Question: when diffrent birds eat diffrent food do they get bigger in size and could they get fatter or tinner

Sean Kelly answered on 15 Nov 2014:

Sure. If a bird can find and eat really nutritious food that gives them lots of energy, they can become bigger and stronger (just like us). Similarly, if they cannot find a lot of food or if they food they can find isn’t very healthy and doesn’t give them enough energy, they will probably get thinner. This happens to a lot of the birds we have in Ireland. For example, in summer, when we have lots of sunshine to help plants grow, there is a lot of food available to help birds get bigger and stronger. In summer there is lots of fruits and insects. However, in the winter, when the days are dark and short, there is less food available and birds will find it difficult to find enough food to stay healthy and strong. There is less fruit available in winter and lots of insects cannot survive the cold. This means in winter a lot of our birds become thinner and weaker as the food is less available and this food is probably less nutritious too. This is why winter is such a difficult time for wildlife as food becomes less available.

This is probably the main reason that birds only breed in spring and summer, as there is more food available for both the parents and their chicks. If the parents made a mistake and had their chicks in winter, there most likely wouldnt be enough food for the chicks to survive.