Description of the Pre-Hatching Calls of the Clark's Grebe (Aechmophorus clarkii)

In birds, pre-hatching calls are part of the communication behavior between parents and offspring, and may serve multiple functions. The Clark's Grebe (Aechmophorus clarkii) has a wide distribution in Mexico, and in 2015 we monitored a reproductive colony in the lagoon of Zumpango in central Mexico. We describe and measure the pre-hatching calls of two individuals from two different clutches. Eggs were about 22–25 days old. We obtained 5.16 minutes of recordings, with 81 calls made up by a frequency-modulated note and with an average call duration of 8.05 milliseconds and a peak dominant frequency of 828.20 Hertz (max 870.40; min 771.38). Calls were emitted at intervals of 1.38 seconds. This is the first description of pre-hatching calls in the Clark's Grebe, a poorly studied waterbird in Mexico.