Siena International Photo Award (SIPA)
This is one of the photo contests with the highest international participation ever. 2019 edition has received nearly 48.000 images from amateur and professional photographers from 156 countries worldwide.
Closes: 10 January 2021
Australian Photography Awards
Australian Photography Awards is on the hunt for Australia’s most original, honest and thought provoking photography. It is open to any persons residing within Australia or any person living outside of Australia with Australian citizenship
Closes: September 2021
EAAPF Waterbirds Photo Contest
Open to everyone. It aims to raise awareness of the importance of the conservation of migratory waterbirds and sustainable management of their habitats in the East Asian-Australasian Flyway (EAAF)
Asferico Concorso (International Nature Photography Competition based in Italy)
I just found it. It's open to everyone and has a 'no-nesting birds' ethics clause which I love!
Closes: around late November 2021