Chris' Eastern Screech Owl Nest Box Cam

The images presented on this site come from a nest box for eastern screech owls (Otus asio) in urban Austin, Texas. During the day, sunlight from the entry hole provides illumination. When sunlight isn't available, infrared illuminators take over to ensure uninterrupted viewing. Although the infrared illuminators cumulatively emit less than one tenth of a watt of light, they provide more even illumination than the sunlight coming through the entry hole, so the best images are acquired after dark. Because black & white cameras offer better low-light sensitivity than color cameras, and because color photography is essentially impossible with single frequency illumination, a black & white camera is used here. As it happens, the box is being used by gray-phase screech owls, so we're not missing much color-wise, anyway.

More information to come. (The owls are working faster than I am.)

News

• 2000-05-13 - After repeated searches, I finally caught site of both owlets, alive and well this afternoon. One was concealed amongst the foliage of some of the upper most branches in the nest box tree, and the other was in a small, adjacent tree, sleeping in a fork of the trunk about six feet above the ground. I suspect the owlet fell out of the nest box tree at some point last night, and climbed the nearest available tree that wasn't wrapped with a predator guard. Since its new perch was so near the ground, and even nearer the top of a chain link fence routinely climbed by free roaming house cats, I decided to move the owlet to the nest box tree if at all possible. Even as it watched me, I was able to carefully reach up and grasp it, walk over to the nest box tree, and cary it up a step ladder to a promising limb. Positioning it next to the limb, I then waited for the owlet to disengage it claws from the flesh of my hand and climb onto the limb. (I expected this to be an issue.) It seems that an owlet makes no distinction between being held by something, and holding onto something, because it not only didn't let go of me, but became agitated and adopted a threat posture as I stood there waiting for it to climb onto the limb, and it stood there waiting for me to magically vanish from between its talons. After a minute or so of this, I resorted to manually lifting the talons out of my hand, after which the annoyed owlet stepped easily onto the limb. Within a few minutes, as the owlet jumped to another limb, and began climbing toward the foliage above, a mocking bird began mobbing the youngster. A few minutes of chasing away the mocking bird bought the owlet the time it needed to vanish into the outer branches of the tree, and all was well. I have since removed the predator guard from the trunk of the nest box tree so that if either owlets finds itself on the ground again, it will have a proper tree to climb. At this point, I believe they can out climb any predator they're likely to encounter. (Given the way the owlet clamped itself to my hand, I couldn't read the unique part of the number on its band without turning it upside down, so I have no idea which owlet it was.)
• 2000-05-12 (9:00 PM CDT) - The shy owlet moved out onto the owlet rail at 8:26 PM, and is perched there now. Heavy thunderstorms are approaching the area, which could make for a wet and windy introduction to the outside world, or it might encourage the owlet to return to the box. We'll see, and I'll be checking for owlets that need a hand to get back into their tree.
• 2000-05-12 (4:00 AM CDT) - The curious owlet is successfully jump-flapping between nearby branches (fledglings can't really fly), and the adults have begun an aggressive defense of the area around the nest box tree. When walking near the tree, the adults make low passes over my head while clapping their beaks, and issuing sets of three quiet, hollow-sounding, high-pitched hoots. They are capable of mounting a far more violent defense if they decide it's required - their talons can easily draw blood - but they can see I'm not attacking the fledgling, and they probably recognize me and regard me as more of a pest than a threat, in any case. I find this defensive behavior to be a helpful indicator of the presence of fledglings, and appreciate the parents providing that information. BTW, Gehlbach states that at fledging an owlet is only 68.6% of average adult size, and the appearance of the curious owlet is consistent with that.

  A day in the life. From noon on the 9^th to noon on the 10^th a time lapse movie of activity in the nest box was recorded. The entire day is captured in 3,708 frames and passes in just two minutes and three seconds, at thirty frames per second. If you don't mind the fast pace, the jerky time-lapse action, and the 34 megabyte download, have a look.

• 2000-05-11 (10:00 PM CDT) - The curious owlet successfully left the box this evening around 9 PM CDT, and was contentedly perched on a tree branch about twenty feet in front of the box when I went looking for it about an hour later. The adults will bring it food there, and will step up their efforts to entice the shy owlet from the box by calling to it from nearby branches, and by reducing, or withholding, food deliveries. Since both owlets hatched on the same day, and appear to be equally well developed, all that remains is for the shy owlet to decide that it is ready to leave the box. Gehlbach finds that broods of two screech owlets require 1.7 +/- 0.5 days to leave their nest (substantially less time than larger broods require), so we can expect the shy owlet to decide to leave sometime afer sunset tomorrow, or, at the outside, the night after. Meanwhile, the parents are still delivering meals to the owlet in the nest box.
• 2000-05-07 - Banding day. Sallie the raptor rehabilitator, and supplier of these adopted owlets, came by today and placed an official leg band on each of the owlets. The curious owlet, previously referred to as number one, received 1005-04357, and the shy owlet, number two, received 1005-04358. Thus identified, there's a chance that after they've fledged and found territories of their own, we'll someday learn a bit about what became of them.

  Also done today was the installation of an owlet rail. It's roughly 24 inches long, and positioned a few inches beneath, and in front of, the entry hole. This should provide a good place to test untried wings and to plan the particulars of a first flight. Those first flights are likely to take place on May 10^th, if the owlets conform to the 27.5 (+/- 1.8) day mean time to fledging established by Gehlbach.

• 2000-05-05 (retroactive) - The photos from the fifth are finally available. Note that, differences in cameras nothwithstanding, the color of the owlets has changed considerably since the last set of photos were taken on April 29^th, and those changes bring with them increasingly promising flight feathers.
  • Full view of the nest chamber with owlets. Scale may be obtained from the climbing slats on the back wall of the box which are spaced at one inch intervals (measured from the top of one slat, to the top of the next). Photo: Large, Medium.
  • Owlet one crouched, but curious. Photo: Large, Medium.
  • Owlet two standing semi-upright against the back wall, feeling a bit threatened. Photo: Large, Medium.
  • Owlet two standing semi-upright in front of camera compartment glass, feeling a little less threatened. Most of owlet one is visible to the side. Photo: Large, Medium.
• 2000-05-05 (12:30 AM CDT) - A practice perch has been installed in the box by removing the peg board face of a wall module and installing a length of tree branch across it. This not only provides a safe place to practice climbing and perching, but creates a new vertical level in the box while adding two inches (the depth of the module) to its useable width. In a box stuffed with rapidly growing owlets, the extra space seems likely to come in handy.

  (A design goal for this box was that all camera modules, left, right and ceiling, should have completely unobstructed views of the entire interior area. Since the side sockets are two inches deep, the wall modules had to be that deep, and a facing board was required to keep the useable floorspace down at the intended 8 x 8 inches. Since there is no ceiling camera at present, and I wanted to know whether a perch would be useful, I'm prepared to violate that desing goal for a while.)

  During the coming weekend, at the recommendation of the raptor rehabilitator who provided these owlets for adoption, an "owlet rail" (to borrow a term from the creator of the OwlCam site) will be installed outside the box's entry hole, parallel to the front of the box. It will provide the owlets a place to stretch their wings outside, and a path (as much as I can arrange it) to a nearby tree limb so that the owlets won't be rushed into their first dangerous attempt at flight merely by the natural desire to leave the nest. In a conventional tree cavity nest, climbing out of the nest and exploring the host tree on foot is a normal activity. The reason not to have an owlet rail is that it provides useful footing for predators as well as owlets. (Climbing predators - house cats - have killed eight owlets and two breeding females in nest boxes in this yard in the previous two years, even without the assistance of an owlet rail.) That's why there hasn't been a rail so far. However, there is also danger in making the owlets attempt their first flight as they leave the box for the first time; if they don't make it to a limb of their tree, they'll be left sitting in the grass below in even more immediate danger. They will not be able to climb up the trunk of the tree because this year it is covered with aluminum flashing to prevent predators from climbing it, which is probably why these owls have survived. So, the rail is a judgement call, but its temporary installation seems to strike a good balance among the primary dangers facing the owlets during the coming week.

  This entry should include new color photos of the owlets, of course, but in keeping with a string of hardware failures that have bedevilled this project (one monitor, one CPU, one hard disk), my digital camera has now died. Unlike the other dead bits which had provided years of service, the camera was still quite new, which suggests to me that Olympus could work a bit harder at its quality control. That griping aside, conventional photos were taken, and will be available just as soon as I have them developed, scanned, and so on.

  A change of habit. On Sunday, April 30^th, the female did not spend the day in the box with the owlets. I was afraid she'd been killed during the previous night, but her food deliveries to the box that night proved she was still very much alive. Although she spent some of Monday in the box, she hasn't spent a day there since. My trusty reference books do not appear to document this behavior, so there's room for conjecture about this change of habit. The most satisfying conjecture I've heard thus far is that she's avoiding the crowding and disturbances inside the box by roosting somewhere nearby, from which she can still observe and defend the box.

  BTW, yesterday, I observed one of the owlets refuse food for the first time. Up 'till this point, I'd been convinced that owlets were larger on the inside than the outside, and could be stuffed with lizards, mice, birds and bugs until there were no more remaining for the parents to catch. Turns out I was wrong; they really can get enough to eat and, I'm pleased to report, they do.

• 2000-04-29 (12:40 AM CDT) - Over the last five days, the owlets have developed considerably. No longer lumps on the floor of the box, they've learned to sit and stand upright (and even to scratch with one foot while balancing on the other), to clap their bills and hiss, to flap their wings (lack of flight feathers notwithstanding), and yesterday one made the first attempt at climbing the rails on the front of the box (not much luck, but a worthy first effort). And, as it's been five days since the last set of photos, here's a fresh look at the youngsters:
  • Owlet one sitting on open box front with draughtsman's scale, inches shown. He was clinging to the front of the box when I opened it, and calmly chose to go on sitting there. Photo: Large, Medium.
  • Owlet one sitting on open box front, content to watch the proceedings. Photo: Large, Medium.
  • Owlet two sitting upright next to camera compartment glass. Elements in background indicate owlet sits about 5.25" high. Standing would be another matter, however. Photo: Large, Medium.
  • Owlet two in a standing crouch, not especially happy with the human invasion of its tiny world. Reflection in camera compartment glass. Photo: Large, Medium.
• 2000-04-24 (4:30 AM CDT) - The color camera proved not to be of much use, so it has been removed from the box and the old wall module has returned to the left hand socket. Things look normal again. Meanwhile, it has been five days since the last set of color photos of the owlets were taken, so here's a new set of photos. Not surprisingly, the owlets have changed quite a lot in appearance and size.
  • Owlets with scale - The snoozing owlets are shown here with a U.S. quarter dollar coin (just under 1 inch, or 2.54 cm, in diameter) for scale. Photo: Large, Medium.
  • Barely interested owlet - While one slept through the entire module swap, the other owlet took some interest in the disturbance, but not very much; it went back to sleep about ten seconds later. (Oh, him again.) Note the improved clarity of the owlet's eyes relative to their state on the 19^th. Photo: Large, Medium.
  • Another look at the heap of owlets. Photo: Large, Medium.
  • Snoozing owlet - If it really sleeps as peacefully as it appears to do in this photo, I'm envious. (This photo was taken during the module swap on the 23^rd.) Photo: Large, Medium.
• 2000-04-23 (2:30 AM CDT) - A module containing a color video camera has been installed in the box's left hand socket, in place of the wall module everyone is accustomed to seeing. It's a 1.5 lux camera, so it's useless at night, but it just might be useful during the day while sunlight is shining through the entryway. Early experiments with the prototype box indicated that even then it was useless, but the prototype went through six or seven entryway designs as I searched for a good balance between acceptability to owls, and protection from predators. The camera was tested against the first of those designs, but not the one currently in use, which allows more light to enter, so it seemed to be worth a fresh test. If the images are any good, I'll manually switch over to the color camera during the day today, and will switch back to the normal monochrome camera as the sun sets. If the images are useless, I'll pull the module out the next time the parents are away.
• 2000-04-22 - The owlets are slowly getting the hang of sitting upright, although they often lean on each other as they do so.
• 2000-04-20 - Over the last several days the female seems to have concluded that the owlets are large enough to thermoregulate, so she has begun leaving them alone during the night while she hunts for them. The male, of course, continues his hunting duties. Recent prey items have primarily been geckos, but there have also been two or three mice, and one sparrow. Oh yes, and one Texas blind snake which the female found slithering among the nest materials. The male had a similar meal a few weeks back, so the box is probably snake-less at this point. Being a beneficial snake in an owl nest is clearly a thankless job.

  While the owlets can now swallow small prey, large items like mice still must be torn apart for them by the female. Male screech owls do not have an instinct for tearing-up food for owlets, so they just deposit large prey items in their nest cavities and let their mates handle the feeding duties. Here is a 4.5 minute, 33.7 MB QuickTime movie recorded yesterday of the female feeding a mouse to the owlets. The mouse was delivered earlier in the night by the male, who is the family's premier hunter. (The server on which the movie is stored is suffering serious hardware problems at present, so don't be too surprised if it's unavailable or unreliable. Replacement parts are on order.)

• 2000-04-19 (3:00 AM CDT) - The owlets made such enthusiastic attempts to take a just delivered medium sized gecko from the beak of the female that she gave it to one of them. After dropping it and spending a few moments feeling around for it, the lucky owlet located it and quickly swallowed it whole. Well, nearly whole - the lizard's tail hung out of the youngster's mouth for a while. This is the first time I've observed one of these owlets eating a whole food item. Until now everything they've eaten (chiefly geckos and mice) has first been torn into small pieces by the female.
• 2000-04-19 (2:00 AM CDT) - I'd intended to open the box and photograph the owlets every seven days, but decided that every five days would be more instructive. Since about five and a half days have passed, here are photos of the owlets in large and medium sizes.
  • Owlets in context - The entire 8" x 8" floor of the box is shown, with a U.S. quarter dollar coin (just under 1 inch, or 2.54 cm, in diameter) for scale. Photo: Large, Medium.
  • Owlet in closeup - This is probably one of the first times it has ever opened its eyes. The eyes begin cloudy and clear-up as the owlet grows. The fluffy, white lump beneath the owlet's head and neck should be head of other owlet. Photo: Large, Medium.
  • Sleeping pile of owlets closeup - The owlet seen in closeup above sleeps on top of its sibling. Unless I miss my guess, the head of the second owlet appears beneath the head of the first, and its back end is visible above the head and shoulders of the first. Large, Medium.
• 2000-04-14 (1:33 AM CDT) - The owlets have been expertly fed portions of geckos on two occasions already this morning, so it looks like everything will work out. In both cases the female fed them as much as she judged appropriate, then ate the remainder herself.
• 2000-04-13 - At 9:20 PM CDT two orphaned owlets, hatched earlier in the day, were placed in the nest box, along with the shells of the eggs from which they'd hatched, and a large, dead mouse. This provided the female owl with living offspring, plausible props, and a good cache of food for the owlets, respectively, to get this most active phase of her motherhood off to a good start. The infertile eggs were removed and examined; there was little, if any, indication of embryo development in either. Five minutes later the female returned to the box, and within a minute she began brooding the owlets. She soon removed the egg shells to a corner of the box, consuming part of one while she was at it. After quite some time she took an interest in the mouse, and eventually began tearing at it, but there was no clear indication that she fed any of it to the owlets. Some time later she left the box with the mouse in her beak. She came back a few minutes later without it, and there's no telling what became of it. Since then, the male has delivered several geckos and one large moth. She ate one of the geckos (small, insectivorous, nocturnal lizards) and the moth, but spent some time tearing up the second gecko (instead of swallowing it whole as she has always done in the past) and manipulating the owlets beneath her, so it's possible that she fed it to them. Obviously, it's crucial that she feed the owlets, and if there's reason to think she's failing in this duty, the owlets will be returned to human care tomorrow. (Whichever way it works out, thanks to Sallie for making this possible.)
• 2000-04-12 (10:30 PM CDT) - The female owl's tolerance for disturbance has been tested, and she passed beautifully. She left the box the instant I began unravelling the ropes attached to the mounting bracket's pulleys, and then watched all that followed from a nearby limb. Once the box was lowered to the ground, the side camera and roof modules were removed and altered slightly, glass was cleaned, photos of the eggs were taken (no sign of hatching), the modules were replaced and the box was hoisted back into the tree and secured to its mount. The whole process took about eleven minutes, and three minutes after that, the female was once again incubating her eggs. Tomorrow night we'll have a go at replacing the eggs with orphaned screech owl hatchlings, or eggs soon to hatch.
• 2000-04-12 - A video examination of the two eggs at around 6 AM this morning showed no signs of hatching, so there is essentially no chance remaining that the eggs are viable. While the owls are capable of renesting, after speaking with some people with experience in this area, it seems that renesting will only take place if something happens to the eggs. Since this pair of owls are doing a first rate job of defending the nest site, it isn't very likely that anything will happen to the eggs, so the female could go on futiley incubating them until her summer molt begins. Not a satisfactory situation. One option is for me to remove the eggs, but such an "attack" could easily convince the owls to renest elsewhere, and never return. A second option is to place orphaned screech owl eggs or hatchlings in the nest and allow this pair to raise them to adulthood. This must, of course, be done in conjunction with state approved wildlife rescue workers. I have opted for the latter course of action, and, at the request of the rescue worker I spoke with today, will be briefly taking down the nest box tonight to verify that the female owl will return to the box after such a disturbance. (This will also give me a chance to clean that big smear off of the camera compartment glass.) That'll probably happen around 10 PM CDT tonight. If the female returns to the box after this test disturbance, we'll place the orphans in the nest at the next available opportunity.
• 2000-04-10 - A careful video examination of the two eggs around 6 AM this morning showed no signs of hatching, nor was there any obvious indication of a change by 8 PM this evening. Also, impending hatching is usually indicated by "peeping" sounds from the eggs, but as of 5 AM this morning no such sounds have been heard from the nest box. Maximum incubation time is understood to be 34 days, so if something's going to happen, it seems that it must happen in the next day or so. If the eggs do not hatch, there's a good chance the pair will try again with a new clutch, although there is no guarantee that they will choose the same nest site. In practice, though, they probably have few, if any, other sites to choose from, given the competition for nest cavities at this time of year, and the shortage of such cavities in the urban landscape they inhabit. The male, by the way, continues to spend the day in the box with the female.
• 2000-04-06 - The male spent the day in the box with the female again. He arrived around 10:00 AM CDT, and stayed until he commenced his hunting duties at sunset.
• 2000-04-05 - The likely date for hatching of the first egg is Friday, April 7^th. How obvious this will be on the web cam remains to be seen, but potentially visible activity on the part of the female will likely include her careful visual examination of the hatching egg and resulting owlet, and should include the removal of the fragments of the egg shell. She may consume the fragments in order to regain the nutrients used in creating the shell, or she may simply dump them outside. Removal of the fragments is important to the survival of the second egg - if it were to become partially enclosed by a large enough fragment, the supply of air to the fetus in the second egg could fall below survivable levels.
• 2000-04-04 - The male owl has spent the last two days (the 3^rd and 4^th) in the nest box with the female. He may have been providing some defense against starlings again, but it seems at least as likely that he was taking shelter from a system of thunder storms that had parked itself over Austin.
• 2000-03-26 - The male owl has spent the last three days (24-26) in the nest box with the female. As I understand it, this is more-or-less unheard of behavior, and the female didn't seem too happy about it at first. Regardless of how rare this behavior actually is, it is certainly timely; in the days prior to the 24^th, the female was tirelessly harassed by starlings. This harassment, including being pounced on by starlings with beaks full of nest-building materials, kept her awake most of the day, at times in a subdued threat posture. In principle, jumping on top of a screech owl should be a very dangerous proposition for a starling, but a screech owl incubating eggs may not be willing to risk exposing her eggs to attack while she stands to bring her primary weapons--her talons--to bear on the intruder.
• 2000-03-22 - Movies of food deliveries. Most food deliveries last only a matter of seconds and, as a result, are seldom seen on the web cam. Here are movies of two food deliveries - one is short and typical (12 sec., 1.5MB), the other is long and unusual (2:21, 17.3MB). As with all movies on these pages, Apple's QuickTime software is required.
• 2000-03-18 - It looks as though a Texas blind snake is sharing the nest box with the owl and eggs. While reviewing archived images from the nest box, it became clear on several occasions that something was moving through the nest materials, and that the female owl was watching it just as I was. Based on what little could be seen, and the discovery of the snakes in my nest boxes in previous years, it seems most likely that the source of the motion is a Texas blind snake. An 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. He explains the presence of the snakes:

  "Four times I watched adult screech owls bring in live blind snakes, coiled in their bills instead of dangling like the carcasses of other snakes. Certainly the blind snake's writhing defensive behavior and smooth cylindrical body, smeared with repellent secretions, make it difficult to kill. But the owls do try to kill the snakes, as I saw one unsuccessful attempt and an apparently successful one. Dropping them alive into nest cavities can be nothing more than thwarted feeding behavior. The delivered snakes subsist on fly and ant larvae and pupae, based on their stomach contents. However, deprived of renewed food sources at fledging time, they must crawl out of nest cavities back to their usual underground habitat. In six unmanipulated instances live individuals disappeared from nest boxes two to seven days after fledging."
  Gehlback, F. R. 1999 The Eastern Screech Owl, pp. 120-121.

  This particular owl, for whatever it's worth, does not appear to be interested in eating the snake. I have observed her watching it on several occasions, but she hasn't made any motion toward it, although it is literally within a few inches of her (the bottom of the box measures only 8" x 8").

  It should be noted that the while there are "nest materials" in the box, eastern screech owls do not build nests, and did not place the materials in the box. Those materials were placed there by myself and several starlings. The female owl formed the depression in which she laid her eggs by using her chest to push away some of those materials.

  Additional blind snake information on the 'net includes Blind snake predation by Barry Sullender, and the Blind snake entry of the Encylopaedia Britannica.

• 2000-03-09 - Confirmation of two eggs. Two eggs would be an unusually small clutch for eastern screech owls. The great majority of early season nests contain 4 eggs. (Gehlbach, F. R. 1994. The Eastern Screech Owl, pg. 87.) However, our viewing angle isn't ideal for egg counting, so the presence of additional eggs can't be ruled out. (I built a chamber for a roof-mounted camera into this nest box, but the owl moved in before I could take advantage of it. Next year.)
• 2000-03-08 - First sight of two eggs.
• 2000-03-07 - First sight of an egg. Normally, a female screech owl will take-up exclusive residence in a nest cavity 5.7 +/- 1.9 days before laying, and she will lay her first three eggs over 3-4 days. There will be longer intervals between subsequent eggs. This female seems to have waited until the last minute to take up residence in this nest box. Incubation requires 30.3 +/- 1.8 days, and takes longer during warmer weather. (Gehlbach, F. R. 1994. The Eastern Screech Owl, pg. 81, 93, 94.)
• 2000-03-06 - The female is back, and spends a quiet day in the box. Starlings poke their heads in on a few occasions, but don't raise an alarm at the sight of her.
• 2000-03-05 - After spending Saturday listening to angry songbirds conduct loud, anti-owl protests, the female decides to spend Sunday elsewhere.
• 2000-03-04 - First day-long occupancy of the box was Saturday the 4^th. This suggests the first egg is likely to be laid late Thursday (March 9^th), or Friday (the 10^th). The local songbirds spend the day in the surrounding treetops loudly protesting the presense of owls on their turf after the male owl, ejected from the nest box by the female mid-morning, grabbed a bird at a nearby bird feeder for a snack as he flew off to his daytime roost.

Gallery

A proper gallery will yet be created, but here are a few stills that provide a clearer look at the owls than the typical web cam image.

• Male, 2000-02-06
• Female, image 1, 2000-02-09
• Female, image 2, 2000-02-09
• Female, image 3, 2000-02-09

Some of the other stills and movies from the prototyping phase are also on-line.

Items From Past Years

• Chris' Screech Owls

Related Sites

• "View Nesting Birds" page - a world-wide list of nest sites that can be visited via the Internet. Active nest sites are clearly designated.
• OwlCam - interesting content, and a proprietor who has provided me advice on many occasions.