drosen's blog

From 1979 through the 1990’s the wage gap had been consistently approaching an equilibrium, however, progress has stagnated over the past 20 years and the reason for this is unclear. Current, unadjusted statistical analysis shows that the typical woman, who represents the median value, makes 0.83 cents per every dollar a typical man makes per hour worked. However, this value does not take into other factors such as industry or education and more advanced studies have shown wage gaps of 8.4% when these variables are accounted for. While these factors clearly have a significant impact in tandem, the individual contributions of these differences are subject to questioning as well. Understanding the data and dynamics of both higher education and the industries that are dominated by women are crucial to correctly interpreting why this difference exists.

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 on 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.

Avian species, particularly those in the African and Asian regions,  have developed a wide array of breeding techniques that have been driven by one factor, successful inheritance of their genes. Two particular forms of breeding, cooperative and brood parasitism, have been observed to closely overlap, implying correlation.  Cooperative breeding, where several non-paternal individuals assist with care are frequently targeted by brood parasites, who trick these species into caring for their young as well. This study serves to investigate whether the evolutionary basis of these two forms of breeding are a coincidence secondary to similar environments or the site of an evolutionary arms race between these two conflicting breeding styles that is driven by brood parasitism.

4) What do the researchers think that their findings mean (i.e. how do they interpret their findings)

    Ultimately, they determined that a cuckoo chick is able to predictably increase its call rate to offset its low gape area as these 2 features are the dominating factors that inform parents of nutritional needs. However, they are not fed as frequently as they would prefer and they suspect this is to avoid exhaustion of the host parents. Instead, they demand a similar amount of food as a standard warbler nest (4) for an extended duration.  This is counterintuitive as a cuckoo chick does not have any stake in the survive of the host parents, but they suspect that a constraint must prevent the cuckoo from the predicted optimal feeding rates.

3) What, exactly, did the researchers find (i.e., what were their data)?

In regards to the call experiment noted above, the researchers observed that there was a linear correlation between brood size and call frequency. They then created several regression equations in an attempt to quantify the impact of each factor.  After manipulating the call rates of clutches they determined that the regression equation derived is: feeds delivered per hour = 2:28 (maximum number of gapes displayed) + 2.30 (maximum number of chicks calling) + 8.23. This equation was exclusive to 6-7 day old chicks so they manipulated the factors so that they could apply this to chicks of any age. The resulting regression equation thus derived was: feeds delivered per hour =0:0162 (gape area displayed (in mm2 )) + 0.178 (calls per 6 s) + 8.2. When analyzing the cuckoo chicks they determined that 1. A cuckoo chick intakes the amount that 4 warblers would normally require to survive and that a Cuckoo that is 6-8 days old has a call frequency that matches that of 4 warbler chicks. 2. This increased intake is not related to size,  as black birds and song thrushes, even with augmented warbler calls, did not receive the same amount of food. However, in the presence of a cuckoo call they did receive more food. They then used the equation 0162 (gape area displayed (in mm2 )) + 0.178 (calls per 6 s) + 8.23, to determine if the cuckoo’s reduced gape area would in turn increase their call frequency in a predictable fashion.

2) What, exactly, did the researchers do to try to answer their question?

They first used a regression equation to determine the independent effects of gaping and calling in regards to effect on parental care. They then correlated these 2 factors and determined that both factors in tandem appear to be the most optimized means of conveying nutritional needs. To determine the effect of the begging call they compared to responses of the parents subjected to 49 nests with either 2 or 4 chicks that were 6/7 days old. They then amplified the call in the experimental groups with either a playback of 1 or 4 additional chicks and compared these results to the control groups that did not have any vocal augmentation. Once they created a regression model that best quantified these results they then applied this formula to chicks of other ages.The compared the parental response by transposing blackbird and song thrush chicks into warblers nests as they rival the cuckoo chicks in size. They then tested the response of the parents in the presence of these experimental species performing their  natural displaying (large gaping) that was augmented by a cuckoo call.

1) What question were the researchers trying to answer?

The researchers were trying to discover why common cuckoo chicks are able to successfully parasitize warbler nests. Specifically,  they are researching the complex behavior that is displayed by the cuckoo and warbler chicks in an effort to quantify the effect each signal type (gaping displays and call frequency) has on the parental individuals in regards to how much food they provide. To begin,  they first tested the various impacts of different response levels and discovered that multiple signals offered more precise information regarding how much food the chicks required, the age of the individual as well as the size of the brood. However, they then transition to the effect of a cuckoo parasite on a nest of warblers and note that one cuckoo requires the nutrition needed for approximately 4 warbler chicks. They question how only a cuckoo chick, with its enormous size,  is able to trick the foster parents into continually bringing it large amount of food.

To confirm their suspected correlation between cooperative passerines and parasitic species they used phylogenetic comparisons of the fauna in the aforementioned areas. Their results showed that a large percentage of the species targeted by parasitic individuals in these areas were indeed cooperative breeders. Their theories were confirmed after comparing the growth rates of cuckoo (parasitic) chicks in biparnal and group care settings. In larger groups (3+) cuckoos grew at a faster rate with decreased levels of death due to smaller predation rates.  However, these potential benefits were seldom realized as larger groups were able to defend from parasitism more efficiently. Finally, they determine that cooperative behavior is driven by their increased reproductive success secondary to their defensive measures.

Cooperatively breeding passerines are targeted by parasitic species more frequently and due to their heavy cost, defense mechanisms in the form of mobbing have also evolved in response to this.  Feeny and his team initially began their study due to the overlapping concentrations of cooperatively breeding passerine species and parasitic species in australian and african regions.Furthermore, the driving force between these interactions is unclear and they note that this may be a coincidence secondary to the unpredictable environments they both inhabit. They proposed that 3 non mutually exclusive theories that could have driven the evolution of this behavior: 1. The parasitic offspring receive the greatest care, cooperative nests are more easily visible due to their activity and finally cooperative breeding may be selected for as they can better defend their nests from parasites.

Throughout the course of our existence the human race has been thought to be responsible for a staggering level of extinction events. However, through the means given to us by modern medicine, we now have the ability to save one individual breed of man’s best friend, the canis lineage, from a rapidly spreading retrovirus. Before a decision is made I believe that an intrinsic worth or value should be assigned to each breed that is determined by their practical use and popularity. From this value, we can then identify the most prefered breeds and then make a decision based on this value from a nation-wide voting system that is similar to the system used in presidential elections. After personally weighing the importance of the breed to mankind and their popularity I believe that the German Shepherd should be vaccinated against the retrovirus.