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Why Monitor Eastern Bluebird Nest Boxes?
In Wisconsin, Eastern Bluebirds have traditionally never been abundant because good habitat is lacking in the state. But in the late 1960’s, 1970’s and early 1980’s, Breeding Bird Surveys done by the USGS on the same stretches of roadway on a yearly basis, started revealing alarming drops in what bluebird populations we had (partly due to severe weather in 1976-77 on their overwintering grounds [Davis & Roca 1995]; see Table 1). The other three main cavity nesters (chickadees, swallows & wrens) did not show a similar drop in population.
Armed with this information, the WDNR approached citizen groups around the state to attempt to stimulate an interest in an artificial nest box program to “bring back” this imperiled species. The Bureau of Endangered Resources of the WDNR called a meeting at Schmeeckle Reserve in Stevens Point in February of 1986 (Don Bragg, WDNR Retired, Personal Communication). As a result of this meeting, the Bluebird Restoration Association of Wisconsin (BRAW) was formed on March 15, 1986. BRAW has worked to increase the population of this species ever since.
Table 1. Population trends for Eastern Bluebirds and other cavity nesting species
in Wisconsin and North America based on Breeding Bird Surveys by the USGS.
SPECIES |
1966-1979:WI |
1980-2005:WI |
1980-2005:NA |
|---|---|---|---|
+ EABL |
-10.5% |
+4.5% |
+2.5% |
TRES |
+3.2% |
+0.4% |
-0.2% |
BCCH |
+1.1% |
+1.2% |
+0.4% |
HOWR |
+0.6% |
+1.0% |
+0.0% |
History of Bluebird Production in Wisconsin by BRAW Monitors.
How well have we done? Table 1 shows that bluebirds made a solid comeback from 1980-2005 (+ 4.5%/year), even better than in North America as a whole (+2.5%/year). Some, perhaps most of the credit for the resurgence in the bluebird population, can be attributed to the extensive, artificial nest box program implemented by BRAW.
Table 2 compares BRAW data for the 2005 & 2006 season. Bluebird fledglings increased by a robust 19.4% and by 0.6 birds/nest box in 2006 compared to 2005. Tree Swallows, on the other hand, dropped by 22%. The ratio of bluebirds to swallows increased by 1.2 bluebirds/swallow. Box numbers were almost identical between the years. When bluebird numbers increase and swallow numbers decrease, it is a sign that the trails are starting to mature throughout the state. By that I mean, as we place and relocate boxes to better bluebird habitat by using the criterion of bluebird occupancy, they naturally attract a higher and higher percentage of bluebirds and fewer swallows and this change is demonstrated by data such as that in Table 2.
Table 2. Comparison of Eastern Bluebird and Tree Swallow fledglings
in 2005 & 2006.
Year |
EBF |
EBF/Box |
TSF |
TSF/Box |
Total Boxes |
EBF: TSF |
|---|---|---|---|---|---|---|
2006 |
21,102 |
3.50 |
6,574 |
1.1 |
6,021 |
3.2:1 |
2005 |
17,670 |
2.94 |
8,440 |
1.4 |
6.016 |
2.1:1 |
Figure 1 shows data collected by BRAW members since 1994. For the past 5 years bluebird production has shown a dramatic improvement. This change has been made possible by improved production techniques discovered by the research of Joe O’Halloran and others in the BRAW monitoring community and subsequently implemented. It is now likely that the bluebird is experiencing stable or increasing populations throughout most of its range in Wisconsin. In a very real sense, then, it joins the Bald Eagle, Osprey & Peregrine Falcon, among others, in the fraternity of birds that have been brought back from the brink of extinction in WI, by citizens concerned for their survival.
Figure 1. *Number of fledgling Eastern Bluebirds & Tree Swallows,
and number of nest-boxes presented, from 1994 to 2006.
*Note that most BRAW monitors dropped paired boxes in 1997, and most also dropped crowded single boxes in 2002 (Graph prepared by Dr. Peter Dunn, Dept. of Biology, UW-Milwaukee).
Table 3 shows bluebird production for the Aldo Leopold Audubon Trail that I coordinate (21 other monitors helped in 2006). We started in 2002 averaging well below the state average with only 1.33 fledglings/box. Four years later, we have increased our fledgling rate by 435% to 5.79/box (3.5 statewide) and rank 1st, 2nd or 3rd for all production categories in Wisconsin (trails of over 50 nest boxes). This feat occurred in spite of expanding our trail by 355 boxes during that time (note: new nesting sites take time to occupy).
This dramatic change has been done through hard work and by gaining insights into the behavior of bluebirds and other cavity nesting songbirds. One must “learn how to think like a bluebird”. I believe that the information we have gained can improve any bluebird trail anywhere in the eastern U.S. (including the Audubon trail which is being expanded to 782 nest boxes in the 2007 season). See Table 4 for details.
Table 3. Eastern Bluebird productivity on the Audubon Bluebird Trail, 2002-2006.
| STATISTICS YEARS |
NEST BOXES ON TRAIL |
TOTAL FLEDGLINGS & FLEDGLINGS/BOX |
% OF BOXES w DOUBLE BROODS |
% OF BOXES w TRIPLE BROODS |
|---|---|---|---|---|
| 2002 | 89 |
188/1.33/Box |
3.4% |
0 |
| 2003 | 164 |
351/2.14/Box |
12.8% |
0 |
| 2004 | 184 |
719/3.91/Box |
29.9% |
0 |
| 2005 | 381 |
1732/4.55/Box |
40.4% |
2.4% |
| 2006 | 444 |
2568/5.79/Box |
55.2% |
5.2% |