Modeling a cross-ecosystem subsidy: forest songbird response to emergent aquatic insects

Schilke, Paul R; Bartrons, Mireia; Gorzo, Jessica M.; Zanden, M. Jake Vander; Gratton, Claudio; Howe, Robert W.; Pidgeon, Anna M.

doi:10.1007/s10980-020-01038-0

Cited by 9 publications

(11 citation statements)

References 43 publications

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“…However, habitat generalists must also possess the foraging flexibility to take advantage of aquatic subsidies. For example, while avian aerial insectivore abundance is positively associated with emergent aquatic insects, suggesting that they regularly use such prey, species from other more specialized avian feeding guilds (e.g., bark-probers) do not show the same relationships with emergent insects (Schilke et al, 2020). This is unsurprising because aerial insectivores include a diversity of flying insects from several different aquatic orders in their diet (Twining et al, 2018b), while feeding modes like bark-probing or ground-foraging preclude the capture of flying emergent insect prey (Schilke et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Use of Fatty Acids From Aquatic Prey Varies With Foraging Strategy

et al. 2021

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Across ecosystems, resources vary in their nutritional composition and thus their dietary value to consumers. Animals can either access organic compounds, such as fatty acids, directly from diet or through internal biosynthesis, and the extent to which they use these two alternatives likely varies based on the availability of such compounds across the nutritional landscape. Cross-ecosystem subsidies of important dietary nutrients, like omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA), may provide consumers with the opportunity to relax the demands of synthesis and rely upon dietary flexibility rather than internal metabolic processes. Here, we examined how dietary flexibility and distance from a lake influenced the degree to which generalist insectivores relied upon dietary n-3 LC-PUFA from emergent aquatic insects versus n-3 LC-PUFA synthesized from precursor compounds found in terrestrial insects. We used bulk and compound-specific stable isotope analyses to understand spider and insectivorous bird (Blue Tit; Cyanistes caeruleus) reliance on aquatic and terrestrial resources, including dietary PUFA sources, along a riparian to upland gradient from a lake. We simultaneously investigated n-3 LC-PUFA synthesis ability in nestlings using 13C fatty acid labeling. We found that riparian spiders took advantage of emergent aquatic insect subsidies, deriving their overall diet and their n-3 PUFA from aquatic resources whereas nestling birds at all distances and upland spiders relied upon terrestrial resources, including PUFA. Our 13C labeling experiment demonstrated that nestling tits were able to synthesize the n-3 LC-PUFA docosahexaenoic acid from the dietary precursor α-linolenic acid, suggesting that they are not limited by aquatic resources to satisfy their LC-PUFA requirements. Overall, this study suggests that habitat generalist insectivores vary in the degree to which they can shift diet to take advantage of high-quality aquatic resources depending upon both their foraging flexibility and internal synthesis capacity.

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Section: Introductionmentioning

confidence: 99%

Use of Fatty Acids From Aquatic Prey Varies With Foraging Strategy

et al. 2021

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“…While our analysis of emergent aquatic insects indicated strong influences of land use and water quality in streams, the relationships between bird abundances and emergent insects were more nuanced and species-specific, especially with respect to the emergent insect metric we generated in this analysis and the majority of bird species (Figures 3A, 4A). This finding is in contrast to evidence that indicates many aerial insectivorous birds, and to some degree, other insectivorous birds, are highly reliant on aquatic-to-terrestrial subsidies (e.g., Kautza and Sullivan, 2016;Schilke et al, 2020;Sullivan et al, 2021). Our ability to detect this reliance with publicly available biomonitoring data was potentially hampered in several ways.…”

Section: Detecting Cross-boundary Effects Of Poor Water Quality Remaimentioning

confidence: 66%

“…Our ability to detect this reliance with publicly available biomonitoring data was potentially hampered in several ways. For example, the relationships between emergent insects and aerial insectivorous birds are diffuse in both time and space, such that the timing of the Breeding Bird Survey (early summer) and the precise locations of monitoring routes may have occurred outside the direct influence of emerging insects from nearby streams or lakes, i.e., the majority (>70%) of emergent insect deposition from streams and lakes generally falls within 100 m of the waterbody (Gratton and Vander Zanden, 2009;Muehlbauer et al, 2014;Schilke et al, 2020). Beyond these mismatches inherent to the monitoring data sets, differential access to water and habitat use among riparian-to-upland obligate species, detrimental effects carried over from nonbreeding habitats, or landscape topography (e.g., ravines vs. lowelevation streams) are all expected to affect the foraging ecology of aerial insectivores.…”

Section: Detecting Cross-boundary Effects Of Poor Water Quality Remaimentioning

confidence: 99%

“…Available open-access macroinvertebrate data with broad spatial coverage are limited in temporal scope; additional years of emergent insect data could improve future analyses. Additionally, future work that makes concerted efforts to achieve tighter spatial and temporal synchronization between aerial insectivorous birds and their insect prey at watershed (and larger) scales (e.g., Schilke et al, 2020) will be an important step in further exploring the links between broad-scale water quality, emergent insects, and bird diets, fitness, and reproductive success (e.g., Twining et al, 2018).…”

Section: Consequences Of Losing Aquatic-terrestrial Connections Via Imentioning

confidence: 99%

“…Numerous explanations for aerial insectivore declines have been proposed, including nesting and over-wintering habitat loss, airborne pollutants, widespread pesticide use associated with insect-population collapse, climatic shifts, and land-use change (Hallmann et al, 2014(Hallmann et al, , 2017Sullivan et al, 2021); many of these causes are likely to be acting in concert (Spiller and Dettmers, 2019). Whereas the precise causes for declines in several aerial insectivorous birds remain unknown, a shared reliance on flying insects and population declines across species within the foraging guild implicates decreasing or fluctuating insect food quantity or quality (Paquette et al, 2013;Twining et al, 2018;Schilke et al, 2020; but see Imlay et al, 2017). Although aerial insectivores feed on a combination of terrestrial and aquatic insects, many species exhibit a nutritional reliance on subsidies of aquatic emergent insect prey (Gray, 1993;Iwata et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

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Conservation Across Aquatic-Terrestrial Boundaries: Linking Continental-Scale Water Quality to Emergent Aquatic Insects and Declining Aerial Insectivorous Birds

Manning

Sullivan

2021

Front. Ecol. Evol.

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Larval aquatic insects are used to assess water quality, but less attention is paid to their adult, terrestrial life stage, which is an important food resource for declining aerial insectivorous birds. We used open-access water-quality, aquatic-invertebrate, and bird-survey data to study how impaired water quality can emanate from streams and lakes through changes in aquatic insect communities across the contiguous United States. Emergent insect relative abundance was highest across the West, in northern New England, and the Carolinas in streams, and highest near the Great Lakes, parts of the Southwest, and northern New England for lakes. Emergent insects declined with sedimentation, roads, and elevated ammonium concentrations in streams, but not lakes. The odds that a given taxon would be non-emergent increased by up to 2.0× as a function of pollution tolerance, underscoring the sensitivity of emergent aquatic insects to water-quality impairment. However, relationships between bird populations and emergent insects were generally weak for both streams and lakes. For streams, we observed the strongest positive relationships for a mixture of upland and riparian aerial insectivorous birds such as Western Wood-Pewee, Olive-sided Flycatcher, and Acadian Flycatcher and the strongest negative association for Purple Martin. Different avian insectivores responded to emergent insect abundances in lakes (e.g., Barn Swallow, Chimney Swift, Eastern Wood-Pewee, Common Nighthawk). In both streams and lakes, we observed stronger, but opposing, relationships between several aerial insectivores and the relative abundance of sensitive insect orders (E)phemeroptera, (P)lecoptera, and (T)richoptera (positive), and pollution tolerant individuals (negative). Overall, our findings indicate that emergent insects are negatively correlated with pollution tolerance, suggesting a large-scale loss of this nutritional subsidy to terrestrial environments from impaired aquatic ecosystems. While some bird populations tracked scarcities of emergent aquatic insects, especially EPT taxa, responses varied among species, suggesting that unique habitat and foraging behaviors likely complicated these relationships. Strengthening spatial and temporal concordance between emergent-insect and bird-survey data will improve our ability to interpret species-level responses over time. Thus, our analysis highlights the need for developing conservation and biomonitoring strategies that consider the cross-ecosystem effects of water quality declines for threatened insectivorous avifauna and other terrestrial wildlife.

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Marine subsidy promotes spatial and dietary niche variation in an omnivore, the Keen’s mouse (Peromyscus keeni)

Davidson

Starzomski

El‐Sabaawi

et al. 2021

Ecology and Evolution

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Marine‐derived resource subsidies can generate intrapopulation variation in the behaviors and diets of terrestrial consumers. How omnivores respond, given their multiple trophic interactions, is not well understood. We sampled mice (Peromyscus keeni) and their food sources at five sites on three islands of the Central Coast of British Columbia, Canada, to test predictions regarding variation in the spatial behavior and consumption of marine‐subsidized foods among individuals. About 50% of detections (n = 27 recaptures) occurred at traps closest to shoreline (25 m), with capture frequencies declining significantly inland (up to 200 m). Stable isotope signatures (δ13C and δ15N), particularly δ15N, in plant foods, forest arthropod prey, and mouse feces were significantly enriched near shorelines compared with inland, while δ13C patterns were more variable. Bayesian isotope mixing models applied to isotope values in mouse hair indicated that over one‐third (35–37%) of diet was comprised of beach‐dwelling arthropods, a marine‐derived food source. Males were more abundant near the shoreline than females and consumed more marine‐derived prey, regardless of reproductive status or availability of other food sources. Our results identify how multiple pathways of marine nutrient transfer can subsidize terrestrial omnivores and how subsets of recipient populations can show variation in spatial and dietary response.

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Modeling a cross-ecosystem subsidy: forest songbird response to emergent aquatic insects

Cited by 9 publications

References 43 publications

Use of Fatty Acids From Aquatic Prey Varies With Foraging Strategy

Use of Fatty Acids From Aquatic Prey Varies With Foraging Strategy

Conservation Across Aquatic-Terrestrial Boundaries: Linking Continental-Scale Water Quality to Emergent Aquatic Insects and Declining Aerial Insectivorous Birds

Marine subsidy promotes spatial and dietary niche variation in an omnivore, the Keen’s mouse (Peromyscus keeni)

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