Sex ratios and the city: Secondary offspring sex ratios, parental corticosterone, and parental body condition in an urban-adapted bird

The Trivers–Willard hypothesis states that mothers should adjust their offspring sex ratio according to their own condition and the environment they face during breeding. Past tests of this hypothesis have focused on how natural variation in weather, food availability, or predation pressure shapes sex allocation trade-offs. However, anthropogenic activities, such as urbanization, can alter all of the above characteristics presenting animals with novel challenges in optimizing their brood sex ratio. Previous research has examined how urban living influences individual body condition in several bird taxa, but few have explored subsequent impacts on secondary offspring sex ratio. One likely mediator of the link between environmental conditions, parental condition, and sex ratios is corticosterone (CORT), the primary glucocorticoid in birds. Research on CORT’s influence on sex ratios has focused solely on maternal CORT. However, for species with biparental care, paternal CORT or the similarity of maternal and paternal phenotypes may also help ensure that offspring demand matches parental care quality. To test these hypotheses, we explore offspring secondary sex ratios in European starlings (Sturnus vulgaris). We did not find an effect of site or parental body condition on the production of the more costly sex (males). Instead, we found preliminary evidence suggesting that the similarity of maternal and paternal CORT levels within a breeding pair may increase the likelihood of successfully fledging sons. Maternal and paternal CORT were not significant predictors of secondary sex ratio, suggesting that parental similarity, rather than parental CORT alone, could play a role in shaping secondary offspring sex ratios, but additional work is needed to support this pattern. Starlings are considered an urban-adapted species, making them a compelling model for future studies of the relationship between urbanization, parental body condition, and sex ratios

Indirect effects of urbanization: consequences of increased aggression in an urban male songbird for mates and offspring

Behavioral traits are often the first response to changing environmental conditions, including human induced rapid environmental change. For example, animals living in urban areas are often more aggressive than rural animals. This is especially evident in songbirds; males of several species display elevated aggression in urban habitats. Increased male aggression has been associated with reduced parental care, but the consequences of this trade-off for males, social partners, and offspring in the context of urbanization remains unclear. We explored the effects of increased urban male aggression on the life history traits, parental care, and offspring outcomes of song sparrows (Melospiza melodia). We predicted that urban males would reduce paternal investment and result in urban females providing greater nestling care or reduced fledging success in urban habitats compared to rural. Contrary to our prediction, aggressive urban males did not decrease care but visited the nest more often compared to rural males. Additionally, urban birds had higher nest and fledging success compared to rural, though this was largely due to higher nest predation in rural habitats. Our study is among the first to evaluate trade-offs associated with elevated aggression expressed by urban animals and adds to a growing body of evidence that urban habitats provide benefits to some species

The development of behavioral and endocrine coping styles in nestlings from urban and rural sites

Urbanization is increasing globally and altering the stressors that animals face in their everyday lives. Organisms often differ in their coping styles—both behavioral and endocrine—across urban to rural habitats. For example, urban animals are often bolder, more exploratory, and mount stronger glucocorticoid stress responses compared to their rural counterparts. While these coping styles are important in shaping fitness across the urban-to-rural gradient, it remains unclear when these differences arise in the life of organisms. We explore the development of coping styles in European starling nestlings (Sturnus vulgaris), an urban-adapted species. We test whether breathing rate, handling struggle rate, and bag struggle rate differ across sites and find no difference in the behavioral coping styles of nestlings raised in urban versus rural sites. We also explore differences in baseline and stress-induced glucocorticoids, finding that urban nestlings develop a stronger stress response than rural birds before fledging the nest. We find no significant correlations between behavioral and endocrine traits for urban or rural birds, which supports the two-tiered model of coping styles. One possibility is that behavioral and endocrine differences develop at different times over the lives of organisms. Our findings support prior work suggesting that behavioral and endocrine coping mechanisms act independently of one another, and suggests that endocrine coping mechanisms develop in early life and before differences in behavioral coping styles might arise. Future work on the mechanisms leading to early-life differences in coping styles—from genetics to maternal effects to environmental effects—is needed to best predict how urban-adapted organisms cope with environmental change. Studies across a greater number of sites will help disentangle site from urbanization effects

Some interrelationships between a community work and training program and selected indices of family functioning

This was an exploratory study of some of the relationships between a Community Work and Training Program and the family functioning of certain participants in that program. The CWT projects studied were those operated by the Public Welfare Departments of Clackamas and Marion Counties, Oregon during the three –year span between January 1, 1965 and December 31, 1967. Participants\u27 names were randomly selected from the records of the two welfare offices and the respondents interviewed during the summer of 1968. A questionnaire was developed which consisted of twenty primarily open-ended questions and this was administered to a total of sixty couples. The questions focused on changes in parental, child, financial, marital and social functioning which occurred during the time the husband participated in the work training project. To identify these changes a list was drawn up of fourteen indices of family functioning and these indices were later categorized under two general headings, external and internal to the family. The basic hypothesis was that the CWT Program contributed to positive family functioning. This was expanded into a guiding hypothesis which stated that family functioning is improved through participation in the CWT Program and that this improvement is associated with the program, work itself and the social work services provided by the welfare departments. To determine the validity of these hypotheses a number of null hypotheses were then advanced and tested. The findings of the study were as follows. Internal family functioning was improved during participation on CWT and this improvement affected the total family unit. External functioning, however, deteriorated and this was attributed to the reduced income resulting from the families’ dependence for support upon Public Welfare. The improved internal functioning was associated with the social work services provided and with the work itself. This improvement was evident despite the reported failure of the program to meet the two most important expectations of the participants, namely material benefits and vocational training. The most important limitations noted in the research were two. The first was the lapse of time which occurred between the interviews and the period when many of the participants actually worked on the program. Inevitably, such lapse of time had some effect on respondents’ recall. Second in importance in considering the possible application of the findings was the fact that some 15.58% of the respondents from Marion County were Spanish-Americans. This minority group would conceivably not be representative of another area. Among the program’s negative features mentioned by participants was the lack of choice available in job assignment and the inadequate compensation for performance on the job. Despite these, however, the overall conclusion reached by the research group was that participants in the CWT projects saw the program as beneficial in helping to maintain family life