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Frequently Asked Questions
 
How big are the owls?
Why are female raptors bigger than the males? That seems backwards.
How long do they live?
Do the owls mate for life?
What are their names?
When do the babies' eyes open?
How long does the mom sit on the eggs? Does the dad sit on the eggs too?
When do the owls sleep?
How old are the babies when they leave the nest?
Why do the babies have “fur” instead of feathers?
Why do the babies leave the nest before they can fly? That seems really dangerous.
Do the babies return to the nest after fledging?
How can you tell what kind of bug was delivered?
What happens to the trash (feathers, etc.) in the owl box?
How can you tell which owl is trilling?
Why don't you position the camera to reach the back of the owl box?
Don't the owls hate having the light on all the time, even at night?
Are your plans for building the owl box available?
Why do you use a black and white camera, rather than color?
Can you please provide more details about the Magic Fingers Squirrel Control Device?
 
 
How big are the owls?
Screech owls are small birds, about the same weight as a bobwhite quail. They are 6 to 9 inches long. The female screech owls are larger than the males, which is a common pattern among raptors (hawks, eagles, etc.). When we see our female and male side by side, we can easily tell them apart. According to Dr. Fred Gehlbach,* typical females weigh 170-190 grams (6-7 oz), compared with typical males at around 140-160 grams (5-5 ½ oz).   ^
 
Why are female raptors bigger than the males? That seems backwards.
Trust evolution (aka Mother Nature) to fine-tune all these details. Gehlbach speculates that it's an advantage for females to be large, because (1) a larger female can lay larger eggs, and hatch larger chicks, (2) she has more reserves of body mass to help her survive times when food is scarce or temperatures are cold, (3) she is the main defender of the nest when it contains eggs or chicks, and larger size helps her fight better (in the case of screech owls, the foes would be starlings or squirrels).
In contrast, the male raptor's most important job may be to fly endless deliveries of groceries to the female and chicks during the nestling period. A lighter bird might fly more efficiently (less wing loading), and can carry almost the same "payload" as a somewhat heavier bird. But the small male doesn't require as much food to maintain his smaller body, so a greater proportion of the food he catches can go to feeding the female and chicks.   ^
 
How long do they live?
They can live as long as 14 years, according to Fred Gehlbach, although the average life span seen in Gehlbach’s extensive study was only a few years. Starvation is a common cause of death. In the city, many owls are hit by cars as they hunt insects or frogs under streetlights at night. Pesticides also kill owls (i.e., an owl may eat a poisoned insect). Domestic cats kill many owls, especially juveniles. Natural parasites, such as roundworms, may weaken owls to the point that they cannot hunt effectively.   ^
 
Do the owls mate for life?
Yes, they do mate for life (although, as noted above, “life” may not be very long). Owls which lose their mate quickly seek out a replacement.  An interesting discovery from Dr. Gehlbach’s research was that a small number of “super-moms” (fewer than 15 percent of the females) produced more than half of the offspring in the population.   ^
 
What are their names?
Most of the time Connie and Tom refer to the parents as "male" and "female"; occasionally they refer to them as "Madame" and "Monsieur". C&T did name some of the 2009 chicks, based on their behavior. "Digger" (full name: "Digger the Demented") was named because he scratched furiously at the bottom of the box, presumably searching for food. This showered his siblings with wood shavings and debris. (There was also a "Digger the Demented" in the 2008 brood.) "Miss Piggy" was the largest and greediest owl in the 2009 brood. We assumed she was female because of her size. As the owlets matured, she would park her large self in the entryway, blocking her siblings, and grab a majority of the food offerings from the parents. "Reluctant" was the last owlet to fledge in 2009; he was named because of his reluctance to leave the nest box, as captured in the 4/30/09 video.   ^
 
When do the babies' eyes open?
Eyes usually open 8 to 10 days after the eggs hatch.   ^
 
How long does the mom sit on the eggs? Does the dad sit on the eggs too?
Mom sits on the eggs about a month. Dad does not sit on the eggs.   ^
 
When do the owls sleep?
The short answer is that owls work the night shift, so they have to get most of their rest during the daytime.
“Roosting” refers to the time which birds spend resting quietly on a perch, when they are not traveling, feeding, or interacting with other birds. Birds which hunt or feed during daylight hours settle onto a roost for the night. Owls hunt during night hours, so they roost during the day. One of the problems which owls have on their day roosts is that birds like bluejays, cardinals, mockingbirds, and wrens will find them and yell at them (called “mobbing” when it involves a number of protesting birds). These birds have a good reason to complain: any of them (or their babies) might end up as owl food at some point! Following the sound of mobbing bluejays is a good way for “owl watchers” to locate owls on their day roosts. We used this trick to discover which trees “our” owls were using at different times of the year.   ^
 
How old are the babies when they leave the nest?
They leave the nest (fledge) approximately a month after hatching.   ^
 
Why do the babies have “fur” instead of feathers?
Actually, that fuzzy-looking stuff is down (a type of feather), and the chicks are covered with it at the time they hatch. Downy feathers provide good insulation, which helps chicks keep warm, since they can’t regulate their body temperature very well until they are 12 or 14 days old. Adult birds also have a layer of downy feathers, mostly on their breast and belly, which is covered by additional layers of vaned feathers, which are stronger and more waterproof than the downy feathers. Vaned feathers form the structure of the wing and tail. Tiny fibers on the leading edges of the wing feathers help the owl fly silently, without any flapping or whistling wing noises which might scare the owl’s prey. It is amazing to watch the owlets grow a complete suit of these complex structures in only 30 days.   ^
 
Why do the babies leave the nest before they can fly? That seems really dangerous.
Although humans tend to think of nest boxes or natural tree cavities as safe havens, they do pose some dangers for cavity-nesting birds. You could get trapped by a predator inside a box, or drowned by a big rainstorm which suddenly flooded your tree cavity. As a result, cavity-nesting birds probably try to get their babies to “fledge” (leave the nest box or tree cavity) as soon as they are big enough. Although the baby owls can’t really fly at the time they fledge, they can flap their wings enough to sort of parachute safely to the ground. However, on the ground, they might get eaten by a cat, so it’s important that they quickly climb back up a tree. To help them avoid this danger of being temporarily on the ground, we attach a long branch to connect the nest box with the main part of the tree. The owlets have used this branch to climb safely into the upper part of the nest tree on the night they fledged.  Around the time of fledging, the parents are very defensive and concerned about the safety of the owlets. If we get too close, the parents signal their annoyance by “bill claps” (a sharp snapping noise made by their beaks). Once, Connie got bopped on her forehead by a concerned parent who was telling her to please scram.   ^
 
Do the babies return to the nest after fledging?
No. Once they have left the owl box and climbed into the tree they do not return. However, it must be very scary to jump out of a box into a big world which you’ve never seen before. We have seen fledglings (usually the youngest and smallest of the brood, which were last to fledge) which hopped outside for a second and then hopped right back in again. These little ones did make it out just fine a night or two later, and joined their bigger brothers and sisters.   ^
 
How can you tell what kind of bug was delivered?
If we are watching the live camera, we can often see and identify the food item as it arrives in the entrance of the box. Unfortunately, this is difficult if you are viewing online, because the food “handoffs” are very quick (quicker than the rate at which images are uploaded). Sometimes we can tell from sounds on the microphone in the box--katydids and june bugs sound crunchy. We have also noticed that when the owls eat a moth inside the nest box, the air quickly fills with specks which look like tiny snowflakes: these are actually the scales which moths and butterflies have on their wings!
cockroach moth  
Cockroach deliveryMoth delivery   ^
 
What happens to the trash (feathers, etc.) in the owl box?
The female removes most feathers and other large debris from the owl box. Bones, feathers, and insect legs which are swallowed by the owls are mashed up and compacted in the owl’s gizzard, and later regurgitated. We sometimes find these “owl pellets” and dissect them to see what we can identify. Inside the nest box, there is always a population of tiny beetles and ants which live in the nesting material and probably clean up some of the leftovers. “Acrobat ants” are a common species (the name comes from the fact that they sometimes look like they are doing a handstand), and we have read that they don’t bother the baby owls. However, they might attack other animals which try to get into the box, so overall the ants may be beneficial to the owls, even if they do consume some food scraps.
Fred Gehlbach also discovered that some of the most successful owl nests had small snakes living in the nesting material. These snakes (Texas blind snakes) resemble earthworms. In the nest box, the blind snakes presumably eat insects which might otherwise parasitize the baby owls. However, the owls did not “install” these helpful cleaners on purpose: instead the snakes arrived as potential meals which were just fumbled during the handoff.
feathers  
Cedar waxwing feathers removed from the box in 2009   ^
 
How can you tell which owl is trilling?
The male owl sings on a lower note than the female, at least for one of their common songs, the “monotonic trill”, which is a sort of tremolo on one note. We compared the monotonic trills to notes on our piano. The male's trill is an E above middle C on the piano, and the female's trill is A above middle C (although she is bigger, she has a higher trill). Lloyd claims that the owl in his box on Bellewood street always trills on a D-sharp instead of an E (and then he asked when our piano last got tuned !). The “monotonic trill” is used for communication among owls in a family, and by males during courtship and nesting. The “descending trill” seems to be used to assert claim to a territory, or ownership of a nest box. For example, almost every time the male delivers food to the nest box, the female greets him with a descending trill, he transfers the food, gives a monotonic trill, and departs.   In spite of their name, we do not hear many “screeches” from these owls. Screeches signal alarm, and are mainly given in defensive situations.   ^
 
Why don't you position the camera to reach the back of the owl box?
The field of view of the camera is fixed by the lens, and is sort of a cone (that is, the field of view increases with distance from the camera. Since distance is limited by the size of our box, floor-to-ceiling, we had to make a compromise. The camera is positioned to show as much of the bottom as possible, but to also show part of the entryway so we can watch food deliveries.   ^
 
Don't the owls hate having the light on all the time, even at night?
The light source for the camera puts out infra-red wavelengths, which are not the same as the visible wavelengths put out by a regular light bulb. If you look into the box entrance at night, the interior of the box does not appear to be lit up, since human eyes do not detect this infra-red light. Of course, owl eyes are not the same as human eyes. Owl eyes also differ from the eyes of other birds in having a high proportion of rod cells, which help them see in very low light. However, from what we have read, there is no conclusive evidence that owls can see in the infra-red range. Perhaps the interior of the box appears dimly lit to them; we don’t know. They certainly don’t seem to mind it.   ^
 
Are your plans for building the owl box available?
See the .pdf attached to this website, "Owl Box Construction", for a link to the plans we used for the box. A second set of notes on cameras and wiring is in progress.   ^
 
Why do you use a black and white camera, rather than color?
Mostly because it’s cheaper.   ^
 
Can you please provide more details about the Magic Fingers Squirrel Control Device?
See "Owl Box Construction".      ^
 

*Gehlbach, F. R. 1994. The Eastern Screech Owl: Life history, ecology, and behavior in the suburbs and countryside. Texas A and M University Press, College Station.