The hobbies – birds of prey that belongs to the falcon family – were photographed close to Dungiven in Co Derry.
Jim Wells, chairman of the NI Raptor Study Group, said the sighting is the “most exciting thing I have witnessed in 29 years of birdwatching”.
A hobby sighting in the North of Ireland is considered extremely rare.
“They are an absolutely wonderful little bird,” Mr Wells told BBC Radio Foyle’s Mark Patterson Show.
“The fact they have been discovered near Dungiven is quite remarkable.”
Mr Wells said hobbies – also known by their scientific name of Falco subbuteo – are being spotted further north due to climate change.
“All over Britain we are seeing concrete evidence of species more associated with southern Europe moving north.
“That’s reflecting the increase in temperatures particularly in the May to August period.”
Fellow birdwatcher Lindsay Hodges spotted the hobby while looking for a pair of kestrels she had seen the previous week.
“I glimpsed the silhouette of a bird on a branch quite some distance away and knew immediately I wasn’t looking at a kestrel.”
She described the sighting as “absolutely extraordinary.”
Estimates suggest there are now around 2,000 pairs of hobby falcons across the UK with the majority in southern England.