Red-footed and masked boobies stable isotope data

Animals that co-occur in a region (sympatry) may share the same environment (syntopy), and niche differentiation is expected among closely related species competing for resources. The masked booby (Sula dactylatra) and smaller congeneric red-footed booby (Sula sula) share breeding grounds. In addition to the inter-specific size difference, females of both species are also larger than the respective males (reversed sexual size dimorphism). Although both boobies consume similar prey, sometimes in mixed-species flocks, each species and sex may specialize in terms of their diet or foraging habitats. We examined inter- and intra-specific differences in isotopic values  (δ13C and δ15N) in these pelagically feeding booby species during the incubation period at Clarion Island, Mexico, to quantify the degrees of inter- and intra-specific niche partitioning throughout the annual cycle. During incubation, both species preyed mainly on flyingfish and squid, but masked boobies had heavier food loads..., This study was conducted at Clarion Island, Revillagigedo Archipelago, Mexico (18°21’7.53” N, 114°43’18.61” W)
Individual masked and red-footed boobies were captured at their nest by hand or using a hand net from a distance of 1–2 m.
A few drops of blood (~ 0.15 mL) were collected from the brachial vein of individual birds using a 25 G needle and non-coated capillary tubes. The blood samples were placed on glass microscope slides and air-dried. Whole blood reflects the diet assimilated during the previous 3–4 weeks (Vander Zanden et al., 2015), and whole blood samples therefore provide information on the bird’s diet during the incubation and/or pre-laying period. Body feathers were collected from the ventral part of adult birds and stored in individual paper bags. Body feathers were considered optimal given that they are easy to collect and do not impair the flight ability of the sampled birds (Jaeger et al., 2009; Bighetti et al., 2022). In contrast to whole blood, body feathers integr..., , # Red-footed and masked boobies stable isotope data

[https://doi.org/10.5061/dryad.573n5tbg4](https://doi.org/10.5061/dryad.573n5tbg4)

The data is composed of δ13C and δ15N values obtained from blood and feathers from red-footed and masked boobies breeding on Clarion Island, Revillagigedo Archipelago.

## Description of the data and file structure

The values presented are carbon values and nitrogen values from blood samples (PO) and feathers, collected from female and male, red-footed and masked boobies.

* Date of study: March 2017 and 2018
* Project name: Variations in inter-specific and sex-related niche partitioning in pelagic boobies during their annual cycle
* There are 2 different species of boobies in the dataset collected from 1 island (Isla Clarion) in the Revillagigedo Archipelago.

Contains **112** values from stable isotopes of red-footed and masked boobies. Carbon (δ13C) and nitrogen (δ15N) values are in ‰.

The data set has three relevant **factor** variables:

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