CONSERVATION OF MARINE BIRDS IN OTHER LANDS (continued 2)
Reading edition
11. Bleik 1974 60 1952 90 Regnell 1957
1964 75 Brun 1969a
12. Sør-Fugløy 1974 10 1940 10,000 Soot-Ryen 1941
1961 4,000 Brun 1963
1966 1,100 Brun 1969a
13. Nord-Fugløy 1967 9,000 1963 15,000 Lütken 1965
14. Loppa 1974 500 1966 800 Brun 1969a
15. Hjelmsøy 1974 70,000 1964 110,000 Brun 1965
1967 95,000 Brun 1969a
16. Gjesværstappene 1973 580 1967 750 Brun 1969a
17. Sværholtklubben 1973 20 1966 25 Brun 1969a
18. Omgangsstauran 1973 70 1967 85 Brun 1969a
19. Syltefjorden 1974 9,000 1966 12,300 Brun 1969a
20. Hornøy 1974 500 1964 730 Brun 1969a
21. Reinøy 1974 110 1964 160 Brun 1969a
22. Kjøfjord 1970 21 — —
23. Skogerøy 1970 8 1967 6 Brun 1969a
24. Sagfjord 1970 9 1967 12 Brun 1969a
25. Kobbholmfjorden 1970 2 1967 1 Brun 1969a
Estimates of Total Seabird Population in Norway
In addition to the more detailed censuses of the cliff-breeding species dealt with so far, notes have been made on all seabirds observed during numerous flights along the Norwegian coast. Although a first attempt at putting a figure to all seabird species in Norway may be somewhat premature, it is believed that even an extrapolation combined with an educated guess is of some value until more accurate censuses covering the whole coast can be made. Although the data (Table 1) are arranged in the same way as the results from "Operation Seafarer" in the British Isles (Cramp et al. 1974), it must be stressed that the accuracy of the Norwegian figures, at least for the non-cliff-breeding birds, is far inferior to the very fine British data. The table includes data for two petrels (Hydrobates pelagicus, Oceanodroma leucorrhoa), which in Norway breed on Røst (well north of the Arctic Circle), where they have adapted to a delayed breeding season with egg laying in August because of the conflict of their nocturnal habits with the continuous daylight due to the midnight sun. Of the present population trends that are given for each species in Table 1, all auks except the black guillemot (Cepphus grylle) are decreasing, whereas the gulls, the gannets, and the fulmars are increasing.
Table 6.
Population trends in colonies of the common murre
(Uria aalge)
in Norway. Numbers for 1964 and 1974 are, when not censused those years, extrapolated from present trends, using estimated yearly decrease or increase from all available census figures.
Locality Number of breeding pairs[77] Percentage yearly decrease (-) or increase (+)
1964 1974
1. Utsira 2 1 -12.2
2. Utvær 23 14 -5.5
3. Veststeinen 32 27 -1.6
4. Klovningen 30 39 +2.8
5. Einevarden 28 31 +1.0
6. Runde 7,438 6,000 -2.2
8. Røst 9,700 6,800 -3.6
9. Værøy 2,400 1,750 -3.2
10. Nykvåg 453 350 -2.6
11. Bleik 75 60 -2.3
12. Sør-Fugløy 1,844 10 -68.5
13. Nord-Fugløy 13,201 3,681 -13.6
14. Loppa 900 500 -6.1
15. Hjelmsøy 110,000 70,000 -4.6
16. Gjesværstappen 853 556 -4.4
17. Sværholtklubben 27 19 -3.2
18. Omgangsstauran 94 68 -3.3
19. Syltefjorden 13,299 9,000 -4.0
20. Hornøy 730 500 -3.9
21. Reinøy 160 110 -3.8
23. Skogerøy 5 12 +10.1
24. Sagfjord 16 6 -10.1
25. Kobbholmfjord 1 5 +26.0
Total 161,341 99,566 -4.9
Table 7.
Status of the thick-billed murre
(Uria lomvia)
in Norway (cf. Fig. 3)
.
Locality Year No. of breeding pairs Percentage of total Uria population
1. Vedøy, Røst 1974 15 0.3
2. Værøy 1966 20 0.9
3. Hjelmsøy 1974 850 1.2
4. Gjesværstappene 1973 25 4.3
5. Syltefjord 1970 90 0.9
6. Hornøy 1966 55 8.1
7. Reinøy 1964 1 0.6
8. Kjøfjord 1970 1 4.8
Estimated number, Norway, 1974 >1,000 ca. 1.0
Table 8.
Status of the razorbill
(Alca torda)
in Norway (cf. Fig. 4)
.
Locality Year No. of breeding pairs Percent
1. Kjør 1970 1 <0.1
2. Utsira 1970 25 0.1
3. Utvær 1970 16 0.1
4. Veststeinen 1970 22 0.1
5. Klovningen 1970 12 <0.1
6. Einevarden 1970 45 0.2
7. Runde 1974 2,800 9.5
8. Sklinna 1974 15 0.1
9. Lovunden 1968 8 <0.1
10. Røst 1974 3,900 13.2
11. Værøy 1974 800 2.7
12. Nykvåg 1966 250 0.8
13. Bleik 1968 28 0.1
14. Sør-Fugløy 1974 15 0.1
15. Nord-Fugløy 1967 10,000 33.8
16. Loppa 1969 750 2.5
17. Hjelmsøy 1974 7,000 23.7
18. Gjesvær 1973 2,500 8.5
19. Sværholtklubben 1973 18 0.1
20. Omgangsstauran 1973 6 <0.1
21. Kongsøy 1966 8 <0.1
22. Syltefjorden 1966 1,200 4.1
23. Hornøy 1967 65 0.2
24. Reinøy 1967 55 0.2
25. Kjøfjord 1970 9 <0.1
26. Skogerøy 1970 4 <0.1
27. Jarfjordnes 1970 3 <0.1
Total ca. 30,000
Since the coastline of Norway is about the same length as the coastline of Great Britain and Ireland, it is interesting to compare the population figures (Table 12), although the accuracy is very different. Populations of auks and gulls are similar in both areas, but the species composition is different. There are more terns in the British Isles, but skuas (Catharacta skua), shags (Phalacrocorax aristotelis), and great cormorants (P. carbo) are present in similar numbers. The most striking difference is the very small number of procelli-forms and gannets in Norway compared to Britain and Ireland, where they are almost as numerous as the gulls and the auks.
Table 9.
Status of the fulmar
(Fulmarus glacialis)
in Norway
.
County Number of localities Number of breeding pairs
Nordland 6 140
Møre and Romsdal 7 945
Sogn and Fjordane 2 11
Rogaland 2 2
Total 17 1,098
Table 10.
Population increase of the gannet
(Sula bassana)
in Norway (cf. Fig. 5)
.
Colony Year established Mean yearly growth rate 1969-1974 (%) No. of breeding pairs
1969 1970 1971 1972 1973 1974
1. Runde 1946 8.4 330 331 383 422 450 494
2. Mosken ca. 1960 5.4 50 83 77 60 62 65
3. Nordmjele 1967 83.3 7 36 65 103 127 145
4. Syltefjord 1961 14.5 28 29 44 48 51 55
Total 12.8 415 479 569 633 690 759
Yearly growth rate (%) 15.4 18.8 11.2 9.0 10.0
Discussion
Impact of Human Activity
Direct Exploitation
According to Norwegian laws, all seabirds, with the exception (for some odd reason) of the gannet and fulmar, can be hunted from 21 August to 1 March. However, only the two species of murre and the razorbill are still regularly hunted and, although no statistics support it, an estimate based on interviews with some of the hunters reveals that murres and razorbills are shot in the ratio of about 50:1. One man can shoot as many as 380 murres and razorbills during a winter season as a sideline to fishing. Although not many hunt on this scale, an absolute minimum of 5,000 murres and razorbills are killed this way each season.
A new law based on modern principles of conservation has been under consideration for several years, and this will mean an improvement. However, the speed of the decline of the auks, particularly the murres, makes it imperative to stop this hunting immediately, and it is of very little economic importance to the few who take part. Some illegal "fishing" for auks still takes place at Røst and Vaerøy, where fishnets are anchored over wooden frames outside the auk colonies at the beginning of the nesting season. At Vedøy on Røst in 1972, up to 80 murres were taken daily. Thus an estimated total of 500-700 murres were taken that year—about 5% of the breeding population on this island.
Egg collecting was important during World War II, but in these more affluent times and because of the relative inaccessibility of the auks' nests, egg collecting is now both less attractive and less important. Human disturbance of the breeding colonies, however, is gradually becoming a more serious factor.
Table 11.
Comparison of annual growth rate and breeding success in two colonies of gannets
(Sula bassana).
Mosken Nordmjele
Annual growth rate Breeding success (%) Annual growth rate Breeding success (%)
1969 62 —
1.66 5.14
1970 51 61
0.93 1.81
1971 36 46
0.78 1.58
1972 33 62
1.03 1.23
1973 50 35
1.05 1.14
1974 12 39
1969-1974 1.05 40 1.83 46
Fishing Gear
Although on a scale different from that in western Greenland, drift-net and longline fishing for Atlantic salmon (Salmo salar) outside the 19-km (12-mile) limit off the northern Norwegian coast present a serious mortality hazard to some seabirds. Reliable data exist only for the longline fisheries. In the 1969 season (with 75 effective days from mid-March to mid-June), one boat using 1,040 hooks per day caught 294 birds: 52 fulmars, 3 gannets, 43 kittiwakes, 107 murres, and 89 puffins. No razorbills were identified, but they may have been included in the murre figure. If this sample is representative, the 100 or so Norwegian boats using longlines plus about 20 Danish boats (which used 4,000-6,000 hooks per day and consequently caught more birds) would have caught roughly 10,000 fulmars, 600 gannets, 9,000 kittiwakes, 21,000 murres, and 18,000 puffins in the 1969 season. The drift-nets in Norwegian waters are reported to be less damaging to seabirds than are the longlines, but even without adding the figures from the drift-nets, the numbers are substantial in view of the size of the Norwegian breeding populations.
Table 12.
Comparison of the number of seabirds breeding on the coasts of Great Britain and Ireland (Cramp et al. 1974) and on the coast of Norway.
Species Number of breeding pairs[80]
Great Britain and Ireland Norway
Fulmarus glacialis 306,000 1,100
Puffinus puffinus > 175,000 —
Hydrobates pelagicus 105 or 106 103 or 104
Oceanodroma leucorrhoa 104 102
Sula bassana 138,000 760
Phalacrocorax carbo 8,100 12,000
P. aristotelis 31,000 33,000
Stercorarius skua 3,100 1[81]
S. parasiticus 1,100 8,000
Larus ridibundus 74,000 4,000[82]
L. canus 12,000 (150,000)[82]
L. fuscus 47,000 9,000[82]
L. argentatus 333,000 (260,000)[82]
L. marinus 22,000 (40,000)[82]
Rissa tridactyla 470,000 510,000
Sterna sandvicensis 12,000 —
S. dougalli 2,300 —
S. hirundo 14,000 (13,000)[82]
S. paradisaea (31,000) (21,000)[82]
S. albifrons 1,800 —
Alca torda (144,000) 30,000
Uria aalge (577,000) 100,000
U. lomvia — 1,000
Cepphus grylle 8,300 22,000
Fratercula arctica (490,000) 1,250,000
Total ca. 3,000,000 ca. 2,500,000
Use of fishing gear close inshore, especially pound nets set near colonies of diving seabirds, can take a heavy toll under special weather conditions. In 1969 at Runde, 85 birds, mainly auks, shags, and some diving ducks, were caught in one net in 24 hours; this is an exceptionally high figure. The total loss of diving seabirds in pound nets per year in Norway (about 6,000 nets fishing for 40 days) was estimated to be at least 40,000 birds in 1969. The data are too unreliable to give species composition, however, since fishermen rarely make note of this.
Amounts of fish offal from offshore trawlers, drift-netters, and longline fishing boats have increased in recent years, and some seabirds, particularly kittiwakes, fulmars, and gannets make use of this new and readily available food source. Thus, although the use of fishing gear is a serious threat to seabird survival, fish waste from the same boats provides an abundant food supply for the more pelagic species.
Pollution
No quantitative investigation similar to those made in Great Britain, Netherlands, and Belgium (Tanis and Bruyns 1968) has been carried out on the impact of oil pollution on seabirds in Norway. The northern Norwegian population of the most threatened species, murres and razorbills, winter in North Sea coastal areas where oil pollution and oiled birds have most frequently been found. It is possible that whole populations winter every year in the same area, and if they happen to be in a heavily polluted area, a particular population may be seriously affected. Such an occurrence is believed to have caused the dramatic decline in the Sør Fugløy population (cf. Table 5).
Although not yet serious, pollution by persistent toxic chemicals such as organochlorines and mercury is a problem even in northern Norway, because the northbound coastal current brings water masses, plankton, and nekton from areas with industrial wastes. Analysis of the eggs of herring gull (Larus argentatus), murre, razorbill, and kittiwake in 1972 showed relatively low levels of mercury; the only species with a relatively high level of mercury (mean 0.58 ppm) was the gannet (Fimreite et al. 1974). This elevated toxic burden may have caused a reduced breeding success for the gannet. Analysis of concentrations of PCB's and DDT/DDE showed that the levels of these organochlorines were generally also lower in Norwegian seabirds than in those of Britain (Fimreite et al. 1977).
Protection and Necessary Conservation Measures
Total protection of some of the important seabird colonies (including the surrounding nearshore waters) has proven very effective, especially when the protection is so strict that landing is prohibited for a specified period during incubation and fledging. However, to reduce the rapid decrease of some species, a total hunting prohibition of those species must be instigated, oil pollution must be reduced, and the fisheries must be regulated to reduce the mortality caused by fishing gear.
Natural Factors Influencing Breeding Success
The factors discussed so far are all results of human activities which directly or indirectly influence seabird mortality. Yearly production or breeding success is, however, also influenced by a number of natural factors such as food supply, availability of suitable nest sites, predation, climate (weather), and population-dependent factors (age, breeding experience, population density). For the gannet, whose breeding success has been studied in some detail (Brun 1974), it was concluded that the differences in exposure (to severe weather) and in breeding experience were the most important factors responsible for annual fluctuation in breeding success. For such species as murres, razorbills, and puffins, food supply is an important limiting factor. If the spawning of the fish species that constitute their main food items fails 1 year for some reason, it may be very difficult for the seabirds to find an adequate alternative food supply and most of the chicks starve to death. To a lesser degree, food supply is limiting for the kittiwake, which seems to be more influenced by bad weather (Norderhaug et al. 1977).
Conclusion
Two opposite population trends have been observed—the decline of the coastal-bound murres and razorbills and the increase and spread of the more pelagic gannets, fulmars, and kittiwakes. These changes are attributed to a number of factors, which include the following:
• The diving murres and razorbills spend a major part of their time swimming on the surface and are thus more susceptible to surface oil pollution than are the pelagic species.
• The coastal-bound murres and razorbills are quite heavily hunted, whereas there is no regular hunting of the pelagic species.
• The pelagic species are mainly surface feeders and do not swim under water, and are thus less affected by the drift-nets than are diving birds.
• The pelagic species are the principal beneficiaries of recently increased supply of fish offal from trawlers.
Acknowledgments
The program was originally sponsored by Tromsø Museum, later University of Tromsø, and has been financially supported by the Norwegian Research Council for Science and Humanities and the Norwegian Game Fund. The research grants are gratefully acknowledged. I also thank my field assistants and the many local people at the breeding sites who have been most helpful.
References
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