Incubation behaviour of the African jacana

Abstract

In African jacanas all parental care is by males. The male's daytime attendance of the nest (= incubation constancy) averages 53% and is characterized by frequent, short ‘on’ and ‘off shifts in which he leaves the nest, on average, 35 times per day. Ambient temperatures affect both the incubation constancy and the duration of ‘on’ and ‘off’ shifts: on the coldest (x̄ = 22,9°C) of 4 days of variable weather in which egg and ambient temperatures were monitored together with the male's incubation behaviour, the incubation constancy was 70,9%, the eggs were unattended 28,1%, the ‘on’ shifts were long (x̄ = 22,5 min) and the ‘off’ shifts short (x̄ = 8,4 min). In contrast, on the hottest day (x̄ = 31,3°C) the eggs were unattended 56,5% of the day; they were incubated 6,9% and shaded 36,6%. Both ‘on’ (x̄ = 4,7 min) and ‘off’ (x̄ - 6,3 min) shifts were short. At night, when the eggs were constantly incubated, their temperature remained constant at 34,1 °C (SD = 0,4; n = 69) whereas in daytime their temperature ranged between a daily mean of 33,2–37,1°C (n = 4 days) and between extremes of 27,0–39,6°C. On a hot day (x̄ - 30,0°C) when the male was prevented from shading the test egg its temperature reached a lethal level (43,8°C) in 30 min. It is suggested that the high ambient temperatures prevailing in the African jacana's breeding range have facilitated the evolution of a uniparental care system in this species, but the males’ unusual incubation behaviour associated with high temperatures may also have led to the high clutch predation rate found in this species.