DOI: 10.5061/dryad.fttdz0909
title: Data from: Marked differences in foraging area use and susceptibility to predation between two closely-related tropical seabirds

description: Ecological theory predicts that closely-related species must occupy
 different niches to coexist. How marine top predators achieve this during
 breeding, when they often gather in large multi-species colonies and are
 constrained to central-place foraging, has been mostly studied in
 productive temperate and polar oceans with abundant resources, but less so
 in poorer, tropical waters. Here, we track the foraging movements of two
 closely-related sympatric seabirds—the white-tailed and red-tailed
 tropicbirds Phaethon lepturus and P. rubricauda—breeding on Aldabra Atoll,
 Seychelles, to investigate potential mechanisms of niche segregation and
 shed light on their contrasting population trends. Combining data from
 GPS, immersion, depth and accelerometry loggers, we show that the two
 species have similar behaviour at sea, but are completely segregated
 spatially, with red-tailed tropicbirds flying further to feed and using
 different feeding areas than white-tailed tropicbirds. Using nest-based
 camera traps, we show that low breeding success of both species—which
 likely drives observed population declines—is caused by high nest
 predation. However, the two species are targeted by different predators,
 with native avian predators mainly targeting red-tailed tropicbird nests,
 and invasive rats raiding white-tailed tropicbird nests when they leave
 their eggs unattended. Our findings provide new insight into the foraging
 ecology of tropicbirds and have important conservation implications. The
 extensive range and spatial segregation highlight the importance of
 considering large-scale protection of waters around tropical seabird
 colonies, while the high level of nest predation provides evidence in
 support of rat eradication and investigating potential nest protection
 from native avian predators.
description: The data collection methods are in the paper and its electronic
 supplementary materials. 
description: # Data from: Marked differences in foraging area use and susceptibility to
 predation between two closely-related tropical seabirds
 [https://doi.org/10.5061/dryad.fttdz0909](https://doi.org/10.5061/dryad.fttdz0909) This dataset is published in the following paper: Fayet AL, Sanchez C, Appoo J, Constance J, Clucas G, Turnbull LA, Bunbury N (2023) Marked differences in foraging area use and susceptibility to predation between two closely-related tropical seabirds. Oecologia. [https://doi.org/10.1007/s00442-023-05459-x](https://doi.org/10.1007/s00442-023-05459-x) There are three datasets: one with the birds' **GPS** **tracking data** and all associated variables such as accelerometer data, immersion data, and environmental data (*GPS\_data.csv*), one on **diving data** from a subsample of birds with depth loggers (*Dive\_data.csv*), and one on **causes of nest failures** (*Predation.csv*). ## Description of the data and file structure All variables in each file are listed below, those whose name is self-explanatory are not detailed.   **GPS\_data.csv** Each row corresponds to a GPS location.   ·       datetime: date and time of the GPS location (local time, UTC + 04:00) ·       Species: RT = red-tailed tropicbird, WT = white-tailed tropicbird ·       Bird: bird identity (unique ring number) ·       Stage: INC = incubation, CR = chick-rearing ·       Sex: M = male, FEM = female, NA = unknown ·       Nest: nest unique ID ·       day.night: whether the location was taken during day (day) or night time (night) ·       hour.since.sunset (unit = hours) ·       Latitude (unit = decimal degrees) ·       Longitude (unit = decimal degrees) ·       Coldist: distance from colony, in km ·       Location: nest (&lt; 0.15km from the nest), colony (≥ 0.15km but &lt; 1km from the nest), or sea (≥ 1km away from the nest) ·       Tripdist: trip cumulative distance since start of the trip, in km ·       Speed: ground speed, in km/h ·       turning.angle (unit = degrees) ·       tortuosity (arbitrary unit) ·       dist: distance from last location, in km ·       trip: trip number, for this particular bird (locations &lt; 1km away are given a zero) ·       Latitude\_interp: interpolated latitude, in decimal degrees ·       Longitude\_interp: interpolated longitude, in decimal degrees ·       coldist\_interp: distance from colony calculated from interpolated locations, in km ·       dist\_interp: distance from last location calculated from interpolated locations, in km ·       tripdist\_interp: cumulative distance since start of the trip calculated from interpolated locations, in km ·       speed\_interp: speed calculated from interpolated locations, in km/h ·       turning.angle\_interp: turning angle calculated from interpolated locations, in degrees ·       tortuosity\_interp: tortuosity calculated from interpolated locations (arbitrary unit) ·       GPS: whether the bird has a GPS (1 = yes, 0 = no) ·       GLS: whether the bird has a GLS (1 = yes, 0 = no) ·       ACC: whether the bird has an accelerometer (1 = yes, 0 = no) ·       Totaltimewet: total time the GLS was wet over a 1-min window, in seconds ·       Landings: number of dry to wet transitions over a 1-min window ·       Takeoffs: number of wet to dry transitions over a 1-min window ·       nb.drybouts: number of dry bouts over a 1-min window ·       nb.bouts: number of bouts over a 1-min window ·       meanlight: mean light level over a 1-min window (arbitrary unit) ·       sdlight: sd of light level over a 1-min window (arbitrary unit) ·       staticY: static acceleration along the Y axis, in g ·       staticZ: static acceleration along the Y axis, in g ·       pitch (unit = degrees) ·       yaw (unit = degrees) ·       dynamicX: dynamic acceleration along the X axis, in g ·       dynamicY: dynamic acceleration along the Y axis, in g ·       dynamicZ: dynamic acceleration along the Z axis, in g ·       ODBA: overall dynamic body acceleration, in g ·       Pressure (from depth logger, in mbars) ·       temperature (from logger, in degrees Celsius) ·       WBF: wing beat frequency, in Hz ·       Sway\_fqcy: sway frequency, in Hz ·       Surge\_fqcy: surge frequency, in Hz ·       mean\_dynamicX: mean dynamic acceleration along the X axis, in g ·       mean\_dynamicY: mean dynamic acceleration along the Y axis, in g ·       mean\_dynamicZ: mean dynamic acceleration along the Z axis, in g ·       max\_dynamicX: max dynamic acceleration along the X axis, in g ·       q: square root of sum of squares of X, Y and Z, in g ·       minX: minimum acceleration along the X axis, in g ·       minY: minimum acceleration along the Y axis, in g ·       minq: minimum acceleration along q, in g ·       maxX: maximum acceleration along the X axis, in g ·       maxY: maximum acceleration along the Y axis, in g ·       skewX: skewness along the X axis (arbitrary unit) ·       skewY: skewness along the Y axis (arbitrary unit) ·       skewZ: skewness along the Z axis (arbitrary unit) ·       skewq: skewness along q (arbitrary unit) ·       kurtX: kurtosis along the X axis (arbitrary unit) ·       kurtY: kurtosis along the Y axis (arbitrary unit) ·       kurtZ: kurtosis along the Z axis (arbitrary unit) ·       inclination (unit = degrees) ·       azimuth (unit = degrees) ·       azimuth\_var: azimuth circular variance, in degrees ·       trendX: trend in raw acceleration along X axis, in g/s ·       trendY: trend in raw acceleration along Y axis, in g/s ·       trendZ: trend in raw acceleration along Z axis, in g/s ·       trendq: trend in raw acceleration along q, in g/s ·       depth: depth of the bird underwater, in m ·       vertical\_speed: change in depth per second, in m/s ·       dive\_yn: whether bird in dive or not (1 for depth &lt; 0.2m, 0 above, averaged over the 1-minute window) ·       divenb: number of dives during the window ·       behaviour\_final: bird behaviour predicted by the best model (nest, flapping flight, gliding flight, foraging, sitting on the sea at night or during the day) ·       tripID: unique ID of the foraging trip ·       trip\_complete: whether the GPS recorded the full trip (complete or incomplete) ·       chlA\_monthly\_mean: average chlorophyll A at the location in the past month, in mg/m3 ·       SST\_monthly\_mean: average SST at the location in the past month, in degrees Celsius ·       Bathymetry: water depth at the location, in m   **Dive\_data.csv** Each row corresponds to a bird. ·       Species (RT = red-tailed tropicbird, WT = white-tailed tropicbird) ·       Bird: Bird ID ·       totaldives: total number of dives ·       mean.depth: mean depth of the dives, in m ·       max.depth: maximum depth of the dives, in m   **Predation.csv** Each row corresponds to a nest. ·       Year ·       Location: subcolony (La Gigi, Gionet, Point Tanguin, Picard, Outer La Gigi) ·       Islet: unique ID of the islet ·       Species (RTTB = red-tailed tropicbird, WTTB = white-tailed tropicbird) ·       Nest: unique ID of the nest ·       Stage at failure: whether nest at egg or chick stage when it failed (for some chicks, size is given: hatchling, small chick, S/M chick, M chick, L chick) ·       Breeding success: failed, successful, or still active (when camera taken down), NA means breeding success is unknown ·       Cause of failure: died when hatching, egg abandonned, egg broken (unknown reason), egg broken by tropicbird itself, heavy rain, heron, high tide, likely heron, (likely) rats when egg left unattended, NA(no failure), pied crow, red-tailed tropicbird invading nest, unknown, unknown but egg left unattended ·       Stage of failure: whether nest failed at egg or chick stage (hatchling, small chick, S/M chick, M chick), unknown, NA (no failure) ·       Rats on islet?: whether rats were seen on the islet (not necessarily at the nest), yes/no ## Sharing/Access information The GPS data are also available on the BirdLife Seabird Tracking Database. [https://www.seabirdtracking.org/](https://www.seabirdtracking.org/) ##