Responses of nectar‐feeding birds to floral resources at multiple spatial scales

Schmid, Baptiste; Nottebrock, Henning; Esler, Karen J.; Pagel, Jörn; Pauw, Anton; Böhning‐Gaese, Katrin; Schurr, Frank M.; Schleuning, Matthias

doi:10.1111/ecog.01621

Cited by 44 publications

(63 citation statements)

References 67 publications

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“…Only study plots providing high abundances of floral Protea resources hosted Sugarbirds (Schmid et al. ). We thus restricted the observation of the foraging activity of Sugarbirds to the 14 study plots where Sugarbirds occupied permanent territories (Appendix : Fig.…”

Section: Methodsmentioning

confidence: 95%

A bird pollinator shows positive frequency dependence and constancy of species choice in natural plant communities

Schmid

Nottebrock

Esler

et al. 2016

Ecology

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Animal pollinators mediate reproduction of many plant species. Foraging theory suggests that animal pollinators exhibit preferences for common plant species in natural communities (positive frequency-dependent foraging) and temporary single-species specialization (flower constancy) during foraging bouts. Positive frequency dependence may favor common plant species; flower constancy may enhance conspecific pollen transfer particularly in rare plant species. Previous experimental studies suggest that avian pollinators are unlikely to exhibit these behaviors. We studied foraging behavior of Cape Sugarbirds (Promerops cafer), the main avian pollinator of many Protea species, using focal-plant and focal-bird sampling, assisted by high-resolution maps of the spatiotemporal distribution of Protea individuals and their flowering status. We found that Sugarbird's visitation preference increased with species' relative floral abundance, and that individual Sugarbirds tended to visit single species in sequence. Flower constancy during foraging bouts was significantly higher than expected from random plant-animal encounters at the scale of pollinator movements. Positive frequency dependence may favor the reproduction of abundant plant species while flower constancy may be particularly important for rare plant species. This first simultaneous study of both behaviors in a natural plant-pollinator system shows that bird pollinators exhibit both types of behavior and, in this way, possibly influence plant community structure.

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Section: Methodsmentioning

confidence: 95%

A bird pollinator shows positive frequency dependence and constancy of species choice in natural plant communities

Schmid

Nottebrock

Esler

et al. 2016

Ecology

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“…Two other plant genera ( Leucospermum and Erica ) are important nectar sources for animal pollinators in the study region. However, both genera rarely co‐flower with Protea (Collins and Rebelo , Schmid et al ). Moreover, Leucospermum only occurs at few of our study sites and Erica produces less nectar per inflorescence and stand than Protea (Turner et al , Heystek et al ).…”

Section: Methodsmentioning

confidence: 99%

“…Many Protea species depend on pollination by nectarivorous birds that are the most important pollinators of Protea (Collins and Rebelo , Schmid et al ). In particular, Cape sugarbirds Promerops cafer and orange‐breasted sunbirds Anthobaphes violacea account for more than 85% of bird pollinator visits (Schmid et al ). Both bird species in turn strongly depend on floral nectar and their abundance increases with the amount of Protea nectar sugar per hectare (Schmid et al ).…”

Section: Methodsmentioning

confidence: 99%

“…We monitored individual flowering phenologies for a subsample of 6943 plants (51 to 1245 plants per species) by counting flowering inflorescences at up to three visits during the flowering seasons in 2011 (March to December) or 2012 (March to August, Schmid et al ). For a subsample of 850 plants in the core zones (4 to 80 plants per species; average 45 plants per species), we harvested two inflorescences, measured their size and the proportion of open florets, and extracted their nectar by centrifugation (Armstrong and Paton ).…”

Section: Methodsmentioning

confidence: 99%

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Sugar landscapes and pollinator‐mediated interactions in plant communities

et al. 2016

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Pollinator‐mediated interactions between plants can play an important role for the dynamics of plant communities. Pollination services depend on the abundance and the foraging behaviour of pollinators, which in turn respond to the availability and distribution of floral resources (notably nectar sugar). However, it is still insufficiently understood how the ‘sugar landscapes’ provided by flowering plant communities shape pollinator‐mediated interactions between multiple plant species and across different spatial scales. A better understanding of pollinator‐mediated interactions requires an integrative approach that quantifies different aspects of sugar landscapes and investigates their relative importance for pollinator behaviour and plant reproductive success. In this study, we quantified such sugar landscapes from individual‐based maps of Protea shrub communities in the Cape Floristic Region, South Africa. The 27 study sites of 4 ha each jointly comprise 127 993 individuals of 19 species. We analysed how rates of visitation by key bird pollinators and the seed set of plants respond to different aspects of sugar landscapes: the distribution of nectar sugar amounts, as well as their quality, taxonomic purity and phenology. We found that pollinator visitation rates strongly depended on phenological variation of site‐scale sugar amounts. The seed set of focal plants increased with nectar sugar amounts of conspecific neighbours and with site‐scale sugar amounts. Seed set increased particularly strongly if site‐scale sugar amounts were provided by plants that offer less sugar per inflorescence. These combined effects of the amount, quality, purity and phenological variation of nectar sugar show that nectar sugar is a common interaction currency that determines how multiple plant species interact via shared pollinators. The responses of pollinator‐mediated interactions to different aspects of this interaction currency alter conditions for species coexistence in Protea communities and may cause community‐level Allee effects that promote extinction cascades.

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“…; Hegland ; Schmid et al . ). Empirical studies of the scales at which pollinators respond to floral densities (e.g.…”

Section: Conceptual Modelmentioning

confidence: 97%

Effects of fire on pollinators and pollination

Brown

York

Christie

et al. 2016

Journal of Applied Ecology

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Summary Increased incidence of landscape fire and pollinator declines with co‐extinctions of dependent plant species are both globally significant. Fire can alter species distributions, but its effects on plant–pollinator interactions are poorly understood so its present and future role in coupled plant–pollinator declines cannot be assessed. We develop a conceptual model of fire effects on plant–pollinator interactions. We review the empirical literature in the context of this model to identify important knowledge gaps regarding the processes underlying these effects and the phenotypic traits of flowering plants and pollinators mediating these effects. Fire generates, and plant–pollinator interactions respond to, heterogeneity at multiple spatial scales. There is evidence of local‐scale fire effects on these interactions, but landscape‐scale effects are poorly understood. Nest location and floral resource utilization primarily mediate pollinator survival during and after fire. Voltinism and mobility traits are potentially important, but poorly studied. Plant traits mediating flowering responses to fire include growth form, phenology and potentially bud location, seasonal changes in bud exposure and response to bud damage. Synthesis and applications. We suggest management actions and an agenda for future research to fill knowledge gaps currently inhibiting predictions of fire effects on plant–pollinator interactions. Fire regimes promoting floral diversity at local scales provide a surrogate means of managing pollinators and pollination while empirical research continues. Above‐ground nesting, univoltine pollinators may be particularly vulnerable under expected fire regime changes. Improved knowledge of traits mediating the exploitation of landscape heterogeneity could be used to enhance the persistence of these species. Ultimately, our conceptual framework could be used as a basis for understanding fire effects on aggregate network properties to inform fire management strategies buffering plant–pollinator networks against secondary species extinctions.

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Responses of nectar‐feeding birds to floral resources at multiple spatial scales

Cited by 44 publications

References 67 publications

A bird pollinator shows positive frequency dependence and constancy of species choice in natural plant communities

A bird pollinator shows positive frequency dependence and constancy of species choice in natural plant communities

Sugar landscapes and pollinator‐mediated interactions in plant communities

Effects of fire on pollinators and pollination

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