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]

 

Tree Swallow Nesting Details 6/28/2021

Shollenberger – Ellis Creek

2007

2008

2009

2010

2011

2012

2013

2014

2015

2016

2017

2018

2019

2020

Total
2007-2020

eggs

158

123
175
224
254
211
246
179
261
248
250
229
247
238

eggs

3,039

chicks

113

106

151

201

185

202

221

154

208

221

199

207

213

187

chicks

2,568

Fledge

70

59

70

153

157

168

160

117

123

145

176

189

195

133

Fledge

1,915

Mortality

43

47

81

48

28

34

61

37

85

76

23

18

18

54

Mortality

653

%

38.05

44.34

53.64

23.88

15.14

16.83

27.60

24.03

40.87

34.39

11.56

8.70

8.45

28.88

%

25.43

Houses

20

20 

20

26

28

28

28

28

28

28

28

28

28

28

Houses

26

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