Recently, when a group of second-graders visited the hawk platform, I was barraged with questions. They all wanted to know what I was doing, what the telescope was for, how many birds I had seen, did I live here, etc. etc. I guess one of them had observed me for a while, when he flat out asked me:
“Is this job boring?”
Perceptive kid, I thought. “Well, it is, sometimes,” I admitted.
Today, for example, the hawk flight amounted to 11 birds. For a full 8 hours of observation, that’s not much. Boredom definitely lurked, but I found some diversion in listening to a Chipping Sparrow that has established a territory right next to the hawk platform, but hasn’t found a mate yet.
Flipping through old issues of Birding the other day, I came across a review by Paul Hess of an article on the song of the Chipping Sparrow, written by Wan-Chun Liu and Donald Kroodsma, and published in 2007 in The Auk. Liu and Kroodsma looked at variation in the Chipping Sparrow’s song, and found that the species has two song types with distinct social functions. The dawn song is a fast series of short songs – 21.6 songs per minute, of 1.2 seconds length – while the daytime song is longer, and more widely spaced. The dawn song, sung from low perches, serves to advertise territorial boundaries and is primarily aimed at neighboring males, while the daytime song, sung from high perches, is aimed at attracting a female. Once paired, males stop singing during the day, but continue singing the dawn song – for as long as there are neighboring males around. Removing a bird’s neighboring males caused it to cease singing its dawn song; when the neighbors were returned, the bird resumed its dawn singing (Liu & Kroodsma 2007, cited in Hess 2008).
The Chipping Sparrow near the hawk platform is still unpaired, and sang throughout the day, or at least until 3:30 PM. Liu and Kroodsma found that the daytime song is not abruptly different from the dawn song, but rather that the bird tends to gradually sing longer songs, and fewer songs per minute, after sunrise. I started counting the songs of ‘my’ Chipping Sparrow at 9:56 AM, well after sunrise. I counted for three-minute intervals, and found him singing 16 songs in 3 minutes at that time, i.e. 5.3 songs per minute. About an hour later, I sampled another three minutes of his song, and this time found him singing 14 songs, or 4.7 songs per minute.
Then, at 11:25 AM, he was singing 6.3 songs per minute, while at 11:53 AM, he was back to 5.3 songs per minute. After noon, he took a long breather but resumed his singing at 1:30 PM with renewed vigor, now singing 7.0 songs per minute! The songs were getting longer too, from 2.5 – 3.5 seconds to almost 4 seconds for some songs now. He was keeping it up and 15 minutes later was still singing 6.7 songs per minute. At 2:45 PM I sampled his song three more times, and now heard him singing 7.0, 6.3, and 6.0 songs per minute respectively.
Liu and Kroodsma found an average of 6.4 songs per minute for daytime singing of Chipping Sparrows in Massachusetts. My Michigan Chipping Sparrow today sang on average 6.1 songs per minute. He actually sang slightly more songs – with more variation in song length and length of pauses between songs – later in the day.
All in all I timed 164 of his songs, but he probably sang more than 2,000 today. The ones I heard were all meant to attract a mate. Whether a female, so perceptively described by Kroodsma as “the silent architect of the male’s song” in the latest issue of Birding, was listening or not, I don’t know.
But today, I was.
Hess, Paul (2008) “Chipping Sparrow Songs” in “News and Notes” section of Birding, Volume 40, Number 1, January/February 2008. (A review of a 2007 article by Wan-Chun Liu and Donald E. Kroodsma in Auk 124:44-52)