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Posts categorized screech owl.

The continuing story of the Hildacy Screech Owls…

By Mike Coll, Hildacy Farm Preserve Manager

When I last wrote about the owls in the Hildacy nest box it was in March of this year and I was hopeful that the pair would attempt to breed again and would this time be more successful than they were in 2014. The pair in fact did make another attempt but unfortunately this year’s nest again produced no young.

The particulars of this year’s story begin with the female owl (the red phase owl) roosting in the box every day this spring except for one and on that day I observed the gray male owl in the box. I took this to be a sign that the pair had mated again and a week or so later the female began laying eggs.

However, unlike the previous year, this year I never saw the male owl again. The female, who should have been spending almost all of her time incubating the eggs (while being fed by the male), was instead forced to go out at night and hunt for herself. I once even observed her calling from the box, which is the opposite of the secrecy that birds usually display once they have laid eggs. My guess is that the male owl met an unfortunate fate. He may have been hit by a car or killed by a local Great-horned Owl, but it seems very unlikely that he would have abandoned his mate at such a crucial point.

When it became apparent that the male owl was not going to return, I made a somewhat futile attempt to act in his stead. Adult owls consume about one mouse per night, so I decided (after discussing the situation with wildlife rehabers at the Wildlife Clinic at the Schuylkill Center) that I would purchase frozen mice online (normally marketed to people feeding pet snakes) and supplement her diet the way the male owl would have. Each night I thawed out a mouse, waited for the owl to leave the box, and tossed the mouse into the box with the help of a long pole. It seemed like she started to expect these feedings and was able to spend much more time incubating and less time hunting. Eventually I decided that it would be less invasive to place the mouse out in front of the box and let her come grab it herself. Here is the slow-mo footage of her coming to get a mouse, captured with an infrared camera:

I continued feeding her for the better part of a month but the eggs never hatched and one day she simply abandoned the nest. I think it is likely that the eggs were either never actually fertilized by the male or that they were unable to survive the first few cold nights (before I started feeding her) when the owl was out hunting.

While this is obviously a disappointing result, I think it illustrates how precarious each year’s breeding cycle is. All factors must be accounted for in order for a species to successfully reproduce and many times this does not occur for one reason or another.

But, there is always next year and with that in mind I took the opportunity to replace the old box with a new more structurally sound version that also contains an upgraded HD camera.







The new camera has a larger bank of infrared lights, higher resolution and provides much more clear audio than the previous one.
After abandoning her nest, I didn’t see the owl at all during the summer. But a few nights ago I heard a Screech Owl calling from behind my house and then on 9/27 she spent the day roosting in the new box.

Hopefully, this owl will continue to use this box as a roost throughout the winter and then locate a new mate in the spring.

Owl box spring cleaning (and story update)

By Mike Coll, Hildacy Farm Preserve Manager

Almost every day this winter our resident female, red phase Screech Owl roosted in the box behind the spring house. This is the continuation of a story that has been ongoing for the past 5 years since I initially placed an owl box in that location (and then replaced it with a box that included a camera). For the first 3 years a gray phase male Screech Owl roosted in the box. Each spring he called from the entrance of the box but did not successfully attract a mate. This changed last year in early April with the appearance of a red phase female. Following her arrival the pair spent a few days together in the box. About two weeks later the female had laid a clutch of 3 eggs (laying one egg every other day). For the next 29 days the red female diligently incubated the eggs, leaving the box for only a few minutes each night. During this period her mate did the hunting, constantly bringing mice, frogs and insects to the box and feeding her.
However, for reasons unknown to me, none of the eggs hatched. It appeared that the female owl ate each of the eggs exactly 29 days (the expected incubation time) from the date that the eggs were laid (also eating only one every other day). I can only surmise that she somehow knew that the eggs weren’t viable (maybe they became cold?) and her instinct was to not let an available source of protein go to waste.

After the failure of the eggs, I didn’t see either owl for nearly a month. But at some point the red female began to roost in the box again and since then she has been a fixture there, usually sticking her head out to catch the last few rays of sun each evening before going out for the night.

In fact, the presence of the Red Owl has been so consistent that I haven’t wanted to disturb her by cleaning out the box. So when I looked at the camera yesterday and noticed that she was roosting elsewhere, I jumped at the opportunity to clean the box and do some repairs. Some of the metal flashing that prevents squirrels from climbing into the box needed to be reattached and I also added a bungee cord around the trunk to further support of the box itself.

The inside of the box was littered with 15-20 owl pellets and the feathers of what appeared to be a Downy Woodpecker, a Blue Jay and possibly some others. I scraped all of this out of the box and then added an inch or so of fresh wood chips. I then replaced a good number of the feathers that were in there because they seemed like an interior design choice that the owls had made. I first noticed feathers in the box just before the eggs were laid and I expect that she may use them as bedding.

This morning I was happy to see the female back in the box. I hope she likes what I did with the place.

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I expect that the male has remained in the area even though I haven’t seen him. We should know by the first few weeks of April if the pair will make another attempt at breeding.

Hildacy Preseve: Red Owl lays eggs

By Mike Coll, Preserve Manager

About 2 weeks after the Red morph Screech Owl first arrived at the box she began laying eggs.








Screech Owls generally lay a clutch of 2-6 eggs at a pace of one egg every other day.  As of yesterday when this video was taken she has laid 3 eggs.

So far both owls have continued to stay in the box during the days.  As night falls the male owl leaves the box to hunt and periodically returns to feed the female, who spends most of the night incubating the eggs.  In the video it seems like the male feeds her something small like an insect, but on other occasions he has returned with mice or frogs from the nearby wetlands.  The female does leave the box occasionally during the night, possibly to get a drink of water or stretch her wings, but she is never gone for more than about 20 minutes.

Screech owls incubate their eggs for approximately 4 weeks before they hatch.  If this holds true, the young owls should emerge during the 3rd week of May.

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Hildacy Preserve: Screech Owl pair

By Mike Coll, Preserve Manager

Two days after my first ever sighting of a red morph Screech Owl I was pleased to see both the grey and red morph owls together in the box.  It is now my view that the red morph is a female and the grey morph is likely the same male owl that has been roosting in the box throughout the winter.

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You can see in this picture that the head of the lighter colored owl (red morph) is slightly larger than the grey owl, again suggesting that it is a female.

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The pair stayed in the box all day yesterday, alternately preening the other’s feathers.  Today only the female owl has returned to the box, but I think that is still a hopeful sign.



Hildacy Preserve: Red morph Screech Owl

By Mike Coll, Preserve Manager

Yesterday I got an answer to a question I had been wondering about for a few years:  Is it always the same Screech Owl that I see roosting in my owl box?












The answer, apparently, is no.

Screech Owls come in two different color “morphs” or variations- grey morph and red morph.  Previously I had only observed the grey variety (right) but yesterday the head of a red morph (above) was peering out of the box, giving me the first clear indication that the box is being used by more than one individual.

Curiously, this new owl fell right in line with the patterns of the other owls that have used the box.  In fact I had observed a grey morph owl in the box every day for the past few months until this red one took up residence without even a single day break.  Also, the red morph sat in the box opening at dusk, flew out just before dark, returned at some point in the predawn hours and is currently sleeping in the box just as every other Screech Owl that I have observed there has done.  Were it not for the obvious difference in plumage I would not have even suspected that a new owl had moved in.

With breeding season for Screech Owls virtually upon us, the implications of this changing of the guard are unclear to me.  I have assumed previously that the owl(s) I was seeing was a lone male who had not yet found a mate.  This notion was supported in part because last spring I could hear the owl calling from the box- as a lone male would.  But knowing now that it has been more than one owl (possibly many different individuals) some residents could have been female as well.

I wonder if this new owl took the box by force in a territorial battle or if the box was abandoned willingly by the previous resident.  I wonder also where the owl that was there last has gone now.  And I wonder if any of these owls will choose to breed in the box in the upcoming months.  As is often the case, an answer to one question only serves to create a host of new questions yet to be answered, keeping me continually fascinated by the secret lives of these nocturnal creatures.


Owl box 2.0

By Mike Coll, Hildacy Farm Preserve Manager

Shortly after writing about the success I was having with a Screech Owl box that I installed behind the springhouse at Hildacy Farm Preserve, I encountered a setback. Squirrel intrusion! My first attempt to prevent squirrels from taking over the box had consisted of a 14-inch-wide piece of metal flashing wrapped around the tree trunk both above and below the box. This seemed to deter those pesky intruders for the better part of a year, but the persistence of squirrels can never be doubted.

At some point in mid December, a squirrel figured out that he could jump from above the flashing, land on the top of the box (which is also covered in metal to prevent claws from gripping), and somehow contort himself into the entrance hole. At that time I had seen the owl sitting in the opening of his box every evening for a month straight and then one night he was not there and it was the next day I first noticed a squirrel coming out of the box. Futilely I tried to shoo the squirrel from the box and, in response, the squirrel simply jumped from a height of 15 feet (about 30 times his body length!) to the ground and ran away- sure to return once I had moved on. Once the squirrels had entered the box the owl did not return. Among other things, squirrels almost immediately fill their nest cavities up with leaves and overall they are terrible roommates. Squirrels also outweigh Screech Owls by a fair margin (Screech Owls are only 7-10 inches tall).

I knew that the only thing to do was to take down the box, clean out the squirrel bedding, put more flashing up on the tree, and try again. However, upon taking the box down I found that there would be more to this project because the box (which was originally a converted Wood Duck box) had rotted through and the entrance was badly chewed by squirrels and so the project would truly have to start from scratch.

I began again with a box of roughly the dimensions described here. In an attempt to make this new box seem familiar to the old one, I replicated the particular structure of the previous entrance.

Since the first box (version 1.0) was originally a Wood Duck box, it had a four-inch entrance hole cut in it rather than a three-inch hole (the size preferred by owls.) To remedy this, I’d cut a three-inch hole in a separate piece of wood and attached it the front of the box over the larger hole. I had seen the owl spend a great deal of time sitting in that “stepped” opening. So, in the new box I again made a four-inch hole and covered it with the same piece of wood I had used on the entrance of the first box. I have no idea if things like this are helpful or not but it seemed sensible to try to keep as many factors constant as possible.

I also built a perch onto the front of the new box. My hope is that, if an owl ever raises young in the box, the newly fledged birds will have a place from which to start their first flights. This was something I had attempted on the old box but the perch I built was not strong enough and soon fell down. The new perch is made from a real tree branch that I attached at two points. I also painted the box dark brown to protect it from the elements. I covered the roof and front of the box with metal flashing to help water to run off.

Another important aspect of this box is the bracket that I built to anchor it to the tree. Since the box is going 15 feet up in a tree you can imagine the difficulty of trying to stand on a ladder, hold a screw gun in one hand and the box in the other, and at the same time accurately drive screws.

An simple bracket can be made using wood strips that are cut at complimentary angles. The bracket (which is much smaller than the box) can be more easily attached to the tree and the box is then hooked onto the bracket. The picture on the right shows the wood strips on the back of the box, the ones on the bracket look like the inverse of these.

The interior of the box also contains some features customized for the owl lifestyle. There is an interior perch that I bought from a pet supply store. This offers a place for the adults to sit while they feed young on the floor of the box. I also scraped a ladder of sorts into the wall below the entrance hole to offer footholds to help young birds climb out of the box. In the picture below you can also see the “stepped” entrance hole.

It was at about this point that I had the bright idea that I should put a camera inside the box since I was going to all this trouble anyway! I did some research and found a very small camera that transmits a wireless signal and has the wide field of view and short focal length required in a bird box. It can also record audio and has infrared lights that allow it to illuminate the box at night without disturbing the owl. This camera can also be connected to a USB port allowing it to transmit a live video feed straight to a computer. Unfortunately, it’s produced only in the UK, which caused a host of technical problems that I will not bore you with. Suffice it to say, I figured it out eventually and the project continued.

To accommodate the camera system, I designed a weatherproof box that would sit on the roof of the owl box. I decided to power the camera with a series of long extension cords rather than deal with battery replacement. Here is a view of the interior of the camera box looking down from the top.

Looking up from the inside of the box (below the perch), the camera is visible.

And the final product with the camera box sealed and painted on top.

With everything in place, all that was left to do was set the box back on the bracket and hope that the owl would appreciate the hard work I had put in. Towards the beginning of February, I lined the bottom of the box with wood shavings (used as bedding by owls) climbed to new heights on my ladder to affix more squirrel baffles, and put the new box in place. Two days later I checked the video feed on my computer and found that the owl had returned and was resting comfortably inside the box.

For the rest of February and March, the owl, who is presumably a lone male, stayed in the box almost every day. In the evening, he spends about half an hour sitting in the box’s opening, taking in the last rays of sun and waking up before his evening hunt.

Most nights he can be heard calling for a mate from the entrance of the box. The linked video below captures his call. He starts off slowly then really gets going towards the middle.

This video shows the owl preening his feathers and then leaving the box for the night.

But the saga continues! The camera I initially installed failed completely and I was forced to wait for a replacement from the company overseas. Last week I finally received the replacement and (on a day when the owl was not in the box) went up and swapped out the cameras. This picture also shows most of the squirrel baffling above and below the box.

(photo by Kristen Buck)

Now the camera is functional and the owl has been visiting the box regularly. I have not yet seen him with a mate but he continues to call. Mid April is the beginning of breeding season for Screech Owls in this part of the country so it is possible that in the near future we will have a pair to watch.

I’ll keep you posted.


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