Plasticity in guarding superb starlings

Cooperatively breeding vertebrates are common in unpredictable
environments where the costs and benefits of providing offspring care
fluctuate temporally. To balance these fitness outcomes, individuals of
cooperatively breeding species often exhibit behavioral plasticity
according to environmental conditions. Although individual variation in
cooperative behaviors is well-studied, less is known about variation in
plasticity of social behavior. Here, we examine the fitness benefits,
plasticity, and repeatability of nest guarding behavior in cooperatively
breeding superb starlings (Lamprotornis superbus). After demonstrating
that the cumulative nest guarding performed at a nest by all breeders and
helpers combined is a significant predictor of reproductive success, we
model breeder and helper behavioral reaction norms to test the hypothesis
that individuals invest more in guarding in favorable seasons with high
rainfall. Variation in nest guarding behavior across seasons differed for
individuals of different reproductive status: breeders showed plastic nest
guarding behavior in response to rainfall, whereas helpers did not.
Similarly, we found that individual breeders show repeatability and
consistency in their nest guarding behavior while individual helpers did
not. Thus, individuals with the potential to gain direct fitness benefits
exhibit greater plasticity and individual-level repeatability in
cooperative behavior.