The Effect of Climate Change on the Ectoparasite

The Effect of Climate Change on the Ectoparasite Population Found on Songbirds in Northern VirginiaResearch Question:What is the effect of climate change on the ectoparasite population found on songbirds in Northern Virginia?Personal Engagement:When I was six months old, my parents gave me a stuffed animal duck, which I promptly named “Ducky”. My parents tell me that after I laid eyes on that cute stuffed animal, I couldn’t stop looking up. Everywhere my parents took me I would look for birds, running after them to get a closer look when I could. When I was about ten, my parents thought it would be fun if I could join others in birdwatching sessions, which is when they found the Northern Virginia Teen Birding Club. I was much younger than everyone else in the club, but just as eager to watch birds and learn.About two years after I joined the club, the founder/leader of the club, Fred Atwood, a teacher at the Flint Hill School in Oakton, VA, told me about “bird banding”. I had no idea what “banding” entailed, but as soon as he mentioned holding birds, I was ready to get involved. At first I only watched others band and recorded their observations, as I didn’t have enough experience or training to do the banding myself. But over time I was able to do more and more, one year I could hold them, the next I could take them out of ground traps, and the next I could actually put the bands on them. One of the things that caught my attention was that birds could contract ticks and lice like people, and that these ectoparasites can be extremely harmful to birds, sometimes even causing a bird’s death. In ninth grade, I was interested in using the data collected from banding while I was in the club in my science project. I crudely analyzed the data to examine whether there were differences in frequency of ectoparasite infestations among species, but my experiment showed no significant difference. In tenth grade, I continued my investigations with the club’s data and analyzed the data for differences between the percentages of birds bearing ectoparasites between sexes of birds, this time using data that the club had collected since 1984, but again nothing significant was revealed.This year, research led me to find that scientists have speculated that ectoparasites would be adversely affected by climate warming in the coming years (Carlson et al., 2017; Ogden et al., 2008). It is my hope that this experiment will reveal whether this theory is born out in populations of songbirds that are frequently infested with ectoparasites.Background Information:Ectoparasites are parasites that live on the skin of birds. They can be passive, or be extremely harmful by damaging the bird’s feathers or damaging their fragile bones by eating through the skin. This can be catastrophic for birds, causing them to lose the ability to migrate or even fly at all. This leaves them extremely vulnerable to predators, which they could normally avoid by flying away.This experiment follows up on an earlier experiment that studied the effect of the sex of birds on the likelihood of the birds bearing ectoparasites. These ectoparasites include, but are not limited to, ticks, mites, and lice. The data for this experiment were collected using a technique called “bird banding”. This technique involves setting up mist nets, which are “the most commonly used method for capturing birds for research” (Keyes and Grue, 1982). Mist nets are extremely thin, yet durable nets, which are placed in locations that birds frequently fly through. The birds are unable to see the nets and fly into them. This does not harm the birds because the nets are very soft and flexible. Once the birds are caught in the nets, they are carefully removed in order to be examined. The major observations recorded during the examination are weight, wing length, sex, age, and whether they bear ectoparasites (Photos 1 and 2). These observations are recorded in a notebook, and then transferred into a spreadsheet, which is stored on a computer. The earlier experiment involved five years’ worth of data (2010-2015), coinciding with the author’s membership in the Northern Virginia Teen Bird Club. The results of the prior experiment demonstrated that male songbirds had a statistically equivalent percentage of birds carrying ectoparasites as female songbirds (29% of males to 29.6% of females).The data set used for the present experiment are more robust, dating back over 30 years, thereby increasing the ability to detect more subtle differences, if they exist. Further, because each banding entry also contains the date when the bird was banded, the analysis is able to consider possible changes over time. The purpose of this follow up experiment is to determine whether the average annual temperature affects the likelihood of Oscines (songbirds) bearing ectoparasites, as recent studies have revealed that climate change may be negatively affecting parasites (Carlson et al., 2017; Ogden et al., 2008). Numerous songbird species were included in this study, and the data were collected over the course of the past 31 years by the Northern Virginia Teen Birding Club and Fred Atwood, who is a biology teacher at a local high school and the leader of the Northern Virginia Teen Birding Club. The temperature data used for this experiment were collected by the NCDC (National Climatic Data Center).Research Hypothesis: If the birds were banded during years with higher average temperatures, then the percentage of birds bearing ectoparasites will decline because of the negative effects of higher temperatures on ectoparasites.Null Hypothesis: There is no correlation between the annual average temperature and the percentage of birds bearing ectoparasites.Variables:Independent Variable: The independent variable for this experiment is the average temperature in Northern Virginia during the years the birds were banded. The climate data was collected by the NCDC in Arlington, Virginia, the closest region with available data to Oakton, Virginia, where the banding occurred. The annual average temperature was averaged for sets of five years, 1984-1988, 1989-1993, 2001-2005, 2006-2010, and 2011-2015. The data were grouped into sets of  five years because if measured by individual years, the number of trials (birds) would vary greatly. In sets of five years, each set contains at least 100 individual birds. The gap between 1993 and 2001 is due to a lack of available banding data.Dependent Variable: The dependent variable in this experiment is the percentage of birds bearing ectoparasites. This was chosen because as ectoparasite populations decline, the number of birds bearing ectoparasites would be expected to decline as well. These data were gathered using the process of bird banding, and the examination of birds for the presence of ectoparasites (see picture 1) requires no tools.Controlled Variables: Due to the nature of observational experiments, it is extremely difficult to control any variables. The method of data collection and the location of the banding were the only variables controlled in this study.Uncontrolled Variables: The large time frame over which the data were collected and the relatively large amount of data result in many uncontrolled variables, such as pesticide use in the area and annual variations in precipitation, which may have an effect on the ectoparasite population. This means that causation cannot be determined from this study.Apparatus: Because this is an observational study, all of the data has already been collected and the only apparatus required is a spreadsheet with the complete set of data, a computer (a MacBook Air 2015), and a calculator (the TI-84 C Silver Edition). The data sets come from the Northern Virginia Teen Birding Club and the National Climate Data Center (NCDC).Method:The banding data used in this experiment consist of two date ranges recorded roughly eight years apart. The “old data” were collected between 1984 and 1993 and the “new data” were collected between 2001 and 2015. The data used in this experiment are comprised solely of songbirds because they make up almost half of all birds in the world (The Editors of Encyclopaedia Britannica, 2017). The climate data used in this experiment were found on the NCDC Climate Data Online database for each year from 1980-2015. The data were grouped into sets of five years (1984-1988, 1989-1993, 2001-2005, 2006-2010, 2011-2015) and the mean temperature was averaged for each of the five years to get a five year mean temperature. A Chi Squared test was conducted to measure the significance of the data tested in the experiment and a correlation coefficient was calculated to determine whether there was a negative relationship between average temperature and the percentage of songbirds with ectoparasites. The tests were conducted on the data present in Raw Data Tables 1 and 2 in the Appendix.Safety, Ethical, and Environmental Concerns: Because this is a data-based study, no risks were imposed on any individual, animal, or the environment. The methods used for recording temperature data pose no risks and the bird banding process resulted in no harm to any individuals or birds. The data collection process was completely independent of this study. All safety, ethical, and environmental risks have been considered and no precautions were needed for the analysis of pre-existing data.Results: When analyzing the data, the set for 1984-1988 had to be removed due to a lack of trials (less than 100 individual birds). The comparison between the average temperature and the percentage of birds bearing ectoparasites for the 4 remaining sets of years yielded a correlation coefficient of -0.627, indicating moderate negative correlation. This negative correlation is apparent in the scatterplot data and trendline. The chi-squared test yielded a p-value of 3.4 × 10-8 with a chi-squared value of 37.62 and three degrees of freedom. The p-value is lower than 0.05 and the chi-squared value is larger than the critical value of 11.34 for 0.05 with three degrees of freedom, indicating statistical significance. Conclusions: Because of the moderate negative correlation and the indicated statistical significance, the hypothesis can be accepted and the null hypothesis can be rejected. While this experiment only proves the hypothesis true for the region of Northern Virginia alone, its results could be true for other areas, and the implications would be huge. While the decline of ectoparasites may be beneficial in the short term for birds, the long term effects could be catastrophic, as “parasites can be stabilizers or destabilizers” (Combes, 1996) and “play a major role each time ‘something’ disturbs living beings at the populational level” (Combes, 1996). This means that some bird populations could grow out of control and cause the deaths of themselves and other populations as they consume all available resources in their region. These large scale implications could be verified by a similar study with data set that covers a larger time frame and area, and this study could be improved by limiting the number of confounding variables.Appendix:Raw Data Table 1 (2001-2015):2001-20052006-2010 2011-2015 Birds with parasites9168135Birds without parasites13494267Raw Data Table 2 (1984-1993):1984-19881989-1993Birds with parasites12179Birds without parasites33140Raw Data Table 3 (NCDC Climate Data):DateTemperature (Fahrenheit)Elem->TAVGTMAXTMINYearAnnual MeanTempMean MaxTempMean MinTemp198059.568.150.919815967.550.4198257.666.448.8198358.466.949.8198457.86649.6198558.166.749.5198657.766.44919875866.949.219885766.347.8198956.965.148.719906069.250.7199160.269.351.1199256.765.148.3199357.766.449199458.267.449199557.966.649.1199656.86548.619975866.94919986068.451.5199958.967.85020005765.348.6200158.567.449.6200259.368.150.4200356.464.148.6200457.965.949.920055866.349.7200659.167.850.5200758.967.550.3200859.167.650.7200957.365.449.2201059.768.251.2201159.968.351.5201261.570.152.8201358.866.850.7201458.566.850.1201560.168.651.6Photo 1: The wing of a White-breasted Nuthatch with licePhoto 2: The wing of a White-Breasted Nuthatch being examined for ectoparasitesBibliography:Carlson, Colin J., et al. “Parasite Biodiversity Faces Extinction and Redistribution in a Changing Climate.” Science Advances, vol. 3, no. 9, 2017, doi:10.1126/sciadv.1602422.Ogden, N.h., et al. “Projected Effects of Climate Change on Tick Phenology and Fitness of Pathogens Transmitted by the North American Tick Ixodes Scapularis.”Journal of Theoretical Biology, vol. 254, no. 3, 2008, pp. 621–632., doi:10.1016/j.jtbi.2008.06.020.Combes, C. (1996). Parasites, biodiversity and ecosystem stability. Biodiversity And Conservation, 5(8), 953-962. doi:10.1007/bf00054413Keyes, B. E., & Grue, C. E. (1982). Capturing Birds with mist nets: A Review. North American Bird Bander, 7(1). Retrieved October 20, 2017, from Editors of Encyclopædia Britannica (Ed.). (2017, August 24). Songbird. Retrieved September 20, 2017, from