Birds Prefer to Feed near Predators than Feed near a Competitor. by Emerson Harris. Center for Teaching and Learning Glenn Powers 3o March 2018

Transcription

1 Birds Prefer to Feed near Predators than Feed near a Competitor by Emerson Harris Center for Teaching and Learning Glenn Powers 3o March 2018

2 Abstract; Will the presence of a competitor (squirrel) vs. the presence of a predator (owl) affect the bird foraging behavior more? My experiment will show which option is safer for a bird while foraging: facing a competitor or a predator. To set up my project, I hung two identical feeders about 10 feet away from each other. I put a fake squirrel on the crook of the branch that one of the feeders was hung on. A fake owl was tied to a tree about 4 feet away from the other feeder. Both fake animals were at eye level to their feeder. The feeder near the owl consistently had more seeds eaten by the birds, compared to the feeder near the squirrel. The mean of the number of grams eaten near the owl is 153 grams eaten for the entire experiment. The mean for the feeder by the fake squirrel is 81 grams eaten. I found that birds would rather risk being attacked by a predator, than risk getting no nutrients at all after losing to a competition. Introduction: Will the presence of a competitor (squirrel) vs. the presence of a predator (owl) affect the bird foraging behavior more? Birds face many foraging challenges, the birds must determine the safest way possible to gather food. The birds know that without food they will starve. They also realize that every time they venture to find food, they risk getting eaten by a predator such as an owl. Birds often feed in the morning, and again just before sunset to avoid predators. My experiment will show which option is safer for a bird while foraging: facing a competitor or a predator. I predict that the birds will visit the feeder with the squirrel more because although the birds would theoretically gather less feed when competing against a squirrel, when gathering near an owl, the bird may retrieve more feed without any competition, but then again risks being eaten. Prior research that relates to my topic is when birds feed. British Trust for Ornithology found that birds are most likely to feed in three peaks. The first typical time for feeding is early in the morning. This is the best time slot because the birds are able to regain the lost nutrients from the night. The later frenzy is just before dark with similar reasoning, the birds taking on extra reserves in order to get through the night. Another less popular time to feed is the middle of the day. This is usually when individual birds have to feed because of the competition during the ideal safe feeding times. The less dominant species may be forced to eat during this time. Bird foraging behaviors near a predator and competitor are important facts to realize, understand and investigate, before the experiment is assessed. An article on compared bird foraging behaviors around predators to our ability to walk and talk at the same time. However, running and talking at the same time requires more effort and causes us to lose our breath faster. Birds can fly and gather feed simultaneously with ease. When the birds must fly from a predator and gather seed, their energy is drained, so they must gather more nutrients to make up for it. Birds often risk going out in a dangerous feeding time, rather than go during a safe time with competition. Methods: The materials I used to study the foraging behaviors of the birds are: a fake squirrel, a fake owl, black oil sunflower seeds, two identical feeders and a tracking camera. To set up my project, I hung two identical feeders about 10 feet away from each other. I put a fake squirrel on the crook of the branch that one of the feeders was hung on. A fake owl was

3 tied to a tree about 4 feet away from the other feeder. Both fake animals were at eye level to their feeder. I used the black oil sunflower seeds to attract the largest variety of Maine birds ( I filled each feeder to the top after measuring the remaining feed in grams every time I checked the feeders. I recorded the grams of feed left in each feeder with a table. On March 6, 2018 I moved both feeders to a location closer to the edge of the woods because when my experiment was based further into the woods, the squirrels interrupted my experiment by tampering with the feeders and devouring the black oil seeds. Results: Date Collected 2/6/18 2/9/18 2/12/18 3/2/18 3/9/18 3/12/18 Owl Feeder (Grams eaten) 93 grams 143 grams 156 grams 233 grams 126 grams 156 grams Squirrel Feeder (Grams Eaten) 53 grams 43 grams 126 grams 66 grams 26 grams 172 grams

4 *The y-axis unit for both graphs is grams. The feeder near the owl consistently had more seeds eaten by the birds, compared to the feeder near the squirrel. The one outlier was on March 12, 2018 when the squirrel feeder had 172 grams eaten and the owl feeder had 165 grams eaten. The mean of the number of grams eaten near the owl is 153 grams eaten for the entire experiment. The mean for the feeder by the fake squirrel is 81 grams eaten. The average difference (the mean of the squirrel values subtracted from the owl values) is approximately 88 grams. The range of the owl feeder data is 140 grams. The squirrel feeder range 126 grams. Generally, there is an upward trend in the data for the feeder by the fake owl until the ninth of March, when the amount dropped. The data for the feeder near the squirrel is not as consistent, because it increases and decreases throughout the experiment, while always remaining lower than the corresponding owl feeder values, with the exception of the last data point. Conclusion: Winter birds of Maine will choose to forage near a predator rather than face a competitor near their feed. In my experiment, birds visited the feeder near the owl more consistently than the feeder next to the squirrel. The squirrel feeder had more seed eaten one time during the experiment, and had only 7 more grams eaten than the owl feeder during that time. This is the only evidence against that contradicts the claim. Since the average amount of feed eaten from the squirrel feeder is 81 grams, while the average amount eaten from the owl feeder is 153 grams, it is truthful to say the owl feeder received more bird visitors. This corresponds with the British Trust for Ornithology research because they explained that some birds choose to feed during predator dense times due to the competition associated with the safe feeding times. I found that birds would rather risk being attacked by a predator, than risk getting no nutrients at all after losing to a competitor. My findings are important because the results are counterintuitive. One would expect that a bird would rather face a competitor than a predator, but the data shows just the opposite. It also

5 shows that squirrels are a large contributor to how many birds visit the feeder. Squirrels will repel birds far better than owls. All in all, I found that birds choose to feed near a predator, because if they don t get eaten, they collect more feed than they would when facing a competitor. In order to study this further, I would experiment with different species of competitors and predators. This would expand the research further beyond squirrels and owls. It would ensure that the patterns in my data can be generalized over any competitor and any predator.