warnercnr.colostate.edu/class_info
Introduction: The Grasshopper Sparrow (Ammodramus savannarum) population is thought to be declining in most of its breeding range, including Colorado. As for most grassland birds, the primary threats are habitat loss and degradation. The preferred nesting habitat of the sparrow is mixed-grass habitats including prairie, hayfields, pastures, and grassy fallow fields. The species nests on or near the ground in open-cup nests, and its nest is usually associated with some plant cover. The sparrow nests from mid-April to late-July in north-central Colorado, and the Environmental Learning Center (ELC) has had what is considered healthy nesting populations. The golf mushroom is an important food resource for Grasshopper Sparrows during the spring nesting season.
Grasshopper Sparrows feed on the runners of this fungus which lie just beneath the soil. There is an edible and an inedible form of the mushroom. The golf mushroom gets it name from the fact that it leaves a hard outer shell that comes to the surface in fall and during winter these “golf balls” can be seen on the surface. During the “golf ball” stage, the previous spring’s edible form can be determined by markings on the ball that resembles writing. The ELC has a variety of invasive, noxious weeds on its property, and CSU plans on grazing the ELC this summer using special goats that feed on noxious weeds. Unfortunately, these goats will also eat the edible golf mushrooms. Grazing is an allowable activity under the management guidelines of the City of Fort Collins Department of Natural Resources, as long as some appropriate mitigation has been agreed upon. Suitable mitigation in this case will involve restoring native grassland fields in NE Colorado that CSU owns by seeding these fields with golf mushrooms at densities similar to the ELC. You are hired by CSU to develop the mitigation plan and the first task is to assess the density of edible golf mushrooms on a representative 1.0 ha plot of mixed-grass habitat at the ELC. So, to determine the appropriate mitigation, you must first estimate the density of edible golf mushrooms. Golf mushrooms can be cryptic and difficult to find on snow, therefore, the count of golf mushrooms needs to be adjusted by the proportion of golf mushrooms actually counted. That is, you need to estimate p, the probability of detecting a golf mushroom. To accomplish this task, you choose to use a multiple occasion, closed population estimation procedure (a type of capturerecapture technique). The detection (“capture”) history for each edible golf mushroom will be input into program MARK to estimate the abundance of edible golf mushrooms in the pasture from the previous spring. The design of the study is to search for “golf balls” on >6 occasions, and to record the capture history for each “golf ball” that is located 1 or more times. Procedure: [Data required for this study will be collected during this field lab and analyzed next week.] 50 m x 100 m For data collection, 5-8 observers will search for “golf balls” on each occasion within a 50 m x 100 m area. Each group of observers will line up on the baseline (to be identified) and walk in a straight line to the other side of the pasture while searching for “golf balls” seen nearby (the amount of time that you search will be limited). Normally, once an object of interest is found it is “marked” and re-released into the population where it has the potential to be recaptured on subsequent occasions. When you find a “golf ball” you will quickly examine it to see if it has what appears to be a number. If it does you will record the number and the trapping occasion. If it does not you will record the number 0 (to indicate an inedible golf ball) and the trapping occasion. [So for every “golf ball” that you encounter you will enter a number and the trapping occasion.] At the end of our survey period, the sequence of occasions that a particular nest is located represents its capture history, and the 1 st occasion that a “golf ball” was located is considered when it was marked. Capture history data allow us to estimate the capture probability per “golf ball”; and, to determine if p varies by time (capture occasion), individual “golf ball” (individual heterogeneity), or by whether a “golf ball” had been captured previously (behavior). In our lab, think about what might cause p to vary by time, heterogeneity, or behavior? These data will be summarized into the capture histories (in X-matrix form) for analysis via MARK. Capture Histories constitute the data required for analysis, and take the form: There are as many capture histories as there are unique objects/individuals captured during our survey. [Something to think about] Is there a way to estimate the entire population of “golf balls”, i.e., edible and inedible combined using the data collected today? While collecting data, keep in mind the following assumptions of this methodology: • Geographic Closure: The population has a defined boundary. • Demographic Closure: No birth, death, immigration, and emigration occur during the survey, i.e., over all occasions. In terms of nests, this means that nests are not gained or lost during the time period. • No tag loss. Must be able to tell if the nest has been tagged before or not. • No measurement or sampling error. All nests are identified and recorded correctly. Homework Assignment (Worth 100 points; Report due in class March 1): By the end of Friday, please email Beth your data in an excel file with two columns: occasion and “golf ball number”. So if you collected data on occasions 1, 3, & 5 and on occasion 1 detected golf ball nos. 88 and 113; detected no golf balls on occasion 3, on occasion 5 detected golf ball numbers 4 and 77, then your data will look like. You will learn the skills in a few weeks to analyze these data in program MARK. After analyzing the data, a report will be due that encompasses both the data collection and data analysis. While you cannot finish the report until after doing the analysis, it is always a good idea to write up as much of the report as possible prior to the analysis (e.g., methods, parts of the introduction and objectives) while data collection is still fresh in your memory. Remember, the key parameter to estimate is the density of edible golf mushrooms in the pasture to be impacted by the grazing. This density will be used to determine the appropriate mitigation. Your report should be written in the basic scientific format: 1. Introduction — State the problem and purpose (objectives) of the study, etc. 2. Study Area and Methods – provide information on the study area, methods of data collection (field procedures and process), methods of data analysis, etc. 3. Results — what did you find out? What were the results of your analyses? Did you find evidence of variation in time, behavior, or heterogeneity in p? What statistical results are important to provide to the reader? Tables? Figures? 4. Discussion — what do you conclude from your study and what interpretations can you make? What do you recommend to your supervisors for the appropriate mitigation? How confident are you in your recommendation? How do your results compare with other studies of grasshopper sparrows? 5. Literature Cited — This is a scientific report and thus, just as in FW370, you should include citations to pertinent literature, literature on Grasshopper Sparrows is a good start. Your report must include at least 5 citations of journal articles. 6. Also include an Abstract and an appropriate Title as if you were submitting this paper to the general manager of the Department of Natural Resources. Follow the guidelines covered in past scientific writing courses such as FW 370 on what information should be covered in each section. Proper organization of your report will constitute a portion of your grade on this and all remaining lab assignments. You can also find additional information about the Grasshopper Sparrow in journal publications by searching the libraries scientific databases such as “Web of Science”. Below are 2 general web pages that you can start at but these are not journal articles: If you use materials from publications (or web sites…but web sites do not count as the journal citations), make sure to properly cite your sources! If you use passages word-for-word, they should be quoted and cited, but quotes should be rare, i.e., most scientific writing involves paraphrasing passages to make specific points with the inclusion of a citation.
