Higher rate of nest lost among primary than secondary females: infanticide
in the great reed warbler?
Bensch, S. & Hasselquist, D.
Behavioral Ecology and Sociobiology 35:309-317. 1994.
An individually marked population of great reed warblers Acrocephalus
arundinaceus was studied between 1984 and 1991 in South Central Sweden.
The fates of 279 nests were analysed for the 25 days following clutch initiation.
The average frequency of nest loss (43%) did not differ significantly between
years or between four periods of the breeding season. After a breeding
failure, 70% of the females laid a replacement clutch, most of them together
with the same male. On polygynous territories, males assisted the female
who first hatched young regardless of her initial mating status. According
to the actual status of the females attending the nests, for each day nests
were classified as being of either monogamous (M), primary (P) or secondary
(S) status. From egg-laying to fledging the rate of nest loss decreased
among nests of primary status whereas it increased among nests of monogamous
and secondary status. During the egg-laying period, the rate of nest loss
was 3 times higher among nests of primary than among nests of monogamous
and secondary status. Thus, the high loss level among nests of primary
status during the laying period was closely associated with the presence
of a female with a less advanced nest on the territory. All nests were
situated in reed beds above deep water and most of them at a height at
which possible inter-specific nest predators would have caused disturbance
to the nest itself. The suspicion that secondary females committed sexually
selected infanticide was supported by an experiment with dummy eggs that
revealed bill peck markings identical to those obtained from great reed
warblers.