As a result of the recent sight of an untagged NBI in Manchester (UK) it's worth to remember other non-ringed birds that have been spotted in the last decade. On http://rarebirdspain.net there's information on those records in Spain.
Sightings of NBI in Spain are extremely rare during 20th century. The only known observation of this species was in Doñana, Southern Spain, in 1958. Nevertheless in 2004 one specimen was observed in very good condition in La Aldehuela (more than 1000 m osl), Ávila (Central Spain) between December 17th and 22th. Apparently, the bird was there since one month before.
|Northern bald ibis in Ávila (M. Rouco)|
|Another image of the same animal (M.Rouco)|
During the same month another individual was seen in Extremadura. In this case, it was a young bird observed between December 1st and 6th and again, between March 24rd and 27th, 2005, near Trujillo, Cáceres.
|Young NBI in Cáceres, on the ruins of de Santo Domingo church (J. Briz)|
The potential arrival of Moroccan birds is very unlikely, given the distance and the lack of observations in the last decades. Apparently, both birds came from any private owned zoological park having its birds untagged and whose facilities are inadequate to keep birds safe and secure.
More recently, a SEO/BirdLife's team spotted another untagged NBI in southern Spain. In this case was, again, one young bird. Different sightings belonging, probably, to the same bird occured between February and May 2012, in the area of the Campiñas of Eastern Seville. This location is not far from the place were "proyecto Eremita" are been released and where they nest. It this case, we cannot rule out that any wild-born bird from released individuals has escaped to the compulsory tagging.