DOI: 10.5061/dryad.pk0p2ngm5
title: Caribbean Roseate Tern nest survival and monitoring data

description: Determining how site characteristics influence reproductive success can
 help guide conservation planning for declining wildlife populations. For
 colonially-breeding seabirds, nest survival and predation risk can be
 influenced by both colony and nest site characteristics such as colony
 size, nest density, and nest location. We evaluated reproductive success
 of a declining population of Roseate Terns (Sterna dougallii) in the U.S.
 and British Virgin Islands to identify primary causes of nest failure and
 investigate the influence of colony and nest site covariates on nest
 survival. In addition, we measured the influence of colony characteristics
 on chick provisioning to determine if resource competition in larger
 colonies affected foraging rates. Monitoring was conducted in 2017–18 via
 motion-triggered cameras, which enable 24-hour monitoring with minimal
 nest disturbance. Nest survival was defined by both hatch success and
 early chick success, defined as a chick surviving from hatching through
 the 4th post-hatch day. We monitored 118 nests in 6 colonies over the 2
 breeding seasons. We found that predation was the primary cause of nest
 failure. Both hatch and nest success increased with colony size, and
 neither nest survival nor predation probability were influenced by
 individual nest site characteristics. Provisioning rates were comparable
 among colony sites and did not vary with colony size. Our results suggest
 that directing management efforts toward enhancing colony size, rather
 than focusing on nest site characteristics, can be beneficial for tropical
 seabird conservation.
description: We monitored 6 tropical Roseate Tern colonies over 2 breeding
 seasons in 2017-18 in the US and British Virgin Islands to investigate the
 effects of colony and nest-site characteristics on nest survival,
 predation risk, and chick provisioning rates. Nests (n = 118) were
 monitered via remote motion activated nest cameras. Camera data was
 analyzed manually. Site covariates were measured at each individual nest
 site. Nest survival, predation, and provisioning data were all derived
 from camera imagery.
description: Byerlyetal2020_dailysurvival: dataset
 formatted for daily nest survival/predation analyses, with one row per
 individual nest per day of surviving from monitoring initated to either
 day of nest failure or last day monitored. Data collected in the US and
 British Virgin Islands, 2017-18. Survival
 variables: Individual nest ID
 ("nest") Camera site ID
 ("cam") Colony size, in number of breeding
 pairs ("n") Colony site
 ("island") Colony site location
 ("terr") Date of each day/row
 ("date") Date of each day/row in Julian
 date format ("julian") Estimated date first
 egg per nest was laid ("lay_date")
 Estimated date first egg per nest was laid in Julian date format
 ("LD") Date first egg per nest hatched
 ("hatch_date") Date first egg per nest
 hatched in Julian date format ("HD") Nest
 age at start of initiation onward, in number of days old
 ("age") Whether or not one egg per nest
 successfully hatched, as 0 = no, 1 = yes ("hatch")
 Whether or not one chick per nest survived to 4 days
 post-hatching, as 0 = no, 1 = yes ("chick")
 Whether or not a nest survived the entire period from laying to
 4 days post-hatching, as 0 = no, 1 = yes ("survive")
 Whether or not a nest was depredated, as 0 = no, 1 = yes
 ("pred") Nest monitoring interval in days
 ("t") Number of days monitored, starting
 from 1 (date of monitoring initiation) and ending at last day monitored
 ("obvs") Nest site
 variables: Nest type ("type", as
 covered or bare [exposed]) Substrate at nest
 ("ground") Vegetation type at nest
 ("veg") Nest placement within colony
 ("place") % cover at nest site
 ("per_cover") Tallest vegetation height at
 nest site in cm ("str_veg") Tallest rock
 height at nest site in cm ("str_rock")
 Maximum height of cover at nest site in cm
 ("max_str") Density of nests per camera
 site as number of nests per area of camera view in
 m<sup>2</sup> ("dens") Distance
 to nearest neighbor nest in m ("nn") Index
 of breeding Laughing Gull presence at colony
 ("nest_lagu") Index of breeding tern
 presence at colony ("nest_tern"). 
 Byerlyetal2020_nestdata: contain the same data
 as Byerlyetal2020_dailysurvival, but formatted as one
 row per nest, with additional covariates: Survival
 variables: Date nest monitoring began
 ("start_date") Date monitoring ended,
 either due to chick suriviving to the 4th day post hatch or the nest
 failing ("last_date") Nest site
 variables: Cause of nest failure
 ("cause") as no failure ("NA"), predation
 ("P"), non viable egg ("NV"), abandoned
 ("A"), or unknown ("u") Type of
 predator ("pred_type") as hermit crab ("HC"), Laughing
 Gull ("LAGU"), roof rat ("RAT"), red-tailed hawk
 ("RTHA"), yellow-crowned night-heron ("YCNH"), Great
 Egret ("GREG"), Roseate Tern ("ROST"), or unknown
 predator ("U") 
 Byerlyetal2020_NestSurvivalModels: Annotated R
 code for modeling daily nest survival and predation rates
 Byerlyetal2020_provisioningdata1.csv: chick
 provisioning dataset with one row per day per nest per nest for the first
 4 days post chick hatch. Variables:
 Individual nest ID ("nest")
 Year of monitoring ("year")
 Colony site ("island") Colony
 site location ("terr") Colony size, in
 number of breeding pairs ("n") Date of
 monitoring day ("date") Date of monitoring
 day in Julian date format ("Julian") Day of
 nest survival from 1-4 ("day") Period of
 chick age for days 1-2 ("early") and 3-4
 ("late") Number of fish delivered to chick
 per day ("fish_n") Number of fish delivered
 to chick per hours monitored ("hourly")
 Mean estimated length of fish brought to chick in cm
 ("length") Mean estimated width of fish
 brough to chick estimated from dorsal to ventral sides
 ("width") Number of chicks per nest
 ("chick_n") 
 Byerlyetal2020_provisioningdata2.csv: chick
 provisioning dataset with one row per provisioning event per nest for the
 first 4 days post chick hatch Variables:
 Individual nest ID ("nest")
 Camera site ("cam") Colony site
 ("island") Colony size, in number of
 breeding pairs ("n") Date of provisioning
 event ("date") number of chicks per nest
 ("chick_n") Day of nest survival from 1-4
 ("day") Period of chick age for days 1-2
 ("early") and 3-4 ("late") Time
 of provisioning event ("time") Hour in the
 day of provisioning event (standardized from 7:00 am ["1"]
 onward) type of prey brought to chick
 ("type") as fish ("F") or unknown
 ("NA") Category of fish type brought to
 chicks as dward herring ("DH"), false pilchard ("FP"),
 or other ("NA") Estimated length of fish
 brought to chicks in cm ("length")
 Estimated width of fish brough to chick estimated from dorsal to
 ventral sides ("width") Estimated volume of
 fish brought to chick as l x w ("volume")
 Length of fish via a standardized visual index developed by
 Shealer (1998) and based on the mean length of a roseate tern bill (~35
 mm), with prey length then assigned to categories of tiny
 (<b>≤</b>18 mm), small (18–35 mm), medium (35–52 mm), and
 large (&gt;52mm) ("shealer_length")
 Estimated wet mass of prey based on regression equation in
 Shealer (1998) where <i>x</i> is total length in millimeters
 (which we defined as the mean length in mm from each size category) and
 <i>y</i> is wet mass in grams:<i>
 </i><sup><i></i></sup>. This translated to index wet mass categories of tiny (<b>≤</b>0.1 g), small (0.1–0.4 g), medium (0.4–1.3 g), and large (&gt;1.3 g).