The importance of brood size, offspring age, and male size for parental care behaviour was studied in the common goby, Pomatoschistus microps. In field observations, the aggression of nest guarding males was measured as attacks towards a finger when disturbing the nest. Attacking males had larger and more developed clutches compared to non-attacking males, but did not differ in body size. In another set of observations nest guarding males were exposed to a predator (eelpout, Zoarces viviparus) and subsequently chased away from their nests. Time away from the nest decreased significantly with egg developmental stage, i.e. with the time the male had spent guarding a particular brood. However, no correlations with male body length or numbers of eggs in the nest were found. We conclude that male common gobies evaluate future reproductive success by using brood age and brood size as cues for making decisions about risk-taking and aggressive behaviour during parental care.
The purpose of this study was to determine the role played by functional experience in the development of the dustbathing behavior system in junglefowl. Small groups of birds were raised either in a rich environment with sand and earth, or in a poor environment with a wire mesh floor. Dustbathing and other behaviors were recorded at intervals between 2 and 9 months of age. The results showed that the form of the individual behavior patterns as well as the organization of extended bouts of dustbathing developed normally in chicks raised in a dustless environment. Further, the frequency of occurrence of dustbathing and the diurnal rhythm did not differ between groups raised in the two environments. Functional experience was necessary for the development of dust recognition, but some stimuli came to be recognized as "dust" more easily than others.