This is how she put it, which made logical sense to me:
"If it is really hot where you live, those new feathers on the youngsters are going to grow in a little slower than normal because feather growth responds to the ambient temps....if it is cold outside, feathers grow in faster. When it is hotter, birds will thin down their coats or, in this case, not put as much nutrition into growing feathers as they will into growing the bird because protection against the cold is not a priority. Fall/winter chicks always put feathers on faster than spring/summer chicks."
She then went on to show pics of chicks at the same age point, but one was born mid March, while the other was born later April. There was a noticeable difference between the two...
"If it is really hot where you live, those new feathers on the youngsters are going to grow in a little slower than normal because feather growth responds to the ambient temps....if it is cold outside, feathers grow in faster. When it is hotter, birds will thin down their coats or, in this case, not put as much nutrition into growing feathers as they will into growing the bird because protection against the cold is not a priority. Fall/winter chicks always put feathers on faster than spring/summer chicks."
She then went on to show pics of chicks at the same age point, but one was born mid March, while the other was born later April. There was a noticeable difference between the two...