Swallow Study

Tree Swallow Nests in the Petaluma Public Wetlands

The swallows nesting in boxes at Shollenberger/Alman Marsh/Ellis Creek are Tree Swallows, Tachycineta bicolor.

On 5 April 2007, I began monitoring 20 swallow boxes build by PWA docent Andy LaCasse. The boxes, located in Shollenberger and Alman Marsh, are monitored using the protocols of a study called Golondrinas de las Americas, which employs naturalists ranging from Alaska to Argentina. In late 2009, five of these boxes were relocated and six newly constructed were erected in Ellis Creek. In April of 2011, two more houses were added to those in Ellis Creek.

PWA’s goals in monitoring these houses are manifold:

  • Determine the usefulness of our nest boxes
  • Learn about the natural history and nesting results
  • Teach others about the importance of our nest boxes
  • Ensure nest boxes are not used by nonnative birds
  • Provide habitat for Tree Swallows and Blue Birds
  • Monitor, clean, and maintain the boxes to improve the odds of chicks fledging
  • Contribute to the Golondrinas study
  • Share data with PRBO Conservation Science and other interested parties

Ten years have now passed since I started monitoring the Tree Swallows in Shollenberger Park and, since 2014, Ellis Creek Oxidation Ponds and Tolay Lake Regional Park. There are 57 houses in total and the results from each territory differ with Shollenberger not doing as well as the other areas. Why this is the case is not known. However, in 2017, I intend to move a few houses out of Shollenberger to Ellis Creek where the houses are spread further apart. Hopefully, this will improve the mortality rate at the latter.

Still to do in 2016 is the task of cleaning the houses in preparation for 2017. Most are preliminarily cleaned at the end of their nesting cycle in late July – early August. But some need a more thorough cleaning or house replacement. This is done in October – November once the days are cooler and the tick population subsides.

If you are interested in getting involved in any capacity, please let me know. Efforts to improve the Tree Swallow / Bluebird mortality rate in addition to being extremely interesting are also challenging and rewarding especially when one’s efforts culminate in good results.

Details on how these nests are monitored and any questions concerning the below data can be obtained by contacting me, Len Nelson, at [email protected]

2007 eggs _ chicks _ fledge __ mortality _ houses

1st nesting 99 73 49 24 (32.9%)
2nd nesting 59 40 21 19 (47.5%)
Totals 158 113 70 43 (38.1%) 20

2008

1st nesting 89 74 41 33 (44.6%)
2nd nesting 34 32 18 14 (43.8%)
Totals 123 106 59 47 (44.3%) 20

2009

1st nesting 105 96 50 46 (47.9%)
2nd nesting 70 55 20 35 (63.6%)
Totals 175 151 70 81 (53.6%) 20

2010

1st nesting 189 171 151 20 (11.7%)
2nd nesting 132 108 _ 71 37 (34.3%)
Totals 321 279 222 57 (20.4%) 36

2011

1st nesting 189 127 113 14 (11.0%)
2nd nesting 162 134 114 20 (14.9%)
Totals 351 261 227 34 (13.0%) 38

2012

1st nesting 164 149 131 18 (12.1%)
2nd nesting 47 53 37 16 (30.2%)
Totals 211 202 168 34 (16.8%) 28

2013
1st nesting 145 131 111 20 (15.3%)
2nd nesting 101 90 49 41 (45.6%)
Totals 245 221 160 61 (27.6%) 28

2014
1st nesting 156 133 109 24 (18.0%)
2nd nesting 23 21 8 13 (61.9%)
Totals 179 154 117 37 (24.0%) 28

2015
1st nesting 144 109 84 25 (22.9%)
2nd nesting 117 99 39 60 (60.6%)
Totals 261 208 123 85 (40.9%) 28

2016
1st nesting 145 132 82 50 (37.9%)
2nd nesting 103 89 63 26 (29.2%)
Totals 248 221 145 76 (34.4%) 28

Bluebirds (BB) and Tree Swallow (TS) results: In 2016, 9 of the 145 chicks (6%) that fledged were BB but only 1 of the 28 houses (4%) were occupied by BB.

10 Year Cumulative for Shollenberger – Ellis Creek:
1st nesting 1,321 1,111 846 265 (23.9%)
2nd nesting 754 651 376 275 (42.2%)
Totals 2,075 1,762 1,222 540 (30.6%) 28

For the last 3 years, I have also been monitoring and maintaining on a regular basis bird houses at the Ellis Creek Oxidation Ponds (10 houses) and at Tolay Lake Regional Park (17 houses).

Here are the results for these 2 locations:

2014 – Ellis Creek Oxidation Ponds:

eggs chicks fledge mortality houses
1st nesting 63 55 51 5 (9.10%)
2nd nesting 28 23 21 2 (8.7%)
Totals 91 78 72 7 (9.0%) 10

2015 – Ellis Creek Oxidation Ponds:

1st nesting 62 51 50 1 (2.0%)
2nd nesting 29 27 20 7 (25.9%)
Totals 91 78 70 8 (10.3%) 10

2016 – Ellis Creek Oxidation Ponds:

1st nesting 51 47 41 6 (12.8.0%)
2nd nesting 33 26 24 2 (7.7%)
Totals 84 73 65 8 (11.0%) 10

Bluebirds (BB) and Tree Swallow (TS) results: In 2016, no Bluebirds occupied any of the 10 houses there.

2 Year Cumulative (EC-OXI)
1st nesting 171 154 142 12 (7.87%)
2nd nesting 90 76 65 11 (14.5%)
Totals 261 230 207 23 (10.0%) 10

2014 – Tolay Lake Regional Park:

eggs chicks fledge mortality houses
1st nesting 76 64 55 9 (14.1%)
2nd nesting 30 28 18 10 (35.7%)
Totals 106 92 73 19 (20.7%) 16

2015 – Tolay Lake Regional Park:

1st nesting 75 54 47 7 (13.0%)
2nd nesting 58 41 25 16 (39.0%)
Totals 133 95 72 23 (24.2%) 17

2016 – Tolay Lake Regional Park:

1st nesting 84 63 59 4 (6.3%)
2nd nesting 40 32 31 1 (3.10%)
Totals 124 95 90 5 (5.3) 17

Bluebirds (BB) and Tree Swallow (TS) results: In 2016, 12 of the 90 chicks (13%) that fledged were BB and 4 of the 17 houses (23%) were occupied by BB.

3 Year Cumulative (Tolay Lake Regional Park)
1st nesting 235 181 161 20 (11.0%)
2nd nesting 128 101 74 27 (26.7%)
Totals 363 282 235 47 (16.7%) 17

The Tree Swallow – Bluebird houses are visited on a 7-10 day basis. Those that are easier to access (SP-EC) can get more frequent visits if observed conditions warrant it and if time is available. In 2016, diatomaceous earth was used whenever any mite condition was suspected and even after eggs were laid and before they hatched as a preventative measure. This action is believed to have had the desired result. In 2017, the intention is to use it in all cases after eggs are laid and before they hatch.

Please let me know should you have any questions.

Len Nelson

PWA Shollenberger Docent

[email protected]

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