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

Abstract

Fruits are important resources for autumn migrating passerines and we show that site-related patterns in the physiology of two species, as measured by plasma metabolite profiling, are associated with local variation in fruit availability and biochemical composition. Results suggest potentially important physiological consequences of both fruit abundance and their nutritional quality for refueling birds at critical stopover sites.

Higher rates of prebreeding condition gain positively impacts clutch size: A mechanistic test of the condition‐dependent individual optimization model

“…Although females can theoretically benefit from fattening quickly, not all females appear to do so, which may stem from several factors, including: (a) physiological/behavioural capability to gain in condition, (b) resource availability and (c) mate quality. First, individuals demonstrate a substantial amount of variation in foraging behaviour (Rigou & Guillemette, 2010;Woo, Elliott, Davidson, Gaston, & Davoren, 2008), prey selection (Smith, Miller, Merchant, & Sankoh, 2015), metabolic or physiological limitations in mass gain (Cornelius, Boswell, Jenni-Eiermann, Breuner, & Ramenofsky, 2013;Dierschke, Delingat, & Schmaljohann, 2003), and digestion or assimilation efficiency (Bond & Esler, 2006;McWilliams & Carasov, 2001), many of which have been shown to change with age (Angelier, Schaffer, Weimerskirch, & Chastel, 2006;Desrochers, 1993;Elliott et al, 2014;Zimmer, Ropert-Coudert, Kato, Ancel, & Chiaradi, 2011). Although our current techniques for ageing (e.g., Carney, 1992) in our colony are unreliable (H. G. Gilchrist, unpublished data), and instances of recapturing known-age individuals are rare, higher fattening females may represent an age class that is more experienced in foraging, reproducing and more invested in reproduction (Froy, Phillips, Wood, Nussey, & Lewis, 2013;Martin, 1995).…”

Oxidative balance in birds: an atoms‐to‐organisms‐to‐ecology primer for ornithologists

“…On Block Island, a stopover site for millions of songbirds each autumn off the coast of Rhode Island, USA, arrowwood viburnum ( Viburnum dentatum ) fruits are highly prized by birds, presumably due to their unique combination of abundant, high‐quality fats, and both fat‐ and water‐soluble antioxidants (Smith et al. , , Alan et al. , Bolser et al.…”

“…Building fat stores of good quality in a short time is necessary for animals that must burn large amounts of high-energy fuel to complete their migrations (McWilliams et al 2004). Studies show that fruit-rich stopover habitats produce birds with higher fattening signatures (circulating triglycerides) in their blood than similar, but fruit-poor, habitats (Smith and McWilliams 2010). However, birds may also consume fruits for additional nutritional benefits.…”

“…Research has shown that birds are able to discriminate among fruits based on their color, and hence anthocyanin content, and prefer anthocyanin-enriched foods when presented a choice (Schaefer et al 2008). On Block Island, a stopover site for millions of songbirds each autumn off the coast of Rhode Island, USA, arrowwood viburnum (Viburnum dentatum) fruits are highly prized by birds, presumably due to their unique combination of abundant, highquality fats, and both fat-and water-soluble antioxidants (Smith et al 2007, 2015, Alan et al 2013, Bolser et al 2013. Influxes of migratory birds to Block Island during peaks in fall migration are regularly followed by increases in rates of arrowwood removal (Smith and McWilliams 2014a).…”

“…The mechanisms underlying this phenomenon have yet to be investigated. Particularly revealing would be the studies that manipulate fat condition of migrants (e.g., Smith and McWilliams 2014b) and/or track fattening rates in birds using plasma metabolites such as triglycerides (e.g., see Smith and McWilliams 2010), and then also measure antioxidant capacity, damage, or particular antioxidants (e.g., Pérez-Rodríguez et al 2015). Partitioning blood sampling to focus on dawn, midday, and evening feeding, when hungers for different requirements are expected to differ (e.g., Beaulieu and Schaefer 2014), would also be most illuminating.…”