When you download the picture, you will not see the link. You must add it. Try to copy this:

[pixabay](https://pixabay.com/photos/spring-bird-bird-tit-spring-blue-2295434/)

And add it under the photo.

Then you will see this

pixabay

This way you have sourced it and it is not considered plagiarism.

But, important is the link that you show as source to be exactly where you found the picture on internet.