Ingrid Schwabl - Academia.edu (original) (raw)

Papers by Ingrid Schwabl

Data from: Social monogamy versus polyandry: ecological factors associated with sex-roles in two closely related birds within the same habitat

Why mainly males compete and females take a larger share in parental care remains an exciting que... more Why mainly males compete and females take a larger share in parental care remains an exciting question in evolutionary biology. Role-reversed species are of particular interest, because such exceptions′ help to test the rule. Using mating systems theory as a framework, we compared the reproductive ecology of the two most contrasting coucals with regard to sexual dimorphism and parental care: the black coucal with male-only care and the bi-parental white-browed coucal. Both species occur in the same lush habitat and face similar ecological conditions, but drastically differ in mating system and sexual dimorphism. Black coucals were migratory and occurred at high breeding densities. With females being obligatory polyandrous and almost twice as heavy as males, black coucals belong to the most extreme vertebrates with reversed sexual dimorphism. Higher variance in reproductive success in fiercely competing females suggests that sexual selection is stronger in females than males. In contrast, resident white-browed coucals bred at low densities and invariably in pairs. They were almost monomorphic and the variance in reproductive success was similar between the sexes. Black coucals were more likely to lose nests than white-browed coucals, probably facilitating female emancipation of parental care in black coucals. We propose that a combination of high food abundance, high population density, high degree of nest loss, and male bias in the adult sex ratio are ecological conditions that facilitate role reversal and polyandry in coucals and terrestrial vertebrates in general

Ibutton incubation data

This file contains the ibutton data used for the analysis of absence bouts, total absence duratio... more This file contains the ibutton data used for the analysis of absence bouts, total absence duration, and the diurnal pattern of incubation in black coucals and white-browed coucals

Incubation pattern

This file contains the data for of the binomial analysis of sex specific incubation pattern of co... more This file contains the data for of the binomial analysis of sex specific incubation pattern of coucal

Journal of Evolutionary Biology, 2015

Why mainly males compete and females take a larger share in parental care remains an exciting que... more Why mainly males compete and females take a larger share in parental care remains an exciting question in evolutionary biology. Role-reversed species are of particular interest, because such 'exceptions' help to test the rule. Using mating systems theory as a framework, we compared the reproductive ecology of the two most contrasting coucals with regard to sexual dimorphism and parental care: the black coucal with male-only care and the biparental white-browed coucal. Both species occur in the same lush habitat and face similar ecological conditions, but drastically differ in mating system and sexual dimorphism. Black coucals were migratory and occurred at high breeding densities. With females being obligatory polyandrous and almost twice as heavy as males, black coucals belong to the most extreme vertebrates with reversed sexual dimorphism. Higher variance in reproductive success in fiercely competing females suggests that sexual selection is stronger in females than in males. In contrast, resident white-browed coucals bred at low densities and invariably in pairs. They were almost monomorphic and the variance in reproductive success was similar between the sexes. Black coucals were more likely to lose nests than white-browed coucals, probably facilitating female emancipation of parental care in black coucals. We propose that a combination of high food abundance, high population density, high degree of nest loss and male bias in the adult sex ratio represent ecological conditions that facilitate role reversal and polyandry in coucals and terrestrial vertebrates in general.

Physiological and Biochemical Zoology, 2008

Ecological immunologists are interested in how immune function changes during different seasons a... more Ecological immunologists are interested in how immune function changes during different seasons and under different environmental conditions. However, an obstacle to answering such questions is discerning the effects of biological factors of interest and investigation artifacts such as handling stress. Here we examined handling stress and its effects on constitutive (noninduced) immune function via two protocols on captive red knots (Calidris canutus). We investigated how constitutive immunity responds to handling stress, how quickly these changes take place, and the practical implications for researchers interested in sampling baseline immune levels. We found that Staphylococcus aureus and Candida albicans killing increased with handling stress while total leukocyte and lymphocyte concentrations decreased. However, although corticosterone increased significantly and rapidly in response to handling stress, none of the 10 measures of constitutive immunity that we tested differed significantly from baseline within 20 or 30 min of capture. Thus, researchers interested in baseline immune function should sample animals as soon as possible after capture, but studies in species not easily sampled in less than 3 min (such as red knots) could still yield useful results.

Keeping Time Under the Midnight Sun: Behavioral and Plasma Melatonin Profiles of Free-Living Lapland Longspurs (Calcarius lapponicus) During the Arctic Summer

Journal of Experimental Zoology Part A: Ecological Genetics and Physiology, 2012

Polar environments are characterized by discrete periods of continuous light or darkness during t... more Polar environments are characterized by discrete periods of continuous light or darkness during the summer and winter months, respectively. Because the light/dark cycle serves as the primary Zeitgeber to synchronize rhythms of most organisms, its seasonal absence in polar regions poses challenges to the circadian organization of organisms that reside in these environments. Although some species become arrhythmic, others, such as migratory songbirds, are able to maintain an intact diurnal rhythm during polar summer. This suggests that birds may switch to alternative environmental cues, such as daily changes in light intensity and ambient temperature, which may have the potential to reset the biological clock. However, identifying the low-amplitude Zeitgeber that synchronizes rhythms in free-living polar-dwelling animals has been difficult to demonstrate. In this study, we measured behavioral and melatonin profiles of free-living Lapland longspurs (Calcarius lapponicus) near Barrow, Alaska (71°N) during the continuous daylight of summer in the Arctic. Diel cycles in activity and male singing were apparent throughout the polar day with a quiescence period of 4-5 hr starting around 24:00 Alaska Daylight Time. This inactivity corresponded with elevated melatonin profiles. In contrast, territorial aggression of males in response to a conspecific intruder was not dependent upon time-of-day. Diel changes in light intensity and ambient temperature were negatively associated with daily melatonin profiles after taking into account time-of-day effects. These results suggest that photic and thermal cues may act either as alternative Zeitgeber cues, or possibly masking agents. Distinguishing between these two possibilities will require further study.

Journal of Experimental Zoology Part A: Ecological Genetics and Physiology, 2013

Florida scrub-jays (Aphelocoma coerulescens) in the suburbs breed earlier than jays in native hab... more Florida scrub-jays (Aphelocoma coerulescens) in the suburbs breed earlier than jays in native habitat. Amongst the possible factors that influence this advance (e.g., food availability, microclimate, predator regime, etc.), is exposure to artificial lights at night (LAN). LAN could stimulate the reproductive axis of the suburban jays. Alternatively, LAN could inhibit pineal melatonin (MEL), thus removing its inhibitory influence on the reproductive axis. Because Florida scrub-jays are a threatened species, we used western scrub-jays (Aphelocoma californica) to investigate the effects of LAN upon reproductive hormones and melatonin. Jays were held under conditions in which the dark-phase of the light:dark cycle was without illumination and then under low levels of LAN. Under both conditions, birds were exposed first to short-days (9.5L:14.5D) that were gradually increased to long-days (14.5L:9.5D). At various times, blood samples were collected during the light part of the cycle to measure reproductive hormones (luteinizing hormone, LH; testosterone, T; and estradiol, E 2). Similarly, samples to assess melatonin were collected during the dark. In males, LAN caused a depression in LH levels and levels were $4Â greater under long-than short-days. In females, there was no effect of LAN or photoperiod upon LH. LAN resulted in depressed T levels in females, although there was no effect on T in males. E 2 levels in both sexes were lower under LAN than under an unlighted dark-phase. Paradoxically, MEL was higher in jays under LAN, and under long-days. MEL did not differ by sex. LAN disrupted the extraordinarily strong correlation between T and E 2 that existed under unlighted nocturnal conditions. Overall, our findings fail to support the hypothesis that LAN stimulates the reproductive axis. Rather, the data demonstrate that LAN tends to inhibit reproductive hormone secretion, although not in a consistent fashion between the sexes.

Journal of Comparative Physiology A, 2009

Take-down policy If you believe that this document breaches copyright please contact us providing... more Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Ibis, 2010

The immunocompetence handicap hypothesis (ICHH) posits that the hormone testosterone mediates a t... more The immunocompetence handicap hypothesis (ICHH) posits that the hormone testosterone mediates a trade-off between investment in reproduction and immunological condition. In this study, we tested the ICHH in the Red Bishop Euplectes orix, a polygynous weaverbird. Males of this strongly sexually dimorphic species show an elaborate courtship display to attract females and compete aggressively with other males for nesting sites in breeding colonies. We experimentally elevated testosterone levels in breeding male Red Bishops kept in an aviary with a subcutaneous implantation of testosterone-releasing pellets. We then compared behaviour, development of territory size and immunological condition (as assessed through a white blood cell count) of the experimental group with a control group treated with placebos. In addition, we measured the primary and secondary response to phytohaemagglutinin (PHA) to investigate the effect of testosterone on both innate and acquired immunity. Males with elevated levels of testosterone enlarged their territories and conducted more courtship behaviour, while showing a decrease in health, expressed by an increased heterophil ⁄ lymphocyte ratio compared with the control group. Males of the control group showed an increase of the secondary response to PHA, as expected under the assumption that repeated exposure to an antigen enhanced the immune response due to acquired immunity. However, males with experimentally increased testosterone levels did not show such an enhanced immune response in the secondary PHA test (although sample size and power of the statistical tests were low), indicating that testosterone treatment might directly or indirectly suppress some component of the acquired immune response.

The decision to provide parental care is often associated with trade-offs, because resources allo... more The decision to provide parental care is often associated with trade-offs, because resources allocated to parental care typically cannot be invested in self-maintenance or mating. In most animals, females provide more parental care than males, but the reason for this pattern is still debated in evolutionary ecology. To better understand sex differences in parental care and its consequences, we need to study closely related species where the sexes differ in offspring care. We investigated parental care in relation to offspring growth in two closely related coucal species that fundamentally differ in sex roles and parental care, but live in the same food-rich habitat with a benign climate and have a similar breeding phenology. Incubation patterns differed and uniparental male black coucals fed their offspring two times more often than female and male white-browed coucals combined. Also, white-browed coucals had more 'off-times' than male black coucals, during which they perche...

Proceedings of the Royal Society B: Biological Sciences, 2012

At higher latitudes, most organisms use the periodic changes in day length to time their annual l... more At higher latitudes, most organisms use the periodic changes in day length to time their annual life cycle. At the equator, changes in day length are minimal, and it is unknown which cues organisms use to synchronize their underlying circannual rhythms to environmental conditions. Here, we demonstrate that the African stonechat ( Saxicola torquatus axillaris )—an equatorial songbird—can use subtle solar cues for the annual timing of postnuptial moult, a reliable marker of the circannual cycle. We compared four groups that were kept over more than 3 years: (i) a control group maintained under constant equatorial day length, (ii) a 12-month solar time group maintained under equatorial day length, but including a simulation of the annual periodic change in sunrise and sunset times (solar time), (iii) a 14-month solar time group similar to the previous group but with an extended solar time cycle and (iv) a group maintained under a European temperate photoperiod. Within all 3 years, 12-m...

Data from: Sex roles, parental care and offspring growth in two contrasting coucal species

Supplementary material from "Sex roles, parental care and offspring growth in two contrasting coucal species

The decision to provide parental care is often associated with trade-offs, because resources allo... more The decision to provide parental care is often associated with trade-offs, because resources allocated to parental care typically cannot be invested in self-maintenance or mating. In most animals, females provide more parental care than males, but the reason for this pattern is still debated in evolutionary ecology. To better understand sex differences in parental care and its consequences, we need to study closely related species where the sexes differ in offspring care. We investigated parental care in relation to offspring growth in two closely related coucal species that fundamentally differ in sex roles and parental care, but live in the same food-rich habitat with a benign climate and have a similar breeding phenology. Incubation patterns differed and uniparental male black coucals fed their offspring two times more often than female and male white-browed coucals combined. Also, white-browed coucals had more 'off-times' than male black coucals, during which they perched and preened. However, these differences in parental care were not reflected in offspring growth, probably because white-browed coucals fed their nestlings a larger proportion of frogs than insects. A food-rich habitat with a benign climate may be a necessary, but—perhaps unsurprisingly—is not a sufficient factor for the evolution of uniparental care. In combination with previous results (Goymann <i>et al</i>. 2015 <i>J. Evol. Biol</i>. <b>28</b>, 1335–1353 (doi:10.1111/jeb.12657)), these data suggest that white-browed coucals may cooperate in parental care, because they lack opportunities to become polygamous rather than because both parents were needed to successfully raise all offspring. Our case study supports recent theory suggesting that permissive environmental conditions in combination with a particular life history may induce sexual selection in females. A positive feedback loop among sexual selection, body size and adult sex-ratio may then stabilize reversed sex roles in competition and parental care.

The Neurobiology of Circadian Timing

Leading authors review the state-of-the-art in their field of investigation, and provide their vi... more Leading authors review the state-of-the-art in their field of investigation, and provide their views and perspectives for future research Chapters are extensively referenced to provide readers with a comprehensive list of resources on the topics covered All chapters include comprehensive background information and are written in a clear form that is also accessible to the non-specialist Leading authors review the state-of-the-art in their field of investigation, and provide their views and perspectives for future research Chapters are extensively referenced to provide readers with a comprehensive list of resources on the topics covered All chapters include comprehensive background information and are written in a clear form that is also accessible to the non-specialist

Lower corticosterone stress response in european blackbirds (Turdus merula) born in a city than in a forest

Hormones and Behavior, 2005

Blocking androgen and estrogen action does not affect territorial behavior in female Black Coucals

Annual Variation in Hypothalamic LHRH Plasma ans Pituitary LH and Testosterone Production of Migratory Garden Warblers Sylvia-Borin

Data from: Social monogamy versus polyandry: ecological factors associated with sex-roles in two closely related birds within the same habitat

Why mainly males compete and females take a larger share in parental care remains an exciting que... more Why mainly males compete and females take a larger share in parental care remains an exciting question in evolutionary biology. Role-reversed species are of particular interest, because such exceptions′ help to test the rule. Using mating systems theory as a framework, we compared the reproductive ecology of the two most contrasting coucals with regard to sexual dimorphism and parental care: the black coucal with male-only care and the bi-parental white-browed coucal. Both species occur in the same lush habitat and face similar ecological conditions, but drastically differ in mating system and sexual dimorphism. Black coucals were migratory and occurred at high breeding densities. With females being obligatory polyandrous and almost twice as heavy as males, black coucals belong to the most extreme vertebrates with reversed sexual dimorphism. Higher variance in reproductive success in fiercely competing females suggests that sexual selection is stronger in females than males. In contrast, resident white-browed coucals bred at low densities and invariably in pairs. They were almost monomorphic and the variance in reproductive success was similar between the sexes. Black coucals were more likely to lose nests than white-browed coucals, probably facilitating female emancipation of parental care in black coucals. We propose that a combination of high food abundance, high population density, high degree of nest loss, and male bias in the adult sex ratio are ecological conditions that facilitate role reversal and polyandry in coucals and terrestrial vertebrates in general

Ibutton incubation data

This file contains the ibutton data used for the analysis of absence bouts, total absence duratio... more This file contains the ibutton data used for the analysis of absence bouts, total absence duration, and the diurnal pattern of incubation in black coucals and white-browed coucals

Incubation pattern

This file contains the data for of the binomial analysis of sex specific incubation pattern of co... more This file contains the data for of the binomial analysis of sex specific incubation pattern of coucal

Journal of Evolutionary Biology, 2015

Why mainly males compete and females take a larger share in parental care remains an exciting que... more Why mainly males compete and females take a larger share in parental care remains an exciting question in evolutionary biology. Role-reversed species are of particular interest, because such 'exceptions' help to test the rule. Using mating systems theory as a framework, we compared the reproductive ecology of the two most contrasting coucals with regard to sexual dimorphism and parental care: the black coucal with male-only care and the biparental white-browed coucal. Both species occur in the same lush habitat and face similar ecological conditions, but drastically differ in mating system and sexual dimorphism. Black coucals were migratory and occurred at high breeding densities. With females being obligatory polyandrous and almost twice as heavy as males, black coucals belong to the most extreme vertebrates with reversed sexual dimorphism. Higher variance in reproductive success in fiercely competing females suggests that sexual selection is stronger in females than in males. In contrast, resident white-browed coucals bred at low densities and invariably in pairs. They were almost monomorphic and the variance in reproductive success was similar between the sexes. Black coucals were more likely to lose nests than white-browed coucals, probably facilitating female emancipation of parental care in black coucals. We propose that a combination of high food abundance, high population density, high degree of nest loss and male bias in the adult sex ratio represent ecological conditions that facilitate role reversal and polyandry in coucals and terrestrial vertebrates in general.

Physiological and Biochemical Zoology, 2008

Ecological immunologists are interested in how immune function changes during different seasons a... more Ecological immunologists are interested in how immune function changes during different seasons and under different environmental conditions. However, an obstacle to answering such questions is discerning the effects of biological factors of interest and investigation artifacts such as handling stress. Here we examined handling stress and its effects on constitutive (noninduced) immune function via two protocols on captive red knots (Calidris canutus). We investigated how constitutive immunity responds to handling stress, how quickly these changes take place, and the practical implications for researchers interested in sampling baseline immune levels. We found that Staphylococcus aureus and Candida albicans killing increased with handling stress while total leukocyte and lymphocyte concentrations decreased. However, although corticosterone increased significantly and rapidly in response to handling stress, none of the 10 measures of constitutive immunity that we tested differed significantly from baseline within 20 or 30 min of capture. Thus, researchers interested in baseline immune function should sample animals as soon as possible after capture, but studies in species not easily sampled in less than 3 min (such as red knots) could still yield useful results.

Keeping Time Under the Midnight Sun: Behavioral and Plasma Melatonin Profiles of Free-Living Lapland Longspurs (Calcarius lapponicus) During the Arctic Summer

Journal of Experimental Zoology Part A: Ecological Genetics and Physiology, 2012

Polar environments are characterized by discrete periods of continuous light or darkness during t... more Polar environments are characterized by discrete periods of continuous light or darkness during the summer and winter months, respectively. Because the light/dark cycle serves as the primary Zeitgeber to synchronize rhythms of most organisms, its seasonal absence in polar regions poses challenges to the circadian organization of organisms that reside in these environments. Although some species become arrhythmic, others, such as migratory songbirds, are able to maintain an intact diurnal rhythm during polar summer. This suggests that birds may switch to alternative environmental cues, such as daily changes in light intensity and ambient temperature, which may have the potential to reset the biological clock. However, identifying the low-amplitude Zeitgeber that synchronizes rhythms in free-living polar-dwelling animals has been difficult to demonstrate. In this study, we measured behavioral and melatonin profiles of free-living Lapland longspurs (Calcarius lapponicus) near Barrow, Alaska (71°N) during the continuous daylight of summer in the Arctic. Diel cycles in activity and male singing were apparent throughout the polar day with a quiescence period of 4-5 hr starting around 24:00 Alaska Daylight Time. This inactivity corresponded with elevated melatonin profiles. In contrast, territorial aggression of males in response to a conspecific intruder was not dependent upon time-of-day. Diel changes in light intensity and ambient temperature were negatively associated with daily melatonin profiles after taking into account time-of-day effects. These results suggest that photic and thermal cues may act either as alternative Zeitgeber cues, or possibly masking agents. Distinguishing between these two possibilities will require further study.

Journal of Experimental Zoology Part A: Ecological Genetics and Physiology, 2013

Florida scrub-jays (Aphelocoma coerulescens) in the suburbs breed earlier than jays in native hab... more Florida scrub-jays (Aphelocoma coerulescens) in the suburbs breed earlier than jays in native habitat. Amongst the possible factors that influence this advance (e.g., food availability, microclimate, predator regime, etc.), is exposure to artificial lights at night (LAN). LAN could stimulate the reproductive axis of the suburban jays. Alternatively, LAN could inhibit pineal melatonin (MEL), thus removing its inhibitory influence on the reproductive axis. Because Florida scrub-jays are a threatened species, we used western scrub-jays (Aphelocoma californica) to investigate the effects of LAN upon reproductive hormones and melatonin. Jays were held under conditions in which the dark-phase of the light:dark cycle was without illumination and then under low levels of LAN. Under both conditions, birds were exposed first to short-days (9.5L:14.5D) that were gradually increased to long-days (14.5L:9.5D). At various times, blood samples were collected during the light part of the cycle to measure reproductive hormones (luteinizing hormone, LH; testosterone, T; and estradiol, E 2). Similarly, samples to assess melatonin were collected during the dark. In males, LAN caused a depression in LH levels and levels were $4Â greater under long-than short-days. In females, there was no effect of LAN or photoperiod upon LH. LAN resulted in depressed T levels in females, although there was no effect on T in males. E 2 levels in both sexes were lower under LAN than under an unlighted dark-phase. Paradoxically, MEL was higher in jays under LAN, and under long-days. MEL did not differ by sex. LAN disrupted the extraordinarily strong correlation between T and E 2 that existed under unlighted nocturnal conditions. Overall, our findings fail to support the hypothesis that LAN stimulates the reproductive axis. Rather, the data demonstrate that LAN tends to inhibit reproductive hormone secretion, although not in a consistent fashion between the sexes.

Journal of Comparative Physiology A, 2009

Take-down policy If you believe that this document breaches copyright please contact us providing... more Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Ibis, 2010

The immunocompetence handicap hypothesis (ICHH) posits that the hormone testosterone mediates a t... more The immunocompetence handicap hypothesis (ICHH) posits that the hormone testosterone mediates a trade-off between investment in reproduction and immunological condition. In this study, we tested the ICHH in the Red Bishop Euplectes orix, a polygynous weaverbird. Males of this strongly sexually dimorphic species show an elaborate courtship display to attract females and compete aggressively with other males for nesting sites in breeding colonies. We experimentally elevated testosterone levels in breeding male Red Bishops kept in an aviary with a subcutaneous implantation of testosterone-releasing pellets. We then compared behaviour, development of territory size and immunological condition (as assessed through a white blood cell count) of the experimental group with a control group treated with placebos. In addition, we measured the primary and secondary response to phytohaemagglutinin (PHA) to investigate the effect of testosterone on both innate and acquired immunity. Males with elevated levels of testosterone enlarged their territories and conducted more courtship behaviour, while showing a decrease in health, expressed by an increased heterophil ⁄ lymphocyte ratio compared with the control group. Males of the control group showed an increase of the secondary response to PHA, as expected under the assumption that repeated exposure to an antigen enhanced the immune response due to acquired immunity. However, males with experimentally increased testosterone levels did not show such an enhanced immune response in the secondary PHA test (although sample size and power of the statistical tests were low), indicating that testosterone treatment might directly or indirectly suppress some component of the acquired immune response.

The decision to provide parental care is often associated with trade-offs, because resources allo... more The decision to provide parental care is often associated with trade-offs, because resources allocated to parental care typically cannot be invested in self-maintenance or mating. In most animals, females provide more parental care than males, but the reason for this pattern is still debated in evolutionary ecology. To better understand sex differences in parental care and its consequences, we need to study closely related species where the sexes differ in offspring care. We investigated parental care in relation to offspring growth in two closely related coucal species that fundamentally differ in sex roles and parental care, but live in the same food-rich habitat with a benign climate and have a similar breeding phenology. Incubation patterns differed and uniparental male black coucals fed their offspring two times more often than female and male white-browed coucals combined. Also, white-browed coucals had more 'off-times' than male black coucals, during which they perche...

Proceedings of the Royal Society B: Biological Sciences, 2012

At higher latitudes, most organisms use the periodic changes in day length to time their annual l... more At higher latitudes, most organisms use the periodic changes in day length to time their annual life cycle. At the equator, changes in day length are minimal, and it is unknown which cues organisms use to synchronize their underlying circannual rhythms to environmental conditions. Here, we demonstrate that the African stonechat ( Saxicola torquatus axillaris )—an equatorial songbird—can use subtle solar cues for the annual timing of postnuptial moult, a reliable marker of the circannual cycle. We compared four groups that were kept over more than 3 years: (i) a control group maintained under constant equatorial day length, (ii) a 12-month solar time group maintained under equatorial day length, but including a simulation of the annual periodic change in sunrise and sunset times (solar time), (iii) a 14-month solar time group similar to the previous group but with an extended solar time cycle and (iv) a group maintained under a European temperate photoperiod. Within all 3 years, 12-m...

Data from: Sex roles, parental care and offspring growth in two contrasting coucal species

Supplementary material from "Sex roles, parental care and offspring growth in two contrasting coucal species

The decision to provide parental care is often associated with trade-offs, because resources allo... more The decision to provide parental care is often associated with trade-offs, because resources allocated to parental care typically cannot be invested in self-maintenance or mating. In most animals, females provide more parental care than males, but the reason for this pattern is still debated in evolutionary ecology. To better understand sex differences in parental care and its consequences, we need to study closely related species where the sexes differ in offspring care. We investigated parental care in relation to offspring growth in two closely related coucal species that fundamentally differ in sex roles and parental care, but live in the same food-rich habitat with a benign climate and have a similar breeding phenology. Incubation patterns differed and uniparental male black coucals fed their offspring two times more often than female and male white-browed coucals combined. Also, white-browed coucals had more 'off-times' than male black coucals, during which they perched and preened. However, these differences in parental care were not reflected in offspring growth, probably because white-browed coucals fed their nestlings a larger proportion of frogs than insects. A food-rich habitat with a benign climate may be a necessary, but—perhaps unsurprisingly—is not a sufficient factor for the evolution of uniparental care. In combination with previous results (Goymann <i>et al</i>. 2015 <i>J. Evol. Biol</i>. <b>28</b>, 1335–1353 (doi:10.1111/jeb.12657)), these data suggest that white-browed coucals may cooperate in parental care, because they lack opportunities to become polygamous rather than because both parents were needed to successfully raise all offspring. Our case study supports recent theory suggesting that permissive environmental conditions in combination with a particular life history may induce sexual selection in females. A positive feedback loop among sexual selection, body size and adult sex-ratio may then stabilize reversed sex roles in competition and parental care.

The Neurobiology of Circadian Timing

Leading authors review the state-of-the-art in their field of investigation, and provide their vi... more Leading authors review the state-of-the-art in their field of investigation, and provide their views and perspectives for future research Chapters are extensively referenced to provide readers with a comprehensive list of resources on the topics covered All chapters include comprehensive background information and are written in a clear form that is also accessible to the non-specialist Leading authors review the state-of-the-art in their field of investigation, and provide their views and perspectives for future research Chapters are extensively referenced to provide readers with a comprehensive list of resources on the topics covered All chapters include comprehensive background information and are written in a clear form that is also accessible to the non-specialist

Lower corticosterone stress response in european blackbirds (Turdus merula) born in a city than in a forest

Hormones and Behavior, 2005

Blocking androgen and estrogen action does not affect territorial behavior in female Black Coucals

Annual Variation in Hypothalamic LHRH Plasma ans Pituitary LH and Testosterone Production of Migratory Garden Warblers Sylvia-Borin