Methods
Tracking data
The validity of our modelling approach hinges on constructing ENMs from
multiple colonies. We thus compiled the most comprehensive database of
tropical seabird tracking data to date, featuring 16 species
representing 60 colonies around the globe and totalling
~12000 individual trips (Table 1; Supporting
information). Species that had more than 10 tracking studies were
modelled individually. Tropicbird Phaethon and frigatebirdFregata species were grouped respectively (Table 1) to boost
sample size and make family level models, acknowledging that foraging
differences between species within these families have been observed
(e.g.
Mott et al. 2016). Noddy Anous species were modelled as a family
group (following evidence of foraging niche overlap;
Surman
& Wooller 2003, Shephard et al. 2018), and large tern Thalasseusand Hydroprogne species were aggregated into a meta-family group
for modelling. The exceptions were sooty terns, which were modelled as
an individual species (despite few tracking studies) because of their
unique, highly pelagic foraging niche among terns (Surman & Wooller
2003). Wedge-tailed shearwaters were also modelled separately for short
trips and long trips because we had good a-priori knowledge of
dual-foraging behaviours during breeding on the GBR (Congdon et al.
2005, McDuie et al. 2015) and in New Caledonia (Weimerskirch et al.
2020), and sufficient tracking studies to do so. Both individual species
(e.g. brown booby BRBO) and family groups (e.g. large terns TERN) are
hereafter referred to as “modelled species”.
Table 1 Summary of quantity and coverage of tracking data analysed for
each species, and the grouping of species with less data.