Fróðskaparrit - 01.01.2009, Blaðsíða 187

RINGMERKINGAR AV FØROYSKUM GRÁSPURVUM ÁRIN11963-2007
185
were recaptured or recorded again. Of these,
55% were controlled alive, either as resighted
or recaught. Half of the recoveries were re-
ported within the first 7.7 weeks after ringed,
25% already after 3.1 weeks. The last 25%
were reported later than 53.8 weeks after
being ringed (Table 2). However, both the
probability and the time of recoveries de-
pend on the age of the bird when ringed
(Figure 2 and Table 2): of the birds ringed as
full-grown, 36% were recovered but only 8%
of those ringed as juveniles in theirs first au-
tumn (Table 2). While half of the house spar-
rows ringed as juveniles were recovered
within the first 3.9 weeks, the median value
for those ringed as pulli was 41 weeks (Table
2).
Of the ringed house sparrows, 98 birds
were found dead. In most cases (68%), the
cause of death was unknown. However,
when known, "killed by cat" was the most
common reason (Figure 3). The Faroese
house sparrow lives for 1.3 years, on average
(Figure 4). Thus, the mortality-rate is high in
the first period of life. Already after 1.1
month, 25% of those ringed as nestlings or
juveniles in their first autumn had died, After
4.1 months, half of thern were dead and 14.7
months after, only 25% of the ringed house
sparrows were still alive (Figure 4).
• Stóra Dímun
• Tvoroyri
0 5 10km
7°\/y • Sumba
Figure 1. Locations of villages where house sparrows
have been ringed in the Faroe Islands during the years
1963-2007.
The oldest house sparrow was found
dead on Nólsoy 9.9 years after he was ringed
asa nestlingon thesame place, in June 1987.
Remarkably, this bird has also been recorded
twice before on Nólsoy: at the first, 7.6 years
Age when ringed Number ringed R ecovery rate (%) Time between ringing and recoveries (weeks) Median Ist quartile 3rd quartile Average
Pulli 373 9.7 41.0 4.3 229.1 120.9
7 st calendar year 845 8.3 3.9 7.7 33.5 33.9
After 1st calendar year 186 36.0 5.0 2.9 7.7 6.6
All ages ' 2 167 70.4 7.7 3.1 53.8 52.0
* Included in this number are 112 birds of unknown age and 651 full-grown birds but age otherwise unknown.
Table 2. Ringing and recovery data by age, of house sparrows ringed in the Faroe Islands during the years 1963
to 2007.