The Greenland White-fronted Goose Anser albifrons flavirostris

Body mass (g)
Body mass (g)
4000
3500
3000
2500
Males
2000
04-15-99 04-20-99 04-25-99 04-30-99 05-05-99 05-10-99
Date of capture
4000
3500
3000
2500
Females
2000
04-15-99 04-20-99 04-25-99 04-30-99 05-05-99 05-10-99
Date of capture
Figure 4.1. Changes in body mass of staging adult male
and female Greenland White-fronted Geese caught at
Hvanneyri, west Iceland in spring 1999. Fitted regression
lines are best fit least squares linear regression
models. 2
20th April 1999 (MS19), the average body masses
of arriving birds were 2.75 kg (adult males) and
2.51 kg (adult females). Assuming that the birds
arriving at Hvanneyri were a representative sample
of those departing Wexford, this meant that
in 1999, geese arriving in Iceland had used 327 g
and 277 g of fat respectively, assuming all the difference
to be fat. This is slightly less than predicted
by the Pennycuick calculation, but more than by
the energetic flight range methods. However,
these calculations are based on average values,
and may not represent the true situation during
the 1999 spring migration episode. These estimates
suggest that the geese had not depleted all
the reserves accumulated over the mid-winter
minimum body mass in Ireland (see chapter 3).
Using the same regression models, and a mean
departure date of 5th May 1999 (MS19), geese
accumulated an average of 369 g (15% in adult
females) and 451 g (a 16% increase in body mass
in adult males) during their 15-day stay in Iceland.
These data are based upon observed lengths
of stay of collared birds at Hvanneyri, which were
slightly shorter than the average for the satellite
tagged individuals. Nevertheless, the accumulation
of 24.6 and 30 g body weight per day for females
and males respectively is impressive during
this short stopover. Their estimated mean
departure masses were thus 3.21 and 2.88 kg (for
adult males and females) when departing for west
Greenland from Hvanneyri, 129 and 96 g respectively
heavier than the departure mass from Ireland.
An alternative approach is to establish a calibration
factor for field scores of abdominal profiles,
based on the body mass of known individuals of
known abdominal profile scores. There was a
good correlation between the API score and body
mass amongst the geese caught at Hvanneyri (Figure
4.2). Since large numbers of geese were scored
every day at Hvanneyri (although not specifically
assigned to sex class), this enables the generation
of mean body mass values for geese staging at
the farm using the relationships shown in Figure
4.2 and assuming a sex ratio of parity. The results
of this are shown in Figure 4.3. Mass accumulation
does not appear linear (as suggested by catch
data alone), suggesting that the catch data may
actually slightly underestimate mass accumulation
by the end of the staging period. Because the
caught birds were cannon-netted over bait, it
could be that the capture technique selected for
birds in poor condition attracted to rich sources
of food.
Despite the many assumptions made in these simple
calculations, it does appear that geese arrived
in Iceland with a residue of the body stores accumulated
on the winter grounds and then very
rapidly increased body mass there. If it is assumed
that the geese at Wexford are typical of those else-
Body mass
Body mass
4000
3500
3000
2500
Adult Males
2000
0 1 2
Abdominal profile score
3 4
4000
3500
3000
2500
Adult Females
2000
0 1 2
Abdominal profile score
3 4
Figure 4.2. Relationship between abdominal profile
score and body mass of captured adult male and female
Greenland White-fronted Geese at Hvanneyri,
spring 1999. 3
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