DOI: 10.5061/dryad.m498n
title: Data from: Predictive modelling of habitat selection by marine predators with respect to the abundance and depth distribution of pelagic prey

description: 1. Understanding the ecological processes that underpin species
 distribution patterns is a fundamental goal in spatial ecology. However,
 developing predictive models of habitat use is challenging for species
 that forage in marine environments, as both predators and prey are often
 highly mobile and difficult to monitor. Consequently, few studies have
 developed resource selection functions for marine predators based directly
 on the abundance and distribution of their prey. 2. We analysed
 contemporaneous data on the diving locations of two seabird species, the
 shallow-diving Peruvian Booby (Sula variegata) and deeper diving Guanay
 Cormorant (Phalacrocorax bougainvilliorum), and the abundance and depth
 distribution of their main prey, Peruvian anchoveta (Engraulis ringens).
 Based on this unique data set, we developed resource selection functions
 to test the hypothesis that the probability of seabird diving behaviour at
 a given location is a function of the relative abundance of prey in the
 upper water column. 3. For both species, we show that the probability of
 diving behaviour is mostly explained by the distribution of prey at
 shallow depths. While the probability of diving behaviour increases
 sharply with prey abundance at relatively low levels of abundance, support
 for including abundance in addition to the depth distribution of prey is
 weak, suggesting that prey abundance was not a major factor determining
 the location of diving behaviour during the study period. 4. The study
 thus highlights the importance of the depth distribution of prey for two
 species of seabird with different diving capabilities. The results
 complement previous research that points towards the importance of
 oceanographic processes that enhance the accessibility of prey to
 seabirds. The implications are that locations where prey is predictably
 found at accessible depths may be more important for surface foragers,
 such as seabirds, than locations where prey is predictably abundant. 5.
 Analysis of the relative importance of abundance and accessibility is
 essential for the design and evaluation of effective management responses
 to reduced prey availability for seabirds and other top predators in
 marine systems.
description: piquero_bayes.datpiquero_bayes.dat is the ADMB data file for running Bayesian analysis of habitat selection by Peruvian Boobies as presented in Boyd et al. "Predictive modelling of habitat selection by marine predators with respect to the abundance and depth distribution of pelagic prey".piquero_bayes.tplpiquero_bayes.tpl is the ADMB source code for running Bayesian analysis of habitat selection by Peruvian Boobies as presented in Boyd et al. "Predictive modelling of habitat selection by marine predators with respect to the abundance and depth distribution of pelagic prey".guanay_bayes.datguanay_bayes.dat is the ADMB data file for running Bayesian analysis of habitat selection by Guanay Cormorants as presented in Boyd et al. "Predictive modelling of habitat selection by marine predators with respect to the abundance and depth distribution of pelagic prey".guanay_bayes.tplguanay_bayes.tpl is the ADMB source code for running Bayesian analysis of habitat selection by Guanay Cormorants as presented in Boyd et al. "Predictive modelling of habitat selection by marine predators with respect to the abundance and depth distribution of pelagic prey".ReadMe