Study

Phylogenetic and ecological determinants of the neotropical dawn chorus

Berg, Karl S.; Brumfield, Robb T.; Apanius, Victor

Proceedings of the Royal Society B, 2006

Peer-reviewedcomparative studywild

What they did

Recorded the order in which species began singing during the dawn chorus at a neotropical forest site, and tested that order against ecological traits including eye size, foraging height and diet, and against phylogenetic relatedness.

Studied in: Aves
Sample size: species entering the dawn chorus at an Amazonian site

What they found

Entry time was strongly structured rather than arbitrary, and related to visual and ecological traits — species with larger eyes relative to body size, and those foraging in darker strata, tended to begin earlier — with a substantial phylogenetic signal.

What it means

The authors' reading, and ours. Where they differ, that difference is the point.

How the authors put it

The species sequence within a dawn chorus reflects light sensitivity and foraging ecology rather than an arbitrary convention.

How NatureHQ reads it

The most conspicuous feature of a dawn chorus is that it is not simultaneous: species enter in an order, and the order repeats. This is the best attempt to explain it, and it explains part of it — eye size and where a bird feeds account for a real share of the variation and not all of it. It is also one of very few dawn chorus studies from the tropics, where the chorus is larger, more species-rich and far less seasonal than the temperate one every other explanation was built on.

Limitations

One site; the sequence at other tropical sites may be structured by different traits.
Correlational — eye size predicts entry time and does not demonstrate that light sensitivity causes it.
Light levels at the perch were not measured directly for each species.