[Bluebird-babble] 2007 nestbox summary

[Christina.Mitchell at UCHSC.edu]

Hi, all--

 

Sadly, but inevitably, our breeding season has come to an end.  We have 71 nestboxes on 39+ acres in central Colorado--pinyon/juniper/scrub oak habitat at about 7200' in the rain shadow (eastern flank) of the northern Sangres. We've had nestboxes up for 7 years, but this is the first year I've monitored them during the breeding season.  (In the past, we've simply cleaned out the boxes at the end of the season and guessed at what might have used them.)  This summer, we had 7 different species using the nestboxes; 23 boxes were used by birds (and lots by mice and chipmunks) and 2 boxes by 2 different species (Violet-green Swallows moved in right after White-breasted Nuthatches fledged).  The big species surprise was one pair of Western Bluebirds; we've never had them summer in our habitat before.  

 

Here's the summary.  

 

Mountain Bluebird:  26 eggs; 14 fledged; 53.8% success. (We had 2 very late nests--total of 10 eggs--that never hatched and probably never had a chance.  If I adjust for those, the rate was 87.5%.  I like that better, although 53.8% is better science.) 

Western Bluebird:  6 eggs; 6 fledged; 100%  

 

Non-bluebird species-

White-breasted Nuthatch:  14 eggs; 14 fledged; 100% 

Violet-green Swallow:  37 eggs; 29 fledged; 78.4% 

Mountain Chickadee:  18 eggs; 18 fledged; 100% 

Juniper Titmouse:  11 eggs; 5 fledged; 45.5% 

Ash-throated Flycatcher:  9 eggs; 8 fledged; 88.9% 

Total:  121 eggs; 94 fledged; 77.7%  

 

The juniper titmice either were the unluckiest or made the worst choices.  Only 1 of 3 nests raised any young at all; eggs were removed early on by some critter (snake? chipmunk?) in the other 2.  The Violet-green Swallows had the highest (and only, actually) mortality among the nestlings--5 dead in 2 boxes, no apparent sign of predators, unknown cause of death.  

 

It was a very fun undertaking.  We have 30 more nestboxes that were unmonitorable this year (placed too high or built so that the bottom opened--great for cleaning, but not for monitoring). My husband's going to reposition or and/or revamp those over the winter, so I'll have even more next year.  Thanks to Kevin and the CBP for providing the encouragement and support to get me motivated to give it a try!

 

Tina Mitchell

Coaldale, CO

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