CSI Bluebird

Hayden Hollingsworth
Hayden Hollingsworth

It’s one thing to have the proper setting for bluebird nesting but quite another to successfully raise a brood. Nature is not the kind mother as she is often depicted.  In her realm are enemies of all sorts whose overriding instinct is self-preservation. Bluebirds are no exception; they are easy prey.

Resources are available for those who have an interest in this backyard hobby; more about that later.  First we must turn our attention to the threats that swirl about such an endeavor.

Criminal activity abounds, despite the best efforts one can make.

In the two groups I have nested this year, foul play has visited both sets.  First, there was the orderly nest with four eggs.  I wasn’t sure when the brooding period started and the hatching occurs usually between 11 and 19 days, generally in the short end of the time frame.  When I next looked there were four brand-new chicks and much feeding activity.  It is usually between 17-21 days before they fledge so I didn’t check the nest for about a week.  When I did, much to my disappointment, the nest was totally empty.  A crime had been committed—bird-napping.

The usual suspects were close at hand:  sparrows and house wrens, but there were bodies to be found.  These perps usually kill the chicks by pecking their eyes out, then perch on the house top and sing of their savagery.  The nest was immaculate with no trace of violence.  Had I misjudged their age on my first viewing and they fledged sooner than I thought?  Perhaps, but not likely; I cleaned out the empty nest and watched.

In just a few days I was rewarded with a new pair who went busily about constructing their pine straw nest.  In no time at all there were 5 beautiful eggs and I was back in business.  Determined to know the day they hatched I checked the nest frequently and on the third day of brooding, to my shock the nest again empty but totally intact.  When sparrows and house wrens commit mayhem on eggs, they usually just destroy them and if they carry away the evidence of their handiwork, remnants usually remain and are scattered about in the vicinity of the box.  A careful search revealed no trace leaving but two possible answers. The eggs may have been sterile.  When that happens the male will carry the infertile egg away, tucking it under his beak.  How the adults know that’s the case is a mystery.  To have five sterile eggs would seem unlikely.  The other, and an entirely more likely solution, would be a snake. That would explain the disappearance of the first brood.  As all detectives know, we look for similarities in modus operandi that would tie one crime scene to another.

Proper bluebird boxes have a six-inch cylinder as a snake guard attached to the stand and the box should not be under a tree where snakes will drop from above.  That left only one possibility that seemed reasonable.  This snake was big, persistent, and able to defeat the snake guard cylinder.  Had he eaten the all hatchlings, he would not have been able to get out of the one-inch hole until he digested them, so one should bear that in mind when checking a nest with young.  The eggs could be devoured and crushed easily, allowing immediate escape.  In the Aldous Huxley children’s book, The Crows of Pearblossom, you can read the ingenious solution the birds devised to defeat the snake.  I did not think bluebirds have read the book, but if you have children, it will become one of their favorites.

Sometimes CSI produces no culprit but suggests measures to prevent further felonies.  Such was the case here.  A trip to the hardware store provided me with a 2 foot square of hardware cloth which I positioned atop the snake guard.  If there is a snake big enough to circumnavigate that, I don’t want to see him.  In the past summers there have been third nestings.  I hope that will be the case here.  Over the last dozen years my backyard has produced upwards to a hundred bluebirds.  I hope my run of bad luck is soon ended.

If you are interested in your own bluebird aviary check out www.virginiabluebirds.org.  Locally, Earl Morris is the dean of bluebird scholars and will be happy to talk with you at 776-1640.  His colleague, Tom Clifton (389-2942), is the master constructor of Petersen boxes and is equally expert.  He will build you a house and they will install it.

Nature may not be kind but it is truly amazing and worth preserving.  Good luck!

By Hayden Hollingsworth

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