High levels of habitat loss and fragmentation limit reproductive success by reducing home range size and provisioning rates of Northern saw-whet owls

Hinam, Heather L.; Clair, Colleen Cassady St.

doi:10.1016/j.biocon.2007.11.011

Cited by 125 publications

(69 citation statements)

References 93 publications

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“…Finally, we believe that the present results (directly illustrated by a recent study on the decreasing of a species of owls in Alberta, Canada [50]) have immediate practical relevance to biodiversity and conservation efforts, specially considering the long period of time necessary for cleared forests to regenerate [51]. It also adds a new ingredient to the SLOSS debate [52] and highlights the necessity of more wellplanned surveys [53] on fragmentation effects in the long run.…”

Section: Discussionsupporting

confidence: 55%

Unveiling a mechanism for species decline in fragmented habitats: fragmentation induced reduction in encounter rates

Wosniack

Santos

Pie

et al. 2014

J. R. Soc. Interface.

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Several studies have reported that fragmentation (e.g. of anthropogenic origin) of habitats often leads to a decrease in the number of species in the region. An important mechanism causing this adverse ecological impact is the change in the encounter rates (i.e. the rates at which individuals meet other organisms of the same or different species). Yet, how fragmentation can change encounter rates is poorly understood. To gain insight into the problem, here we ask how landscape fragmentation affects encounter rates when all other relevant variables remain fixed. We present strong numerical evidence that fragmentation decreases search efficiencies thus encounter rates. What is surprising is that it falls even when the global average densities of interacting organisms are held constant. In other words, fragmentation per se can reduce encounter rates. As encounter rates are fundamental for biological interactions, it can explain part of the observed diminishing in animal biodiversity. Neglecting this effect may underestimate the negative outcomes of fragmentation. Partial deforestation and roads that cut through forests, for instance, might be responsible for far greater damage than thought. Preservation policies should take into account this previously overlooked scientific fact.

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Section: Discussionsupporting

confidence: 55%

Unveiling a mechanism for species decline in fragmented habitats: fragmentation induced reduction in encounter rates

Wosniack

Santos

Pie

et al. 2014

J. R. Soc. Interface.

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“…If insufficient food is sourced, reproductive output may be reduced (Hinam & St. Clair, 2008) or the breeding process can be interrupted for the duration of the nutritional restriction (Wingfield et al, 1998).…”

Section: Fine-scale Mechanism-limited Resource Accessmentioning

confidence: 99%

Consequences of impediments to animal movements at different scales: A conceptual framework and review

Cosgrove

McWhorter

Maron

2017

Diversity and Distributions

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Aim: The persistence of animal populations depends on individuals moving successfully around a landscape, but habitat fragmentation can hinder this by reducing functional connectivity. The proximate cause of population declines in fragmented habitat is dependent on the spatial and temporal scales of movement restrictions. Location: Global.Methods: We present a conceptual framework highlighting the relationship between spatial and temporal scales, and three mechanisms through which detrimental impacts can occur when movement is disrupted in fragmented landscapes: limited resource access, restricted demographic exchange and impeded gene flow. We then review the literature to identify the proportion of studies conducted on each mechanism and whether biases existed in how often each was studied among different geographic zones or taxa. A random selection of 250 articles was classified by the mechanism, geographic region and taxon studied in each article.Results: Our conceptual framework highlighted that each of the three mechanisms tends to be characterized by movement restriction at progressively larger spatial and temporal scales. In our literature review, we found that the overwhelming majority (77%) of articles investigated impeded gene flow, and only 17% and 10% explored restricted demographic exchange and limited resource access, respectively. Work on limited resource access was disproportionately low for particular taxonomic groups, such as reptiles and amphibians.Main conclusions: Distinguishing which mechanisms are disrupted in a particular system is crucial because addressing each is likely to require a distinct conservation management response. We encourage greater focus on the less-studied mechanisms of restricted demographic exchange and limited resource access. K E Y W O R D Sdemographic rescue, food availability, genetic diversity, habitat fragmentation, habitat loss, literature review, matrix, spatial scale, structural connectivity

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“…Habitat fragmentation disrupts multiple processes over progressively larger spatiotemporal scales (Lindenmayer & Fischer 2006). Movement restrictions within a home range can limit resource access, at intermediate scales demographic exchange is impeded, while at large scales gene flow is inhibited (Lindenmayer & Fischer 2006;Hinam & St. Clair 2008). Our results suggest the home range scale of effect is the first to become apparent.…”

Section: Scale Of Woodland Effectmentioning

confidence: 56%

“…Food availability has a pronounced effect on stress levels within individuals (Maxwell et al 1992;Clinchy et al 2004;Hinam & St. Clair 2008;Barrett et al 2015). Variation in food abundance was the best predictor of GCs in the common murre (Uria aalge; Kitaysky et al 2007).…”

Section: Using Physiological Measures To Understand Mechanisms Causinmentioning

confidence: 99%

“…The concentrations of different types of white blood cells in circulation change in response to stressors; in birds, heterophil concentrations increase while lymphocytes decrease (Johnstone et al 2012). Individuals can have elevated stress levels in landscapes containing less habitat (Hinam & St. Clair 2008). This could be due to mechanisms such as food availability, predation pressure, or energetic costs.…”

Section: Introductionmentioning

confidence: 99%

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Why are woodland-dependent avian insectivore populations vulnerable to declines in highly-modified landscapes?

Cosgrove¹

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Habitat loss, fragmentation, and degradation are the leading causes of faunal population declines.Substantial effort has been invested in identifying how these landscape changes are related to population parameters. However, to effectively mitigate declines, we must understand the underlying mechanisms impacted by landscape change. Woodland-dependent avian insectivores seem particularly vulnerable, and decline at rates disproportionately greater than other foraging guilds. This pattern suggests that reduced food availability in less-wooded landscapes may be a contributing factor. However, the evidence supporting this hypothesis is sparse. I adopted a multidisciplinary approach to investigate the mechanisms driving population changes of an avian insectivore in highly-modified landscapes by integrating physiological indices with measures of prey availability and landscape structure. First, I presented a framework for conceptualising how the spatiotemporal scale of fragmentation influences the mechanisms impacting populations. I then used the eastern yellow robin (Eopsaltria australis) in the Brigalow Belt South bioregion of southern Queensland to test the importance of local and landscape factors on robin site occupancy, prey density, and robin condition. I also investigated whether an index of chronic stress could be used to predict changes to robin occurrence and identify potential threats to the population. I concluded this work by conducting a supplementary feeding experiment to determine whether food availability was causing the variation in robin condition. A pilot study conducted in the study region four years earlier found that robins were more physiologically stressed (had higher heterophil:lymphocyte ratios) in sites with less woodland in the surrounding landscape, but site occupancy was unrelated to woodland cover. Re-examining the same study system, I established that woodland cover was now the strongest predictor of iii occupancy. While woodland cover at a local scale (within 500 m) was important for robin persistence, woodland cover at a broader scale relevant to dispersal movements (within 5 km) was not. While my stress index could not accurately predict the precise locations of future extirpations, patterns of stress indices (birds were more stressed where woodland cover was lower) did foreshadow a change to the pattern of occurrence. Extirpations from sites with low levels of woodland cover were balanced by colonisations of more-wooded sites. Surprisingly, I found that arthropod prey density was greater at sites that had less surrounding woodland. This result was primarily driven by a large number of Formicidae (ants). However, Formicidae have low nutritional value and once they were excluded from the results, soil moisture, not woodland cover, became the primary determinant of arthropod density. I predicted that robin condition would be strongly associated with arthropod density, but this was not the case. Instead, robins had elevated stress levels at sites with apparently more-favourable...

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High levels of habitat loss and fragmentation limit reproductive success by reducing home range size and provisioning rates of Northern saw-whet owls

Cited by 125 publications

References 93 publications

Unveiling a mechanism for species decline in fragmented habitats: fragmentation induced reduction in encounter rates

Unveiling a mechanism for species decline in fragmented habitats: fragmentation induced reduction in encounter rates

Consequences of impediments to animal movements at different scales: A conceptual framework and review

Why are woodland-dependent avian insectivore populations vulnerable to declines in highly-modified landscapes?

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