If you’re like me, you don’t have air conditioning in your house. Therefore, you’ve probably noticed the dawn chorus outside your window well before you’re fully awake. It usually begins around 30 minutes before sunrise, and continues for about 45 minutes after the sun breaks the horizon. Several theories have been proposed to explain the timing and frequency of birdsong during this early morning concert; these include foraging efficiency (it’s more efficient to sing before you can see well enough to forage, then once it’s bright enough, eat like crazy), ability to detect predators (evolution would tend to favor those individuals that could see their predators when they were singing… otherwise becoming an easy breakfast), and sound transmission (sounds should carry clearer and further in still morning air than they would in the more turbulent atmosphere characteristic of later in the day). As one of his major findings, Karl Berg discovered a correlation between eye size and time of first song for birds in a broadleaf forest in Ecuador. His findings support the idea that light levels are an important driver in the pattern of birdsong during the dawn chorus. You can download his paper here.

Last week I co-taught (along with Ben Baiser and our advisor, Julie Lockwood) the Rutgers Field Techniques course down in Tuckerton, NJ, where we assigned three field projects to three groups of students. One project was to investigate the pattern of birdsong in the dawn chorus in the Pine Barrens. The group hypothesized that birds which tend to forage in the canopy would begin singing earlier than those that foraged on the forest floor (inefficient foraging hypothesis). Those that forage primarily in the mid-story would fall somewhere between the two extremes. After two days of field recording and observing bird foraging behavior the group found a statistically significant relationship between foraging niche and time of first song. Interestingly, this relationship was the reverse of what they expected (ground-foragers began singing first, while canopy-foragers began singing the latest). While this field course was primarily intended as an exercise in how to design a field experiment to test a hypothesis, collect and analyze data, and present results, these preliminary findings provide an interesting starting point for a comparative study between a variety of habitats. The group concluded that they should collect light penetration data in order to further evaluate the difference between the New Jersey pine forest and the Ecuadorian broadleaf forest site from Berg et al. (2006).

In preparation for teaching the course, on May 25th, I used two Rode nt5 omni-directional microphones (thanks Casey!) to record the dawn chorus at the Hutcheson Memorial Forest, in Somerset NJ. I began the recording at 4:39am and recorded until just after 7:00am. The recording was made on a Marantz PMD670 compact flash recorder. Below is the entire recording in two parts, with the only edit being the removal of 27 seconds where a plane flew overhead. I hope to make more recordings, both here and elsewhere, and post them as I go. I’ll have the pine barrens recording up sometime soon as well. Enjoy listening to the dawn chorus, and testing your identification skills along the way!

Enjoy
David

Part 1. This one begins at 4:29am, so there’s a good amount of “quiet time” at the beginning, although you can hear the birds in the old field adjacent to the forest already singing. Something, a screech owl, I think, does a freakout call+bill clapping right over the recorder about 19 seconds into the recording. It repeats it again soon after, from a little farther away.

[audio:DawnChorus_HMF_Pt1.mp3]
Dawn chorus recording (Pt 1)
Hutcheson Memorial Forest, Somerset, NJ
David La Puma
Marantz PMD670
Stereo; 2 Rode nt5 microphones
Edited in Audacity 1.2.5
Converted to mp3 in iTunes 7.6.2

Part 2. This recording continues where part 1 ended, at about 6:00am.

[audio:DawnChorus_HMF_Pt2.mp3]
Dawn chorus recording (Pt 2)
Hutcheson Memorial Forest, Somerset, NJ
David La Puma
Marantz PMD670
Stereo; 2 Rode nt5 microphones
Edited in Audacity 1.2.5
Converted to mp3 in iTunes 7.6.2

Taking too long to load? want to download the mp3 file?
Here are the links:
http://woodcreeper.com/audio/DawnChorus_HMF_Pt1.mp3
http://woodcreeper.com/audio/DawnChorus_HMF_Pt2.mp3