Please cite this data as follows, and pay attention to the rights documented in the rights.txt:
Please respect the rights declared for each dataset in the download: 
2014. EOD - eBird Observation Dataset. doi:10.15468/aomfnb
naturgucker.de: naturgucker doi:10.15468/uc1apo
iNaturalist.org: iNaturalist research-grade observations doi:10.15468/ab3s5x
(see website) doi:10.15468/ee6ps6