An important question is whether all segments of a population 
present in certain areas along migration routes or on wintering grounds 
are equally susceptible to trapping. For example, in a location that 
serves both as a stopping point during migration and as a wintering 
area, there is a question, discussed later in the report, whether the 
migrating birds are as easily trapped as the wintering birds. If the 
migrants are not as easily trapped, trapping at the location does not 
smple the population present in a representative manner. 
In using recoveries as a basis for migration studies, it 
should be kept in mind that: 
l. <A bird removed from the population by means other 
than live-trapping is not available to be taken 
at some other time or place. 
2. The proportion of the banded population that is 
removed at any one point is influenced by the 
hunting effort in relation to the number of birds 
available. Although substantiating data are lack- 
ing it seems logical to assume that the proportion 
of birds removed from the population is not constant 
among the various shooting localities. 
3. It has been demonstrated with a limited series of 
bandings that the offer of a reward encouraged a 
return of three times as many bands as normal. 
This indicated that many bands are never tured 
in. It seems logical that even limited publicity 
campaigns affect the proportion of the bands 
turned in and reduce the validity of the data for 
comparison purposes. 
Other factors such as the heavy kill associated with opening 
days, the length of time birds would normally stay in a particular area, 
variations in weather, changes in the legal open season, and ehanges in 
habitat and habits of the species, all influence the number of banded 
birds taken. Although there may be some tendency for these factors to 
average out over a period of years, care should be taken in weighing 
their effect when comparing banding data. Unfortunately, at present we 
have no reliable method for determining correction factors for these 
various items. This leaves us no alternative but to use the recovery 
data at face value and adjust our conclusions by use of circumstantial 
evidence and our knowledge of the habits of the species. 
Recovery bands, whether from birds shot, trapped, or found 
dead, will always be in direct proportion to man's activities. In the 
settled parts of the continent, the birds will be hunted wherever they 
are found during the open season. Recoveries from shooting within the 
United States, therefore, come the closest to being reasonably represent- 
ra 
