Barn Owls on the Side of the Road
Part of the Young Naturalist Awards Curriculum Collection.
When I first started this project, I was planning to look for and study the nest of the two great horned owls that live on my farm during the winter in Bliss, Idaho. We usually spend the weekends at my farm, and when I get there I like to explore and see what has changed from the previous week. I knew that the great horned owls usually appeared around January, and I was looking forward to observing them. During the summer I had been watching five barn owls that were living in a wooded part of my property. One of those five was an adult and the other four were juveniles. It is interesting that there were five owls living together because the Sibley Field Guide to Birds says that barn owls are usually solitary birds (Sibley, 234). Maybe they were living together because four of the owls were juveniles. During the summer I observed these owls and watched them grow. Fall and winter approached, and I noticed that when the great horned owls arrived to take their winter roost, the barn owls all but disappeared. I was wondering where the owls had gone. Then one evening, my parents and I were going to a movie in the nearby town of Jerome when I started to notice many dead barn owls lying around the highway. This really surprised me, and I started to count them. I was amazed by how many I counted and was surprised that I had not noticed the quantity of dead birds before. I convinced my parents to drive me back on that road for several more weekends. I wanted to find out if the owls had died in specific areas, or if they just generally got hit along the highway.
Barn Owl Information
The barn owl (Tyto alba) is a nocturnal raptor. It is a beautiful bird that is common throughout the world, and according to Paul D. Frost, the only continent where it is not found is Antarctica (Frost, p. 219). Barn owls are very easy to recognize. They have a pale face with a heart-shaped ring of golden feathers surrounding it, a large patch of white fluffy feathers around their beaks, and a few brown feathers around their dark black eyes. The neck has golden or white feathers with small black dots all over them. The back has gray feathers with white dots mixed with black dots. The colors between the owls vary, and some of the owls are darker in color than others. The underside of the body is white. The edges of the feathers on the underside of the wing have black stripes and gray ends and are mostly white. The tops of their wings are brown but have black stripes just like the underside. Their legs have no feathers, and their talons are long and curved. Their tail feathers are just like their wing feathers except that the tops of the feathers have more white. A barn owl looks very different from other owls. It has a distinct look and is easy to pick out.
To find out what the owls ate, I collected owl pellets from under the tree where the great horned owls roosted, and I also gathered pellets from under the tree where the barn owls had roosted in the summer. It appeared that they both ate small rodents, but the great horned owls also ate larger animals, and they had the advantage of size, as seen by the size of the pellets. Maybe competition was one of the reasons the barn owls had left.
When I observed the barn owls this summer, they were roosting most of the time in a Russian olive tree, in a small woodland area next to a planted field. A few times while they were not yet used to me and I approached them, I must have startled them and some flew away. I noticed that their flight was somewhat choppy. They would quickly beat their wings and then glide. They flew low and were always paying attention to the ground. They did not fly in straight lines and would go up and down and around and then back again. In his book North American Owls, Jim Burns says that barn owls generally fly at levels of 10 feet or less before they dive into their prey (Burns, p. 95). I knew this level of flight could be particularly hazardous on the highways, particularly on the highway I was observing because we have a lot of semitrailer traffic. (On a Saturday on our highway one can count an average of 20 semis traveling in one direction every five minutes.) I had also read that barn owls have great difficulty flying in strong winds (Great Britain Barn Owl Trust web site). I had watched this, and I had to agree. This made me wonder if this could also create problems for the owls on the highway because semis can create wind tunnels with their size and speed. In fact, while we were stopped on the side of the highway so I could take pictures of the dead owls, I could feel the wind as the big semis passed. They even shook our parked car. Small pebbles on the road would some times get kicked up and would hit me. I could imagine that these factors affected the barn owls' chances of survival on the highway.
The Great Britain Barn Owl Trust also says that a weak barn owl with wet feathers may be unable to fly. I had found some barn owl feathers in the summer, and I tested this by weighing the feathers and then wetting them, shaking them and weighing them again and then doing it one more time. I wanted to see if a wet owl might have problems flying because of the added weight. I was surprised by the change in the weight of the feathers.
Results of the feather weighing
|
0.44 g - Big feather dry 0.16 g - Small feather dry 0.68 g - Big feather wet1 0.28 g - Small feather wet1 0.79 g - Big feather wet2 0.32 g - Small feather wet2 |
The weight issue was interesting to me because if what the Great Britain Barn Owl Trust says is true, then a barn owl may struggle to fly back up if it has the added weight of a mouse and also encounters the wind created by passing traffic.
Another issue I thought about was what was actually killing the owls. The highway allows cars to travel at 75 mph and semis to travel at 65 mph. What made me think of this was that one day on our way to a swim meet at 5:30 a.m. one Saturday, we had almost hit two owls, but they were able to escape their death. If we had been a semi, the height of the vehicle would have killed the birds.
Questions
I had many questions. Had the barn owls I had watched in the summer suffered a fate similar to the dead ones that lay by the side of the road? How far did owls travel in order to find food? Why were all the dead birds on the side of the highway barn owls and not other owls or raptors? Were the owls getting hit because they were young and inexperienced hunters? Were the winds created by the trucks, and the weight of their prey, affecting their flight? Why were they hunting by the highway? Was it because mice are easier to see as they cross the road with the lights of the cars shining on them? Why did the mice cross the road? Was the sound of the cars affecting the owls' sense of direction when they tried to escape being hit? Were the lights from the cars affecting their vision? The questions were endless, and I had to narrow my research. In the end I just wanted to know why so many owls were dying on this particular stretch of road.
Hypothesis
My hypothesis was that there would be significantly more dead owls close to the dairies and granaries along the highway because the grain used to feed the cows would attract the mice that the owls like to feed on. I also hypothesized that there would be more dead owls if the areas along the highway contained places for the owls to roost, such as highway overpasses and trees.
Method
I started to count the dead owls I saw, and I put them in two categories: center divider and side margin. The center divider is the area that separates the two-lane highways. The side margin was just the side of the road. My dad called out the mile markers and I spotted dead owls. My parents soon joined in on the counting. On Sunday evenings we ended up going home via Jerome in order to count dead owls. As we counted the owls, I tried to make observations that described each mile in order to get an idea of which features existed in each mile. I categorized each mile with descriptions like Granary, Corn Field, Dairy, Town, Exit, Overpass, Underpass, and Trees. Every time I passed that stretch of highway, I tried to find something that could contribute to the death of the owls. I noticed, for example, that some overpasses have solid bottoms while some are open. The open ones appear to be better roosting places. I was trying to see if there was any correlation between these features and structures and the amount of dead owls in that section.
Results
There were variations in the number of dead owls I counted from week to week. There were times when I had remembered having seen a specific bird in a specific place, and it was not there the following week. Some of the changes may have been the result of scavengers like coyotes that eat the dead birds. I also saw many rock chucks on the sides of the road, but they are vegetarian (Alden, p. 64) and are probably not interested in the owls. I imagine that humans might on occasion pick up the dead birds. In Idaho a license is required, but I saw many "perfect" birds that might have appealed to a human. Lastly, the counts vary because as the owls decompose, they become harder to see from a moving car. In fact, one day when I got out of the car to take pictures of the owls, I found a decomposed owl that I would not have noticed and thus would not have counted. Many of the dead owls were easy to see because they were hit in flight and their wings were outstretched. I noticed that 80% of the dead owls were in the center divider. I think this is because they tend to fly in from the sides and are flying into the road when they get hit.
From the results, I noticed that 26% of the dead owls were within a four-mile stretch beside several large dairies that feed their cows a mulched corn product. The cows were fed very close to the highway. These stretches also had roosting places.
As a control, I did one observation on a 10-mile stretch of highway in the opposite direction of the one I studied. I counted a stretch of the highway in the direction of Boise, and I only saw four dead barn owls in a 10-mile stretch. I wanted to see how many owls got hit in a stretch of the highway that was close to the stretch I was studying but did not have dairies, feedlots, or granaries. This stretch contained no dairies, but it was interesting that two of the dead owls in that stretch were near a farm that had a few cows.
Conclusions
Given the information I collected, the number of owls killed within the miles containing granaries and dairies was higher, but there was also a large number of owls killed near towns and their exits. The highest death toll was from Mile 11 to 23, which has granaries, a dairy, and a town. Sixty-nine percent of the owls died in this section. The stretch of the highway I studied has an unusually high number of dead birds compared to the control stretch of highway I looked at. This would indicate that some factors on the stretch I was studying had contributed to the death of the barn owls, and that they were not dying in equal numbers along the highway. My results seem to point to the fact that there are more dead barn owls near dairies and granaries. There are also many dead owls in sections that have towns.
Barn owls coexist with man. We cannot move towns, but maybe we should not feed cows 15 feet from the highway. Having food available makes it hard to deter mice and thus hard to keep the owls away. A possible solution for the owls is making safe habitats that are away from the main highway. Some kind of rodent control in those areas might help, but poison would not be the answer because then the owls might be poisoned as well. We need to care and make an effort for the barn owls, because aside from being amazing animals, they also help farmers to control rodent populations, which can destroy crops. Britain uses a nesting-box program and a supplemental feeding program that is away from the roads (Great Britain Barn Owl Trust), and this might help. But maybe the answer is counter-intuitive and really should be about a mouse supplemental-feeding program, located away from the road. I wonder if the dairies have as many mice in the summer when the fields are planted and there is no need for the mice to search for food.
I will count the owls this summer and see what happens to the numbers. An interesting next step in this project would be to walk the most owl-deadly stretch of highway and count the dead birds. I would probably mark and number the dead birds to get a better idea of how many were getting hit per week. I would do this throughout the year to see how the barn owl death rate changes with the seasons.
In science, everything is related. Solutions to problems might be in places that we do not expect, like studying mice in order to save barn owls. What makes science so interesting is that there are so many angles to a problem, and even a person like me can look at something and make observations and come up with ideas. There are so many questions to ask and so many things to look at. I plan to continue to observe these owls as the year continues and the seasons change, and I hope to have the barn owls back at my farm again this summer.
Bibliography
Alden, Peter. Mammals: The Concise Field Guide to 197 Common Mammals of North America. New York: Houghton Mifflin Company, 1987.
Burns, Jim. North American Owls: Journey Through a Shadowed World. Wisconsin: Willow Creek Press, 2004.
Conserving the Barn Owl and Its Environment. Great Britain Barn Owl Trust. Retrieved from the World Wide Web on 2 February 2007. http://www.barnowltrust.org.uk/index.html.
Frost, Paul D. Birds of Prey: Majestic Masters of the Skies. New York: Paragon Books, 2006.
Sibley, David Allen. The Sibley Field Guide to Birds of Western North America. New York: Chanticleer Press, Inc., April 2003.