|
Vol. 51 No. 8, 2012
Effects
of Habitat Quality on the Number of Alloparents and Nest Provisioning
Rates in a Cooperatively Breeding Tropical Passerine
Phetprakhai Wonkson*, Tommaso Savini, and George A. Gale
Conservation Ecology Program, King Mongkut’s University of Technology Thonburi, Bangkok, Thailand
Phetprakhai Wonkson, Tommaso Savini, and George A. Gale (2012)
Habitat quality is likely to impact group size, provisioning behavior,
and nesting success of cooperatively breeding birds; however,
predicting the direction of these effects is particularly challenging.
We investigated the influence of habitat quality on the number of
alloparents in breeding groups and whether the presence or the number
of alloparents influenced nest survival, provisioning rates, and
individual breeder workloads in the Puff-throated Bulbul (Alophoixus pallidus),
a tropical understory passerine. We used arthropod biomass as a proxy
for habitat quality of 17 territories. We also analyzed data from 143
nests from 41 breeding groups during 3 breeding seasons to assess
effects of alloparents on reproductive success. Habitat quality was not
significantly correlated with the number of alloparents per group (p = 0.07), the number of fledgling produced (p =
0.08), or the provisioning rate (p = 0.99). The number of fledglings
produced was also not significantly correlated with the number of
alloparents (p = 0.71). Overall provisioning rates were marginally higher for groups with no alloparents compared to groups with alloparents (p = 0.055), but provisioning rates of breeders significantly declined with increases in alloparent numbers (p
< 0.05). The lack of simple habitat effects on the number of
alloparents may have been due to a complex suite of factors affecting
both the production and dispersal of offspring and the recruitment of
unrelated alloparents. The lack of a correlation between nesting
success and alloparent numbers may have been due to the inability of
adult birds to dissuade most predators in this system.
Key words: Alophoixus pallidus, Provisioning, Puff-throated Bulbul, Variable social structure, Alloparents.
*Correspondence: E-mail:phetpat@hotmail.com
|
