|Peterson nestbox left open at end of season|
The photo above is not one of the nestboxes we monitor. But I liked the symbolism of it for this end-of-season recap post. We saw several boxes like this one at the St. Olaf College natural lands this morning -- they've been cleaned out at the end of the bluebird breeding season and left open to discourage mice and house sparrows from using them over the winter. (See http://bbrp.org/wp-content/uploads/2012/01/Trail-Guide-Final1.pdf) The boxes we monitor are all of the Gilbertson PVC pipe style, which don't have doors that open.
Here are our final bluebird trail numbers for the year:
Trail 1, Rice County, mostly south of Northfield: 7 pairs and 4 single nestboxes
- 72 bluebird eggs were laid in 11 nestboxes
- 57 bluebird eggs hatched
- 46 bluebird chicks fledged
- Tree swallows used 5 nestboxes and fledged 32 chicks
- Chickadees started to use one nestbox but never laid eggs
- House wrens used 4 nestboxes and fledged 22 chicks
Trail 2, Goodhue County, prairie habitat: 1 pair and 2 single nestboxes (we took on the monitoring of these boxes in late April)
- 19 bluebird eggs were laid in four boxes
- 18 bluebirds hatched
- 18 bluebirds fledged
- Tree swallows also used two of the boxes and fledged 12 chicks
|Male bluebird on top of "sparrow spooker"|
We did not successfully raise any birds in the pair of nestboxes we put up this year on our own property. That was where house sparrows killed a chickadee early in the season. In mid-season, we attracted both tree swallows and bluebirds. The tree swallows seemed to be building a nest, but did not lay eggs and eventually disappeared. The bluebirds nested and hatched a clutch of four eggs in a box where we had put up a wren guard, but when they were a few days old, the nestlings vanished from the nest. This was very distressing; we were alerted that something might be wrong when we could see the male calling repeatedly and flying to and from the box, and when we checked the box later that day we found the babies were gone without a trace, but the nest was intact. Our Rice County bluebird mentors said that most likely house wrens, but possibly sparrows, could have removed the chicks. We will see if we can find a better location next year -- one farther from the house and from large trees -- to see if we have better luck. We can't in good conscience keep trying to attract bluebirds, tree swallows or chickadees to locations where there is a recurring pattern of attacks.
Bluebirds raised two broods in quite a few of our boxes this year, but we did not have any bluebirds successfully raise three broods this summer, despite the early spring. The closest we came was in our earliest nesting location. There, we had a clutch of five successfully hatched and fledged by the second week of May. A second clutch of five was hatched in the same box in early June, but all five nestlings perished within a few days of hatching; we found them dead in the box. Soon afterward a new nest was started in the other of the paired nestboxes. Four out of the five eggs hatched and they fledged in late July. Since our theory about the dead nestlings was that their mother had been killed, the final clutch on that site may have involved the same male and a new female, or even a whole new pair, but we can't be sure.
It's been a fascinating season. We've had a lot of pleasure, a lot of learning as we went, some distress and heartache, and much wonderful outdoor time every week as we monitored the boxes. We have felt honored by this precious opportunity to observe the private lives of cavity-nesting songbirds and try to keep them safe. We look forward to next year!