DOI: 10.5061/dryad.nk98sf80m
title: Least tern disturbance observations and colony survey data

description: Coastal birds that rely on sandy beaches for breeding are vulnerable to
 catastrophic flooding events resulting from tropical cyclones. The effects
 of storm surge on annual productivity depend on the propensity and success
 of renesting attempts post-storm. From 2017-2021, I investigated the
 effects of storm surge on Least Tern (Sternula antillarum) annual
 productivity, renesting probability, and nest and chick survival after
 storms on Mississippi’s Gulf of Mexico Coast. Tropical cyclones made
 landfall during peak breeding period in three of these years, resulting in
 complete overwash of all colonies. Observers monitored daily nest
 survival, productivity (max fledge count/max nest count), and frequency of
 disturbance from avian predators at each colony. Total annual productivity
 (fledge count/ nest count across the study area) summed across colonies
 ranged from 0.00-0.07 in storm years and 0.29-0.66 in non-storm years.
 Probability of colony re-occupation declined as a function of storm date
 and increased with pre-storm nest success. Disturbance rate from avian
 predators did not increase post-storm compared to pre-storm periods. Nest
 survival increased with colony size and decreased in both late-season
 (non-storm) and post-storm time periods. Mean probability of chick
 survival was 0.20 ± 0.06 SD for peak nesting period in non-storm years,
 whereas mean predicted chick survival was 0.003 – 0.004 in storm years and
 in renesting periods in all years. Storm surge resulted in nearly complete
 loss of Least Tern breeding productivity despite renesting attempts and
 colony re-occupation after storms. I found no evidence that avian
 predation increased post-storm as a result of habitat changes; rather,
 similarly low productivity was observed for late-season breeding attempts
 in non-storm years. Repeated storm surge events could pose a serious
 threat to the viability of Mississippi’s coastal-nesting Least Tern
 population, and protection of Least Terns during early and peak nesting
 seasons is critical for ensuring breeding success.
description: # Least Tern Disturbance Observations and Colony Survey Data
 This dataset contains
 multiple raw data files as .csv format, .txt files with Bayesian models
 written in BUGS code used to estimate Least Tern nest and chick survival,
 and the R script used to clean, collate, and analyze the data. ##
 Description of the data and file structure
 **colony.storm.names.update.csv** This file contains beach width (m)
 measurements and presence or absence of dunes for each Least Tern colony
 in this manuscript. **ColonySurveys.zip** This file contains three .csv
 files with raw Least Tern colony survey data. These data were collected
 weekly to twice per week at all mainland colonies. The first five columns
 contain information about the survey: Site (site name, typically in
 reference to the nearest cross street that meets Highway 90), Date, Time,
 Species, and Survey Type (Exterior if conducted outside of the colony,
 Interior if surveyed by walking through the colony). Most surveys were
 conducted by a single observer, with counts of adults, nests, downy
 chicks, feathered chicks, and fledglings entered into the Adults1, Nests1,
 Downy1, Feath1, and Fledgeq columns. The Adults2, Nests2, etc. columns
 were occasionally used to enter data recorded simultaneously by a second
 observer, typically for training purposes. For this manuscript, only the
 first columns for each metric were used. The columns labeled AdultsPED,
 NestsPED, etc. indicate how counts were obtained: D for direct count, E
 for estimate, and P indicating presence but no count attempted. Chicks1
 refers to counts of downy chicks (ages 1-9 days approximately), Feath1
 refers to counts of feathered chicks (ages 10-20 approximately), and
 Fledge1 refers to counts of fledglings. The Notes column contains optional
 notes entered about the survey. All instances of missing data are filled
 with NAs; missing data were primarily the result of not recording certain
 information during a given visit, whether intentionally or intentionally.
 For example, survey time and adult counts were not consistently recorded
 during earlier survey years (because nest count was the primary focus in
 determining breeding colony size), and second-observer counts were only
 occasionally recorded throughout the study period.
 **DisturbanceDatasets.zip** This file contains five .csv files with
 disturbance data collected during each breeding season of this study
 (2017-2021). Disturbance observations were collected continuously by
 stewards during their work shifts at Least Tern colonies. The first six
 columns contain information about the work shift: Site (name of colony),
 Date, Start Time (beginning of the work shift or observation), End Time,
 Observers (observer initials), and Species (species engaged in reaction to
 disturbance; almost always Least Tern [LETE], a few observations of Black
 Skimmer [BLSK] present in data but not included in analysis). Each row
 represents a single instance of disturbance, with Source noted using the
 definitions given in the manuscript, distance (m) between the source and
 the edge of the colony when the terns first began to react (Distance),
 duration of reaction in minutes (Duration), and proportion of the colony
 engaged in four possible reactions: None, Alert (these two combined
 starting in 2020), Flush, and Defensivee. **LETE_storm_script.R** This
 file contains the R script used to clean, collate, and analyze all the
 data files used in this manuscript. **logexpos_survival_Reff.txt** This
 file contains the logistic exposure nest survival model written in the
 BUGS language to assess the effects of time period and colony size on
 Least Tern daily nest survival probability. **NestSurvivalData.zip** This
 file contains three .csv files with Least Tern nest monitoring data
 formatted for daily nest survival analysis. Fields include Site (colony
 name), Date (date of nest check), Nest.ID (unique identifier for each
 nest), and species (only Least Tern [LETE] used in analysis). Each row
 contains information from a single visit to a given nest, with a binary
 Status field indicating nest is still active (1) or is no longer active
 (0). The 2020 and 2021 files contain codes 1-8 in the Status column to
 indicate more specific information about nest fate; these are defined and
 converted to binary in the accompanying R script prior to analysis. The
 Chicks and Eggs are count fields indicating number of chicks and eggs
 present, respectively, if nest contents were observed. The Expose column
 contains the number of days that have elapsed since the previous visit to
 that nest; first visits to the nest contain NA in this field.
 **productivity_model_Jeffreys_priors.txt** This file contains the
 hierarchical chick survival model written in the BUGS language to assess
 the effects of time period and colony size on Least Tern chick survival
 probability. **storm_colonies.csv** This file contains summary information
 for Least Tern colonies that were impacted by tropical storms during the
 study period. "Site" contains the colony name, "Nests"
 contains the maximum number of nests observed at each colony prior to the
 storm (as a proxy for number of pairs in the colony), "Downy" is
 the maximum number of downy chicks present in the colony prior to the
 storm, "Renest" is a binary field indicating whether the colony
 re-formed after the storm, "Hatch" is the maximum proportion of
 nests that had hatched prior to the storm, "Year" is the
 calendar year, "StormWeek" is a numeric field containing the
 week within the year that the storm occurred, and the "5.7km
 bin" contains the summed colony sizes for all colonies located within
 5.7 km (inclusive of focal colony) prior to the storm to represent the
 number of Least Tern pairs potentially available to re-form the colony
 post-storm, and "IncludedColonies" contains the list of colonies
 that were included within the 5.7 km buffer.