Still on the Move

Now that we are well into autumn, migration is in full swing. Many creatures headed south weeks ago. Among the first were the tree swallows. Think back to the last days of August and you might recall seeing many dozens of swallows lined up on phone lines as they prepared to leave for points south. Another traveler is the common nighthawk. I remember watching and hearing nighthawks when I was growing up. These would be found in most small cities throughout our area during the summer nesting season. Their numbers have seriously declined over the last several decades. Nowadays I look forward to seeing them at dusk as they migrate southward during the late days of August and the first days of September.

One of the greatest spectacles of migration is the movement of broad-winged hawks from their summer nesting homes in the forests of the northeast to their winter haunts in South America. The broad-wings leave en masse at the end of August through to the end of September, after which very few will be seen until next spring. To conserve energy on their long flight south, they typically soar upward in thermal updrafts or winds deflecting off mountain ridges. As they glide up on the lifting wind they look to the south and when they observe other hawks spiraling upward they glide off to another updraft. In this manner they travel several hundred miles each day with hardly any flapping of their wings thus conserving energy. These groups of hawks form a boiling mass of birds that is given the name “kettle.” The largest kettle I have ever observed was about three hundred hawks. Some kettles have been seen with thousands of hawks. The prime time to see broad-winged hawk kettles is the middle of September. Two organization you can check out to learn more about hawks in migration are the Hawk Migration Association of North America (HMANA) at www.hmana.org and NorthEast Hawk Watch at www.battaly.com/nehm/. Look to the right and you will find links to both organizations.

There are two other amazing migrants that we have the chance to observe in our fall skies: the monarch butterfly and the ruby-throated hummingbird. The ruby-throat travels to Central and South America. These small birds waste very little time as they move south. All you see is a glimpse of them as they buzz through just above the tree tops. It is amazing that this small bird can make long distance journeys, sometimes traveling hundreds of miles over oceans with no place to stop for rest or food. I came across a very interesting article online by Bill Hilton, Jr., an ornithologist specializing in hummingbird studies. He describes the work ornithologists have done, including his own, to discover the secrets of hummingbird migration. You can find this article online at http://www.hiltonpond.org/articlehummermigrationmain.html or click on link to the right.

The other well-known migrant is the monarch butterfly. Monarch migration starts at the end of August and lasts until early October. The butterflies that pass us on their way south are ones that hatched and grew up here in the northern latitudes. They never see their parents (not unusual for insects). These insects begin life as an egg on a milkweed leaf. They hatch and grow, undergoing metamorphosis, then travel by themselves on a southward journey to Mexico. All the monarchs in eastern North America travel to the same forests in the Sierra Madre Mountains of south western Mexico. How they know how and where to go on this long journey, no one knows.

To make the story even more interesting, the monarchs we see leaving the Northeast will never return here. Rather, it is their great-great-great grandchildren that will return. Butterflies that grew up here will make their way to Mexico and live there for the winter. In early March they will start the trip northward, but they will never make it back. They will have reached the end of their life, torn and tattered from the long migration and their daily efforts at survival: searching for food and shelter, avoiding predators and surviving dangers like the ravages of wind and rain. But before they die, the females will lay eggs. These eggs will hatch and grow into butterflies that will continue their journey north. But even this next generation will not make it all the way. It will take another two generations of monarchs to make it back here to the Northeast. It will be mid-summer before we see these beautiful butterflies once again.

This marvel of migration is enjoyed and studied by many people. Generally speaking, most of the interest centers on the hawks, though many hawk watchers will record the numbers of monarch butterflies they see flying by. Throughout North America there are hawk migration sites where people gather to watch and count hawks as they soar past. The most famous site is Hawk Mountain along the Kittatinny Ridge in Pennsylvania. There is a hawk watch site outside Albany, NY along the Helderberg Escarpment at Thatcher State Park, and I just learned of a hawk watch on Mount Peter in southern Orange County, NY. This site is purported to be the third oldest hawk watch site in the east and is staffed by volunteer observers. I spent time this past September observing hawks, monarchs and hummingbirds at each of these sites. Here is what I saw.

My observations at Thatcher Park, September 12-14, 2011

Broad-winged Hawk - Sept 12 - 144, Sept 13 - 57, Sept 14 - 28, Total for the three days - 229

Monarch butterfly - Sept 12 - 28, Sept 13 - 46, Sept 14 - 30, Total for the three days - 104

Ruby-throated Hummingbird - Sept 12 - 4, Sept 13 - 0, Sept 14 - 1, Total for the three days - 5

Other Raptors

Bald Eagle - Sept 12 - 4, Sept 13 - 1, Sept 14 - 0, Total for the three days - 5

Golden Eagle - Sept 12 - 1, Sept 13 - 0, Sept 14 - 0, Total for the three days - 1

Sharp-shinned Hawk - Sept 12 - 3, Sept 13 - 0, Sept 14 - 2, Total for the three days - 5

Coopers Hawk - Sept 12 - 2, Sept 13 - 1, Sept 14 - 0, Total for the three days - 3

American Kestrel - Sept 12 - 2, Sept 13 - 1, Sept 14 - 1, Total for the three days - 4

Merlin - Sept 12 - 1, Sept 13 - 0, Sept 14 - 0, Total for the three days - 1

Osprey - Sept 12 - 2, Sept 13 - 2, Sept 14 - 0, Total for the three days - 4

Northern Harrier - Sept 12 - 1, Sept 13 - 1, Sept 14 - 0, Total for the three days - 2

Unidentified Accipiter - Sept 12 - 2, Sept 13 - 3, Sept 14 - 1, Total for the three days - 6

Unidentified Buteo - Sept 12 - 0, Sept 13 - 0, Sept 14 - 1, Total for the three days - 1

Unidentified Falcon - Sept 12 - 0, Sept 13 - 1, Sept 14 - 0, Total for the three days - 1

Unidentified Raptor - Sept 12 - 1, Sept 13 - 2, Sept 14 - 0, Total for the three days - 3

My observations at Mt. Peter, Orange County, NY, September 16, 2011

Broad-winged Hawk 661

Monarch butterfly 361

Ruby-throated Hummingbird 0

Other Raptors

Bald Eagle 11

Golden Eagle 0

Sharp-shinned Hawk 35

Coopers Hawk 5

American Kestrel 14

Merlin 0

Osprey 11

Northern Harrier 1

Unidentified Accipiter 5

Unidentified Buteo 2

Unidentified Falcon 2

Unidentified Raptor 1

The most amazing observation at Mt. Peter’s was the movement of monarch Butterflies. I was at the site from 9:00 in the morning until 5:30 in the evening. During the day, from 9 until 4 we had seen 116 with the majority of those in the afternoon hours. Then from 4 until 5:30 245 monarchs flew by. I have never before seen so many monarchs in such a short period of time. It was like a river of butterflies flowing past. I wonder what conditions created such an amazing spectacle.

While at Hawk Mountain on September 17th I observed several thousand broad-winged hawks in migration. Hawk Mountain posts their observations online at www.hawkmountain.org or clink on link to the right.

Monarch Butterflies observed at Sapphire Elementary School, Monroe, NY, September 19-23, 2011

Monday, Sept 19

10:00-11:00 with Mr. Costa’s class – 3

12:00-1:00 with Mrs. Buonamano’s class – 4

1:00-2:00 with Mrs. Rende’s class – 2

Tuesday, Sept 20

Rainy weather no monarchs observed

Wednesday, Sept 21

10:00-11:00 with Mrs. Zuzek’s class – 5

1:00-2:00 with Mrs. Cassese’s class – 2

Thursday, Sept 22

9:00-10:00 with Mrs. Teel’s class – 1

11:00-12:00 with Mrs. Janeczko’s class – 12

12:00-12:30 during my lunch – 1

12:30-1:30 with Mrs. Cahill’s class – 2

1:30-2:30 with Mrs. McNamara’s class – 3

Friday, Sept 23

Rainy weather no monarchs observed

Monarch Butterflies observed at Smith Clove Elementary School, Central Valley, NY, October 11-14, 2011

Tuesday, Oct 11

9:00-10:00 with Mrs. Rojas’s class – 5

10:00-11:00 with Mrs. Quintana’s class – 7

11:00-12:00 with Mrs. Dell-Webster’s class – 7

12:00-1:00 during lunch – 1

1:00-2:00 with Mrs. Apostolico’s class – 3

Wednesday and Thursday, the 12^th and 13^th were rainy days with no observations made

Friday, Oct 14

8:00-9:00 upon arrival as school – 1

10:00-11:00 with Mrs. O’Dowd’s class – 1

I encourage any class that has the chance to observe monarch Butterflies to record their numbers and e-mail them to me. You can take time to observe monarchs during recess or give students a reward for their hard work by going outside to specifically look for monarchs. Record the time at which the observations were made, the weather conditions and wind direction. Encourage students to be careful in their observations, you don’t want to count the same butterfly twice. Watch carefully to see that the monarch has moved on. If you see another monarch 5 or 10 minutes later you can be assured that it is a different butterfly. Once a butterfly has moved on it is not likely to circle back, after all they are on their way to Mexico. I will keep a track of these observations post them periodically and gladly answer any questions you might have about migration and these amazing migrants.

Painted Turtle Laying Eggs

While in Monroe, NY working with the Sapphire Elementary School I observed this Painted Turtle (Chrysemys picta) laying eggs. It was already well into the act when I found it on the lawn next to a Dunkin Doughnuts parking lot. I observed it digging her nest for about 15 to 20 minutes before she started laying eggs. She laid 7 eggs in about 10 minutes. I watched her burying the eggs for about 20 minutes before I had to leave.

A great reference for Painted Turtles is Thomas Tyning's book, A Guide to Amphibians and Reptiles, in the Stokes Nature Guides series.

King Elementary Owl Pellet Study

I had a wonderful time exploring owl ecology and their prey preference with all of you 3^rd grade ornithologists. Here is a review of what we found.

Mrs. Davis’s class dissected 9 pellets and found 22 mice, 1 shrew, 1 mole and 1 bird.

Mrs. Sirico’s class dissected 9 pellets and found 30 mice, 1 shrew, 0 moles and 0 birds.

Mrs. Kipp’s class dissected 8 pellets and found 25 mice, 0 shrews, 0 moles and 1 bird.

The overall results were 77 mice, 2 shrews, 1 mole and 2 birds. This would seem to contradict my hypothesis of shrews being a second favorite food over moles and birds (I always present the favored prey for owls as a hypothesis answering the question of what owl like to eat). Our results say that birds and shrews are equally favored. Remember though, we have a very small sample of 26 pellets. That number of pellets could have been produced by three or four owls in 3 or 4 nights. Do you think it is a good idea to base our decision on this small of a sample?

Look over other owl pellet dissection results here in my blog. Combining the results from other school would serve to increase our sample size and give us better data that we can use to evaluate my hypothesis that mice are the number 1 favored food, with shrews being the second most favored and moles and birds tied for third favored.

Field Ornithology at King Elementary

Well, the school year is winding down and I am trying to catch up with blogging about my school visits. I did my annual bird survey at King Elementary in Warwick on June 1. Here is what we found.

The weather was hot, not the best birding conditions, but we still found 29 species of birds. Six species were observed by all three classes. Mrs. Flynn’s class was in the field from about 9:20 to 10:00. The temperature was in the mid 80’s with slight haze in the sky and no wind. Mrs. Shoock’s class started looking for birds at about 1:00 and ended at about 1:45. The temperature was in the low 90’s with a strong breeze from the West and a hazy sky. Mrs. Boccia’s class looked for bird from about 2:20 to 3:00 The temperature was in the mid 90’s, very humid, sky with complete high altitude haze and slight breeze from the West.

Here is the total list of birds seen. I have put a letters after each species to indicate which classes observed or heard that bird.

Black Vulture (B, F, S)

Turkey Vulture (B, F, S)

Sharp-shinned Hawk (S)

Coopers Hawk (B)

Red-tailed Hawk (B)

Chimney Swift (B)

Downy Woodpecker (F)

Eastern Phoebe (F)

Eastern Kingbird (B)

Blue Jay (B, S)

American Crow (F, S)

Tree Swallow (S)

House Wren (B, S)

Eastern Bluebird (B, F, S)

Wood Thrush (F)

American Robin (B, F)

Gray Catbird (B, F, S)

European Starling (F)

Cedar Waxwing (B, F)

Yellow Warbler (B, S)

Common Yellowthroat (B)

Chipping Sparrow (B, F, S)

Song Sparrow (S)

Rose-breasted Grosbeak (F)

Red-winged Blackbird (B, F, S)

Brown-headed Cowbird (B)

Baltimore Oriole (F, S)

Purple Finch (F, S)

American Goldfinch (S)

It was exciting to see so many birds even though we were looking for birds during the hottest time of mid-day. The best time to look for birds would be early morning and I am sure if we were to survey birds around the school at that time we might get an additional 5 to 10 more species.

I think every school should establish a yearly list of birds observed or heard at their school. Additional bird studies could be conducted at school, including setting up bird feeders and conducting a feeder watch, and building, setting up and monitoring nest boxes. When students do animal reports they could be encouraged to do reports on birds that live around the school, incorporating their own observations of those birds in their reports.

Today I visited three 4^th grade classes at Lynnwood Elementary School in Schenectady (Guilderland Central School District). We were ornithologists studying owls. As part of our class we dissected owl pellets to learn about what their preferred prey is. Here is what we found.

Mrs. Janssen’s class dissected 10 pellets which contained the bones of 30 mice, 7 shrews, 1 mole and 2 birds.

Mrs. Follonsbee’s with several students from Mr. Miller’s class dissected 13 pellets which contained the bones of 38 mice, 1 shrew, 0 moles and 0 birds.

Mrs. Romano’s class with several students from Mr. Miller’s class dissected 14 pellets which contained the bones of 43 mice, 1 shrew, 0 moles and 0 birds.

A total of 37 pellets were dissected revealing the remains of 111 mice, 9 shrews, 1 mole and 2 birds. As a way of illustrating what a hypothesis is I told them that I had researched what Barn Owls eat and had hypothesized that their most favored food was rodents, such as mice. Shrews were a second favored prey and moles and birds were tied for third. Our findings would seem to support this hypothesis.

In our wrap up discussion I mentioned that there seemed to be a larger than usual number of prey per owl pellet. I speculated that this might be due to the large number of smaller mice found in the pellets. We could see this size difference when comparing skulls, jaw and hip bones. We wondered whether this might reflect the fact that at this time of year there might be many more rodent nests which the owls might find by listening to the squeaks of the young, hence the finding of smaller sized bones of young mice. An owl eating 4 or 5 small young mice might get as full as an owl eating 2 or 3 full grown mice. If we compare the average number of prey animals per pellet to the findings of pellets at a different time of the year we might find evidence supporting this.

The average number of animals per pellet with the Lynnwood students was 3.3 animals per pellet.

We can compare this to the findings from four 4^th grade classes at Leptondale Elementary School in Wallkill (see previous post). These were pellets were collected approximately one month earlier. At Leptondale there were 40 pellets dissected. These contained the bones of 122 mice, 3 shrews, 1 mole and 2 birds. This gives an average of 3.2 prey per pellet. That is not much different than the average found at Lynnwood, perhaps we need to look at owl pellets found even earlier in the year.

Let’s look at pellets collected in mid-winter. I visited the Nazareth Intermediate School in Nazareth, PA in January (see previous post in the blog archive). Working with 14 4^th grade classes we dissected 168 pellets and found 335 mice, 45 shrews, 20 moles and 6 birds for an average of 2.42 prey per pellet. If we look at what Lynnwood students found in March of 2010 there were 111 mice, 5 shrew, 1 mole and 0 birds in 41 pellets for an average of 2.9 prey per pellet.

There does indeed seem to be a difference in the number of prey eaten per pellet at different times of the year. It also seems that there might be a difference in the number of shrew and moles taken at different times of the year. Look over other owl pellets studies that I have done with other schools at different times of the year in my blog archives.

Leptondale Elementary School Owl Pellet Dissection

Ah, spring has run away on me and I am late in getting some of my school visits recorded here on my blog. One of my favorite environmental education activities is owl pellet investigations. It's an incredibly exciting way to learn about owl behavior and there predator-prey relationships.

In May I had my annual visit at the Leptondale Elementary School in Wallkill, NY. The 4th grades do my Owl Ecology session. The culmination of the class is the dissection of owl pellets to learn about what owl eat. Here are the results for all four 4^th grade owl pellet dissections.

Mrs. Psilopoulos’ class dissected 9 pellets and found 28 mice, 2 shrew, 0 moles and 1 bird.

Mr. Zupan’s class dissected 11 pellets and found 35 mice, 0 shrew, 1 mole and 0 birds.

Mrs. Danneman’s class dissected 10 pellets and found 25 mice, 1 shrew, 0 moles and 0 birds.

Mrs. Davis’ and Mrs. Gunderson’s class dissected 10 pellets and found 34 mice, 0 shrews, 0 moles and 1 bird.

The totals for all four classes were 122 mice, 3 shrews, 1 mole and 2 birds found in 40 pellets. That is an average of 3.2 prey per pellet. This average is a little higher than what I often find at other times. What do you think might have caused this higher average?

More food for thought. If an owl produces two pellets a night, how many mice would an owl consume in a year? By eating this many mice do you think the owl helps farmers and orchard growers?

Clearly mice are the most favored prey. With the data we collected it is not clear that shrews are much more favored than moles and birds. More pellets should be dissected to see if there really is a difference. You can order more pellets for yourself (see the link to Pellets,Inc. at left), dissect them and add that data to our findings, or you can look over other reports in my blog from other schools for more data. As a mater of fact, you can look to see what Leptondale students found in past years by looking through the blog archives. My blog is www.schoolyardnaturalist.blogspot.com.

Take some time to wander in the woods and find pellets from owl in your backyard!

Owl Pellet Studies at Altamont and Jefferson Elementary Schools

On Friday, March 25, I visited the Altamont Elementary School and worked with three fourth grade classes. I worked with Ms. DeGennaro, Mrs. Flanagan and Mrs. Vogel’s classes. Here is what we found when we dissected owl pellets.

Ms. DeGennnaro’s class – in 8 pellets dissected we found 20 mice, 1 shrew, 0 moles and 0 birds

Mrs. Flanagans’ class – in 9 pellets we found 24 mice, 1 shrew, 0 moles and 0 birds

Mrs. Vogel’s class – in 8 pellets we found 24 mice, 0 shrews, 0 moles and 0 birds

This is a very small sample to use to determine if my hypothesis (remember I had answered the question, “What is an owl’s favorite foo?” with the hypothesis that mice were the most favored, shrews second most and moles and birds tied for third) was correct. Clearly, mice are the most favored, but before we can say that shrews are the second most favored we have to think about what these numbers mean.

Yes, there were 2 shrews found in the 25 pellets we dissected along with no moles or birds. That may or may not mean that shrews indeed are the second most favored over moles and birds. Our sample size of owl pellets is very small. Because of this we should not be ready to say that shrews are surely the second most favored food. We would want to dissect more pellets to get more evidence. As a matter of fact I did an owl ecology session with 5^th graders at Jefferson Elementary School in Rotterdam today. Here is what we found.

Mrs. Bondi’s class – in 11 pellets dissected we found 32 mice, 0 shrews, 0 moles and 0 birds

Mrs. Walker’s class – in 11 pellets we found 24 mice, 0 shrews, 0 moles and 0 birds

Mrs. West’s class – in 11 pellets we found 29 mice, 7 shrews, 0 moles and 0 birds

Mrs. Fiske’s class – in 9 pellets we found 23 mice, 1 shrew, 0 moles and 0 birds

Mrs. Zanta’s class – in 11 pellets we found 37 mice, 2 shrews, 0 moles and 0 birds

Looking at just the Jefferson Elementary findings we see out of 53 pellets dissected there were 145 mice, 10 shrews and no birds or moles. This confirms what we found at Altamont, mice are the most favored. Now with a larger sample size we can better determine the preference for shrews. With two shrews found by the Altamont students and 10 shrews found by Jefferson students it does appear that shrews are the second favored food. With no moles or birds found at either schools we are still not sure if they are a third favored food. As a matter of fact with no moles or birds found we might presume that they are not eaten at all.

Just as discussed in each class I visited, the more pellets we can dissect the better of an understanding we will have for owl food preference. If we increase our sample size we would get more data that might shed light on the question of what role do moles and birds play in the owl food preference. We can do that by looking at what was found in owl pellets dissections in other schools, including what was found at Altamont and Jefferson Elementary schools in previous years. To do this check out my blog at www.schoolyardnaturalist.blogspot.com to see what the findings at other schools were and then draw conclusions about my hypothesis.

Of course if any student would like to do further studies on their own and dissect more pellets they can get pellets from Pellets,Inc. at www.pelletsinc.com. Naturally if students have more questions they can e-mail me and I would love to help them with their research.

Field Ornithology at Ostrander Elementary School, Wallkill, NY

Here are the results of the spring bird surveys that were done with Mrs. McQuiston, Mrs. Wager, Mrs. Missale and Mrs. Stokes’ 3rd grade classes on Thursday and Friday of last week.

Mrs. McQuiston’s class

Thursday, March 17, 2:00 PM

Temperature – low 50’s

Strong breeze from the west

5 % cirrus cloud cover

Red-tailed Hawk – 2

Ring-billed Gull – 2

Mourning Dove – 3

American Crow – 76

American Robin – 4

Northern Cardinal – 3

Red-winged Blackbird – 8

Common Grackle – 3

House Sparrow – 10

111 birds total among 10 species

Mrs. Wager & Mrs. Missale’s class

Friday, March 18 ,11:40 AM

Temperature – high 50’s

Very strong west wind

99% low cumulus cloud cover

Canada Goose – 315

Red-tailed Hawk – 3 (2 adults, 1 juvenile)

Ring-billed Gull – 1

American Crow – 4

American Robin – 4

European Starling – 4

Red-winged Blackbird – 12

Common Grackle – 7

House Sparrow – 7

360 birds total among 9 species

Mrs. Stokes’ class

Friday, March 18 2:05 PM

Temperature – high 60’s

Very strong west wind

20% cumulus cloud cover

Red-tailed Hawk – 4

Mourning Dove – 3

American Crow – 1

American Robin – 7 Cedar Waxwing – 3

Northern Cardinal – 1

Red-winged Blackbird – 12

Common Grackle – 9

House Sparrow – 10

37 birds total among 9 species

A total of 12 different kinds of birds were observed. Six species were seen by all three groups. The Canada Geese were for the most part in three large groups at very high altitude. These birds were definitely in migration heading north. The large numbers of crows seen on Wednesday with Mrs. McQuiston’s class were likely birds heading back to roost from their daytime feeding areas. These birds streamed past in a loose group over a period of a few minutes. We wondered if we might observe a similar movement on the 17^th. We did not. This was likely due to the high winds that day. The strong westerly winds on the 17^th were about 20 to 30 mph and may have affected how, when and where the crows flew that day on their way from their feeding areas.

A classic way to judge winds speed is the Beaufort Wind Scale developed in 1806 by Sir Francis Beaufort, a British admiral. See link to the right to go to the Wikipedia entry for more information on Beaufort and how to use his scale to measure wind speed.

It would be interesting to observe birds around the school as the season progresses. In a few short weeks many more different kinds of birds will be returning from their winter homes to find nesting areas around the school. At the same time large groups of birds like the Canada Geese and the American Crows will most likely not be seen as this grouping or flocking behavior would not be done during the nesting season. An overall year list of birds would give an idea as to the birds that migrate through to more northerly habitats, return to nest during the warm weather or are resident all year round. Such a list if maintained over a number of years could be used to determine such things as global climate change, habitat change or species change in the environment.

Compare bird observation findings at other schools in my blog. Look through the archived entries to see done at the same schools in different years, on different dates and at different times.

Owl Pellet Study at Ostrander Elementary School

I completed the final owl study class with 2^nd graders at Ostrander Elementary School in Wallkill, NY today. Here are the results of the owl pellet dissections.

Dutka’s class – 8 pellets dissected, prey found – 22 mice, 3 shrew, 0 moles, 1 bird

Lupoli’s class – 8 pellets dissected, prey found – 17 mice, 3 shrew, 1 mole, 1 bird

Nisa’s class – 5 pellets dissected, prey found – 7 mice, 3 shrew, 2 moles, 0 birds

Busse’s class – 8 pellets dissected prey found – 15 mice, 2 shrew, 0 moles, 0 birds

I had presented the following hypothesis to the students in response to the question what is the favorite food of Barn Owls. Mice and other rodents are the most favored food. Shrews, small insectivore mammals are the second favored food. Moles, another small insect and worm eating mammal, and birds, small birds mostly found in barn areas are tied for the third most favored food. What does the data tell us about the hypothesis?

In the 29 pellets dissected there were 77 prey animals found. Of these 77 animals 61 were mice. Mice were definitely the most favored food.

My hypothesis stated that shrews were the second favorite. Is that correct? Of the remaining 16 animals eaten by Barn Owls that produced the pellets we dissected 11 were shrews. What do you think?

Now look at the number of moles and the number of birds eaten, 3 and 2. Though it is not an exact tie, you can’t get any closer to a tie than that. It does seem that moles and birds are tied as the third favorite food.

Finally consider this. There are many other potential prey for the owls, small amphibians, large insects, other small mammals, but it seems from what we found that owls seem to not prey on them. You can research this to find out if Barn Owls might eat other animals. One research source is my blog, www.schoolyardnaturalist.blogspot.com. Check it and see what other data has been collected with owl pellet studies at other schools, including what was found at Ostrander in previous years.

A January Owl Ecology Class

I am late with this post. My apologies to the young ornithologists at the Nazareth Intermediate School in Nazareth, PA. In January I had my annual visit to this school where I did a lesson on Owl Ecology. We talked about the 4 common owls of the Nazareth, PA area, the Eastern Screech-owl (Otus asio), the Great Horned Owl (Bubo virginianus), the Barred Owl (Strix varia) and the Barn Owl (Tyto alba). Our discussion covered the identification, behavior, and habitat needs of these owls. We also talked about how students might do field studies of the owls with the help of their parents or other responsible adults.

We then dissected owl pellets to see what food preferences the Barn Owl has. The pellets we dissected were from western Barn Owls purchased from Pellets,Inc. (see link below to the right). Here is the data we collected.

Thomas/Miller classes 24 pellets, 54 mice, 6 shrews, 2 moles, 1 bird

Kimble/Velekei classes 26 pellets, 52 mice, 4 shrews, 4 moles, 0 birds

Roth/Giemza classes 24 pellets, 57 mice, 6 shrews, 1 moles, 1 bird

Emrick/DeBoer classes 24 pellets, 37 mice, 8 shrews, 5 moles, 1 bird, 1 insect

Genua class 12 pellets, 28 mice, 6 shrews, 3 moles, 1 bird

Reed class 10 pellets, 12 mice, 5 shrews, 1 moles, 0 birds

Rohn/Quinones classes 23 pellets, 45 mice, 4 shrews, 1 mole, 0 birds

Reynolds/McCarron classes 25 pellets, 50 mice, 6 shrews, 3 moles, 2 birds

Analysis

One hundred sixty-eight pellets were dissected by fourteen classes of 4^th graders. A total of 335 mice, 45 shrews, 20 moles and 6 birds were found. In addition to these prey, one pellet included the remains of an insect. These remains appeared to be leg segments from a something like a mole cricket (Gryllotalpidae family). Taken in whole this data indicates that on average Barn Owls eat 2.42 animals per meal (the pellet is a result of a meal – in one night the owls might produce 3 or 4 pellets as they feed, then stop to rest and digest and then go back to feeding throughout the night). This average matches findings with other owl pellet dissections conducted with other schools (see archives for other owl pellet dissection results).

In our discussion before the dissection we had hypothesized that mice would be the favorite food, with shrews second favorite and moles and birds tied for third. It is clear that mice indeed are the most common prey and that shrews are second. It seems though that moles are more often eaten than birds by a factor of three. Look through other owl pellet dissections in the archives of this blog and see if this bears out with the findings in those sessions.

I wonder if the owl ate the insect as a primary prey or if it might have ingested the insect when it ate a mole that had eaten the cricket. Moles feed on underground insects and other invertebrates. It is possible the mole had just eaten the cricket and then was eaten by the owl. Unfortunately I did not take notes as to what else was found in the pellet with the insect parts. If mole remains were found along with the cricket remains that would support the idea that the owl ate a mole that had eaten the cricket. If I ever find insects parts in owl pellets in the future I know that I will be sure to make note of what other prey were found in the same pellet.

The owl food chain affects farmers. Since mice, and these mice are for the most part are field mice (Microtus spp), are the favored prey the owls, eating them affects farm production by reducing the amount of plant crops eaten by the mice. I have a little math exercise I call “Mouse Mathematics” that I will post in the near future that illustrates what this cost savings for a farmer might be. Look for it being posted soon.