Design breakpoints with srcset and sizes

Image credits

http://upload.wikimedia.org/wikipedia/commons/2/27/Podiceps_cristatus_2_-_Lake_Dulverton.jpg
http://upload.wikimedia.org/wikipedia/commons/7/7c/Carduelis_carduelis_close_up.jpg
https://c1.staticflickr.com/9/8116/8655741934_8c48c0c1eb_b.jpg
http://upload.wikimedia.org/wikipedia/commons/c/cc/Common_Kingfisher_Alcedo_atthis.jpg
http://upload.wikimedia.org/wikipedia/commons/6/6c/Long-tailed_Tit_Aegithalos_caudatus.jpg
http://upload.wikimedia.org/wikipedia/commons/4/49/Red_Crossbills_(Male).jpg
http://farm9.staticflickr.com/8519/8559589268_7a8b00e811_o.jpg
http://upload.wikimedia.org/wikipedia/commons/b/b5/Long_Eared_Owl_(9438319240).jpg
http://upload.wikimedia.org/wikipedia/commons/2/2f/Northern-Lapwing-Vanellus-vanellus.jpg