Urban specialization reduces habitat connectivity by a highly mobile wading bird

Abstract

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.

Ecological connectivity as a planning tool for the conservation of wildlife in cities

“…High levels of ecological connectivity within an urban landscape enables animals to move between patchy resources and allows post-breeding dispersal, maintaining gene flow and population viability [ 5 , 6 , 30 , 35 , 45 ]. In contrast, low levels of ecological connectivity restricts access to resources and prevents the movement of individuals and genes, potentially leading to reduced genetic diversity, inbreeding depression and ultimately local extinction [ 20 , 24 , 25 , 31 , 41 ].…”

“…For example, many bird species are able to disperse or commute across inter-patch distances of more than 100 m [ 37 , 38 , 43 ], while amphibian species are likely to be impeded by traffic-heavy roads [ 12 , 19 , 22 ]. To measure connectivity more realistically for different species groups it is important to account for behaviour and ecology [ 15 , 18 , 27 , 30 , 41 , 42 ]. Each species within a community has different habitat requirements and movement capabilities.…”

Urban ecological connectivity as a planning tool for different animal species

“…A high level of ecological connectivity within an urban landscape enables animals to move between patchy resources and allows post-breeding dispersal, maintaining gene flow and population viability (Braaker et al, 2014(Braaker et al, , 2017Mimet et al, 2020;Ossola et al, 2019;Visscher et al, 2018). In contrast, a low level of ecological connectivity prevents the movement of individuals and genes, potentially leading to reduced genetic diversity, inbreeding depression and ultimately local extinction (Hanski, 1999;Keeley et al, 2017;LaPoint et al, 2015;Moilanen & Hanski, 2001;Teitelbaum et al, 2020).…”

“…For example, many bird species are able to disperse or commute across inter-patch distances of more than 100m (Shanahan et al, 2011; Silva et al, 2020; Tremblay & St. Clair, 2011), while amphibian species are likely to be impeded by traffic-heavy roads (Charry & Jones, 2009; Hamer, 2016; Jacobson et al, 2016). To measure connectivity more realistically for different species groups it is important to account for behaviour and ecology (Ersoy et al, 2019; Grafius et al, 2017; Lookingbill et al, 2022; Mimet et al, 2020; Teitelbaum et al, 2020; Tischendorf & Fahrig, 2000). Each species within a community has different habitat requirements and movement capabilities.…”

Great egret (Ardea alba) habitat selection and foraging behavior in a temperate estuary: Comparing natural wetlands to areas with shellfish aquaculture

“…Human alteration of natural landscapes can alter animal movement behaviors and the ecological roles animals play. For example, human-altered landscapes were associated with reduced distance travelled across a range of mammalian taxa [5] and reduced connectivity within a population of birds [6]. In production landscapes where industry or agriculture can alter the natural availability of resources, animals may spend more time and energy travelling to find food and to avoid disturbance, and this may be especially true for larger, more mobile animals [7].…”