86 NEBRASKA ORNITHOLOGISTS' UNION 



ON MIGKATION EECORDS AND ON OUR NEBRASKA RECORDS 



R. H. WOLCOTT, LINCOLN 



At the previous meeting- of this Union the author presented a paper 

 containing a proposed scheme for the accurate nuinerical evaluation of 

 terms relating to the abundance of species, and for an accurate and 

 uniform method of recording migration observations. The experience 

 of the past spring has proven the scheme there presented to be 

 feasible, but has also shown the necessity of certain modifications. 

 With these and with other suggestions concerning the matter of 

 records it is proposed in this paj)er to deal. 



First, the width of the strip included within the scope of observation 

 must be taken into account, and it is evident to any one who attempts 

 to i)ut the scheme into ojieration that the width of the strip which 

 may be included varies with the different species, with the character of 

 the locality, and with the abilit}^ of the observer. Those birds which 

 are small, dull-colored, secretive in their habits, and which remain 

 quiet, require close observation; in the case of those species which are 

 large, brilliant, noisy, and conspicuous in every way it is comparatively 

 easy to detect every individual even to a considerable distance. The 

 author would suggest, to obviate this difficulty, that a strip of uniform 

 width, say 100 yards, should be taken as a standard and that each 

 person apply the corresponding corrections necessary to place each 

 species on the same jilane. 



For instance one observer might be able to enumerate the smaller 

 sparrows or other small birds for a strip only 50 yards wide, the robins 

 in one 200 yards wide, the crows in one a quarter of a mile wide. He 

 would have to multiply the first figures by 2, and divide the others 

 by 2 and 4.4 respectively. Thus reduced the figures would indicate 

 exactly the ratio of abundance. 



It also became evident to the writer from his experience the past 

 season that in many places the method suggested, of enumerating all 

 individuals included within a strip of given width, was not applicable, 

 but that it might be desirable to select given areas chosen with 

 reference to securing- the greatest variety of conditions, with refer- 

 ence to the possibility of exact limitation, and with reference to the 

 g-reatest possible accurate estimation of the birds included therein, 

 and to go over these areas, carefully estimating the total number 

 present in the area selected. In this case comparison would have to 

 be made with some unit of area. The object in proposing the scheme 

 wiiich was sug-gested was to sug-gest certain expedients whereby the 

 observation of bird migTation could be made more accurate, and the 

 results of different observers become comparable. The methods pro- 

 posed will have to be modified to suit the character of the locality and 

 the ability of the observer. Some modification, however, it is believed 



