Plasma testosterone levels of male European starlings (Sturnus vulgaris) during the breeding cycle and in relation to song and paternal care

In temperate-zone birds, seasonal testosterone (T) profiles often vary among species with different mating systems. The trade-off hypothesis suggests that T levels in male birds represent a trade-off between additional mating effort, stimulated by high T, and paternal effort, inhibited by high T. To study the role of T in mediating the trade-off between paternal and mating effort in the facultatively polygynous European starling ( Sturnus vulgaris ), we monitored seasonal fluctuations in T levels and song activity, which functions mainly in mate attraction, and we investigated natural covariation between plasma T levels and male parental and song behaviour during the parental phase. T concentrations peaked during nest building, remained high during the fertile period, and then decreased gradually during the period of paternal care. This resembles the profile typically found in polygynous species with biparental care. Seasonal variation in song activity paralleled seasonal changes in T. The proportion of time spent incubating was significantly negatively correlated with T levels in individual males. There was a positive, but non-significant, correlation between song activity at an additional nest box and T levels during incubation. We suggest that this negative correlation between T and incubation behaviour may be partly explained by T increases in males responding to the presence of prospecting females with additional nestbox occupation and mate attraction song, rather than that high T levels stimulate mate attraction song. During the feeding period, characterized by a very low availability of unmated females, variation in T levels was low and there was no covariation between T and feeding. T levels during the parental phase reflect, but do not seem to directly regulate, the trade-off between parental and additional mating effort and other factors such as opportunities for additional matings may influence the resolution of this reproductive trade-off.

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Chimpanzee fathers bias their behaviour towards their offspring

Royal Society Open Science ◽

10.1098/rsos.160441 ◽

2016 ◽

Vol 3 (11) ◽

pp. 160441 ◽

Cited By ~ 26

Author(s):

Carson M. Murray ◽

Margaret A. Stanton ◽

Elizabeth V. Lonsdorf ◽

Emily E. Wroblewski ◽

Anne E. Pusey

Keyword(s):

Common Ancestor ◽

Paternal Care ◽

Mating Effort ◽

Last Common Ancestor ◽

Paternal Investment ◽

Hominin Evolution ◽

Lactating Mothers ◽

Paternal Effort ◽

Effort Hypothesis

Promiscuous mating was traditionally thought to curtail paternal investment owing to the potential costs of providing care to unrelated infants. However, mounting evidence suggests that males in some promiscuous species can recognize offspring. In primates, evidence for paternal care exists in promiscuous Cercopithecines, but less is known about these patterns in other taxa. Here, we examine two hypotheses for paternal associations with lactating mothers in eastern chimpanzees ( Pan troglodytes schweinfurthii ): paternal effort, whereby males associate and interact more with their own infants, and mating effort, whereby males invest in mothers and offspring for mating privileges. We found that fathers associated more with their offspring than they did with non-kin infants, particularly early in life when infanticide risk is highest. Additionally, fathers and their infant offspring interacted more than expected. Notably, association between fathers and mother–infant pairs did not predict the probability of siring the mother's next offspring. Our results support the paternal effort, but not the mating effort hypothesis in this species. Chimpanzees are one of the most salient models for the last common ancestor between Pan and Homo , thus our results suggest that a capacity for paternal care, possibly independent of long-term mother–father bonds, existed early in hominin evolution.

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Short- and Long-Term Effects of Male-Like Concentrations of Testosterone on Female European Starlings (Sturnus Vulgaris)

The Auk ◽

10.1093/auk/119.2.487 ◽

2002 ◽

Vol 119 (2) ◽

pp. 487-497 ◽

Cited By ~ 7

Author(s):

Elke De Ridder ◽

Rianne Pinxten ◽

Veerle Mees ◽

Marcel Eens

Keyword(s):

Sex Differences ◽

Sturnus Vulgaris ◽

Buffy Coat ◽

Long Term Effects ◽

European Starlings ◽

Immunological Parameters ◽

Mate Attraction ◽

Nest Box ◽

Indirect Measures ◽

Organizational Effects

Abstract European Starlings (Sturnus vulgaris) exhibit marked sex differences in behavior during spring. Song activity, nest-box occupation, the carrying of green nesting materials into a nest hole (typical mate-attraction behaviors), and aggression occur much more frequently in males who also have higher testosterone (T)-levels than females. Here, we examined whether male-like concentrations of T would activate these behaviors in female starlings. We treated females with implants that were either empty (C-females) or packed with T (T-females) during late December. Although elevated T-levels significantly increased song activity in females, the proportion of time spent singing was still much lower than in males. T-treatment in females also failed to induce singing behavior in the nest box, a typical male mate-attraction behavior. Those results suggest both activational and organizational effects of T on singing. Nest-box occupation, carrying of green nesting material into a nest hole, and aggressive behavior were not activated by elevated T-levels, indicating that sex differences in these behaviors are probably based on early organizational effects of steroid hormones. We also evaluated effects of increased T-concentrations on some physiological, morphological, and immunological parameters. T-treatment strongly suppressed tail feather regrowth after experimental plucking, and also delayed onset of molt of wing feathers and slowed its progress. T-implantation caused color of the bill to change from black to yellow, but did not affect body mass. Immune function was determined by using two indirect measures: blood composition (haematocrit and buffy coat values) and indications of infections. Although haematocrit and buffy coat values did not differ between C- and T-females, T-females were significantly more infected with Staphylococcus aureus than C-females at the end of the experiment.

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Immunolabeling provides evidence for subregions in the songbird nucleus accumbens and suggests a context-dependent role in song in male European starlings (Sturnus vulgaris)

Brain Behavior and Evolution ◽

10.1159/000521310 ◽

2021 ◽

Author(s):

Brandon J. Polzin ◽

Sarah A. Heimovics ◽

Lauren V. Riters

Keyword(s):

Nucleus Accumbens ◽

Tyrosine Hydroxylase ◽

Breeding Season ◽

Brain Region ◽

Sturnus Vulgaris ◽

Extrinsic Reward ◽

European Starlings ◽

Mate Attraction ◽

Ideal Candidate ◽

The Core

Birdsong is well known for its role in mate attraction during the breeding season. However, many birds, including European starlings (Sturnus vulgaris), also sing outside the breeding season as part of large flocks. Song in a breeding context can be extrinsically rewarded by mate attraction; however, song in non-breeding flocks, referred to here as gregarious song, results in no obvious extrinsic reward and is proposed to be intrinsically rewarded. The nucleus accumbens (NAc) is a brain region well-known to mediate reward and motivation, which suggests it is an ideal candidate to regulate reward associated with gregarious song. The goal of this study was to provide new histochemical information on the songbird NAc and its subregions (rostral pole, core, and shell), and to begin to determine subregion-specific contributions to gregarious song in male starlings. We examined immunolabeling for tyrosine hydroxylase (TH), neurotensin, and enkephalin (ENK) in NAc. We then examined the extent to which gregarious and sexually-motivated song differentially correlated with immunolabeling for the immediate early genes FOS and ZENK in each subdivision of NAc. We found that TH and ENK labeling within subregions of the starling NAc was generally similar to patterns seen in the core and shell of NAc in mammals and birds. Additionally, we found that gregarious song, but not sexually-motivated song, positively correlated with FOS in all NAc subregions. Our observations provide further evidence for distinct subregions within the songbird NAc and suggest the NAc may play an important role in regulating gregarious song in songbirds.

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