Mohammed Shobrak sent me a paper recently with
some very interesting information about breeding Crab Plovers on the Frarasan
Island. The details below are taken from the paper Almalki, M, Shobrak, M, AlRashidi,
M, dos Remedios, N & Székely, T. (2014). Sex differences and breeding
ecology of a burrow-breeding shorebird, the Crab Plover Dromas ardeola. Wader
Study Group Bulletin 121(3): 169 – 176. The Crab Plover Dromas ardeola
is endemic to the Indian Ocean basin and breeds on islands around the Arabian
Peninsula. Unique among shorebirds, it nests in an underground burrow where it
lays a single white egg and feeds one chick. Molecular sexing of DNA samples of
66 adult Crab Plovers indicated that 26 were males and 40 were females. Males
had significantly longer bill, wing and tarsus lengths than females, confirming
previously published reports on sexual size dimorphism in Eritrea. Observations
of molecular-sexed adults at four nests showed that both parents fed the
chicks; however, females brought food to the nest-burrow more often than males
(67.6% of all cases). The temperature inside active nesting burrows was
relatively stable at 35.0 +/- 0.18°C (n = 11 nests) regardless of ambient
temperature just outside the burrows. This suggests that burrows serve a
purpose in incubation as well as in defence from predation. In the colony, adults
were seen to prevent chicks from multiple burrows from leaving the nest when
their own parents had left the colony, confirming a helper breeding system. Also
interesting was the day/night cycles in chick feeding routines, with higher
provisioning rates during the daytime than at night.
