Local site variation in stopover physiology of migrating songbirds near the south shore of Lake Ontario is linked to fruit availability and quality.

Susan B Smith,Charmaine R Merchant,Amie F Sankoh,Allyson C Miller

doi:10.1093/conphys/cov036

Susan B Smith, Charmaine R Merchant + Show 2 more

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https://doi.org/10.1093/conphys/cov036

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Journal: Conservation physiology	Publication Date: Jan 1, 2015
Citations: 67	License type: cc-by

Affiliation: Rochester Institute of Technology

Abstract

Birds that migrate long distances between breeding and wintering grounds are challenged to find adequate stopover sites that can provide a high-quality source of nutrition in order to refuel quickly and continue on their migratory journeys. Wild fruits are a well-documented component in the diets of many passerines during autumn migration. Thus, fruit availability and the proliferation of shrubs that bear low-quality fruits at important stopover sites may dictate the quality of food resources available for refuelling birds and present a conservation concern. We profiled plasma metabolites of two migratory passerine species at two different stopover sites near the south shore of Lake Ontario during the peak of autumn migration. We also measured diversity, availability and nutritional quality of fruits present at these sites. Site explained most of the variation in plasma triglyceride for both bird species, but was less important than other confounding variables for explaining concentrations of plasma β-hydroxybutyrate and plasma uric acid concentrations. Site differences in fat deposition, as indicated by plasma triglyceride, may in part be explained by the large differences in diversity and availability of high-quality fruits between the two sites. Our results suggest that abundant, lipid-rich native fruits with high-energy density are associated with increased fat deposition during autumn stopovers for some species, although other factors, such as proximity to the Lake Ontario shoreline and the opportunities to refuel in the surrounding landscape, are likely to play a role in stopover site use by birds. It is possible that local site characteristics that influence growing conditions may impact the quality of fruits produced by a plant species, altering the availability of critical nutrients for avian consumers.

Highlights

The extreme energetic demands of long-distance migration make it a challenging and vulnerable period for birds marked by high mortality rates and extreme physiological stress (Sillett and Holmes, 2002; Klaassen et al, 2014)
Cite as: Smith SB, Miller AC, Merchant CR, Sankoh AF (2015) Local site variation in stopover physiology of migrating songbirds near the south shore of Lake Ontario is linked to fruit availability and quality
We investigated the relative importance of potential covariates that may affect circulating plasma metabolite concentrations in the captured birds using Akaike information criterion (AIC) modelling procedures as applied by Smith and McWilliams (2010) and following Burnham and Anderson (2002)

Summary

Introduction

The extreme energetic demands of long-distance migration make it a challenging and vulnerable period for birds marked by high mortality rates and extreme physiological stress (Sillett and Holmes, 2002; Klaassen et al, 2014). Given that dietary macronutrient intake may affect fattening of songbirds and can be reflected in plasma metabolite profiles in captivity (Smith and McWilliams, 2009), studies that relate the physiology of free-living birds with the quality of available fruit resources may provide valuable insight into their potential refuelling performance during stopovers. We used plasma metabolite profiles to correlate patterns of physiological refuelling with fruit resources in two passerine species, blackpoll warbler (Setophaga striata) and white-throated sparrow (Zonotrichia albicollis), captured at two sites with different landscape and vegetative characteristics near the south shore of Lake Ontario This area of the Great Lakes basin region serves as an important stopover location for thousands of passerines each spring and autumn (Bonter et al, 2009) and represents a region of important conservation interest in terms of maintaining suitable habitat that can support these large numbers of migrants each year. We expected that birds captured where high-quality (e.g. high-fat and energy-dense) native fruit abundance is high would have higher plasma triglyceride, lower β-hydroxybutyrate and lower uric acid concentrations than birds captured at a site where fruit resources are less available and may be of lower nutritional quality during autumn stopovers

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