Arzel C

Saari L.

English

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Affiliations: 1 Department of Forest Sciences,  P.O. Box 27, FI-00014 University of Helsinki, Finland (lennart.saari@gmail.com) ;    2 Section of Ecology, University of Turku, FI-20014 Turku, Finland (celine.arzel@utu.fi). Pictures copyright: Janica Candolin. Funding: this project is supported by a grant from the Varsinais Suomi Regional Fund from the Finnish Cultural Foundation. A LONG-TERM STUDY OF BREEDING WATERFOWL POPULATIONS IN THE FINNISH BALTIC SEA   Fig 1. Location of the study area: Aasla in the Archipelago Sea, Finland. Results:  Among the 22 species of waterfowl which have been recorded as breeding pairs at Aasla from 1975 to 2014, 10 have dramatically decreased over the study period whereas 7 have increased. Discussion: Decline in some of the species may be the result of eutrophication, climate change and predation. The coastal area has been under influence of industrial, municipal and agricultural waste waters since the 1950's, but negative signs of eutrophication on waterfowl populations  only  started to be detected at the beginning of the 1990's. Harsh winters in Europe (e.g. 1985-1987) caused crashes in the breeding populations of some species. The arrival of Pine Marten (Martes martes) on the island may also explain the decrease of the breeding population of some species such as Goldeneye.  Comparison with other sites are seeked for. Methods: The data covered the period 1975-2014. The bird censuses were conducted by one observer: Lennart Saari and consisted of a combination of point and round counts. The total study area is about 40 km2 including the terrestrial habitats. The census covered all the inland waters and the seashore. The breeding pair census was repeated 3 times in spring. The breeding pair number was estimated for each species based on the census that best suited its breeding phenology. Only species with more than 5 breeding pairs recorded during the whole study period are presented here. Study site: Aasla is an island located in the  Sea Archipelago, South-western Finland (60 18´N, 21 57´E). Its location, on the fringe of the inner archipelago, makes it a relevant breeding ground for numerous waterfowl. The shore of the island is a succession of open, rocky beach and bays made of reeds. There are also 9 inland lakes in Aasla ranging from oligotrophic to meso-eutrophic.  Table 1. Results of Spearman test per species for the period 1975-2014 (in green  negative correlation, in red positive correlation), mean (SD) number of breeding pairs for the 3 Finnish Bird Atlas periods and total number of pairs recorded during the whole period. Lennart Saari 1 & Céline Arzel 2 Fig 2. Number of breeding pairs of Goldeneye, Common Eider and all species combined observed from 1975 to 2014 at Aasla. 02004006008001000120014001600180020001975 1985 1995 2005Number of pairs Goldeneye Common Eider TOTALSpecies rs P 1st Atlas (1975-79)           2nd Atlas (1986-89)    3rd Atlas (2006-10)Total number of pairsVelvet scoter -- Melanitta fusca -0.925 0.000        22.6 (13.1)                6.3 (2.6)     0 221Common pochard -- Aythya ferina -0.905 0.000        28.4 (15.6)               7.5 (2.5)                0.4  (0.6) 335Tufted duck -- Aythya fuligula -0.821 0.000         69 (29.7)              17.8 (4.3)                6.6  (3.7) 1325Horned grebe -- Podiceps auritus -0.786 0.000          6.8 (1.5)                2.5 (1.9)                 1.2 (0.8) 138Eurasian coot -- Fulica atra -0.774 0.000        53.4 (21.1)                14 (4.2)             11.4 (7.3) 882Goldeneye -- Bucephala clangula -0.737 0.000      262.2 (35.6)             246.3 (48.7)           162 (37.8) 8618Wigeon -- Anas penelope -0.733 0.000        9.6 (4.1)                 2.5 (2.1)     0 120Great crested grebe -- Podiceps cristatus -0.711 0.000      115.4 (37.3)             58.3 (9.2)               33.3 (14.6) 2479Mallard -- Anas platyrhynchos -0.649 0.000      120.6 (24.2)             72 (27)              71.4 (26) 3903Red-breasted Merganser -- Mergus serrator -0.342 0.031       6.8 (2.2)                 11 (2.9)               4 (2.9) 432Teal -- Anas crecca -0.270 0.092       12.6 (7.4)               15.3 (6.6)               14 (6)  509Garganey -- Anas querquedula -0.058 0.723         0.8 (1.3)                 0.3 (0.5)                0.6 (0.9) 11Common merganser -- Mergus merganser 0.003 0.986    49.8 (4.4)                 73.8 (21.5)            51.6 (13.7) 3111Shoveler -- Anas clypeata 0.025 0.877         2.6 (2.1)                 0.3 (0.5)                 1.2 (1.6) 38Water rail -- Rallus aquaticus 0.046 0.778        0.2 (0.5)                   0.8 (0.5)               0.6 (0.6) 33Gadwall -- Anas strepera 0.442 0.004 0 0 0 5Barnacle goose -- Branta leucopsis 0.504 0.001 0 0              0.6 (1.3) 8Greylag goose -- Anser anser 0.592 0.000 0               0.3 (0.5)               3.4 (3.6) 42Red-necked Grebe -- Podiceps grisegena 0.630 0.000          0.8 (0.5)                0.3 (0.5)                 1.2 (0.5) 50Common Eider -- Somateria mollissima 0.637 0.000    279 (62)             522.3 (103.6)          646.8 (99.9) 25531Canada goose -- Branta canadensis 0.652 0.000 0 0              3.4 (2.8) 37Mute swan -- Cygnus olor 0.684 0.000         2 (1)               10.8 (11)              32.6 (10.6) 941TOTAL 0.097 0.552   1042.6 (74.2)            1068.3 (215.8)         1039.3 (125.7) 48768

A long term study of breeding waterfowl populations in the Finnish Baltic Sea

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A long term study of breeding waterfowl populations in the Finnish Baltic Sea

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