DOI: 10.5061/dryad.cfxpnvx9g
title: Data from: Relative brain size is associated with natal dispersal rate and species’ vulnerability to climate change in seabirds

description: The cognitive buffer hypothesis proposes that species with larger brains
 (relative to their body size) exhibit greater behavioural flexibility,
 conferring an advantage in unpredictable or novel environments. Therefore,
 behavioural flexibility – and relative brain size – are likely to be
 important predictors of a species’ vulnerability to anthropogenic
 pressures and, ultimately, extinction risk. However, current evidence
 linking brain size to species vulnerability and extinction risk is
 inconclusive. Furthermore, studies examining the relationship between
 relative brain size and behavioural flexibility have mainly focused on
 foraging innovations, whilst other forms of behavioural flexibility remain
 unexplored. In this study, we collate species-specific information and
 examine links between relative brain size, rates of natal and adult
 dispersal (a measure of flexibility in breeding site fidelity),
 vulnerability to six anthropogenic threats and extinction risk for 131
 species of seabird. We focused our study on seabirds, a highly threatened
 group that displays large variation in both relative brain size and
 dispersal behaviour. We found a significant positive relationship between
 relative brain size and natal dispersal rate, suggesting that relative
 brain size could enhance flexibility in breeding site choice in seabirds,
 consistent with the cognitive buffer hypothesis. However, this
 relationship does not persist when we consider adult dispersal, possibly
 reflecting constraints imposed by mate selection and knowledge transfer in
 seabirds. We also show that relative brain size is negatively associated
 with vulnerability to climate change. These findings have immediate
 application for predicting interspecific variation in species’
 vulnerability to climate change and identifying priority species for
 conservation.
description: <strong>Dataset 1: Brain
 and body size</strong> Published measures of brain size (g) for 131
 species of seabird. Brain size estimates were generated from the
 measurement of adult skulls in museum collections using the endocast
 method. For each species, multiple specimens were measured and a mean
 value was calculated to provide a single, species-specific brain size
 estimate. To account for the allometric relationship between brain and
 body size, we also obtained information on body size
 (g). <strong>Dataset 2: Natal and adult dispersal
 rates</strong> We collated data on natal and adult dispersal
 rates by conducting a systematic literature search using the online
 database, Web of Science. The literature search generated a total of 793
 papers and reports and from these, we extracted natal and adult dispersal
 rates. Here, natal dispersal is defined as the annual proportion of
 fledglings recruiting into a colony different from their natal colony, and
 adult dispersal is defined as the annual proportion of adults relocating
 to a new breeding colony. The final dataset included dispersal estimates
 from 47 studies and 29 species. For studies that provided multiple
 dispersal rate estimates, i.e., for different adult age classes or for
 males and females (n=9), we calculated a species mean value. For this
 final list, we also collated information on age at first breeding and
 fledging time. We selected age at first breeding to reflect the
 species-specific time that is available to prospect different colonies,
 and fledging time to reflect maternal investment. Where multiple
 species-specific values were provided for age at first breeding, we
 calculated the mean weighted by the percentage of individuals that had
 bred by each age. Where a range was provided for fledging time, we took
 the midpoint. <strong>Dataset 3: Extinction risk and
 threats</strong> We extracted a species’ threat status from the
 IUCN Red List database (iucnredlist.org, 2020) and their vulnerability to
 six relevant anthropogenic threats listed under the Threats Classification
 Scheme (v. 3.3, IUCN, 2020). The six anthropogenic threats we considered
 were: climate change, biological resource use (e.g., fishing), human
 intrusions and disturbance, invasive species, energy production and
 mining, and pollution. Threat vulnerability was classified as:
 ‘vulnerable’ or ‘not vulnerable’. We used the IUCN classifications to
 group species into two broader categories of extinction risk. Here,
 species classified as Critically Endangered (CR), Endangered (E) and
 Vulnerable (V) were defined as ‘threatened’, and species listed as Near
 Threatened (NT) and Least Concern (LC) were defined as
 ‘non-threatened’.