IUPS 2013: A case of personality driving phenotype?

I wasn't intending to comment on this session but the experiments of Theunis Piersma at the Royal Netherlands Research Institute intrigued me. Red Knots are wading birds that feed on shellfish; their ability to consume larger prey with harder shells is determined by the size of their gizzard. Interestingly, gizzard size can be experimentally reduced by feeding diets exclusively made with either small, soft shelled prey (such as shrimps). Conversely, diets rich in mussels and cockles can increase the size of the gizzard. Piersma et al discovered through tracking experiments that in wild type birds, which show great variation in gizzard size, birds with larger gizzards demonstrate reduced exploratory behaviour. They presumed that this was due to the fact that these birds were capable of handling a wider range of prey than individuals with small gizzards, so didn't need to travel as far to find adequate food. HOWEVER when they experimentally changed the size of the gizzard in captive populations, they observed no change in exploratory behaviour. This suggests, remarkably, that the personality of the individual, I.e. their level of inquisitiveness and thus exploratory behaviour at an early age, influence the development of the gut as these birds will be able  to base more of their diet on softer shelled prey. To me, this is a fascinating potential case of personality influencing phenotype. This opens up other questions, however, such as to what extent are environmental experiences ( e.g. The weather) Or group dynamics responsible for early exploration.
This was followed by an brief discussion by Gaelle Boudry on how  neonatal gut development can be influenced by milk composition to the extent that this has repercussionsfor later life. Piglets fed on high protein breast milk showed a delayed barrier function ( increased gut permeability) and disrupted immune responses. Quite disturbing when human milk formula compounds during the 1980s had protein levels in excess of those in normal breast milk.