Urban specialization reduces habitat connectivity by a highly mobile wading bird

Background Mobile animals transport nutrients and propagules across
habitats, and are crucial for the functioning of food webs and for
ecosystem services. Human activities such as urbanization can alter animal
movement behavior, including site fidelity and resource use. Because many
urban areas are adjacent to natural sites, mobile animals might connect
natural and urban habitats. More generally, understanding animal movement
patterns in urban areas can help predict how urban expansion will affect
the roles of highly mobile animals in ecological processes. Methods Here,
we examined movements by a seasonally nomadic wading bird, the American
white ibis (Eudocimus albus), in South Florida, USA. White ibis are
colonial wading birds that forage on aquatic prey; in recent years, some
ibis have shifted their behavior to forage in urban parks, where they are
fed by people. We used a spatial network approach to investigate how
individual movement patterns influence connectivity between urban and
non-urban sites. We built a network of habitat connectivity using GPS
tracking data from ibis during their non-breeding season and compared this
network to simulated networks that assumed individuals moved
indiscriminately with respect to habitat type. Results We found that the
observed network was less connected than the simulated networks, that
urban-urban and natural-natural connections were strong, and that
individuals using urban sites had the least-variable habitat use.
Importantly, the few ibis that used both urban and natural habitats
contributed the most to connectivity. Conclusions Habitat specialization
in urban-acclimated wildlife could reduce the exchange of propagules and
nutrients between urban and natural areas, which has consequences both for
beneficial effects of connectivity such as gene flow and for detrimental
effects such as the spread of contaminants or pathogens.