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Final- Foraging Experiment


Final- Foraging Experiment 331

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This 8 page Bundle was uploaded by ROBIN on Friday April 1, 2016. The Bundle belongs to 331 at University of Illinois at Chicago taught by in Spring 2016. Since its upload, it has received 13 views. For similar materials see Ecology in Biology at University of Illinois at Chicago.


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Date Created: 04/01/16
The effects of Foraging on the giving up densities of house sparrows By: Robin Cordero 1 Introduction In order for an organism to survive and reproduce it must find way to optimize their  foraging strategies, that is it must find, capture, and consume food containing the most calories  while expending the least amount of time, in order to maximize their fitness. A forger individual  has three important decisions to make that takes into account the cost and benefits of a particular  food: diet choice, patch usage and habitat selection. For a species to efficiently forage eating  quality food is very important. For this reason, an organism must consume high caloric food  items in order to maximize their energy input.  Furthermore, diet choice takes in consideration  four variables: resource abundance (abundant or scarce), nutritional value (amount of energy  obtain from a prey item), encounter probability (ability to encounter the prey item) and handling  time (how long it takes to handle the prey).  The second decision an organism must take in  consideration is how long and how thoroughly should a forager forage a food patch. Should an  organism forage for long time at the cost of getting caught and eaten or should an organism  change the quality of food as the food patch becomes risky. The point in which a forger stops  foraging a food patch and moves on to another is called the “giving up density”. The giving up  density is measure by food left unconsumed. Usually a low (GUD) indicates a high food  encounter ability and high nutritional food value, while a high (GUD) indicates a higher handling time, a higher metabolic cost, a higher predation risk and higher missed opportunity cost. For this reason, the concept “giving up density “plays a crucial role in understanding an organism  behavior and preference. Similarly, an animal must decide when and where to forage efficiently.  The theory of density­dependent explains how habitat selection is effected by population size.   As population size increase individuals must split into a good and marginal habitat where the  2 reward outcome is very low.  In contrast, when population size is low individuals are able  occupy the best habitat and therefore optimize their rewards.  Understanding how an organism  foraging behavior operates can be key in analyzing the feeding behavior of several organisms,  for this reason an experiment was perform in aims to understand the eating patterns of house  sparrows. House sparrows, also know as passer domesticus, is a well established bird located in  farms, residential areas, and urban areas (Human Society). Often thrived on the food and shelter  that humans provided. They generally feed on livestock, seeds, and discarded foods (Cornell  Lab). In terms of behavior, house sparrows tend to forage in small flocks as to avoid predation.   Likewise, they forage for food on the ground using their hopping skills to move around. More so, house sparrows are very aggressive in protecting their nesting site and territory causing a  devastating threat to several birds. Regarding, their reproductivity house sparrows mature at a  very early age (152 days) and tend to have a clutch size of five per season (Cornell lab).  In all,  understanding the life history of house sparrow can give us insight on their anatomy and  behavior, which can come in handy when evaluating our results. Based on the life history of house sparrows and foraging behavior I came up with three  hypotheses that will attempt to answers our research question. In our experiment, we investigated the effects of food locations on the eating patterns of house sparrows. For this reason, we  organize our experiment using a 2 by2 factorial design that encompassed two factors (food  quality and height location) and two levels of each factor (poor or rich food quality). This  experimental design helped us test the effects of food quality, height location of tray, and their  interaction on the foragers giving up density. Having this in mind, my first hypotheses dealt with  3 the quality food, that is whether the food contain a high or low amount of protein content. I  predicted that food that contain high amount of protein will be consumed more (lower “gud”)  than the low protein content (higher “gud”). Further more, my second hypothesis took into  account to factor location and food quality. I predicted that ground level location with high  protein content will be consume more (lower “gud”) than above location with low protein  content (higher “gud”). My final hypothesis consisted of the interaction between the two variable that is the metabolic cost (rich or poor food quality) and predation risk (where the food patch is  located). I predicted that there will be no interaction between these two variables, meaning that  quality of food (rich/poor) and patch location (above/below) will have no affected on house  sparrows giving up density.  Material and Methods We first gathered all the materials that were needed for the experiment. Materials  included trays, food, sand, sieve, measuring beaker, and an electronic balancer.  Once the  material was collected we then began to label each of the four trays.  The fist tray read “low  protein and low location”. The second tray read “high protein and low location”. The third tray  read “high protein and above location”. The fourth tray read, “high protein and above locations”.  After we finish labeling each of the four trays one of our team member were in charge in  collecting and measuring one liter of sand using a measuring beaker. The second team member  was in charge in collecting and measuring three grams of the food, which included wild bird seed mix and sunflower (chips) using an electronic balancer.  Once collected and measured we began  to pour in one liter of sand in each of the four trays. Then following our labeling we began to  pour in our food in each of the four trays. For our low protein content, we used wild bird seed  4 mix and for our high protein content we used sunflower chips. After the sand and food were  poured in using our hands we began to mix slowly the top of sand with the food in each of the  four trays. Next, we collected all our trays and moved to our location of studied.  Our location of  studied was located in front of SES besides the parking lot were the two big pine trees are  located at. Once we got to our location we began to unload our trays. Using our tray labels we  began to placed the trays in their designated locations.  Two of the trays were put on the ground  while the other two trays were put on top of a tree branch. We also made sure that we set the  trays out during the morning so that were able to collected the remaining of the food that  afternoon. More so, the remaining of the food was collected by passing the sand through a sieve.  Once passed, we collected any food remains on the sieve and weight them on our scale to get the  giving up density. Finally, we repeated the previous steps for a total of three days. After we  gathered and collected our data we did a bar graph and an ANOVA analysis to help interpret our  results.  Results By looking at (Table 1) we see a significant interaction between the two variables studied (food  quality and patch location).  This is also confirmed in (fig. 1) were result were very inconclusive  if whether there is a significant effect of either patch location or food quality. For this reason, the ANOVA analysis shown in (Table. 1) certify with a p­value of 0.0486 that there is indeed  significant interaction between food quality and patch location. 5 House sparrows giving up density High Protein Low Protein ANOVA SUMMARY (Table 1) SS DF MS F P Patch 0.11 1 0.11 0.73 0.4177 location Food 0.05 1 0.05 0.33 0.5814 Quality Food X 0.81 1 0.81 5.4 0.0486 Location Error 1.2 8 0.15 Total 2.17 11 Discussion Our first hypothesis stated that the food quality will have a significant affect on the  giving up density of the house sparrows. However, our result concluded that there is no  significant effect of the food quality on the house sparrow giving up density. This can due to the  fact that house sparrows not only rely on their food quality but also rely on other important factor such as food location. Our second hypothesis showed very similar results as to the first.  The second hypothesis  dealt with the patch location. Our results indicated no significant effects on the giving up density  6 of house sparrows. This can be due to the fact that factors such as an organisms handling time,  predation risk, and missed opportunity cost may have not been significant affected on each of the patch locations therefore showing no significant effect on the giving up density.   Our third hypothesis encompassed both variables: food quality and patch locations. These two variable were tested to see if their interactions play a significant role on the giving up  density of house sparrows. Based on our results we can strongly reject our null hypothesis   the alternative that their is a significant interaction between food and patch location on the giving up density of house sparrows. So not only does food quality affect what house sparrow  forage but the location of where to find the food significantly matters. These results can be  explained by analyzing both the cost and benefits of each food item. By doing this we can see  how predation risk and metabolic cost influences the interaction between food quality and food  patch.  Overall, understanding how organism foraging behavior can be influence by several  factors, such as food patch and food quality can help us further understand how an organism  optimize their foraging strategies in order to survive and reproduce. Reference: 1. Anderson, Ted R. 2006.Foraging Behavior and Food. Biology of the Ubiquitous House  Sparrow: 246­82. 2. House Sparrow. The Cornell Lab of Ornithology: All about Birds. Cornell University: 3. Kurt, Timothy D.2005.  Differences in Badge Sizes of Male House Sparrows at Food  Sources of High and Low Risk | JYI – The Undergraduate Research Journal. The  Undergraduate Research Journal. University of Wisconsin, Madison. 4. Passer Domesticus. AnAge: The Animal Ageing and Longevity: 7 5. Seress, Gábor, Veronika Bókony, János Heszberger, and András Liker. 2011. Response  to Predation Risk in Urban and Rural House Sparrows." Ethology: 896­907 8


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