Bocian; By Matthias Barby (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons.
Wróbel; By Kamil blaszczak (Own work) [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons.
skowronek; By Francesco Veronesi from Italy (Fawn-colored Lark - Kenya_NH8O6243) [CC BY-SA 2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons.
Sikorka; By Estormiz (Own work) [CC0], via Wikimedia Commons.
Słowik; By Frank Vassen from Brussels, Belgium [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons.
Dzięcioł; By Théo (originally posted to Flickr as Mr.Woodpecker) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons.