Corticosterone and migratory fueling in Northern wheatears facing different barrier crossings

Eikenaar, Cas; Fritzsch, Anna; Bairlein, Franz

doi:10.1016/j.ygcen.2013.02.042

Cited by 31 publications

(25 citation statements)

References 38 publications

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“…The reason we think so is that, in terms of fuel load of leucorhoa wheatears, the current dataset is something of an outlier. In our dataset, all but one leucorhoa individuals had a fuel load below 0.2, whereas in other study years on Helgoland, a considerable proportion (> 25%) of leucorhoa wheatears had fuel loads above this value (Delingat et al , Eikenaar et al ). Possibly because of the different migratory challenges the subspecies face (yes/no barrier crossing), leucorhoa wheatears seem to always travel with higher fuel loads than oenanthe wheatears (Delingat et al ).…”

Section: Discussioncontrasting

confidence: 51%

Faster spring migration in northern wheatears is not explained by an endogenous seasonal difference in refueling rates

Eikenaar

Tsvey²,

Schmaljohann

2015

Journal of Avian Biology

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A widespread phenomenon in migrant birds is that they travel faster in spring than in autumn. During migration birds spend most time at stopover sites and, correspondingly, the faster spring migration is mainly explained by shorter stopovers in spring than autumn. Because a main purpose of stopovers is to replenish the fuel used in flight, a higher rate of fuel deposition (FDR) in spring is thought to explain the shorter stopovers and hence shorter total duration of migration in spring. Critical migratory processes, including the onset and extent of pre‐migratory fueling, are endogenously regulated. It is therefore not unlikely that refueling at stopover sites is, at least partly, also under endogenous control. We here tested whether there is an endogenous seasonal difference in food intake and FDR, which could contribute to shorter stopovers and hence faster migration in spring. We measured daily food intake and daily FDR in two subspecies of the northern wheatear Oenanthe oenanthe, temporarily confined at stopover under identical constant indoor conditions in spring and autumn. The two wheatear subspecies differed markedly in absolute food intake and FDR. Within subspecies, however, food intake and FDR did not differ between spring and autumn, indicating that faster spring migration in northern wheatears is not explained by an endogenously controlled seasonal difference in birds’ motivation to refuel. To further substantiate this claim, similar measurements should be taken at other locations along northern wheatears’ migration routes. Comparable experiments in other species could test the generality of our results.

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Section: Discussioncontrasting

confidence: 51%

Faster spring migration in northern wheatears is not explained by an endogenous seasonal difference in refueling rates

Eikenaar

Tsvey²,

Schmaljohann

2015

Journal of Avian Biology

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“…However, studies that have reported positive relationships between baseline CORT and pre-migratory hyperphagia and fattening have predominately been correlative (Fudickar et al, 2013;Holberton, 1999;Holberton et al, 2008;Holberton et al, 1996;Long and Holberton, 2004), while the majority of manipulative studies have found that neither CORT nor CORT-agonist administration increases hyperphagia in birds (Astheimer et al, 1992;Gray et al, 1990;Holberton et al, 2007;Saldanha et al, 2000;Simon, 1989 but see Landys et al, 2004b;Lohmus et al, 2006). Furthermore, studies in Northern wheatears (Oenanthe oenanthe) during migratory stopovers found negative correlations between baseline CORT levels and refueling rates (Eikenaar et al, 2014;Eikenaar et al, 2013). Eikenaar et al (2013) suggested that since CORT levels rapidly decrease after arrival to stopover sites and then steadily increase as birds put on more fat, CORT acts more as a departure signal.…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, studies in Northern wheatears (Oenanthe oenanthe) during migratory stopovers found negative correlations between baseline CORT levels and refueling rates (Eikenaar et al, 2014;Eikenaar et al, 2013). Eikenaar et al (2013) suggested that since CORT levels rapidly decrease after arrival to stopover sites and then steadily increase as birds put on more fat, CORT acts more as a departure signal. This hypothesis fits well with similar studies in Bar-tailed Godwits (Limosa lapponica) (Landys-Ciannelli et al, 2002;Ramenofsky et al, 1995), Red Knots (Calidris canutus) (Piersma et al, 2000), and Gray Catbirds (Dummetella carolinensis) (Holberton et al, 1996), which also found that fatter birds had higher baseline CORT levels.…”

Section: Discussionmentioning

confidence: 99%

Hypothalamic–pituitary–adrenal axis activity is not elevated in a songbird (Junco hyemalis) preparing for migration

Bauer

Needham

et al. 2016

General and Comparative Endocrinology

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During spring, increasing daylengths stimulate gonadal development in migratory birds. However, late-stage reproductive development is typically postponed until migration has been completed. The hypothalamic-pituitary-adrenal (HPA) axis regulates the secretion of glucocorticoids, which have been associated with pre-migratory hyperphagia and fattening. The HPA-axis is also known to suppress the hypothalamic-pituitary-gonadal (HPG) axis, suggesting the possibility that final transition into the breeding life history stage may be slowed by glucocorticoids. We hypothesized that greater HPA-axis activity in individuals preparing for migration may foster preparation for migration while simultaneously acting as a "brake" on the development of the HPG-axis. To test this hypothesis, we sampled baseline corticosterone (CORT), stress-induced CORT, and negative feedback efficacy of Dark-eyed Juncos (Junco hyemalis) in an overwintering population that included both migratory (J.h. hyemalis) and resident (J.h. carolinensis) individuals. We predicted that compared to residents, migrants would have higher baseline CORT, higher stress-induced CORT, and weaker negative feedback. Juncos were sampled in western Virginia in early March, which was about 2-4wk before migratory departure for migrants and 4-5wk before first clutch initiation for residents. Contrary to our predictions, we found that migrants had lower baseline and stress-induced CORT and similar negative feedback efficacy compared with residents, which suggests that delayed breeding in migrants is influenced by other physiological mechanisms. Our findings also suggest that baseline CORT is not elevated during pre-migratory fattening, as migrants had lower baseline CORT and were fatter than residents.

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“…In birds, the elevation of baseline corticosterone (CORT) appears to play a permissive role during migration seasons by stimulating feeding and mass gain, possibly through effects related to insulin (Boswell and Dunn, 2015;Holberton et al, 2007;Landys-Cianelli et al, 2004). During stopover refueling the effects of CORT are complex as plasma CORT levels are positively correlated with fat load and negatively correlated with the rate of feeding and mass gain in migrant wheatears (Eikenaar et al, 2013). High levels of CORT are associated with peak fatness at stopover and may signal departure readiness and, thus, the role of CORT in stopover fattening may be independent of or dependent on interactions with other hormones, such as ghrelin (Eikenaar et al, 2014(Eikenaar et al, , 2013.…”

Section: How Do Birds and Bats Get Fat?mentioning

confidence: 99%

“…During stopover refueling the effects of CORT are complex as plasma CORT levels are positively correlated with fat load and negatively correlated with the rate of feeding and mass gain in migrant wheatears (Eikenaar et al, 2013). High levels of CORT are associated with peak fatness at stopover and may signal departure readiness and, thus, the role of CORT in stopover fattening may be independent of or dependent on interactions with other hormones, such as ghrelin (Eikenaar et al, 2014(Eikenaar et al, , 2013. Cholecystokinin (CCK) is inhibitory to feeding, and recent studies in birds suggest that variation in central CCK signaling can alter the growth rate (Boswell and Dunn, 2015).…”

Section: How Do Birds and Bats Get Fat?mentioning

confidence: 99%

Obese super athletes: fat-fueled migration in birds and bats

Guglielmo

2018

Journal of Experimental Biology

128

112

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Migratory birds are physiologically specialized to accumulate massive fat stores (up to 50-60% of body mass), and to transport and oxidize fatty acids at very high rates to sustain flight for many hours or days. Target gene, protein and enzyme analyses and recent -omic studies of bird flight muscles confirm that high capacities for fatty acid uptake, cytosolic transport, and oxidation are consistent features that make fat-fueled migration possible. Augmented circulatory transport by lipoproteins is suggested by field data but has not been experimentally verified. Migratory bats have high aerobic capacity and fatty acid oxidation potential; however, endurance flight fueled by adipose-stored fat has not been demonstrated. Patterns of fattening and expression of muscle fatty acid transporters are inconsistent, and bats may partially fuel migratory flight with ingested nutrients. Changes in energy intake, digestive capacity, liver lipid metabolism and body temperature regulation may contribute to migratory fattening. Although control of appetite is similar in birds and mammals, neuroendocrine mechanisms regulating seasonal changes in fuel store set-points in migrants remain poorly understood. Triacylglycerol of birds and bats contains mostly 16 and 18 carbon fatty acids with variable amounts of 18:2n-6 and 18:3n-3 depending on diet. Unsaturation of fat converges near 70% during migration, and unsaturated fatty acids are preferentially mobilized and oxidized, making them good fuel. Twenty and 22 carbon n-3 and n-6 polyunsaturated fatty acids (PUFA) may affect membrane function and peroxisome proliferator-activated receptor signaling. However, evidence for dietary PUFA as doping agents in migratory birds is equivocal and requires further study.

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Corticosterone and migratory fueling in Northern wheatears facing different barrier crossings

Cited by 31 publications

References 38 publications

Faster spring migration in northern wheatears is not explained by an endogenous seasonal difference in refueling rates

Faster spring migration in northern wheatears is not explained by an endogenous seasonal difference in refueling rates

Hypothalamic–pituitary–adrenal axis activity is not elevated in a songbird (Junco hyemalis) preparing for migration

Obese super athletes: fat-fueled migration in birds and bats

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