Diel variation in corticosterone and departure decision making in migrating birds

Eikenaar, Cas; Schäfer, Jana; Hessler, Sven; Packmor, Florian; Schmaljohann, Heiko

doi:10.1016/j.yhbeh.2020.104746

Cited by 20 publications

(15 citation statements)

References 48 publications

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“…One possibility is that CORT does not play a mechanistic role in siskin movements in response to food reductions, or that downstream processes, such as receptor levels, are responsible for their migratory behaviors (but see Watts et al, 2019). However, across the avian literature, CORT is correlated with activity during the processes of fledging (Sprague and Breuner, 2010), dispersal (Belthoff and Dufty, 1998), obligate migration (Lõhmus et al, 2003;Eikenaar et al, 2020) and escape behavior (Breuner et al, 1998;Breuner and Hahn, 2003). We therefore think it more likely that we did not observe a relationship between CORT and activity as a function of experimental design rather than biology.…”

Section: Discussionmentioning

confidence: 99%

“…First, elevated levels within the baseline range of CORT support the increased energetic demands of predictable challenges and life history stage transitions (Wada, 2008), such as hatching and parturition (Challis, 2000;McLean and Smith, 2001), fledging and dispersal (Heath, 1997;Belthoff and Dufty, 1998;Sprague and Breuner, 2010), and, importantly, obligate migratory departure (Lõhmus et al, 2003;Eikenaar et al, 2017Eikenaar et al, , 2020. In obligate migrants, CORT stimulates fat deposition and mobilizes protein for fuel (Gray et al, 1990).…”

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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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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“…We temporarily caged birds, pulsed these with a high urge to migrate 6 h before sunset, i.e. before they make their daily departure decisions [41], attached radio-tags and released them on days with weather conditions favourable for migration. The local [42] and the German Bight-encompassing array [43] of digital radioreceiving stations (Motus Wildlife Tracking System, [44]) automatically recorded the response to the treatment.…”

Section: Introductionmentioning

confidence: 99%

No apparent effect of a magnetic pulse on free-flight behaviour in northern wheatears ( Oenanthe oenanthe ) at a stopover site

Karwinkel

Winklhofer

Christoph

et al. 2022

J. R. Soc. Interface.

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Naïve migrants reach their wintering grounds following a clock-and-compass strategy. During these inaugural migrations, birds internalise, among others, cues from the Earth's magnetic field to create a geomagnetic map, with which they navigate to destinations familiar to them on subsequent migrations. Geomagnetic map cues are thought to be sensed by a magnetic-particle-based receptor, which can be specifically affected by a magnetic pulse. Indeed, the orientation of experienced but not naïve birds was compromised after magnetic pulsing, indicating geomagnetic map use. Little is known about the importance of this putative magnetoreceptor for navigation and decision-making in free-flying migrants. Therefore, we studied in unprecedented detail how a magnetic pulse would affect departure probability, nocturnal departure timing, departure direction and consistency in flight direction over 50–100 km in experienced and naïve long-distant migrant songbirds using a large-scale radio-tracking system. Contrary to our expectations and despite a high sample size ( n total = 137) for a free-flight study, we found no significant after-effect of the magnetic pulse on the migratory traits, suggesting the geomagnetic map is not essential for the intermediate autumn migration phase. These findings warrant re-thinking about perception and use of geomagnetic maps for migratory decisions within a sensory and ecological context.

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“…Yet another possibility is that extended activity is a by‐product of hormonal changes, which regulate preparatory activities at seasonal and diel scales (Wingfield 2008, Ramenofsky and Wingfield 2017). Corticosterone is a likely candidate for such a hormone, as higher levels of plasma corticosterone are associated with a higher probability of departure, elevated nocturnal restlessness and earlier departure time in migratory songbirds (Lõhmus et al 2003, Eikenaar et al 2014, 2017, 2018a, 2018b, 2020). Finally, given the correlational nature of the data, we cannot rule out that changes in diel schedules increase the probability of departure that evening, rather than vice versa.…”

Section: Discussionmentioning

confidence: 99%

Evening locomotor activity during stopover differs on pre‐departure and departure days in free‐living songbirds

Morbey

Beauchamp

Bonner

et al. 2020

Journal of Avian Biology

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The length of time songbirds remain at a migratory stopover site is likely regulated by a daily stay/go decision informed by fat stores and weather conditions, but the finerscale timing of this decision and associated pre-departure behaviours are still poorly understood. Using automated radiotelemetry of free-living songbirds captured at a migratory stopover site in spring, we tested whether individuals change their locomotor activity near sunset on their migratory departure day compared to their non-departure days. To do so, we extracted precise transition times between diurnal activity and nocturnal inactivity, which always precedes departure, using changepoint analysis of radio transmission signal strength. Among four warbler species, individuals extended diurnal activity by 8-19 min towards sunset on their departure day. In three species, this extension was significant. In contrast, white-throated sparrows significantly shortened diurnal activity on their departure day by 13 min, also towards sunset. This is the first study to detect and quantify a change in locomotor activity schedule on departure versus non-departure days in free-living songbirds, and is consistent with the hypothesis that birds engage in pre-departure preparatory behaviours near sunset.

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Diel variation in corticosterone and departure decision making in migrating birds

Cited by 20 publications

References 48 publications

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

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

No apparent effect of a magnetic pulse on free-flight behaviour in northern wheatears ( Oenanthe oenanthe ) at a stopover site

Evening locomotor activity during stopover differs on pre‐departure and departure days in free‐living songbirds

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