RESEARCH ARTICLE

PARENTS’ ROLE ON EGG TEMPERATURE HOMEOSTASIS OF A GROUND-NESTING SHOREBIRD: ORIENTAL PRATINCOLE (Glareola maldivarum)

Abstract

Shorebirds in the Order Charadriiformes are primarily ground nesters and most of them do not make an insulated nest. As a result each shorebird family utilizes a unique breeding habitat in the wetland ecosystem. Pratincoles (Family Glariolidae) are a group of desert-adapted shorebirds that breed in arid landscapes. The Oriental Pratincole (Glareola maldivarum) is a rare and endangered shorebird in Sri Lanka, which breeds on sandy shores of lagoons and salt marshes. In a nest with two eggs recorded in a dry salt marsh in Vankalae Ramsar Wetland in Mannar Island in the Northwestern Sri Lanka, we investigated the role of parents’ behavior towards the embryo development of this desert-adapted ground nesting shorebird. The thermal data of the surface of each of the two eggs, and the surrounding environment, which includes the ground temperature of the nesting substrate and surrounding air temperature, were obtained from an automated thermal data logger at 5min intervals for two days (35 hours). We found that the egg temperature under parental incubation is kept at 36.8 oC (SD ± 1.08). As soon as the parent leaves the nest however, a rapid temperature fluctuation in eggs (non-incubating eggs 33.0 – 41.6 0C, mean temperature 35.9 oC (SD ± 2.22) had been observed, which eventually leads to the egg temperature reaching the ground temperature. Both parents incubated eggs to maintain temperature homeostasis. At the same time they were vigilant for predators and displayed aggressive aerial predator evasion behavior. In low (26.6 oC) or high (45.6 oC) temperatures, which is common in semi-desert habitat in Mannar, the brooding parent rarely left the nest unless its partner that stayed ~10m away from the nest on the ground, guarding the nest, could not defend off the predators such as a flock of crows or feral dogs. When the ground and air temperature is mild for the embryo (~32 oC), both birds actively defended their nest. The predator evasion therefore showed a direct effect on the egg temperature fluctuation in Pratincoles since the parent has to leave the nest to evade the predator. The bi-parental incubation pattern of Pratincoles however, enables one parent to incubate while the other bird taking charge of predator evasion in extreme temperatures.

Keywords: Data logger, Glareola, Ground Nesting Shorebirds, Oriental Pratincole, Sri Lanka, Temperature Homeostasis

How to Cite: Jayasinghe,S,Ranasinghe,R.W,Senevirathne,S.S, (2018). PARENTS’ ROLE ON EGG TEMPERATURE HOMEOSTASIS OF A GROUND-NESTING SHOREBIRD: ORIENTAL PRATINCOLE (Glareola maldivarum).WILDLANKA, 6(2):Pages 084-093

Published On:2018-06-30

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