Fat reserves accumulated the prior day drive dawn and dusk chorus singing.

Evidence

The energetic hypothesis states that the amount of fat reserves accumulated in the previous day is responsible for the quantity and loudness of the song broadcast by an individual at dawn or at dusk. … In silveryes (Zosterops lateralis), a small passerine of 11–14 g distributed throughout Australia, New Zealand, and many South Pacific islands, Barnett and Briskie (2007) have observed that the dawn chorus largely depends on the amount of fat accumulated in a singer’s body. They proved that artificially fed males were singing longer and with a higher-quality repertoire. — Almo Farina, Soundscape Ecology, 1703

Categorization

• XREF: connects to: Dawn song functions as preventive territorial defense against intruders in winter wrens. — Almo Farina, Soundscape Ecology: Principles,…, 1710