
Table 5. Occurrence of Marked Nesting Birds Over the Runways 
December 27 = Tebruary 19 



Blue Violet Green ellow Red Total 
Munber nesting 10,000 48,000 41,000 22,000 105,000 
Number marked (492) 1,854 1,682 998 134 
Percent marked (4.9) 369 nip 5 0.13 
Number marked birds 
observed (13) 103 62 ne 0) 179** 
No. represented by 
dyed birds observed* 
est. 550 2,640 1,510 22 0 4,922 
Range (confidence h 2,120 1,130 @) 
limits) to to to to 
655 3,140 1,890 66 
Percent contribution to 
‘breeding bird hazard 67.5 32 0.5 O 100 
Range 57-77 2342 0-18 

* February 14, location 2 and February 15, location 4, omitted pend- 
ing verification of number of unmarked birds seen. 
** Total of both marked and unmarked birds observed was 10,155 
Table 6 presents the best information available at the present 
time on the contribution of unemployed birds to the aircraft hazard. 
Unemployed birds are not evenly distributed over the two islands, but 
are concentrated in areas of greatest habitat disturbance. Marked 
samples are not representative of the whole of Sand Island, but only of 
the areas where marking was carried out. The proportion of marked to 
unnarked birds has been estimated very tentatively, as the unemployed 
population is far from static; repeated observations of the proportion 
of marked to unmarked birds on the ground will have to be made before 
statistical analysis can be attempted. The figures in Table 6 must be 
considered as tentative. Special effort will be made to obtain more 
data. 
Although unemployed birds move around considerably, they are 
most frequently observed at the runway observation points closest to 
the area where they were originally marked. GB birds (Figure 15, Table 
6), for instance, were noted two to three times as frequently at 
location 3 as at locations 2 or 4, and thirteen times as frequently at 
location 3 as at location 1. Similarly, half the observations of BN 
birds came from observation point closest to the area of marking. 
About three-quarters of the observations of BO birds were made at 
locations 2 and 1, Birds from the residential area (00) were seen with 
greatest frequency at locations 1 and 4, indicating a tendency for these 
birds to cruise along the northern shoreline of the island. 
29 
