Declining food availability, corticosterone, and migratory response in a nomadic, irruptive migrant

Robart, Ashley R.; Morado, Melissa I.; Watts, Heather E.

doi:10.1016/j.yhbeh.2019.02.007

Cited by 16 publications

(15 citation statements)

References 66 publications

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“…There can be several reasons that are not mutually exclusive, why frugivorous birds delay their autumn migration. First, birds may try to minimise the costs of migration within the constraints set by food availability (Tyrväinen 1975 ; Robart et al 2019 ). Second, wintering as close as possible may enable earlier spring migration to acquire better quality territory and breeding mate, but this idea needs more research.…”

Section: Discussionmentioning

confidence: 99%

The impact of tree crops and temperature on the timing of frugivorous bird migration

et al. 2020

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Migration has evolved to tackle temporal changes in availability of resources. Climate change has been shown to affect the migration dates of species, which raises the question of whether the variation in the timing of migration is climate or resource dependent? The relative importance of temperature and availability of food as drivers of migration behaviour during both spring and autumn seasons has been poorly studied. Here, we investigated these patterns in frugivorous and granivorous birds (hereafter frugivorous) that are assumed to postpone their autumn migration when there is plenty of food available, which may also advance upcoming spring migration. On the other hand, especially spring migration dates have been negatively connected with increasing temperatures. We tested whether the autumn and spring migration dates of eleven common frugivorous birds depended on the crop size of trees or ambient temperatures using 29 years of data in Finland. The increased crop sizes of trees delayed autumn migration dates; whereas, autumn temperature did not show a significant connection. We also observed a temporal trend towards later departure. Increasing temperature and crop sizes advanced spring arrival dates. Our results support the hypothesis that the timing of autumn migration in the frugivorous birds depends on the availability of food and is weakly connected with the variation in temperature. Importantly, crop size can have carry-over effects and affect the timing of spring arrival possibly because birds have overwintered closer to the breeding grounds after an abundant crop year.

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Section: Discussionmentioning

confidence: 99%

The impact of tree crops and temperature on the timing of frugivorous bird migration

et al. 2020

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“…In summary, pine siskins exposed to experimental declines in food supply in autumn do not show preparative fueling, they are not sensitive to declines in food availability but rather its absence, and low food availability reduces body condition, increases CORT levels and initiates increased activity. Under a different food manipulation protocol, Robart et al (2019) also concluded that siskins do not prepare for autumn movements. In their study, captive siskins in the spring and autumn experienced a reduction in food quality and then a 25% reduction in food quantity.…”

Section: Discussionmentioning

confidence: 99%

“…Food-restricted birds showed increased baseline CORT and decreased body condition, and in the spring (but not the autumn), exhibited increases in activity. Robart et al (2019) suggested that siskins are less behaviorally sensitive to changes in food availability in the autumn, or that their lower body condition in the autumn limits any increases in energy expenditure and activity. Our results are not consistent with these possibilities.…”

Section: Discussionmentioning

confidence: 99%

“…However, low food availability may still be necessary to initiate departure in these species. Captive red crossbills (Loxia curvirostra) and pine siskins (Spinus pinus) experiencing food restriction increase activity in winter and spring but not autumn (Cornelius et al, 2010;Robart et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

“…Captive red crossbills and pine siskins exposed to sudden reductions in food quantity or quality have shown decreases in body condition, increases in CORT and, at certain times of year, increases in activity (Cornelius et al, 2010;Robart et al, 2019). Here, we slowly reduced food availability over 16 days to more explicitly test the sensitivity of birds' responses to changesrather than simply reductionsin food availability.…”

Section: Introductionmentioning

confidence: 99%

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Physiology and behavior under food limitation support an escape, not preparative, response in the nomadic Pine Siskin (Spinus pinus)

DeSimone

Tobalske

Breuner

2020

Journal of Experimental Biology

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Migration allows animals to use resources that are variable in time and/or space, with different migratory strategies depending on the predictability of resource variation. When food varies seasonally, obligate migrants anticipate and prepare for migration. In contrast, facultative migrants, whose movements are unpredictable in timing and destination, may either prepare for migration or escape when resources are depleted. We propose and test two alternative hypotheses regarding the behavioral and physiological responses of facultative migrants to declining food availability. (1) The Prepare Hypothesis predicts that facultative migrants prepare for departure by increasing fuel stores in response to declining food availability, and elevations of baseline corticosterone (CORT) facilitate increased activity. (2) The Escape Hypothesis predicts that facultative migrants do not prepare for departure, body condition declines as food availability declines, and stress-induced levels of CORT induce escape behavior when both energetic condition and food resources are low. We conducted a 16-day experiment, measuring body composition (using Quantitative Magnetic Resonance), activity (using force perches), and baseline CORT in Pine Siskins (Spinus pinus) given ad libitum food or a slow decline, fast decline, or randomly changing amount of food. Our results support the Escape Hypothesis: body condition declined as food declined, decreases in body and fat mass were associated with increases in baseline CORT, and activity increased only when food availability was low. This work suggests that facultative migration in autumn allows birds to escape low resource areas and that the underlying physiological mechanisms differ from those driving both seasonal, obligate migrations and spring nomadic movements.

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A Critical Review of Bioaccumulation and Biotransformation of Organic Chemicals in Birds

Kuo

Rattner

Marteinson

et al. 2022

Reviews Env.Contamination (formerly:Residue Reviews)

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A literature review of bioaccumulation and biotransformation of organic chemicals in birds was undertaken, aiming to support scoping and prioritization of future research. The objectives were to characterize available bioaccumulation/biotransformation data, identify knowledge gaps, determine how extant data can be used, and explore the strategy and steps forward. An intermediate approach balanced between expediency and rigor was taken given the vastness of the literature. Following a critical review of > 500 peer-reviewed studies, > 25,000 data entries and 2 million information bytes were compiled on > 700 organic compounds for ~ 320 wild species and 60 domestic breeds of birds. These data were organized into themed databases on bioaccumulation and biotransformation, field survey, microsomal enzyme activity, metabolic pathway, and bird taxonomy and diet. Significant data gaps were identified in all databases at multiple levels. Biotransformation characterization was largely fragmented over metabolite/pathway identification and characterization of enzyme activity or biotransformation kinetics. Limited biotransformation kinetic data constrained development of an avian biotransformation model. A substantial shortage of in vivo biotransformation kinetics has been observed as most reported rate constants were derived in vitro. No metric comprehensively captured all key contaminant classes or chemical groups to support broad-scope modeling of bioaccumulation or biotransformation. However, metrics such as biota-feed accumulation factor, maximum transfer factor, and total elimination rate constant were more readily usable for modeling or benchmarking than other reviewed parameters. Analysis demonstrated the lack of bioaccumulation/biotransformation characterization of shorebirds, seabirds, and raptors. In the study of bioaccumulation and biotransformation of organic chemicals in birds, this review revealed the need for greater chemical and avian species diversity, chemical measurements in environmental media, basic biometrics and exposure conditions, multiple tissues/matrices sampling, and further exploration on biotransformation. Limitations of classical bioaccumulation metrics and current research strategies used in bird studies were also discussed. Forward-looking research strategies were proposed: adopting a chemical roadmap for future investigations, integrating existing biomonitoring data, gap-filling with non-testing approaches, improving data reporting practices, expanding field sampling scopes, bridging existing models and theories, exploring biotransformation via avian genomics, and establishing an online data repository.

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Declining food availability, corticosterone, and migratory response in a nomadic, irruptive migrant

Cited by 16 publications

References 66 publications

The impact of tree crops and temperature on the timing of frugivorous bird migration

The impact of tree crops and temperature on the timing of frugivorous bird migration

Physiology and behavior under food limitation support an escape, not preparative, response in the nomadic Pine Siskin (Spinus pinus)

A Critical Review of Bioaccumulation and Biotransformation of Organic Chemicals in Birds

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