Can nestlings eat seeds or fruit?

I have seen a lot of black headed bunting recently. Like all buntings they are classified as seed eaters.

male and female black headed bunting near Klimentovo

Yet, every time I see a female black heeded bunting she has got insects in her mouth.

female black headed bunting

These green crickets seem to be very popular. After seeing this a few times,  I have realised that the diet of their nestlings must be insects.

second look at female black headed bunting

Over the last three days or so I have taken a look at other buntings too. It would appear their nestlings' diet is almost identical. Here (below) is a local ortolan bunting seen a couple of nights ago just before dusk.

local ortolan bunting

Finally last evening I saw a corn bunting with the same food.

local corn bunting

So the penny has finally dropped with me. Bunting nestlings don't eat seeds and I began to wonder if it means all nestlings don't. I'm a late starter at birding but I have gone through a few years without looking closely at what food is being brought to nests.

I couldn't find a great deal on google on the general subject of nestlings' food but I did find that a few birds such as zebra finch can be reared on seeds. However even with them a better diet includes some insects..

I'll have to research whether more types of nestling can eat fruit which is a much more viable transport proposition than seeds! 

young stonechat

In this hot weather I am noticing a lot of bird activity is crammed into the two hours before sunset so I am religiously going out then. Talking about young birds, I saw two family groups - one of stonechat and one of semi-collared flycatcher in the same cluster of bushes catching insects just before dusk. I presume the young birds are nearly fully fledged and are getting some last minute training on catching insects before they go their own way?

This blog so far has been about bringing up young birds.

However, you know I'm still enthralled by my new habit of taking video with my camera. Here's one to finish. It's two house martin preening on a wire outside my house.

local house martin preening