drosen's blog

Grade and Sieving (2016) investigated the inter-species impacts of eavesdropping on other species calls when exposed to noise pollution, and used alarm calls of tufted titmice, which are similar to chickadees in mobbing behavior. They found that there was a high correlation between noise pollution and inability to detect alarm calls of titmice, suggesting that highways have significant impacts on cardinal, and possibly other passerine survival. Interestingly enough, titmice “Z calls” used to deter predation are similar in frequency and sonographic structure to that of black-capped chickadee mobbing calls, which could provide insights on impacts of similar alarm calls on noise. Our study unwraps this question to explore the intra-species impacts of noise on mobbing behavior. We chose to focus on the black-capped chickadee, since this species is easily identifiable, common, and is incredibly responsive to mobbing behavior. We created a traditional playback experiment to test for the impacts of intra-species communication through mobbing calls in sites with high and low background noise.

Our data demonstrates that mobbing call response is limited in the presence of excessive anthropogenic noise. However, there were inconsistencies such as the weather, time of day and conditions secondary to having a small sample size that may have skewed our results. For example, one trial in the quiet site had construction one morning, resulting in a reading of 56 dB and a limited response, which supports previous trends found. We expected that the trials performed during poor conditions would yield low-quality results and the data seemed followed this trend. Additionally, the noisy feeder had a higher density of individuals initially present despite studies showing that density in noisy areas should, in theory, be lower. We suspect that this may have been related to the food stores of the feeder as easy access to food may supersede the cost of temporarily inhabiting riskier foraging grounds. Finally, our small sample size per variable tested limited the conclusions that we can make regarding the percentages of response.  

These results were consistent with our prediction, hypothesis and the prevailing literature which suggest that anthropogenic noise pollution has profound effects on the efficacy of vocal communication within avian species.  While our data demonstrates that BCCH communication is inhibited by elevated levels of noise pollution, it is less clear if this has a direct effect on reproductive success or species density. The most recent studies suggest that reproductive success should decline and, in response,  the density of individuals within areas of higher noise pollution levels will decrease accordingly. (Francis et al., 2009) Additional studies focusing on banding and tracking individuals within documented areas of various levels of noise pollution and recording their foraging patterns and nesting sites would help demonstrate this.  We predict that this study would show that BCCHs likely nest in areas with lower noise pollution and actively avoid areas of atypical loud background noise while foraging so as to avoid impairing their predator-evasion strategies.

We conclude that the varied levels of noise pollution observed at the feeders under study resulted in notable differences in response to mobbing calls. Local individuals at the quiet feeder readily responded to all mobbing calls as well as a number of additional individuals that were not present prior to the experimental mobbing calls. Furthermore, mobbing calls played by the noisy feeder with louder background noise elicited a fractional response with only a small portion of the local fauna responding to the call. This difference suggests that black-capped chickadees (BCCH) in close proximity of the quiet feeder as well as individuals outside visible range were able to hear and appropriately respond to the mobbing calls being played while those within close proximity the loud feeder were unable to appropriately respond. It is less likely that individuals outside of our visual perimeter were able to hear and respond to the mobbing calls in the high decibel area due to the elevated levels of background noise. Of note, another variable that could have been controlled was the specific mobbing call used. BCCH are able to determine perceived threat and relay this information via adjusting the syllable composition and rate of their mobbing call (Baker et al., 2002). By using a mobbing call that typically warrants a vigorous response we would expect to observe a larger experimental response, potentially in higher decibel areas.

Black-capped chickadees are year-round residents of Massachusetts that display complex behavioral and social systems in order to maximize their chances of survival through the harsh winter months. To do this they are able to differentiate between a wide range of vocalizations with a wide range of syllables (Grava et al., 2011). Since they do not seek refuge from the weather by migrating like many other Massachusetts residents, they must compensate with other behavioral mechanisms and join multi-species flocks. One such behavior that constantly grabs the interest of researchers is mobbing. Chickadees, among other birds, will group together in an attempt to ward off predators by repeatedly attacking and chasing off the threat. Communication is an essential part of this display, as chickadees must be highly responsive to the call and close enough to hear the call from others.

Introduction

    Human development, globalized transportation and the industrialization of resource harvesting all produce large amounts of anthropogenic sounds that are suspected to have negative effects on local fauna. This effect, coined noise pollution, has been a subject of increasing levels of study as several animal behaviors in both terrestrial and marine systems are thought to have been affected (Francis et al., 2009). These results suggest that increased levels of noise pollution exert pressure on vulnerable species, particularly those that heavily rely on vocal communication.  Evidence shows a correlation between elevated levels of background noise and decreased species density and reproductive success, indicating that areas of high noise likely have some detrimental effect on the local fauna (McKenna et al., 2015).  Anthropogenic noise sources, such as heavy construction or large congregations of humans, are commonplace at Umass Amherst and these factors have likely begun exerting pressure on local fauna, including the black capped chickadee.  

World War II opened the door for women to enter the workspace due to the large number of vacated positions that were available while the males of the country were overseas. Since this initial entry, rate of employed women has been steadily increasing. However, data shows that, on average, women have not been equally compensated since 1979 at the latest and this social issue has been dubbed the “gender pay gap”. Those who support this issue claim that women have been historically paid less on the dollar compared to their male counterparts due to conscious or subconscious discrimination secondary to long standing gender roles and responsibilities. There is debate concerning the validity of these claims and many have questioned the analysis of the data presented; claiming that these views exclude certain variables that can account for these differences. While it is clear that there is a difference between pay, the underlying source of this disparity has not been readily identified.

While a transition to a less female dominated career may help alleviate some of the educational factors regarding the pay difference there another contributing circumstance that is too dominated by the females. There is a direct association between the average age a woman rears a child and a sharp decline in their average pay (Economist) This correlation, dubbed the “motherhood cost” is multifactorial and involves insufficient maternity leave policies and underlying social expectations of child care. Women status post birth are forced to work fewer hours or interrupt their careers entirely in order to raise their children.  This responsibility and lack of flexibility can influence potential future promotions as well as interfere with potential return to the job market. Furthermore, there are social stigmas that make women apprehensive to avoid becoming a housewife or to put their children into a daycare facility to continue with their career (Economist). These issues are compounded by a contrast in the expectations revolving men both in the workplace and at home when considering child care. An increase in true co-parenting culture, better maternity and paternity policies as well as an emphasis on company empathy would help mitigate the professional damage that raising a child can do to one’s career.

There have been many proposed solutions to the educational, maternal and social influences affecting women’s wages, however, implementation of these policies has not corrected the wage gap as predicted. In fact, further education has been shown to negatively impact the wage gap as women who have graduated college, on average, make 75.2 cents on the dollar compared to their male counterparts. This value is argued to be secondary to the majors that are predominantly by females such as the humanitaires or education as these majors, when compared to the STEM (science, technologies, engineering and mathematics) majors pay less on average. Movements have been implemented to increase the female presence in these majors, however, data also supports that females within even these majors are also subject to inequality that accounts for up to 68% of the occupational wage gap.  Despite the persistent issues, education can partially reduce the disparity between men and women, however, there are secondary post graduate circumstances that further inhibit equal treatment.

While women are more likely to graduate college on average, they have a higher concentration in majors such as humanities or education, and when compared to their male dominated counterparts such as computer science or engineering there is a clear variance in pay scale. This concept, known as the “between occupation” wage gap, is thought to be multifactorial, involving cultural barriers that inadvertently coerce women away from male-dominated fields.  Furthermore, there is evidence which suggests that maternal care and stereotypical gender roles at home have unintentional consequences regarding pay. Dueto the social stigma and innate desire to raise young, women typically work fewer hours or are only able to work part-time, which can affect merit based promotions or company favor. Additionally women, on average, have less experience due to career interruptions secondary to social events such as having children.