When it comes to sharing parental responsibilities, birds adapt their behaviour to take shifts to look after their nests, but this behaviour varies widely between different species, finds a study published online in Nature this week. In most cases, this behaviour circumvents natural circadian rhythms governed by the 24-hour light-dark cycles. Instead, it seems that the shift patterns are driven by anti-predation strategies.
Martin Bulla and colleagues analyse data from 729 nests of 32 different shorebird species, monitored over a period of 20 years, to understand how these birds synchronize their daily schedules to take turns in incubating the eggs. Patterns vary widely between species, even under similar environmental conditions. The length of one parent’s incubation bout ranges from 1 to 19 hours, but similarities are observed in closely related species. The way in which the two parents synchronize their rhythms seems to be linked to how the birds fend off predators, the authors note. Birds that actively mob predators tended to have shorter incubation bouts, whereas those that rely on camouflage incubate for longer, presumably to avoid revealing the location of their nests to predators.
The variation in synchronized social rhythms observed in these free-living animals is far more diverse than is seen under laboratory conditions and shows that social cues can have a stronger influence on certain behaviours than the circadian clock.