The development of coherent terminology is critical to dissemination of knowledge. Without a clear understanding of meaning behind words used, much could be lost in any attempt to exchange information between author and reader. In ornithology, as in all other branches of sciences, words and phrases have been developed and defined as needed to describe phenomena we encounter. When necessary, definitions are changed in response to new circumstances, or when new information becomes available that requires clarification of terminology employed. However, care must be taken to prevent confusion when words are redefined, particularly when previous definition of a word remains in wide usage, and/or when other valid words already exist to represent new definition. Belthoff and Ritchison's (1989) paper on in Eastern Screech-Owls (Otus asio), discussed movements of radio-tagged juveniles between their territories, which they left in July, and locations of final radio contact made following fall, winter, and spring. The duration of contact with these birds varied. The majority of final relocations were made in late fall, but one bird was found breeding following spring and a second was thought to be breeding at that time. In their introduction, Belthoff and Ritchison (1989) initially defined as from to first breeding site, following Greenwood (1980). This definition of is commonly accepted and authors of many recently published papers have utilized this definition in analyses of their data (Drilling and Thompson 1988, Haig and Oring 1988, Bowen et al. 1989, James et al. 1989, Small and Rusch 1989, Thompson and Hale 1989). However, Belthoff and Ritchison (1989) also proposed an alternative working definition for as, the movement of individuals to a new location irrespective of whether or not they reproduced after dispersal. There are several problems with this working definition, beginning with a point which Belthoff and Ritchison (1989) acknowledged; this definition matches that of Greenwood's (1980) term dispersal. The authors also failed to define permanent on basis of any time period or behavioral pattern in development of their terminology. We assumed, since Eastern Screech-Owls of this population are apparently nonmigratory and capable of breeding in their first year, that a movement would place these birds in a potential breeding location. In addition, Belthoff and Ritchison (1989) advised caution in interpretation of their data because of limited number of birds in their sample which were alive to enter breeding population following spring. They also pointed out that at least two owls in their sample made further movements from their wintering areas after spending several months in specific home ranges. It was suggested that some young may have been forced to disperse further in response to movements of adjacent adults, or to locate potential mates. Thus, location of a young owl even in midor late may not reflect true natal dispersal following either definition suggested by Belthoff and Ritchison (1989). Contrary to definition of proposed by Greenwood (1980), their data included few individuals which bred or had potential to breed. Nor was there a strong indication that these birds had undergone movement to new areas which would not be extended by further in spring before breeding. Thus, much of data failed to meet criteria outlined in their working definition. Alternative terminology is available which would have been more appropriate to type of data collected by Belthoff and Ritchison. Given similarity between Belthoff and Ritchison's (1989) definition of and original definition of Greenwood (1980) for gross dispersal, perhaps they should have titled their paper Gross of Eastern Screech-Owls. Other possibilities can be found in literature. Various papers have considered similar data in terms of postfledging (i.e., movements of young after they become independent of their parents and leave territory to move to overwintering range; Alonso et al. 1987, Eden 1987, Bull et al. 1988), or similarly defined juvenile dispersal (Gonzalez et al. 1989). Or, they might have employed descriptor winter dispersal (movement from areas to wintering sites), as has been used by Haig and Oring (1988) and Warkentin et al. (1990). Use of term natal dispersal in this paper is confusing because of overlap between working definition proposed by Belthoff and Ritchison (1989) and that of a word already defined in literature (i.e., gross as defined by Greenwood, 1980). It is also misleading because their definition fails to include a component which is widely accepted as being associated with this terminology, i.e., that birds must be in a position to breed or to potentially breed after is completed. In fact only 12.5% (2 of 16) of these birds were known to survive to breeding season of following year. Thus, over 80% of their sample were not known to carry out full extent of as it is more commonly defined, and many of these birds may not have completed their to future breeding areas at time of last telemetry relocation.