of the
 disturbance source in m/s * Trajectory: the angle in compass coordinates
 at which a disturbance source move towards a nest * Turn.angle: the angle
 in compass coordinates at which a disturbance source move towards a nest *
 Density: the density of Least Tern nests within a colony (number of nests
 divided by the area of the mininum convex polygon of a colony) * Size: the
 number of active Least Tern nests in a colony at a given time *
 NNI: nearest neighbor index, an index representing the clustering or
 dispersion of nests in a colony (&lt;1 is clustered, &gt;1 is dispersed,
 =1 is random) * PSOD: the number of potential sources of disturbance
 within ~150 meters of the edge of a colony * Noise: a binary variable
 denoting if a vehicle or pedestrian was playing a podcast aloud on their
 phone as a facsimile of human conversation during a trial (N = no, Y =
 yes) * Alt.ve: denotes if a different vehicle than the base white pickup
 truck was used for an off-road vehicle trial (N = no, Y = yes) *
 Col.Dur: the duration of time that a disturbance source spent within a
 colony (in seconds) * Center: the distance a nest was from the outer edge
 of the minimum convex polygon of the current colony (in meters) * Temp:
 air temperature in Fahrenheit degrees * TempC: air temperature in Celsius
 degrees * Comments: relevant comments that do not fit within the bounds of
 the data collection expectations to provide further context to a given
 situation ## Code/software We used R version 4.2.2 (2022-10-31 ucrt) for
 statistical analyses and we used predominantly R packages including
 "MuMIN", "survival", "coxme",
 "move", "spatialEco", and "adehabitatHR". R
 scripts are broken down by treatment protocols. "Incidental analysis
 code" was used for analyzing data collected during routine human
 activities, "Approach analysis code" was used for analyzing data
 collected during approach trials, and "Pass analysis code" was
 used for analyzing data collected during pass trials. R code was uploaded
 to Zenodo.