Fennoscandian Lesser White-fronted Goose conservation project ...

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eaching a peak of 35 individuals on 23 May. The numbers kept steady around 25 individuals until 25 May (Figure 1). Two pairs and one immature (second calendar-year) bird was still present at the end of the monitoring period on 5 June (Figure 1). Totally 58 individuals were staging at the Valdak Marshes in 1999 (Figure 2), which included 20 adult pairs, 2 pairs of mixed age (one adult and one 2cy), three immature pairs, one single adult and 7 immatures (Table 1). The absolute number of immatures was not very high, but the juvenile proportion was the highest ever since the monitoring began in 1990. In Table 1, percentages of immatures and subadults are given. However, these are not directly comparable to the years 1993–1997 and 1998–1999, since subadults were registered as adults before 1998. The comparable immature percentages for 1998 and 1999 are 6.0 and 12.1 respectively. In 1999 the mean lenght of staging period for adult LWfG pairs was 8.0 days (Figure 3), when the pairs already present at the arrival of the field workers and those still left at the departure of the field workers were omitted. We have not tested for differences between years since we have very little data on individual pairs and how their staging time change between years. We have data for more than one year of only one individual LWfG. This is a male which was caught and colour-ringed (colour ring code red-black-yellow) during moult in Finnmark in 1995. It has been observed staging at the Marshes for 10, 6 and 10 days in the years 1996, 1997 and 1998 respectively (see Aarvak & Øien 1999). In 1999, three LWfG colour ringed at the Valdak Marshes in earlier years were seen. An adult female (colour ring code yellow-black) staged 14 days, while an adult male (colour ring code white-black-yellow) staged four days. The last bird with colour rings (code green-white) arrived too late in the period to be followed properly. 3.2. Autumn staging The year 1999 was the fifth consecutive year when continuous monitoring during the LWfG autumn staging at the Valdak Marshes was accomplished. A total of 43 individuals staged there during a period of three weeks (see Tables 2 and 3). The first single LWfG was seen 16 August. The last observation was at 18:00 on 3 September, when 24 LWfG left the area. Also in previous years all autumn observations are from the period 16 August to 10 September (1981–1996, see Table 3). This yields a range of 26 days. However, continuous observation effort has been limited to the period from 20 August to the first few days of September in the years 1995 to 1998, and we expect that the actual staging period could start earlier, and in some years it might end later than stated in the table. The LWfG mainly utilise the area during late evening, night and early morning. They only rarely stay at the marshes during daytime. As experienced in the years 1995–1997, the LWfG behave quite differently compared with the spring staging period, spending more time being alert and showing a restless behaviour. The absence of the LWfG during daytime could partly be caused by Fennoscandian Lesser White-fronted Goose conservation project – Annual report 1999 40 35 30 25 20 15 10 5 0 90 80 70 60 50 40 30 20 10 0 10 9 8 7 6 5 4 Mean number 1990–98 1999 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Figure 1. Maximum daily numbers of Lesser White-fronted Geese in the period 14 May – 16 June 1999. Daily means for the years 1993–1998 give an overview of the staging phenology. 1993 1994 1995 1996 1997 1998 1999 Figure 2. Maximum daily numbers of Lesser White-fronted Geese (light bars) and the total numbers estimated from the drawings of belly patches (dark bars) observed at the Valdak Marshes in the years 1993–1999. N = 28 1993 Aarvak & Øien: Monitoring of staging Lesser White-fronted Geese at the Valdak Marshes in 1999 19 1994 23 1995 22 1996 20 1997 32 1998 21 1999 Figure 3. Overview of mean staging time of pairs of Lesser White-fronted Geese at the Valdak Marshes in the years 1993–1999 estimated by the belly patch method (see Øien et al. 1996). 25
Fennoscandian Lesser White-fronted Goose conservation project – Annual report 1999 Aarvak & Øien: Monitoring of staging Lesser White-fronted Geese at the Valdak Marshes in 1999 disturbance from local people picking cloudberries (Rubus chamaemorus). As a result, the geese spend the daytime on the adjacent small islands in the innermost part of the Porsangen Fjord. The LWfG have also been observed on the small islets Kråkholman at the boundary of Stabbursnes Nature Reserve (in 1996) and the northwest point of the Oldereidnesset Peninsula (in 1997). 3.3. Breeding success A total of 26 adults and 17 (40 %) juveniles were registered during the autumn monitoring period. Six pairs brought goslings, yielding a mean brood size of 2.8 (Tables 2 and 4). On the Skjåholmen Island, only one pair with two young were seen (see Tolvanen 2000, pp. 28–31 in this report). Breeding success is monitored during post breeding period at the Valdak Marshes, which represent the first staging area before the onset of autumn migration. The observations of brood sizes may explain the variation in the breeding success between years. Mean brood size observed at the Valdak Marshes in the years 1994–1999 is as high as 3.2 26 Photo. In spring 1999, 22 adult Lesser White-fronted Goose pairs were staging at the Valdak Marshes, which is 11 pairs less than in the previous year. The picture shows a pair of LWfG at the Valdak Marshes in May 1999. © Ingar Jostein Øien Table 2. Autumn age ratio and annual brood sizes of Lesser Whitefronted Geese in the years 1981-1999, based on counts during autumn migration at the Valdak Marshes (see also Table 4 for distribution of broods and number of pairs with broods). No data from the years 1982–1986, 1988–1991 and 1993. Year n n n % n Mean Mean Mean ad juv total juv flocks brood1 brood2 brood3 1981 10 18 28 64.3 1 3.6 1987 10 18 28 64.3 1 3.6 1992 24 34 58 58.6 ? 2.8 1994 31 33 64 *51.6 3 2.4 2.2 1.3 1995 61 67 128 52.3 3 3.9 2.2 2.7 1996 16 23 39 59.0 1 2.6 2.9 1.0 1997 25 32 57 56.1 1 4.0 2.6 1.2 1998 29 31 60 51.6 3–1 2.8 2.4 0.9 1999 26 17 43 39.5 6 2.8 1.3 0.8 1 Counts of pairs with broods in autumn. 2 Number of juveniles divided by number of adults (pairs) in autumn. 3 Number of juveniles in autumn divided by number of pairs in spring. * Assumed that the observations are from three independent flocks. Table 3. Overview of the autumn staging period at the Valdak Marshes in the years 1981-1999 (all observations are from the period 16 August – 10 September). Year Observation dates (extremes) Time span First Last Occasional in days 1981 17 Aug (1) 1987 20 Aug (1) 1992 18 Aug 20 Aug (3) 1994 17 Aug 10 Sep 25 1995 19 Aug 06 Sep 19 1996 22 Aug 05 Sep 15 1997 20 Aug 03 Sep 15 1998 17 Aug 02 Sep 17 1999 16 Aug 03 Sep 19 (sd=1.4, n=58), although it varies significantly between years (Aarvak et al. 1997). It thus seems that the production is generally high, when based only on the individuals seen on post-moult. Estimates on brood size can be derived in different ways. Probably, the best estimate is based on the number of juveniles compared with the number of pairs observed (potential breeders) in the pre-breeding period (Mean brood 3 - cf. Aarvak et al. 1997), which yields an estimate of 0.8 goslings per potential breeding pair for 1999. This estimated 0.8 goslings fledged per potential breeding pair yield a ratio of 29.3% juveniles in the autumn/winter population based on the number of juveniles produced during summer in relation to all birds that were present at Valdak in spring. For the years 1994, 1995, 1996, 1997 and 1998 we obtained an estimated proportion of 37.1%, 52.8%, 29.1%, 35.2% and 27.0% respectively, with a mean for all years of 35.1% (sd=9.5). Many studies on arctic breeding geese like Barnacle Goose (Branta leucopsis), Brent Goose (B. bernicla), White-fronted Goose (Anser albifrons) and Tundra Bean Goose (A. fabalis rossicus) use the age composition (first-winter individuals and adults) during mid winter counts as a measure of the breeding success of the preceding breeding season (e.g. Ebbinge 1991). In contrast to what we have found in the LWfG, these studies show that the proportion of juveniles varies heavily between 0 and 60% for Brent Goose, 5–30% for Barnacle Goose and 2–50% for White-fronted Goose (Ebbinge 1989, Ebbinge 1991, Fox & Photo. During the autumn staging period, the Lesser White-fronted Geese spend more on the islets in the inner part of the Porsangen Fjord than at the Valdak Marshes. © Ingar Jostein Øien, June 1997 Gitay 1989).
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