3.4 Age sampling

3.4 Age sampling

The average proportion of juveniles in flocks sampled on 21 occasions was 4.4% (SE = 0.40) (Table 3.2). Sample sizes ranged from 134 to 757 individuals (average = 351) and those that accounted for less than 10% of the total number of geese (calculated from the 3-day mean) in the survey area on that day were excluded. No seasonal effects on the proportion of juveniles in the flocks was apparent (Fig. 3-16).

Table 3.2. Proportion of juvenile Greenland White-fronted Geese in flocks on Hvanneyri farm during autumn in 2017.

Date Location / Field code 1

12-Sep 55 13-Sep Lake Vatnshamravatn 14-Sep Lake Vatnshamravatn 14-Sep Lake Vatnshamravatn 14-Sep 301, 302, 303 15-Sep 38 22-Sep 32 24-Sep Lake Vatnshamravatn 30-Sep Lake Vatnshamravatn 01-Oct Lake Vatnshamravatn 02-Oct 302, 303 04-Oct Lake Vatnshamravatn 04-Oct Lake Vatnshamravatn 04-Oct 100 05-Oct Lake Vatnshamravatn 06-Oct 63 06-Oct Lake Vatnshamravatn 06-Oct Lake Vatnshamravatn 08-Oct Lake Vatnshamravatn 15-Oct Lake Vatnshamravatn 25-Oct 56

Sample size % of total 2 % juveniles

183 30 5.2

134 20 3.9

379 152 47 19 5.6 3.4

142 18 7.6

277 250 194 651 305 757 744 35 17 14 46 24 51 55 3.4 3.3 3.7 3.7 1.0 6.2 4.3

395 132 357 432 291 145 644 238 571 29 10 26 31 21 10 46 18 39 7.6 3.9 5.3 4.6 0.7 5.8 2.1 4.4 5.9

Average 4.4

1 Hvanneyri farm fi el d code. 2 Percentage of the total number of bi rds i n the s urvey area on that day (from the dai l y cens us ).

Figure 3-16. Relationship between the proportion of juvenile Greenland White-fronted Geese in flocks on Hvanneyri farm and date during autumn 2017. Only samples that accounted for >10% of the daily total number of geese (from the daily census) are included (n=21).

Greenland White-fronted Geese in hay meadow in Hvanneyri. Rachel Stroud.