E. Screech Owl Nest Box Cam’ News 2001

[Most recent items at top.]

May 3: Final batch of new items:

May 1: Sallie, our local raptor rehabilitator, examined the body of owlet 825-90098. Without even opening the body she found the probable cause of death: a large hernia projecting through the owlet's belly. Bacterial growth was also evident in the mouth/throat. Sallie reports that in 20+ years of treating injured raptors, she has only seen such a hernia once before: in another Austin-area eastern screech owl owlet brought to her this same spring. That owlet also died. I find the coincidence chilling. I subsequently exhumed the body of 825-90099 to examine it for signs of such a hernia. Although ol' Mom Nature was hard at work disassembling the body, there was a hole in the belly of '99 of approximately the correct size and position to have been the exit point for such a hernia. I can't help but wonder if our local environment has been contaminated with something that affected the development of these owlets. If there are any biologists or related researchers in the audience, a photo of the hernia in '98 is available upon request.

April 30, 10:00 PM: Owlet 825-90098 found dead on ground at foot of crepe myrtle tree. Once again, no obvious cause of death. Because he was found before putrefaction began, Sallie, the local raptor rehabber, has volunteered to dissect him in the hope of establishing the cause of death. The adults have ceased defending any part of the yard, so it seems probable that the third owlet is dead as well.

April 30: There's still an owlet roosting in the crepe myrtle tree, and still no sign of the other owlet. If it has moved beyond the two trees I've been searching, I wouldn't find it, and even if it has remained in the nest box tree, or the crepe myrtle, it could be too well hidden to be found.

April 29: One of the adult owls, probably the female, spent the day on guard duty in the nest box tree. A search of the tree didn't reveal any owlets, but one owlet was found roosting comfortably in the adjacent crepe myrtle tree. Hopefully the other owlet is too well hidden to be seen.

April 28: The youngest owlet leaves the box around 11 AM, and spends the day peacefully sunning itself on the owlet rail of the nest box. At sunset it calmly jumps down from the rail to a nearby branch, and begins its week-long interlude as a brancher under the watchful eye of its parents.

Unfortunately, one of the first two owlets to leave the box, 825-90099, is found dead on the ground near the tree. There is no obvious cause of death. The other eldest owlet is observed alive and well in the tree being guarded by one of the parents, most likely the mother.

April 26: Branching night number one. The eldest owlet left the box and made several unsuccessful attempts to climb the front of the nest box to reach the tree behind it. Since the box wasn't designed to be climbable, the attempts failed, and the final attempt at 8:41 PM caused the owlet to fall to the ground. Because the trunk of the tree was still wrapped with aluminum flashing to protect the nest from climbing predators, the owlet couldn't climb back into the nest tree, and settled instead for hiding a few inches up in the tiny branches at the foot of a nearby crepe myrtle (sp?) tree.

At the time all this happened I was heading home from the office in order to remove that flashing. A quick review of the frames from the external camera indicated that the owlet had fallen. An hour of searching the yard and paying careful attention to the areas most vigorously defended by the agitated adults finally revealed the location of the fallen owlet. With some difficulty I managed to convince the owlet to release its very effective grip on the branches and come with me, while its needle-sharp talons deftly located one of the holes in my leather gloves and sank into a finger. I walked him over to the nest box tree and, once I'd pried his talons out of my gloves and finger, placed him about six feet up in the main crotch of the tree, where all the secondary trunks diverge from the primary.

Interestingly, the very agitated adults held off on attacking me until I'd deposited the owlet in the tree and gone back to photograph him. Which was nice. And now the photo of the owlet standing in the crotch of the tree along with the cables that raise and lower the nest box: [Large] [Medium]. I'm sure he's already climbed to a higher, safer perch.

The second oldest owlet, who hatched ten hours and forty minutes after the eldest, also chose tonight to leave the nest. After calmly sitting on the owlet rail for a few hours, including the time I was searching the yard beneath him for his sibling, at 9:51 PM he took the simple approach to branching and walked along the new wooden bridge to the nearby tree limb. He should be comfortably situated somewhere high in the tree by now. [Large] [Medium]

April 25: While standing on a ladder in the nest box tree shortly before midnight, I realized that the best way to get a photo of an adult screech owl was to annoy it until it was on the verge of attacking. I hadn't set out to annoy anybody; I'd set out to install something that would allow the owlets to walk from the owlet rail to a tree limb, rather than requiring them to jump from the rail to a branch and possibly fall out of the tree if they miscalculate.

You can see in the external camera view that there's now a long piece of wood resting on one end of the owlet rail. It leads out-of-shot to a tree limb about four feet away to which it is securely lashed. It should allow the owlets to start exploring the tree with ease, and would even allow them to return to the box, if they wish. It falls well short of being an aesthetically appealing solution, but I'm guessing it will prove to be effective.

Already proved effective is this method of annoying breeding screech owls: climb into their nest tree in the middle of the night. This earned me a lot of beak clapping, and a number of warning passes just over my head. Since, for a change, an adult was very nearby and anxious for me to know it, it also earned me a chance to take a few photos of an adult screech owl. At least one decent picture resulted. As bothersome as my visit was, it was probably also satisfying for this owl to believe that it could, with perseverance, chase away the big monkey with the ladder. (Had it used its talons, it'd would have been correct, too.) Chalk one up for the little guy.

April 24: Time for more photographs, and for owlet banding. Sallie, my local raptor rehabilitator, came by and placed bands on each of the owlets. They are now officially designated as 825-90097, 825-90098 and 825-90099. Some day there's a slim chance that I'll hear something about them. Sallie emphasizes that in this matter "no news is good news," and I expect she's right. However, if one or more banded owls should some day nest in my box, I will have good reason to believe that they're one of "my" owls. That'd be nice.

As they grow older, the owlets tolerate my visits less and less, and none of them appreciated this last visit one bit. Intially they attempted jump out of the box and run away, but they were all trying to do it at the same time, and none of them even made it into the entryway. After that they mostly chose to play dead. Unfortunately, this didn't make for good photo opportunities, and we couldn't photograph the owlets as they were being banded, because it took four hands to do that. Oh, well.

  • Annoyed owlet, motionless, but glaring. [Large] [Medium]
  • Owlet after falling off perch, without letting go of the perch. This is what comes of playing dead and perching at the same time. [Large] [Medium]
  • All owlets. All playing dead. [Large] [Medium]
  • All owlets. Two playing dead in comically awkward positions, one glaring. I placed two of them on the perch while I cleaned the camera compartment glass. The highly creative postures were their ideas. [Large] [Medium]

Also, here's a movie from the external camera showing a number of food deliveries in a 15 minute period. The time between deliveries has been removed. The time during deliveries has been preserved. (QuickTime; 33.7 MB; 1:19 duration.)

The eldest owlets are now 25 days old and the young one is 23. They can begin leaving the nest box any time. They will leave in the order they hatched, and at roughly one day intervals. They will climb/jump into the tree and then climb into its outer branches where they'll be hidden. They'll spend about a week in this tree, or other nearby trees, as "branchlings" before they learn to fly. Their parents will bring food to them, and will vigorously defend the area near the tree. With luck, I'll be able to spot the owlets in the outer branches during the day and take a few photos. After that, I may never see them again.

I regret the lack of regular updates over the last week. It's been all I could do to keep up with reviewing the frames collected by the cameras.

April 19: Another five days have passed since the owlets were photographed, so the nest box was brought down, and photos were taken. As the owlets grow older, their tolerance for my visits decreases, and on this occasion they all chose to play dead. Over time, I was able to persuade the largest owlet that I was harmless, but I had very little luck with its siblings.

The cooperative owlet seemed to enjoy our encounter once he realized I wasn't going to harm him. During the last half of our encounter, he was comfortably clamped to my hand, and looking intently in all directions at the outside world. I had to make strange sounds to trick him into looking toward me and the camera; the world was a feast of new sights for him and I was a poor substitute.

April 18: The external infrared camera is installed, aligned and operating, now that it has a new power supply, and one of its design flaws has been corrected. A movie of several food deliveries is available. (QuickTime; 15.9 MB; 0:40 duration.)

April 17: The return of cold weather has brought the female owl back to the nest box during the day to ensure that the owlets stay warm.

April 16: The orphan owlet mentioned yesterday was brought by for a visit by Sallie, our local raptor rehabilitator. We opened up the nest box and compared the sizes of the current owlets to the orphan, and concluded that the orphan was a day or two too young to fit smoothly into this family. So it'll be raised by Sallie and her old male screech owl, who will gladly be a surrogate father to it. Once it has learned to fly and been taught to hunt for itself, it'll be released to find its own way in the world, as any screech owl must. He was a splendid little owl; fearless, very curious about his surroundings, and more inclined to explore them than any owlet of his age that I've encountered. That may be how he became separated from his own family, and fell into Sallie's care. [Large], [Medium]

April 15: Daytime temperatures of better than 90 degrees fahrenheit in the shade induced the female to spend the day somewhere other than the nest box.

Efforts to setup the external camera have been plagued by difficulties, including a D.O.A. camera, and power supplies whose output voltages drop under load to levels that can't drive the camera. A replacement camera is already in place, hopefully an adequate power supply can be procured quickly.

An orphan owlet may be adopted Monday night, if it is found to be at a stage of development very similar that of the current owlets. If you see four owlets starting late Monday night, you'll know what happened.

April 14: Another five days, another set of owlet photos:

  • All three owlets. Note the snake at the bottom-right corner of the frame. It went and hid during the photo session, I know not where. Clever snake. It was delivered at 10:40 PM CDT, but appears to have been fumbled by the owlet that received it. It is likely to be a Texas Blind Snake, which will do the owls a favor by eating some of the small insects that find their way into the nest box. This accidental symbiosis between Texas blind snakes and eastern screech owls is documented by Gehlbach, who notes that nest boxes harboring the snakes experience only a 3.6% nestling mortality rate, compared to 10% in boxes without the snakes. [Large] [Medium]
  • Small owlet in hand, wishing it were somewhere else. [Large] [Medium]
  • Big owlet no. 1. [Large] [Medium]
  • Big owlet no. 1 with scale, resisting quantification. [Large] [Medium]
  • Big owlet no. 2, reflecting. [Large] [Medium]

April 12: The male came to visit the nest box today at 4:58 PM CDT. There's no way to know why he visited, but a good guess would be that he was chased from his usual daytime roost (I have no idea where that is) by mobbing birds and he needed to find a safe place to wait while the birds lost interest. He stayed in the box for 13 minutes.

Here's a movie of the rapid-fire food deliveries that occur from time to time. This movie was taken in the early hours of the 12th over a 7-10 minute period during which there were four food deliveries. The time between the deliveries has been removed. (QuickTime; 22.6 MB; 1:12 duration.)

April 10th: While handling the owlets in the closing hour of April 9th, it was easy to feel that they'd all put on a lot of weight during the preceding five days. Watching them in the early hours of April 10th reinforced the impression that they were very well fed because they stopped reacting when their parents came to deliver food. Normally, the arrival of one of the parents results in a burst of activity: owlets standing as erect as they can, and frantically reaching up for food with open mouths. Not so early on the 10th, as you can see from several frames in the archive, including this frame, in which an adult sits in the entryway with food (a gecko) while the owlets take no notice, sleeping soundly in a communal pile. Finding themselves ignored, the parents sometimes waited outside the box for several minutes, and then tried to deliver the same prey items again; sometimes they entered the box and pushed the food at the owlets until one of them woke long enough to lazily accept it; sometimes the parents simply took their hard-earned food and left. Sometimes you're just not appreciated.

(A few hours later owlet digestion had progressed, and food deliveries were again welcomed with enthusiasm.)

Competition for food amongst the owlets works out pretty much as you'd expect: the largest owlets receive most of the food. While the two eldest owlets are pretty evenly matched, they both enjoy a significant size advantage over the youngest owlet. Of necessity, that youngest owlet is quickly learning to compete, pushing its way to the front whenever it can, and hanging onto its food for all it's worth. Late on the 10th the latter skill was illustrated by the delivery of a gecko to the youngest owlet. As the youngest worked to swallow the lizard head-first (the only right way to swallow a lizard), one of the other owlets got hold of the gecko's tail and began to swallow it from the other end. They met somewhere in the middle of the lizard and a tug of war ensued, with the youngest emerging victorious. So much for taking lizards from a baby.

Not all prey items are handled so effectively, however. Moths are plentiful in the small meadow area overlooked by the nest box, and those moths are frequently delivered to the owlets. The owlets reach for their food with eyes completely or partially closed, just as their mother does when reaching for food delivered to her by her mate (this might be an instinctive precaution against accidental eye injuries), and small living items like moths are easily fumbled by owlets in this process. As a result, the nest box has acquired a small population of live-in moths. Oddly, the moths make no concerted effort to leave, and the owls and owlets seem to pay them little or no attention, as though owls have their own prohibition against double jeopardy.

Finally, a point is reached with any growing family when, try as she might, mom can no longer sit on all the kids comfortably, and that point has been reached in this owl family. Late in the afternoon, the female moved for the first time from the crowded floor of the box to the relative tranquility of its experimental perch. I expect that she'll be spending more and more daytime sitting there, and in the entryway, as the floor of the box will only become more and more crowded.

April 9th: More owlet photos. The two eldest owlets are now 10 days old, and the youngest is 8. They have all opened their eyes, and their white baby fuzz is begininng to give way to feathers. Note that it is normal for their eyes to be cloudy at this age. As the owlets grow, their eyes will become transparent.

April 6-8th: Warm days and nights, growing owlets, rapid-fire food deliveries. Food has been mostly geckos (you will see gecko tails hanging out of the mouths of the owlets from time to time), with caterpillars, moths and even a snake thrown in for variety. Both parents are hunting, although the female will take time off during the night to spend with the owlets, possibly to help them stay warm, since even the oldest owlets are still a bit too young to thermoregulate. The owlets are growing rapidly, and are entering that awkward phase of kidhood during which they turn grey as their covering of soft, white baby fluff gives way to the first signs of real feathers. The elder owlets have now opened their eyes for the first time, although they don't open them often, or for long. They are beginning to practice flapping their stubby wings, which must be important to muscle development. Those wings won't be well enough developed to allow the owlets to fly even when they leave the nest box around the end of the month, but they will, for instance, allow an owlet that falls out of a tree to make a soft landing, and will help it climb back to safety.

April 5th: A warm and quiet day. During the afternoon the female repeatedly elected to take a break from sitting on the kids to sit in the entryway. I suspect this is a pleasure for an owl. During the night, the female has divided her time between hunting for the owlets and brooding them. Prey has been small items; lots of geckos and perhaps one nice, big hawk moth. Small prey, and steadily growing owlets, means the female hasn't had to spend much time tearing up food for the owlets, and the male has routinely been able to feed them himself.

There were video dropouts and degradation today. The culprit seems to have been a connector on a length of RG-59 video cable between the computer's video capture card and the splitter. The connector has been removed and reseated. That seems to have done the trick.

An additional camera, weatherproof and equipped with a bank of infrared illuminators, has been ordered. If everything goes well, I should be capturing day and night exterior views of the nest box before the owlets fledge. Hopefully this will provide a good look at the process of the owlets leaving the nest box, and maybe some good frames of the adults in flight to and from the box will also be captured. I probably won't be able to set it up to serve frames continuously, as the interior, side camera does, but will certainly make available any interesting frames that are captured. It should be interesting.

April 4th: It's been five days since the first two owlets hatched and the first photographs were taken, so it's time for new photos.

You can see that the owlets are terrified by my visits. (When they're older, this situation will change.)

Also on the fourth, the female owl decided the weather was warm enough during the day that she could spend some time in the entryway watching the world go by, the first time she's been able to do so since she began incubating more than a month ago. Similarly, when she was sitting in the box, she sometimes sat next to the owlets rather than on them.

Finally, the male owl has at last succeded in directly feeding at least one owlet - not because he's learned to tear apart prey as his mate does, but because the oldest owlets are now large enough that they can somtimes swallow a mid-sized gecko.

April 3rd: Large prey items (birds) are once again on the menu, and nighttime temperatures in the mid- to low-seventies (fahrenheit) allow the female to make extended nighttime excursions from the nest box, possibly to hunt, and certainly to bathe. Also, a movie showing a wayward owlet's struggle to be a part of a feeding session was captured early on the 4th. (QuickTime; 29.5 MB; 1:35 duration.)

April 2nd: The two larger owlets have been sneaking out from under their mother and exploring their surroundings even though they can neither see nor walk. She's not willing to let them explore for long before she hauls them back, but is prepared to indulge them in short excursions. Food has been mostly geckos, and some insects, but no large prey. At the urging of the female, one of the larger owlets managed to swallow a whole moth, while the other swallowed an entire american cockroach. They're a long way from being able to eat whatever is put in front of them, but this is a good start.

April 1st included two noteworthy events. The first was that the female owl left the nest box around 3:23 AM, for reasons best known to herself. The male then arrived a minute later to deliver a bird he'd captured. With the female absent, and the owlets anxious to be fed, he stood over them and attempted to present them with the bird. They blindly clamored for food, waiting for it to be placed in their mouths, and he stood there trying to persuade them to accept the bird, even though it was several times larger than either of them. (See [1], [2] and [3].) In the end, the owlets couldn't understand why they weren't being fed, and the male owl couldn't understand why the owlets refused to be fed, so he took his bird and left the box, possibly feeling a bit confused.

This episode illustrates an important aspect of the division of labor among a breeding pair of eastern screech owls: the females care for the young, and the males hunt. The males know that the young must be cared for, but their instincts tell them nothing about how it's done. So, in this case, the male knows to deliver food for the owlets, but doesn't know how to feed it to them. He depends on his mate to tear apart the prey he provides and to place it in the mouths of the still blind owlets. While this shortcoming of instinct conspired to make the male look hopelessly ill-suited to the task of parenting on this occasion, the flip-side is that the devotion of all his knowledge, skill and time to hunting, assures the family of a steady supply of food.

Once the owlets grow large enough to regulate their own body temperatures, the female will begin hunting for them, as well, but until then the female and the owlets depend for all their food on his specialization in hunting.

The second noteworthy event of the day was the hatching of the fourth egg, which occurred a bit before 2:00 PM. I took the box down a bit after 1:00 AM on April 2 to clean a big splotch of gunk from the side camera compartment's window (the male owl deposited that splotch on the window about five minutes after it was cleaned on the 30th), and took the opportunity to photograph the owlets. The new owlet is only partially visible because its older and larger siblings were sleeping on top of it. If it hadn't been for the gunk, I wouldn't have taken the box down until the fourth, so I did nothing that would disturb the owlets for the sake of better photos. That said, here are the photos:

March 30 was a very busy day. At approximately 2:20 AM, the second egg hatched. Around 1:00 PM, the third egg hatched. At 4:00 PM, the female owl decided to retrieve the sterile, undersized first egg from the corner where she'd abandoned it on March 17 and to resume incubating it. This is a futile gesture, and she must have understood that when she abandoned the egg, but she's incubating it again, anyway.

The male is working hard to supply food to his mate and hungry infants; he's brought two good sized birds, including a male cedar waxwing, and a number of small items like moths. The female now has a cache of food in the corner of the nest box; a valuable insurance policy for an owl with young to feed, and a fourth egg still to hatch.

The growing owlets will be photographed every five days until they've all fledged. The first set of photos were taken this evening. The female watched the process from some nearby branch, and periodically called to the owlets to reassure them. Apparently, I'm considered more of a pest than a life and death threat. That's fine by me. I don't want them becoming friendly with me (much as I'd enjoy it), because other humans cannot be relied upon to have the best interests of the owls (and other wild animals) at heart.

While I had the nest box open, I removed the nest materials brought by the starlings in earlier weeks. This change has been well received by the female owl; she has a lot more room to manuever and spread out now, and she's taking advantage of it. Also, it will give the owlets a lot more freedom of movement in a few weeks.

Enough text; here are the photos of the owlets aged 21 and 7 hours:

Note that the egg in the foreground of most of these photos is the undersized, sterile, first egg.

The female owl was manipulating egg shell fragments at 1:00 PM, 30 March 2001. It's very likely the third egg has hatched.

The first two images, [1] & [2], of the hatchling were captured this morning when madam owl took a thirty second break to sit in the entryway shortly after six in the morning. The chick is the fuzzy pair of lumps in front of the eggs. The lump on the left is the body, and the lump on the right is the head. The female normally likes to leave the box for a few minutes prior to sunrise, but went no futher than the entryway this morning. She probably feels highly protective of her newborn, which will need her help to stay warm for roughly the next ten days, until it has grown large enough to regulate its own body temperature.

The second egg hatched at approximately 2:20 AM, 30 March 2001. The hatchling was aggressively assisted in escaping from the egg by its mother, who appeared to have it free of the egg shell in less than five minutes. (Since all the action was occurring beneath the female owl, it's hard to be too specific.) A 53 second, 22.4 megabyte movie depicting some of this process provides brief, indistinct glimpses of the helpless owlet, and discarded pieces of its eggshell. (QuickTime required.) The female has been eating the remains of the eggshell to reclaim the calcium and other materials she used to create it.

The male stopped-by the nest box around 2:50 AM to look in. Although he couldn't see the hatchling, it's safe bet he could hear it. Shortly afterward he made four or five food deliveries to his mate within a space of 15 minutes. They were all grubs or caterpillars. It appeared that she ate them herself, rather than tearing them up and feeding them to the hatchling.

March 29 has arrived, and the second egg may begin hatching at any time. (Loyal readers will recall that the first egg was underweight, and sterile.) As of the female's first absence from the nest box for the day, which occurred shortly after midnight, there was no indication that hatching had begun. Each egg should begin making "peeping" sounds about 24 hours before it hatches. I have listened for "peeping" sounds from the eggs while standing beneath the nest box, and thus far haven't heard... um... a peep out of them. Still, there's no guarantee that I'd be able to hear the peeping from that distance.

Furthermore, the range of possible incubation times in Gehlbach's study of eastern screech owls1 was 27-34 days, so the 29th is merely the first possible day for hatching; it could come as late as April 5. Average incubation for first eggs was found to be 30.3 ±1.8 days. That makes Sunday, March 30, the best bet.

By the way, if you live in the Austin, Texas, area, have screech owls nesting in your nest box, and have been monitoring them carefully enough to know reasonably well how their breeding is progressing, your owls could be useful as foster parents to orphaned owlets. Drop me a line if you fit the bill. Being able to place orphans with wild owls could save our local raptor rehabilitator a great deal of work, and nobody can raise owlets to be self-sufficient owls better than their parents (adoptive or otherwise).

March 21st: Another day, another 5,760 frames. That's one frame every fifteen seconds for twenty four hours. A dusty, old Mac watches the owls for us, and at about a day and a half, its hard disk is entirely consumed by its collection of compressed moments, so it's important to keep on top of things. It takes about an hour to watch a day go by. The bulk of the day is ultimately discarded, survived only by a few dozen instants that seemed, in the middle of the night, especially clear or novel or instructive. By way of keeping score, 2001 is 144,000 frames down, with roughly 230,400 to go, assuming April and fledging finish together.

I have literally seen every minute of every day of the nesting process this year and last, and then some. My view of the world, however, is essentially confined to that eight tenths of a cubic foot that finds itself within the bounds of the nest box, and this situation I have in common with the brooding owl. Although she leaves the box for some matter of minutes after every sunset and before every sunrise in order that she may stretch her wings, relieve her bowels, and take a bath now and again, she is otherwise a prisoner of eggs, instincts, and nest box walls. For a creature that otherwise spends its life free in the world, taking in a diet of sights and sounds as much as one of mice and moths, I suspect this is an exercise in sensory deprivation.

It seems fair to expect, by way of compensation, that the yearly surge of hormones which is her biological imperative to breed colors her perceptions in rosier shades than we can see reflected in nine hundred forty nanometers of infrared light; a clear advantage to madam owl in this two month endurance event we share.

March 20th: the plague had sense enough to stay abated. There wasn't even one starling visit. Amazing.

Early in the afternoon of the 19th, the starling plague unexpectedly abated following a morning of renewed efforts to build a nest on top of the brooding owl. Perhaps days of negative reinforcement from myself and madam owl finally penetrated those impossibly thick starling skulls. Maybe the notion of raising their young two inches from a predatory bird who will have hungry young of her own, and is three and half times their weight, suddenly struck the starlings as a plan with a potential drawback or two. Then again, maybe they noticed the decoy nest box. Blissfully unencumbered by any facts, but armed with a conviction that the starlings are as dumb as posts, possibility three gets my vote.

We'll see if the plague has sense enough to stay abated.

Electrifying the owlet rail for extended periods in the early morning and late afternoon of Sunday the 18th provided the female owl with her quietest day in a week, as the entryway log for March suggests. You may also notice that the number of nocturnal visits to the box has been lower this last week than it was previously. The male is substituting quality for quantity; he's been bringing one small bird each night (and a few smaller items, too). Large prey like birds should be more difficult to catch than the geckos and other small creatures that he had been supplying, so his hunting skills seem to be rising to meet the challenge to come: feeding both his mate, and three hungry hatchlings. That phase of his life is likely to begin sometime on, or soon after, March 29.

Hopefully, the female enjoyed her slightly peaceful Sunday. With the arrival of Monday, I have to stop playing owl guardian and go back to playing university employee, so there'll be no electrical deterrent to the starling menace. The starlings may yet shift their activities to the decoy woodpecker box installed yesterday, but thus far there's no indication they've so much as noticed it; too single-minded, I expect.

The female owl decided to cease incubating the sterile, first egg early on the 17th. She shoved it to a corner of the nest box floor where it has become obscured by starling nest-building materials. The remaining three fertile eggs are being cared for diligently.

On the starling front, March 17 was a somewhat quieter day for the female owl than were the 15th and 16th. Though no magic bullet, the electrified owlet rail, when I was there to activate it, often provided the invading starlings with an unpleasant surprise that sent them hurtling away to perches less painful. A graph of nest box entryway activity testifies to some of the effect during the periods of 6:30-10:00 AM and 3:30-6:40 PM. (In between, I slept.) The fact that the owl wasn't entirely buried in starling nest-building materials on the 17th is another testament to the effect.

A relevant aside: Built into opposite sides of the nest box entryway are an infrared emitter and sensor. Whenever anything sizeable comes or goes, it breaks the beam of infrared light, and a computer logs the event.

A not-so-relevant aside: Before turning-in that morning, I decided that the inconsistent effect of the electrified owlet rail could be rectified by changing-over to a power supply designed to provide potent shocks. So I set off to the local big-box hardware store to buy an electric fence power unit. To my amazement, I found they'd stopped selling 'em, and considered anyone asking about them to be of suspect moral character. I'm living in the heart of Texas, and I can't buy an electric fence. Whether this is for the better, or the worse, I don't know, but if I'd ever given the matter any thought before now, I'd've sworn it would never happen.

All asides aside, I will be resuming the starling electrification work Sunday afternoon, inconsistent results notwithstanding. Adding to the effort to keep the starlings out of the owl box is a battered, old woodpecker nest box that I've pressed back into service to provide the starlings with an alternate target. If they nest in it, it should make an effective trap. I am informed this "extra nest box" trick is an old one among the maintainers of eastern bluebird boxes. Thanks to the reader who suggested it. (My own eastern bluebird box has never seen a bluebird. Sigh.)

March 16 must have been one of the more difficult days in the life of this female screech owl. A pair of starlings spent the day building their nest on top of her, despite her best efforts to discourage them. At the end of the day, the starlings were as committed as ever to taking over the nest box, and the female appeared to have received a wound to the face beneath her right eye. (Imagine what smaller, less formidable birds are up against when starlings invade their nest cavities.)

As a result of all this, I took a chance in the early hours of the 17th and brought down the nest box in order to electrify its owlet rail. The hope is that during this weekend, when I see starlings perched on the rail, I can remotely deliver to them a stiff dose of 110 VAC. Using 110 VAC probably isn't the best way to deliver a good shock, but for a quick lash-up using parts-on-hand, it should be better than nothing.

The danger in bringing the box down for alterations at this time is that screech owls will sometimes abandon their eggs if they are disturbed too much. (They will not abandon owlets, however.) Given all the abuse this bird had already put up with (including the mounting bracket disaster which is another story), I felt she'd tolerate this disturbance. She did. Not surprisingly, however, when she heard the cables used to lower the nest box being unrolled, she left in a big hurry.

While the box was down, I took the opportunity to remove the starlings' nest materials, clean the camera compartment window, photograph the eggs, and to candle them. The results of the candling are as expected: the first egg is sterile, but the remaining three have been developing.

The female owl probably watched the entire process from a nearby tree; she returned to the nest box the moment I walked back into my house. She then studied her eggs from the entryway for a minute before deciding everything was alright once again and resuming her brooding duties.

The last several days (March 13 and 14) have seen a great increase in harassment of the female owl by European Starlings. The starlings are frequently carrying nest-building materials when they enter the box, and are not sufficiently intimidated by the presence of a screech owl to be persuaded to go elsewhere. In response to the most sustained provocations, she has begun to attack. She has two significant handicaps in this regard: (1) by getting up to attempt an attack, she risks exposing her eggs to damage by the Starlings, and (2) a screech owl's primary weapons are its talons, and they are most effectively employed when attacking from above, which is not possible here.

Last year, the starlings resorted to outright attacks against the female owl to try to drive her from the nest box. In response, it seems as though she found a way to persuade her mate to spend three days with her in the nest box on guard duty. I have often wondered how she communicated to him the need to do so, given that males do not normally roost in the nest cavity with their females. Perhaps he worked it out on his own.

The European Starling is not a native species, just as its name suggests. It was introduced into North America in 1890 (in New York City's Central Park, if memory serves), and since then has spread across the continent. As its interaction with these owls - predators willing and able to prey on Starlings - demonstrates, they are extremely aggressive and pose a threat to native cavity-nesting bird species. They have, for instance, driven my local red-bellied woodpecker from the nest holes it has dug over the years in a nearby dead tree, and have never allowed it to occupy the red-bellied woodpecker nest box I built four years ago no matter how many times I remove their nests and eggs. I often wonder how long I'll continue to have woodpeckers given that I have yet to observe them allowed to nest.

The House Sparrow, a species introduced into North America in 1851, poses a similar threat to our smaller cavity nesting birds (including our many native species of sparrow). Infinitesimally evening-up the score this evening (March 14), the male screech owl supplied his mate with a house sparrow breakfast. If he turns his attention to making meals of the local Starlings, his mate will have reason to be even more grateful, and the woodpeckers won't mind, either.

I have noticed before, and with the arrival of a loud, hail-bearing thunderstorm Sunday night (March 11/12) have had the chance to observe again, that a brooding screech owl enjoys a rain storm. Not necessarily the full brunt of it, but certainly the opening movements. These seem never to fail to induce an owl out of her box for a minute or two. She returns wet and in no special hurry. My guess is it's an opportunity for a quick bath, probably without ever having to leave her tree.

After her ready acceptance of the storm's arrival, it was surprising to watch this owl panicked by the full force of the storm with its pounding thunder, lightning, driving rain and hail. Even if she's only a yearling, none of these things can have been entirely new to her, but she repeatedly leapt up and out of the box as though her life depended on it, only to return some seconds later as disturbed as when she'd left, scattering heavy drops of water across the camera compartment window. This cycle was repeated many times. Maybe the sound of rain and hail on a tin roof was still too new to her to be appreciated, or maybe the tree and the box were swaying and creaking more than she was willing to trust. Perhaps she's always tried to flee from thunder. Possibly, she has her own reasons which a camera cannot reveal.

Given enough cameras, I expect any thunderstorm would be found full of stories, if not explanations.

A short movie of a food delivery was recorded on the 10th, because it's one of many common activities in the nest box that are more comprehensible at thirty frames per second than at one frame per minute. Running time is 18 seconds. File size is 8 megabytes. Format is QuickTime.

The night of 7/8 March proved to be the toughest hunting night since a week of rain ended on the fourth; the female went without a food delivery for almost five hours. The weather is good, so there's no obvious reason for the difficulty.

Food deliveries this year have mostly been geckos, with some moths, and a good number various other small items that were swallowed too quickly to be identified. The largest prey item observed so far was a small bird, or possibly a mouse, that was caught on the fifth. All hunting duties fall to the male owl until the eggs have hatched and the owlets have grown large enough to regulate their own body temperatures, so he has an enormous amount of work ahead of him.

The fourth egg was laid sometime in the afternoon of 6-Mar-2001 (2:36 PM CST is a good guess), thereby maintaining this female's decidedly non-standard laying interval of 2.x days. It looks to be only slightly smaller than the second and third eggs. This promises a good crop of owlets. Expect hatching to begin with the second egg somewhere around March 29.

The third egg was laid sometime on the afternoon of 4-Mar-2001. It's essentially identical in size to the second egg, which is a very good sign.

The second egg appears to have been laid at 2:57 AM, 2-Mar-2001, an unusual 2.2 days after the first. Gehlbach's study of eastern screech owls1 showed a mean time between first and second eggs of 1.1 ±0.3 days. Significantly, perhaps, the second egg is much larger than the first. This may indicate a problem with the first egg, and explain why the female has shown limited concern for it.

By overlaying a regular grid corresponding to the known dimensions of the box's central floor (8" x 8") on an image of both eggs from the roof camera, it is possible to make fairly accurate measurements of the eggs. The first egg, which appears so close to being spherical that I assume it is for this purpose, measures 20.3 x 20.3 millimeters. The second egg is 35.6 x 29.1mm, and therefore is a perfectly normal e. screech owl egg, based on Gehlbach's study. The contrast emphasizes the abnormality of the first egg. Last year's sterile eggs measured approximately 28.4 x 25.8mm and 28.1 x 25.9mm, and therefore were also seriously undersized, though not so much as this year's first egg. Assume the first egg will fail.

The first egg was laid at approximately 9:45 PM, 27-Feb-2001. You can get an idea of how much work it is to lay an egg from this frame. (Afterward, she looked a lot more relaxed.)

  1. The Eastern Screech Owl: Life History, Ecology, and Behavior in the Suburbs and Countryside by Frederick R. Gehlbach. (No, I don't make a cent by providing this link.)

 

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