Over the past two months I’ve been conducting my own version of Donald Kroodsma’s Solstice experiment. I’m not making any claims for the scientific rigor of this very informal experiment, but the results are interesting, and they do conform roughly to Kroodsma’s results.
The X-axis represents the date and the Y-axis represents the number of song-type vocalizations heard.
- Methods
In early Nov. 2009 I established a route of 1.13 miles through Estabrook Park, Milwaukee, WI. This route takes an hour to walk at a relaxed pace. I attempted to start each session as close to dawn as possible and to complete the route in as close as 1 hour as possible. While walking the route I noted all song type vocalizations heard. Each bird making a song type vocalization counted as 1. I did not count additional songs coming from the same individual.
- Results
Nov 7, 2009: 0630-0730. Estabrook Park, WI., 52 degrees, clear skies.
0 song type vocalizations
Nov 14, 2009: 0640-0740. Estabrook Park, WI,. 44 degrees, cloudy.
0 song type vocalizations
Nov 21, 2009: 0650-0750. Estabrook Park, WI,. 45 degrees, cloudy.
1 singing House Finch
Nov 27, 2009: 0710-0810. Estabrook Park, WI,. 45 degrees, cloudy.
0 song type vocalizations
Dec 6, 2009: 0700-0800. Estabrook Park, WI,. 30 degrees, cloudy.
0 song type vocalizations
Dec 13, 2009: 0715-0815. Estabrook Park, WI,. 33 degrees, cloudy.
2 song type vocalizations: house finch, european starling
Dec 20, 2009: 0715-0815. Estabrook Park, WI,. 22 degrees, cloudy.
10 song type vocalizations:
1 house finch
1 robin
1 crow rattle
4 BCCH (2 countersinging)
3 WBNU (2 countersinging)
Dec 21, 2009: 0715-0815. Estabrook Park, WI,. 22 degrees, cloudy.
9 song type vocalizations:
4 BBCH
1 WBNU
2 House Finch
1 Robin
1 DEJU
Dec 24, 2009: 720-820, Estabrook Park, WI,. 32 degrees, cloudy and windy.
2 Song type vocalizations: 1 WBNU, 1 EUST
Dec 26, 2009: 720-820, Estabrook Park, WI,. 26 degrees, light snow, windy.
5 song type vocalizations:
3 BCCH (2 countersinging)
1 WBNU
1 crow rattle
Dec 27, 2009: 720-820, Estabrook Park, WI,. 22 degrees, cloudy.
7 song type vocalizations:
4 BCCH (2 countersinging)
1 WBNU
1 American Robin
1 EUST
- Discussion
I remain skeptical about the significance of the actual winter solstice to birds and its effect on their singing behavior. However, I do think that this experiment demonstrates that the beginning of the singing season falls at approximately the same time as the winter solstice for several common bird species of the eastern North American temperate forests. The species in question are the White-breasted Nuthatch and the Black-capped Chickadee. For the 6 sessions between Nov 7 and Dec 13, no White-breasted Nuthatches or Black-capped Chickadees were heard singing (they were seen or heard calling in all of these sessions, but not singing). After that date, the White-breasted Nuthatch was heard singing on all 5 sessions and the Black-capped Chickadee on 4 of the 5. This change in the singing behavior of these two species accounts for a considerable amount of the increased singing activity evident in the results.