DOI: 10.5061/dryad.1jwstqk74
title: Data from: Competitive interactions among Gymnogyps californianus (California Condor)and other avian scavengers in southern Utah

description: Gymnogyps californianus (California Condors) were reintroduced to southern
 Utah and northern Arizona in 1996, and their presence at carcasses may
 impact the historic scavenger community. Little is known about the
 foraging patterns of G. californianus and its competitors, including
 interactions among scavengers. We deployed a pair of trail cameras on
 carcasses (n = 76), each placed at a unique location point. We used these
 recordings to determine scavenger behavior, including arrival rate, time,
 and order; carrion consumption and feeding time; displacement frequency
 and rate; and visit duration. G. californianus arrived at 12 of these
 carcasses, and an average of 13.5 condors attended a carcass. Condors
 arrived at carcasses within an hour of the first scavenger and on average
 consumed over half the carrion, leaving little for other scavengers. When
 condors arrived, 27% of the carcass had been eaten, compared to 78% when
 condors departed, while consuming ~15 kg of carrion. Visitation rates of
 vultures declined after condors had visited a carcass. To date, the low
 rate of carcass visitation by condors does not produce much competition
 for other scavengers. Condors may reduce the length of time carrion is
 present on the landscape, which has benefits for nutrient cycling and
 controlling the spread of disease.
description: # Data from: Competitive interactions among Gymnogyps californianus
 (California Condor)and other avian scavengers in southern Utah Dataset
 DOI: [10.5061/dryad.1jwstqk74](10.5061/dryad.1jwstqk74) ## Description of
 the data and file structure We aim to document the potential impacts of
 condor reintroduction, including heightened competition within the
 scavenger community and more rapid consumption of carrion. We collected
 data in sheep pastures in southern Utah and quantified several measures of
 exploitation and interference competition. Despite consuming the majority
 of carcasses when present, condors were not frequently detected, even in
 their preferred habitat. Condors currently have such confined impact that
 other scavengers likely have little pressure to switch to alternate food
 sources or habitats. ### Files and variables #### File: Arrival_orders.csv
 **Description:** This dataset lays out the arrival order of the most
 common scavenger, by comparing the day and time that the carcass was
 established with the days and times that scavengers were first detected at
 that carcass. ##### Variables * Carcass: Carcass ID number, unique to each
 carcass * Date established: Time and date the carrion was set out with
 cameras * First vulture: Time and date, according to trail cameras, when
 the first vulture was detected at the carcass. Blank cells indicate no
 vultures were detected. * Vulture detection time: The difference between
 the first vulture and the date established, i.e., the number of days it
 took for the first vulture to be detected by a camera * First condor: Time
 and date, according to trail cameras, when the first condor was detected
 at the carcass. Blank cells indicate no condors were detected. * Condor
 detection time: The difference between the first condor and the date
 established, i.e., the number of days it took for the first condor to be
 detected by a camera * First eagle: Time and date, according to trail
 cameras, when the first eagle was detected at the carcass. Blank cells
 indicate no eagles were detected. * Eagle detection time: The difference
 between the first eagle and the date established, i.e., the number of days
 it took for the first eagle to be detected by a camera * First fox: Time
 and date, according to trail cameras, when the first fox was detected at
 the carcass. Blank cells indicate no foxes were detected. * First coyote:
 Time and date, according to trail cameras, when the first coyote was
 detected at the carcass. Blank cells indicate no coyotes were detected. *
 First raven: Time and date, according to trail cameras, when the first
 raven was detected at the carcass. Blank cells indicate no ravens were
 detected. * First skunk: Time and date, according to trail cameras, when
 the first skunk was detected at the carcass. Blank cells indicate no
 skunks were detected. #### File: Arrival_rate.csv **Description:** This
 dataset directly compares the difference in visitation rates (visits per
 hour) of other scavengers before condors arrive, while condors are present
 at the carcass, and after the last condor has left. ##### Variables *
 Carcass: Carcass ID, unique to each carcass. Condors arrived and left as a
 group, and two groups of condors arrived at carcass 22, which is why it is
 repeated. Otherwise, condors only arrived and fed on any carcass once. *
 First condor arrival: The day and time that the first condor arrived, as
 recorded by trail cameras. * Last condor leave: The day and time that the
 last condor departed, as recorded by trail cameras. * Carcass established:
 The day and time that a carcass was set out with cameras. * Days until
 condor: The difference in days between carcass establishment and condor
 arrival. * Hours until condor: The difference in hours between carcass
 establishment and condor arrival. * Number of condors during: The total
 number of condors present during the feeding bout. Condors are all
 individually marked and were also all present simultaneously. * Number of
 vulture visits before: The number of turkey vulture visits between carcass
 establishment and condor arrival. Visits were classified as any new
 individual landing at the carcass or a detection of a turkey vulture after
 none had been recorded for 15 minutes. * Rate vulture visit before: Visit
 rate of turkey vultures before condors arrived, in visits per hour. The
 number of turkey vulture visits before is divided by the number of hours
 until the condor. * Number of eagle visits before: The number of golden
 eagle visits between carcass establishment and condor arrival. Visits were
 classified as any new individual landing at the carcass or a detection of
 a golden eagle after none had been recorded for 15 minutes. * Rate eagle
 visit before: Visit rate of golden eagles before condors arrived, in
 visits per hour. Number of golden eagle visits before is divided by the
 number of hours until the condor. * Number of fox visits before: The
 number of fox visits between carcass establishment and condor arrival. *
 Number of skunks before: The number of skunk visits between carcass
 establishment and condor arrival. * Last condor leave: The day and time
 that the last condor departed the carcass. * End obs time: The last time
 and day of footage. Usually, when the camera was pulled, but occasionally
 when the SD card filled up or batteries died. * Number vulture visits
 after: The number of turkey vulture visits between condor departure and
 the last video from the camera. Visits were classified as any new
 individual landing at the carcass or a detection of a turkey vulture after
 none had been recorded for 15 minutes. * Rate vulture visit after: Visit
 rate of turkey vultures after condors departed, in visits per hour. *
 Number of eagle visits after: The number of golden eagle visits between
 the condor departure and the last video from the camera. Visits were
 classified as any new individual landing at the carcass or a detection of
 a golden eagle after none had been recorded for 15 minutes. * Rate eagle
 visit after: Visit rate of golden eagles after condors departed, in visits
 per hour. * Number of fox visits after: The number of fox visits between
 the condor departure and the last video from the camera. * Number of skunk
 visits after: The number of skunk visits between the condor departure and
 the last video from the camera. #### File: Carcasses_cleaned.csv
 **Description:** Information on all carcasses set out, including condor
 visitation numbers and initial weight of the carcass. ##### Variables *
 Carcass_ID: A unique number assigned to each carcass, ascending
 consecutively * Number of condors that visited the carcass: The total
 number of individual condors that visited the carcass, using unique
 markers on the condors. NA designates missing data, such as when the
 learner sign shows condors were present, but cameras failed, so we could
 not assess the number of condors. * All_condor_visit: A binary variable
 representing whether condors were present, absent, or unknown (designated
 by an NA), using both feeding sign and trail camera footage. *
 Initial_weight_kg: The weight of the carrion when it was set out, in kg.
 Large carcasses were estimated from published averages; carcasses below 25
 kg were weighed with a scale. #### File: Condor_facilitation.csv
 **Description:** This dataset contains information on condor arrivals at
 carcasses, carrion accessibility, and amounts of carrion remaining. #####
 Variables * Carcass: Unique number identifying which carcass the
 information is tied to. * Number of condors: Total number of individual
 condors that arrived during a condor group's visit, using unique
 patagial tags * Visit number of condor group: The visit number of the
 focal condor group, when only counting condor groups that had already
 arrived (so the majority of visits are the first condor group to visit a
 carcass) * First condor arrival: The time and day that the first condor
 arrived * Last condor leave: The time and day that the last condor leaves
 * Carcass state arrival: The size of openings in the carcass when the
 first condor arrives * Carcass percent consumed arrival: A visually
 estimated percent, from the trail camera recording, of the carrion
 consumed just before the first condor arrived * Carcass state leaving: The
 size of openings in the carcass when the last condor leaves * Carcass
 percent consumed leaving: A visually estimated percent, using trail camera
 recordings, of the carrion consumed after the last condor leaves * Percent
 eaten during condor: The difference between carcass percent consumed
 leaving and carcass percent consumed arrival, or the percent of the
 carcass consumed while condors were attending the carcass. * Duration
 condor group: The difference between the first condor arrival and last
 condor leave, or the duration that the condors were present at the
 carcass. #### File: Displacements_summary.csv **Description:** A table of
 total displacements recorded between species ##### Variables * columns:
 species displaced * rows: species displacing * values: the number of times
 a displacement was recorded #### File: FeedingTimeSp.csv
 **Description:** Results from a Kruskal-Wallis test on feeding times at
 carcasses between scavenger species ##### Variables * Group.1: Species *
 mean: the mean feeding time across visits, in seconds * x: the standard
 deviation of feeding time across visits, in seconds #### File:
 TukeyDisplacementRate.csv **Description:** The results of a Tukey's
 honest significant difference test for displacement rate (displacements
 per hour) across different scavenger species ##### Variables * diff: the
 difference in means of displacement rate between the pair of species *
 lwr: the lower bound of the confidence interval, on the mean difference *
 upr: the upper bound of the confidence interval, on the mean difference *
 p adj: the adjusted p value of the difference in mean displacement rate
 from the pairing #### File: Displacements.csv **Description:** A long-form
 version of displacements_summary, with each species and context for the
 displacement (ie, carcass, group sizes for each species) ##### Variables *
 Carcass: a unique number given to each established carcass in ascending
 order. Carcass numbers may be skipped (if no displacements were recorded)
 or repeated (if several displacements occurred) * Displacer_species: The
 speciesthat  successfully displaces another individual during the
 interaction * Displacee_species: The species displaced by another
 individual during the interaction * Condor_num: The number of condors
 attending the carcass when the displacement occurred * Eagle_num: The
 number of eagles attending the carcass when the displacement occurred *
 Vulture_num: The number of vultures attending the carcass when the
 displacement occurred #### File: VisitTimeDifference.csv
 **Description:** A summary table showing the mean and standard deviation
 of the duration of a visit across scavenger species ##### Variables *
 Group.1: The scavenger species * mean: The mean, in seconds, that an
 individual visited a carcass * x: The standard deviation, in seconds, that
 an individual visited a carcass #### File: Visits_cleaned_prop.csv
 **Description:** Information on each recorded visit, including carcass ID,
 scavenger species, and length of time spent, total and actively foraging
 ##### Variables * ID: A unique ascending number for each visit. The
 dataset was restricted to visits lasting longer than 60 seconds of known
 behavior within a frame, so some visit IDs have already been removed. *
 Visit_per_species: An ascending number for a focal species at a carcass. *
 Carcass: A unique number given to each carcass. Carcass numbers may be
 skipped or repeated in this dataset if no visits existed and passed the
 initial filters, or if multiple visits did, respectively. * Species: The
 scavenger species that visited the carcass * Eaten_arrival: A visually
 estimated percent of the carrion eaten when the scavenger first arrived *
 Eaten_leaving: A visually estimated percent of the carrion eaten at the
 end of the scavenger's visit * Feeding_time: The number, in seconds,
 that the scavenger was actively feeding on the carcass (head down,
 touching carrion) * Number_of_displacements: The total number of
 displacements caused by the scavenger during the focal visit *
 Time_known_behavior: The total number of seconds that we have recorded
 behaviors during a visit. This is the sum of feeding, vigilance, and other
 behaviors such as moving or preening. * Time_total_behavior: The total
 number of seconds that the visit lasted. This includes "known
 behavior" time as well as time where behavior is unknown, such as
 when the individual is briefly off-screen, behind the carcass, or too far
 away to determine behavior accurately. * GUD: Giving-up density. The
 percentage of the carrion eaten during a visit, if the individual does not
 leave due to a displacement by another individual * Feeding_prop: The
 proportion of time spent feeding during a visit. Feeding time is divided
 by the total known behavior. * Max_group: The maximum group size,
 including all other individuals of all species from either arrival or
 departure. #### File: Ornithology-25-012.R **Description:** The R file
 that includes all the code for this analysis. The code is organized within
 headers but is otherwise minimally commented upon. ## Code/software R
 (vers 4.2.1) R packages: tidyverse (vers 1.3.2) lubridate (vers 1.9.0)
 DHARMa (vers 0.4.6) glmmTMB (vers 1.1.8) pgirmess (vers. 2.0.2) ggeffects
 (vers. 1.3.4) ggplot2 (vers 3.4.4)