I "2 2 Jones, Bird Migration in Iowa. J^" j| 



movements of young females, as distinguished from old females, 

 are too few to be of value. 



P>om these notes it appears that the length of time between the 

 arrival of the first males and first females differs at different times 

 during the season, weather playing an important part. It is longer 

 early and shorter late. Speaking generally, the first females 

 arrived a little later than did the bulk of the males. In March 

 this is from a week to three weeks ; in April a little over a week, 

 and in May about five days. There is a gradation from the 

 longer period into the shorter, of course. It is generally believed 

 that young birds migrate later than old ones. I have no general 

 notes bearing upon the subject ; but a great deal of careful study, 

 in this line, was given to certain species, the young males of 

 which were more readily distinguished from the old males and 

 females. Prominent among these were Rose-breasted Grosbeak, 

 Scarlet Tanager, Ruby-crowned Kinglet, Wilson's Warbler and 

 the Orioles. In the case of these species, the old males arrived 

 first, followed in about four days by the young males ; the females 

 arriving a little later still. All of these belong to the later 

 arrivals. 



I am not prepared to say that the young males of other species 

 migrate at relatively the same time. The few notes which I have 

 bearing upon the subject would seem to indicate that they do, at 

 least among the smaller birds which arrive in late March, April 

 and May. That subject will bear much more investigation. 



There were two notable exceptions to this sequence of arrival 

 of old males, young males, and females. One was in May, 1889, 

 when the last great wave was checked by the cold weather of 

 late April. The other in March, 1890, when a month intervened 

 between the second and third waves. At these times not only 

 most of the summer residents, but also many of the transient 

 species arrived mated. Not all individuals, but very many of 

 them. We would expect mating to begin as soon as the females 

 appeared among the host, wherever it might be upon the north- 

 ward journey, just as it does under normal conditions. In these 

 two instances the weather northward must have been such that 

 the males could not move forward ; but southward, favorable to 

 the movement of the females already begun. This state of 



