Missing Eggs and Other Nest Box Challenges

Over the years, I've opened what appeared to be "successful" bluebird boxes only to discover an empty nest.   What happened to the eggs (or chicks)?

The easy answer:  a predator.

But which one?

To solve the mystery, look for clues and compare them to the "nest box problem" chart - on the the North American Bluebird Society's (NABS) website, click here.

I suspect the culprit at Tatanka Bluffs may be a House Sparrow.  I noticed a few when I monitored the boxes in April.  NABS offers several suggestions on how to eliminate House Sparrows and European Starlings.  Unlike our native cavity-nesting species, sparrows and starlings are not protected by state and federal wildlife laws.

House Wren

The other likely suspect:  House Wrens.   However, these wrens are native species - and protected.  You cannot remove their nests and eggs - or harass them.

If you discover wrens nesting along your bluebird trail, you may be in for trouble.  These little dynamos are very territorial and have been know to eliminate competition by destroying (and removing) the eggs and young of bluebirds, chickadees and titmice.

The easy solution -  don't encourage wrens.  

If wrens have established a territory - remember - you are not allowed to harass them.  Let them finish.  Meantime, find a new and better location for your bluebird nest box.  

By the way, I checked the Peterson box over on Stai Coulee today - 4 very hungry nestlings and a hen setting on them.  Outside air temperature 44º F.