We documented use of rattle calls when adult Belted Kingfishers (Megaceryle alcyon) approached or departed active nest burrows, and contrasted rattle-call use during incubation and nestling phases of nesting. Adults rattled on 92.7% of 109 nest approaches and 56.2% of 105 nest departures (P = 0.021) combining both phases of nesting. During the incubation phase rattling occurred on 81% of 36 approaches and 28% of 32 departures (P < 0.001), and during the nestling phase rattling occurred on 99% of 73 approaches and 69% of 73 departures (P < 0.001). Overall, a significantly lower amount of rattling occurred during the incubation phase, both when approaching and departing the nest. Males and females exhibited similar patterns of rattle-call use at nest burrows during both phases of nesting. We suggest that use of rattle calls is more prevalent when approaching the nest burrow, despite drawing attention to the nest location, to advertise a mate's or parent's presence prior to entering the burrow and to avoid injury from the tending adult or nestlings defending themselves against an unknown intruder. We also suggest that adults are more secretive near the nest burrow during the incubation phase, especially when departing, because of a reduced need to communicate with their mate while tending the eggs during lengthy bouts of nest attendance. Nevertheless, it remains unclear why adults use rattle calls as much as they do when departing from the nest, which appears to unnecessarily advertise the nest location.

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