Eastern Screech Owlets in Nest Box

Eastern Screech Owls

Eastern Screech Owlets in Nest BoxFirst, on May 21, four EASTERN SCREECH OWLS successfully fledged from their renovated Wood Duck box in my backyard in Delaware. I had checked their nest every other day to ascertain their April 24 hatch date, which enabled me to calculate a first-egg-date of March 19. The red-phased mother owl would occasionally click her bill as my hand-held mirror appeared above her. I last saw her when her family was ten days old. It was fun checking on the growing owlets, and once they grew feathers, a gray owlet always looked up at my mirror image or camera lens as its red-phased siblings remained huddled, face down.

One day, I discovered 5-mm wide fish scales on the edge of the box’s entrance, proving that parent owls had been snatching swimming prey from the Delaware Run, a small stream that flows through Blue Limestone Park. For several weeks after the owl family left my yard, I would occasionally hear the local paparazzi, including loud Blue Jays and other feeder birds, mobbing one of the small yellow-eyed predators along the wooded hillside behind my home.

American Kestrels

The second update reports a failure. Two AMERICAN KESTREL hatchlings counted on July 15 by Dick Phillips and I had disappeared before our return visit two weeks later. However they died, their parents most likely cannibalized their remains, a behavior that has been documented by others. Three times since our earliest kestrel nests appeared in 1995, a second nest with eggs had followed a successful nest in the same box during the same season, but none produced fledglings. The latest first-egg-date for a successful nest is June 11 in 2008.

For the most part, 2009 was a good year for our kestrels. Eighteen kestrel boxes that hang from electric poles in Delaware County raised 68 “sparrow hawks” from 14 nests after 17 attempts in 16 boxes. The project, started by the Delaware County Bird Club in 1993, has produced 561 falcons since 1995.

Eastern Bluebirds

EASTERN BLUEBIRDS on five of my bluebird trails produced 319 fledglings from 84 nests after 92 nests started with eggs. Before bluebirds can nest, they must survive the winter, a fact that I try to influence by winterizing nestboxes during my last monitoring visit in late summer. I plug or cover all ventilation slots with weather-stripping and other materials and rely on spiders and other arthropods to plug drain holes with cocoons, hibernating individuals and other matter that restrict energy-robbing drafts inside nest chambers. Having a draft-resistant roost site helps bluebirds survive, and they do their part by practicing communal roosting to share body heat. (During the cold evening of 31 January 1986, I found 30 roosting bluebirds among nine boxes in Delaware State Park. During my study, the highest number of bluebirds sharing the same box was seven for a very beautiful sight, indeed.)

Cleaning Out a Nest BoxAs I cleaned my nestboxes prior to the 2009-nesting season, I was elated when I found no winterkilled bluebirds, unlike the depressing days after the 2006-2007 winter when I salvaged 45 winterkilled bluebirds. Furthermore, I found few fecal deposits. Also absent were seeds ground clean by gizzards and regurgitated in packets on the floors of nestboxes. Finding clean nestboxes convinced me that bluebirds had abandoned my trails before winter extremes had a chance to hammer them. I credit the drought of 2008 for failing to deliver enough insects and fruits to carry my bluebirds into the perils of winter.

As I looked forward to bluebirds building nests in April and May, I discussed with other conservationists the possible ramifications of winter ice storms that had swept across Southern Ohio and Kentucky. I worried that such weather might have wiped out Ohio bluebirds wintering there. Bluebirds and robins don’t have the “bill power” to chip thick, encapsulating ice from berries. My worries slowly dissipated in April after a healthy population of bluebirds started to claim boxes on my trails. My annual Mid-May Nest Count found 46 nests for a 48.4% increase more than 31 nests counted in 2008. Perhaps, our bluebirds had wintered in Tennessee or farther south and escaped the Grim Reaper altogether.

More good news came from Northern Ohio, where more nests appeared than expected, prompting bluebirders to wonder if our Ohio trails were hosting blue refugees from Michigan and Ontario. Our northern neighbors also had a drought in 2008, and perhaps bluebirds could not find enough food to sustain them. In Central Ohio, returning or wintering bluebirds rely on poison ivy berries, wild grapes, rose hips and moonseed for survival until warmer temperatures deliver crawling prey.

In 1999, I searched my master data book and found 31 records for nestboxes producing three bluebird families during the same season. From these records, I used first-egg-dates to establish three egg-laying periods within the season. The periods are March 29 (or earlier) through May 15, May 16 through July 5, and July 6 beyond August 10. Using these standards, only two clutches, representing 2.4% of 2009’s 84 successful nests, made up the third nesting period. During the most productive years, as many as 15% of the season’s nests start after July 6. I offer only one observation that might be related to the poor showing of third families. Late last summer, I realized that I had not seen any grasshoppers, and found only one after I started searching for them. If grasshoppers are indicators for the status of other insects with similar life cycles, then perhaps bluebirds were stressed by a food shortage in late summer.

Whatever the reason for a weak third nesting, wintering bluebirds were easy to locate in Delaware State Park for two nocturnal field trips for Jed Burtt’s ornithology students at Ohio Wesleyan University. To prepare for the field trips, I inspected 36 of my 163 nestboxes in the park during daylight hours of January 30 and found fecal material and regurgitated seeds in seven boxes. I knew we would find roosting birds on our field trips on February 3 and 4. On both nights, one by one, students used my machinist mirror and penlight to light up the same nest chamber that sheltered two males and two female bluebirds on both nights. Twenty-one students got a once-in-a-lifetime chance to experience beautiful wild birds only inches from their faces as they became aware of how some birds cope with cold, winter nights. During twenty years of such field trips, we have never witnessed any sign that our spying stresses roosting birds, which is good. We are aware that any activity that would cause the nestbox guests to expend extra energy would be unethical and illegal. In past years, such field trips have also safely encountered solitary Downey Woodpeckers, and once a Northern Flicker had chiseled its way into a nestbox’s slot opening. The large woodpecker had folded its spine like a pretzel in order to fit into a four by five-inch cavity, an observation that gave me a sympathetic neck ache.

As we returned to campus after the second field trip, I cautioned the students in the van that the latest weather forecast sounded ominous for the wintering bluebirds they had just experienced. Finding roosting birds was proof that edible berries were available, but for how long? Would ice and snows erase the bluebirds’ menu? To protect my emotions, I will wear my “science hat” as I set out to sweep my boxes clean before March 15. I hope Mother Nature denies me the need to use my state and federal salvage permits. If I do find winterkilled bluebirds, I will deliver them to the Ohio Wesleyan Zoology Museum, or to Preservation Parks of Delaware County. Dead or alive, bluebirds are precious; their beauty promotes education and effective conservation.

I will report on Tree Swallows and other bluebird trail species at a later date.