Hi there,
Well, Hobby has traditionally been a description rarity here in Ireland, and, while the species no longer requires a description, this has more to do with the changes made with regard to rarity assessment by the IRBC, with a list of 'commoner' rarities (Appendix 2) no longer requiring a formal description, so long as there is an observer name connected with the claim, but these are still published in the rarity report.
That said, there does appear to have been a genuine increase in sightings in recent years, with many records of 2cy birds, sometimes 2 or 3 in one area, remaining at east coast sites for weeks. Given the nature of many sightings on headlands, and the fact that any birds continuing inland would be even harder to pick up, the true numbers occurring may be quite a bit higher than we think, and, of course, if a pair were to breed, I fully realise that the species can be very elusive while on territory. It is also possible that 2cy birds wander widely when they return, and that the spread of the species into a new area tends to be preceded by an increase in such birds, which then return in later years to breed.
However, given the amount of migrant species that are relatively common even in western Britain, occur here reasonably 'frequently' on passage (Common Redstart, Pied Flycatcher, Tree Pipit, Wood Warbler etc) and yet rarely, if ever, breed here, it is always possible that hopes of colonisation by Hobby will come to nothing, but we will never know if we don't keep looking...
Regards,
Harry