I have many nest boxes on my property and sometimes bluebirds will nest in one. The competition from the English Sparrows is ferocious, so when they successfully nested this year I was very happy. I can park my car on the lawn to use as a blind to photograph the bluebirds. I got lots of images of the parents on the box with food to deliver. The only problem was that they would not go in the box to deliver the food while I was there. Eventually the bluebird would scarf down the caterpillar itself. Rather than disrupt the feeding process, I left them alone. I haven't had this problem other places when I've photographed the bluebirds feeding their young. The success of the nest, in the end, was more important than my images. The bluebirds were used to seeing me in the yard and around the nest box . Maybe I would have been more successful without the car. I didn't have time to leave the car in the driveway and then more it continually closer so the birds would have gotten used to it. I would have had to watch to make sure the car wasn't distrupting the feeding and didn't have time for that.