Data from: Breeding Sternula antillarum (Least Terns) disturbance distances and duration of escape behaviors: pedestrians necessitate larger conservation buffers than do passing vehicles
Data files
Apr 17, 2025 version files 320.52 KB
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approach_logs.csv
49.79 KB
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extra.off.nest.obs2022.csv
3.58 KB
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OPPORTUNISTIC_R_DATA.csv
101.04 KB
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pass_logs.csv
111.99 KB
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PDP_logs.csv
28.60 KB
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README.md
25.51 KB
Abstract
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.
Dataset DOI: 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 (<1 is clustered, >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 (<1 is clustered, >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 (<1 is clustered, >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.