Distributional records of birds, scattered in space and time, reach their full potential when fitted together to form a previously unseen pattern. This fact underscores the value of accumulated details of distribution even though single records can be considered trivial when studied alone. Rarely, sufficient information on breeding occurrence of birds in one area is available for two different periods of time. When this happens, some comparisons of interest to general ecologists become possible. For example, the response of the avifauna to habitat change may be studied (Emlen 1974). Or, turnover (versus stability) of the breeding bird species in relation to time may be investigated, as has been attempted with varying degrees of success for certain island avifaunas (Lynch and Johnson 1974).