.hero .hero-media {
  background-image:url://s3.amazonaws.com/imagescloud/images/pq/journee-parcs-quebec/20150623-m.jpg);
}

@media only screen and (min-width: 768px) {
  .hero .hero-media {
    background-image:url(//s3.amazonaws.com/imagescloud/images/pq/journee-parcs-quebec/20150623.jpg);
  }
}