Data for: Incubation behavior and nest predation rates for 21 songbird species studied in Borneo

The Skutch (1949) Hypothesis that nest predation risk constrains parental
nest activity has important implications for the evolution of parental
care strategies, but the required conditions for the hypothesis to operate
have been questioned. We found the necessary conditions existed in a
montane tropical bird community where 95.4% of predation events (n=456)
occurred during daylight hours and almost all predators (n=224) were
visually-oriented. Moreover, incubation strategies for 21 passerine
species were explained by nest predation rates as proposed by the Skutch
Hypothesis. Hourly rates of visits to the nest were lower among species
with higher nest predation rates, and achieved in part by longer on- and
off-bouts. Incubation attentiveness (percent of time incubating) does not
necessarily affect parental nest activity and was not related to nest
predation rates. Nest predation rates were greater in enclosed- than
open-nesting species, counter to long-standing views. Moreover, nest
predation was usually higher in the nestling period when parents were more
actively visiting nests than during incubation for enclosed- but not
open-nesting species. This increase in nest predation in the nestling
period for enclosed-nesting species might indicate proximate predation
responses to parental nest activity that underlie the evolutionary
patterns. Adult mortality also can exert selection on evolved strategies.
Following life history theory, annual adult mortality probability
explained residual variation in incubation behaviors, while accounting for
nest predation, with longer-lived species exhibiting lower nest activity
and attentiveness. Ultimately, the conditions for the Skutch Hypothesis
were clear and evolved behaviors suggest an important influence of natural
selection by nest predation in this montane tropical bird community. At
the same time, different patterns of nest predation between open- and
enclosed-nesting species emphasize a need for further research into how
parental nest activity interacts with nest type to affect predator
detection of nests.