Richard and Diane Van Vleck Personal Pages
The Home Habitat

barn owl fledgling at nest box entrance

Barn Owl
2010 Nesting

2010 was a less than spectacular year for our barn owls. The nesting behavior seemed normal, both adults survived and were present throughout the nesting, and there seemed to be no shortage of meadow voles. However, nesting mortality was extremely high. The photo at right shows the sole surviving nestling on the day it fledged.

Of the clutch of five eggs, one failed to hatch, which is not unusual for any species. And, the first hatchling appeared rather small and less active than normal and died the first day. The next three nestlings to hatch appeared healthy and robust. Almost a month after hatching, a second nestling died, and 18 days later, a third died. Two weeks later, the one remaining nestling fledged. There seems to be no common denominator in the deaths of the three nestlings.

A brief chronology of the 2010 nesting

Feb 9 - One adult in box. First use of box this year - heavy snow cover
Feb 10 - One adult in box - blizzard
Feb 11 - one adult in box
Feb 12-March 10 - box not used for day roost. Any night visits were not monitored.
March 10-March 19 - one owl using box for day roost
March 20 - Two adults in box. In following days, male was present on most days, female always used box as day roost.
March 31 - first egg laid
April 2 - 2nd egg laid
April 4 - 3rd egg laid
April 6 - 4th egg laid
April 9 - 5th egg laid
May 1 - first egg hatched
May 2 - Nestling absent. Female continues to incubate 4 eggs
May 3 - 2nd egg hatched. Nestling appears larger and more active than first hatch.
May 6 - 3rd hatch
May 10 - 4th hatch
May 19 - 5th egg no longer being incubated. 3 nestlings seem ok
June 2 - Female not in box today. 3rd nestling dead and partially eaten. 2 surviving nestlings appear fine. photo
June 3-June 19 - female back in nest box during day. 2 nestlings appear fine.
June 20 - Smaller of two nestlings dead on floor of box.
11:30 am Female begins eating wing of dead nestling, including feathers.
June 21 - Nestling carcass has been removed from box overnight and is draped over entrance perch.
June 22-July 6 - Single nestling ok, adults not roosting in box. photo
July 6 - Single nestling fledges.

barn owl nest box on barn wall

Was the event of June 20 cannibalism?

One reason often cited for many birds of prey having asynchronous hatching is to allow the opportunity for older nestlings to dine on their younger siblings during times of famine. From an evolutionary standpoint, this makes perfect sense, but, I don't think I have yet witnessed this in our barn owl nestings. Judging from the available fresh vole carcasses in the nest box this year, I don't think this was a summer of famine for the owls. And, even when the female was observed eating the wing of the nestling carcass, it appeared that she was more interested in getting it out of the box than using it as a food source, especially when the carcass was ejected from the box that night. The next day the carcass was observed hanging from the entrance perch, having been shoved out of the box by one of the adults. Granted, there didn't appear to be much meat left on it.

2014 Barn owl prey study
2012-2013 barn owl nesting
2011 barn owl nesting
2011 barn owl prey cam
2006 barn owl polygamy
2010 barn owl nesting
2003 barn owl nesting
2003 barn owl prey cam
The attic barn owl nest
Living with barn owls
The barn owl nest box
An interior barn owl box
Barn owl electrocution
The Barn Owl
2014 barn owl nesting - 2017 update 

2010 - 2014 Northern flicker nestings
2014 house wren gourd use
2014 - A dramatic loss of many types of insects
barn swallow artificial nest cups
2014 barn owl nesting - prey study
A new barn swallow shelter for 2013
2010 barn owl nesting
2010 Update
Entire site index (outdated)
Starling traps
Using blinds in the home habitat
Providing perches for birds
Providing snags for wildlife
The ugly young maple
2001 - 2013 nest cams
Use of tomato cages as hunting perches by insectivorous song birds
Vultures, beetles and the resurrection of life

Species of interest in our yard - photos and articles
barn owl American kestrel purple martin barn swallow Eastern bluebird
tufted titmouse Eastern phoebe yellow shafted flicker tree swallow chimney swift
house wren big brown bat Carolina wren brown thrasher catbird
cedar waxwing Northern mockingbird
Yellow warbler Acadian flycatcher

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© 2010, American Artifacts and Richard Van Vleck, Taneytown, Maryland.