Demography of a ground nesting bird in an urban system: are populations self-sustaining?

Urban areas are expanding globally as a consequence of human population increases, with overall negative effects on biodiversity. To prevent the further loss of biodiversity, it is urgent to understand the mechanisms behind this loss to develop evidence‐based sustainable solutions to preserve biodiversity in urban landscapes. The two extreme urban development types along a continuum, land‐sparing (large, continuous green areas and high‐density housing) and land‐sharing (small, fragmented green areas and low‐density housing) have been the recent focus of debates regarding the pattern of urban development. However, in this context, there is no information on the mechanisms behind the observed biodiversity changes. One of the main mechanisms proposed to explain urban biodiversity loss is the alteration of predator–prey interactions. Using ground‐nesting birds as a model system and data from nine European cities, we experimentally tested the effects of these two extreme urban development types on artificial ground nest survival and whether nest survival correlates with the local abundance of ground‐nesting birds and their nest predators. Nest survival (n = 554) was lower in land‐sharing than in land‐sparing urban areas. Nest survival decreased with increasing numbers of local predators (cats and corvids) and with nest visibility. Correspondingly, relative abundance of ground‐nesting birds was greater in land‐sparing than in land‐sharing urban areas, though overall bird species richness was unaffected by the pattern of urban development. We provide the first evidence that predator–prey interactions differ between the two extreme urban development types. Changing interactions may explain the higher proportion of ground‐nesting birds in land‐sparing areas, and suggest a limitation of the land‐sharing model. Nest predator control and the provision of more green‐covered urban habitats may also improve conservation of sensitive birds in cities. Our findings provide information on how to further expand our cities without severe loss of urban‐sensitive species and give support for land‐sparing over land‐sharing urban development.

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“…, Smith et al. ). Nest predation of urban birds is still inadequately understood (Ibáñez‐Álamo et al.…”

Section: Introductionmentioning

confidence: 99%

Land‐sharing vs. land‐sparing urban development modulate predator–prey interactions in Europe

Jokimäki

Suhonen

Benedetti

et al. 2020

Ecological Applications

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“…; Smith et al . ). This means, for example, that nodes with high Self‐influx are also likely to have high Outflux (a pattern found in our original network), and therefore metrics that best predict persistence are likely to be consistent among many real‐world networks.…”

Section: Discussionmentioning

confidence: 97%

“…Dispersal among urban bird populations in Portland, for example, allowed self‐sustaining populations to rescue non‐self‐sustaining groups, thus enhancing overall metapopulation persistence (Smith et al . ).…”

Section: Introductionmentioning

confidence: 97%

Network theory and metapopulation persistence: incorporating node self‐connections

et al. 2017

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Network analysis is gaining increasing importance in conservation planning. However, which network metrics are the best predictors of metapopulation persistence is still unresolved. Here, we identify a critical limitation of graph theory-derived network metrics that have been proposed for this purpose: their omission of node self-connections. We resolve this by presenting modifications of existing network metrics, and developing entirely new metrics, that account for node self-connections. Then, we illustrate the performance of these new and modified metrics with an age-structured metapopulation model for a real-world marine reserve network case study, and we evaluate the robustness of our findings by systematically varying particular features of that network. Our new and modified metrics predict metapopulation persistence much better than existing metrics do, even when self-connections are weak. Existing metrics become good predictors of persistence only when self-connections are entirely absent, an unrealistic scenario in the overwhelming majority of metapopulation applications. Our study provides a set of novel tools that can substantially enhance the extent to which network metrics can be employed to understand, and manage for, metapopulation persistence.

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“…Lesser park and towhees were selected for this study in part because research had been conducted in this area and on this species (Smith et al 2016, Shipley et al 2013 and thus the system is well known. Additionally, and despite the general low abundance of ground nesting birds in urban areas (Hedblom and Söderström 2010), towhees are one of the more abundant bird species in Portland's parks and greenspaces.…”

Section: Study Systemmentioning

confidence: 99%

“…In regards to urban towhees specifically, Bartos Smith et al (2016) found that towhee populations seem to be fairly abundant in urban parks, and are likely self-sustaining. They speculated that towhees may able to produce more young and be relatively successful compared to other ground-nesting birds for a variety of reasons, potentially including omnivorous diet, tendency to use edge habitats, capacity for productivity, and aspects of some urban environments such as low snake abundance.…”

Section: Nesting Microhabitat Use By a Ground-nesting Songbird 14mentioning

confidence: 99%

Nesting Microhabitat Use by a Ground-nesting Songbird: Strict Preferences or Random Choice?

Allen¹

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Nest site choice of birds has the potential to affect predation rates on nests and reproductive success for many bird species, and is thus tied closely to fitness. Vegetation at a particular site influences concealment (and predation rate as a result). Research has shown that birds of various species base nest site choice on variables like nest height, and especially vegetation cover within the microhabitat around a site. I studied nest site choice in ground-nesting birds, which tend to experience high predation rates near the nest site, and therefore might be expected to be particular choosy about vegetation near the nest. I used Spotted Towhees (Pipilo maculatus) nesting in Lesser Park in Portland, OR, as a model species for ground-nesting birds. I compared Spotted Towhees nest sites (n = 15) to both randomly-chosen sites within 10 m of the nests (n = 15; random territory sites) and other randomly-chosen locations throughout the park (n = 25; random park locations) to test whether vegetation structure and floristic composition differed. I measured (1) vegetation height and density near the nest, (2) size and spacing of trees around nests, and (3) floristic composition of vegetation near nests. I found that nest sites and both categories of random sites had dense and equal amounts of vegetation near ground level (0-20 cm above ground), but that nest sites had more vegetation between 21-40 cm and 61-100 cm above ground than random locations. However, there was no evidence that the structure of the tree community or species composition differed between nest sites and random locations.Towhees thus appear to prefer to place nests in locations with greater vertical cover directly over the nest.Nesting Microhabitat Use by a Ground-nesting Songbird 3

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Demography of a ground nesting bird in an urban system: are populations self-sustaining?

Cited by 14 publications

References 83 publications

Land‐sharing vs. land‐sparing urban development modulate predator–prey interactions in Europe

Land‐sharing vs. land‐sparing urban development modulate predator–prey interactions in Europe

Network theory and metapopulation persistence: incorporating node self‐connections

Nesting Microhabitat Use by a Ground-nesting Songbird: Strict Preferences or Random Choice?

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