Incubation behaviour of the Kentish Plover, Charadrius alexandrinus, with special reference to the share of sexes and of effect ground surface temperature

Abstract

1. Incubation behaviour of the Kentish Plover Charadrius alexandrinus was studied at a reclaimed area near Makuhari, Chiba in 1977, with special reference to the share of sexes in diuanal incubation duties and the effect of ground surface temperature.2. Parental attentiveness in the daylight hours was on average 77% in the laying period, 90% and 89% in the early and late stages of the incubation period, and 62% in the hatching period.3. By day the male incubated most of the time (86%) in the laying period as well as hatching period, but the female did in the incubation period (84-85%). It was suggested that the male should brood the clutch during night in the incubation period.4. When the ambieht temperature rose up high or when predators approached the nesting grounds, the male often relieved the female of incubation duties.5. The adult attentiveness was 87% at 31-33°C temperature range (at the ground surface), 93% at 25-30°C and 95% at 34-36°C. Depending upon the ambient temperature, incubation postures were changed: the parent sat closely on the eggs when it was low, but began panting with increasing temperature, and frequently shaded the clutch by standing over it when it rose up to 34°C.6. The observation that the male took most of the diurnal incubation duties in the laying period assumes an interest because it might enable the female to allocate much time for foraging and consequently reduce the energetic load imposed upon her for egg formation.7. The changing incubation behaviours in relation to the ground surface temperature are without doubt adaptive in maintaining the eggs within the optimum temperature range (about 35-36°C) for embryomic development. However, the significance of in relation to the fine adjustment of egg temperature was not clarified by the present study.