Scott+McClintock

Does a sound recording of a predator's call (Cooper's Hawk) effect the feeding behavior of a non-native bird population (Eurasian Tree Sparrows)?
 * Questi** **on**

**Introduction** At my backyard feeder, I have observed Black-capped Chickadees, House Finches, Mourning Doves, Northern Cardinals, and Blue Jays. However, I also have two nesting families of Eurasian Tree Sparrows in my yard and these birds dominate the feeding at my bird feeder.



The Eurasian Tree Sparrow is a non-native bird in the western hemisphere. The original intent by those who brought the birds to St. Louis was to help control insect populations, but that did not happen and the birds soon became a nuisance to grain producers. In the western hemisphere, Eurasian Tree Sparrows can only be found in the greater St. Louis area (~150 mile radius). The population exceeds 15,000 birds as of 2012, and all of t hese sparrows are descended from 12 birds imported from Germany and released in 1870 in Lafayette Park. In 1878, St. Louis saw the invasion of the more aggressive House Sparrow, which began to push the Eurasian Tree Sparrows from its established nesting areas. The House Sparrow was originally introduced in New York City in 1851 and spread rapidly across the country.



The Eurasian Tree Sparrow population has never spread like its cousin the House Sparrow. Some believe that the Eurasian Tree Sparrows range is limited because they cannot compete with their larger cousins. Jim Jackson, from the Missouri Department of Conservation, describes the situation by saying "their relationship is like the gentle country cousins versus the aggressive street urchins." Studies have also shown that Eurasian Tree Sparrows do not migrate and the offspring do not wander far from the nest to establish new territories, keeping them contained in a rather small area of the United States. Another interesting trend is that the Eurasian Tree Sparrow seems to be moving north up the Mississippi river, but not south. This could be caused by habitat differences between the areas north and south of the confluence of the Mississippi and Missouri rivers.



Of the four yards my backyard touches, three of them have bird feeders. This creates a wonderful space to view a rich diversity of birds, but it also invites predators to the area. One frequent guest we spot in our yard is a Cooper's Hawk, which are aerial foragers and predators of the Eurasian Tree Sparrow.



In this experiment, I hope to find the effects a sound recording of a Cooper's Hawk will have on the feeding behavior of a non-native bird population (Eurasian Tree Sparrows). I will test this question by observing the feeding behavior of the Eurasian Tree Sparrows and then introduce the call of a Cooper's Hawk. I will record observations of what happened and also time how long it takes for the Eurasian Tree Sparrows to return to feed. I will also introduce other sounds, not of predators, to see if the sound of a predator itself is causing the behavior or if it is just the presence of any new sound being added to the feeder environment. Feeding behavior will be measured by Eurasian Tree Sparrow presence on the feeder.



This question is important to study because the range of the Eurasian Tree Sparrow is so small in the United States that not many scientists have the opportunity to study them. I am intrigued to find out how a non-native species will react to the sounds of native predators.

I will collect three times a day. The morning and evening observations will be using the sound of a Cooper's Hawk, while the midday test will be the baby crying.

I think that the sound of a Cooper's Hawk will scare away the Eurasian Tree Sparrows, but they will return to normal feeding behavior within 1 minute. I also think that the presence of any loud sound to the feeding environment will cause this behavior and not just the sound of a predator.
 * Hypothesis**

**Materials** Bird feeder Bird seed Bird field guide iPod Mini-Speaker iBird Pro (app) Stopwatch Recording of another sound (here we are using the sound of a baby crying)

1. Observe feeder. Wait for presence of two or more Eurasian Tree Sparrows. 2. Using iPod and iBird Pro, introduce recorded sound of a Cooper's Hawk. 3. Record observations and start timer. 4. For five minutes, measure how long it takes for Eurasian Tree Sparrows to return to feeder. 5. Repeat daily; once in the morning and again at dusk for seven days. 6. To test another sound, repeat experiment during midday and introduce recorded sound of a baby crying. 7. Record observations and start timer. 8. Measure how long it takes for Eurasian Tree Sparrows to return to feeder. Repeat daily.
 * Methods**

Sound recording of a predator (Cooper's Hawk)
 * Independent Variable**

Presence of a non-native species (Eurasian Tree Sparrows)
 * Dependent Variable**

Bird feeder Bird seed Distance of speaker from feeder (23ft) Length of recorded sounds Volume of recorded sounds
 * Control**


 * Results and Analysis**



The average time it took for two or more Eurasian Tree Sparrows to come to my feeder was 1 minute 47 seconds. Once two or more Eurasian Tree Sparrows were present I would record the feeding behaviors I observed (caching, probing, sorting, ground feeding, feeder guarding) and then introduce the recorded sound. The data shows some interesting trends. On average 4.5 Eurasian Tree Sparrows were present when the Cooper's Hawk call was introduced. Usually, the call frightened off the birds at the feeder but occasionally the birds would perk up, but ultimately stay. The data shows that after 30 seconds, a little less than half of the Eurasian Tree Sparrows would return to the feeder. This number increased slowly, but by the end of the five min observation period the number of Eurasian Tree Sparrows was around 62% of beginning population. So while the population of birds at the feeder left the feeder when they heard the call, half of them returned rather quickly, but the population never returned to the same level of feeding (at least not within the 5 minute observation time).

When I introduced the call of the baby crying, there was no change in feeding behavior of the Eurasian Tree Sparrows. In fact, five minutes after the baby call was introduced the number of Eurasian Tree Sparrows actually increased.

My hypothesis was that I thought the sound of a Cooper's Hawk would scare away the Eurasian Tree Sparrows, but they will return to normal feeding behavior within 1 minute. This hypothesis was not supported by the data. The data says that the Eurasian Tree Sparrows are quicker to return than I expected, but ultimately in smaller numbers.

I also thought that the presence of any loud sound to the feeding environment would cause this behavior and not just the sound of a predator. This second piece of my hypothesis was also not supported by the data. The loud sound I used (a baby crying) did not have any immediate effect on the number of feeding birds, and over a 5 minute window, the number feeding Eurasian Tree Sparrows increased.

These results were surprising to me, however I also recognize that their were many other environmental factors that lead to birds presence at the bird feeders. One day while collecting data a squirrel shimmied down to the feeder, hung on by his feet, and had himself a nice long dinner. I didn't have birds return for an hour after that. During another observation I had a Blue Jay visit which scared off all the smaller birds. These, and other factors, would have a part in determining if birds would return to the feeder besides the presence of a predator's call.



I do think that the data collected here does show a trend that could be explored further in future experiments. Variations for future experiments could include: - testing a wide array of different bird and animal calls - testing all species of birds (and not just Eurasian Tree Sparrows) - extending the observation window times to see the effect over a larger period of time - different distances of sound - varying the number times of the call is played (I only played the sound once, but in the wild a hawk may sound more than once)

I think in future experiments it would be interesting to explore the effects of nocturnal predators' calls on diurnal birds.

Also, I saw two other really interesting things while doing my research that were not related to my study, but still really cool. One day, right after I did the sound recording of the baby crying, I had two Northern Flicker's land near my feeder. They were really fun to watch play and feed together! The second was a bald-headed female Northern Cardinal. Learn more about this interesting phenomenon at Bald Birds.



**References **

Chipper Woods Bird Observatory. Eurasian Tree Sparrow. Retrieved July 12, 2012, from @http://www.wbu.com/chipperwoods/photos/eurtreesp.htm

Cornell University. Cooper's Hawk. //All About Birds.// Retrieved July 12, 2012, from @http://www.allaboutbirds.org/guide/Coopers_Hawk/lifehistory

Cornell University. Eurasian Tree Sparrow. //All About Birds.// Retrieved July 12, 2012, from @http://www.allaboutbirds.org/guide/Eurasian_Tree_Sparrow/lifehistory

Crank, Colleen (November 9, 2005). A St. Louis Speciality. //Litzsinger Road Ecology Center Weblog.// Retrieved July 12, 2012, from @http://www.litzsinger.org/weblog/archives/2005/11/

Erickson, Laura (2011, September 28). Eurasian Tree Sparrows vs. St. Louis Cardinals. //Laura's Bird Blog.// Retrieved July 12, 2012, from @http://lauraerickson.blogspot.com/2011/09/eurasian-tree-sparrows-v-st-louis.html

Jackson, Jim (2003, May 2). The Eurasian Tree Sparrow //MDC Online.// Retrieved July 12, 2012, from @http://mdc.mo.gov/conmag/2003/05/eurasian-tree-sparrow

Korotev, Randy (2006, October). Where to find Eurasian Tree Sparrows in St. Louis. //Webster Groves Nature Study Society.// Retrieved July 12, 2012, from @http://levee.wustl.edu/~rlk/wgnss/ets/index.html

Missouri Department of Conservation. Eurasian Tree Sparrows. //MDC Online.// Retrieved July 12, 2012, from @http://mdc.mo.gov/discover-nature/field-guide/eurasian-tree-sparrow

National Audubon Society. Bird Feeding FAQ. Retrieved July 12, 2012, from @http://web4.audubon.org/bird/at_home/bird_feeding/faq.html

National Audubon Society. Get Into Birds. Retrieved July 12, 2012, from @http://getintobirds.audubon.org/

World Bird Sanctuary (March 22, 2009). Eurasian Tree Sparrows. //World Bird Sanctuary blog.// Retrieved July 12, 2012, from @http://world-bird-sanctuary.blogspot.com/2009/03/eurasian-tree-sparrow.html