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Ornis Norvegica
Journal Prestige (SJR): 0.146

Number of Followers: 2

This is an Open Access Journal

Open Access journal
ISSN (Print) 1892-9737
Published by Norsk Ornitologisk Forening

[1 journal]

Selection of territorial habitat in a declining population of Lapland
Longspurs (Calcarius lapponicus)
- Authors: Vegard Bang Fjeldheim, Ingvar Byrkjedal, Terje Lislevand
  Pages: 1 - 11
  Abstract: Cover photo: Male Lapland Longspur in its breeding habitat. Photo: Vegard B. Fjeldheim. The population of Lapland Longspur Calcarius lapponicus has declined drastically in the Scandinavian mountains over the last decades. One hypothesis is that the population decline has been caused by a change in vegetation composition, specifically an increase in lichen cover leading to a possible decrease in seed-producing plants. We tested the hypothesis by recording vegetation composition inside and outside Lapland Longspur territories in a 10 km2 study area at Hardangervidda, southern Norway, where longspurs previously bred in high numbers. Vegetation composition was recorded by percentage coverage in 295 1 x 1 m quadrats laid out evenly over the study area and compared to a similar treatment of 85 points inside 17 territories of Lapland Longspurs. No difference in lichen coverage or coverage by seed-producing plants was found inside versus outside territories. Instead, Lapland Longspurs were found to establish their territories in the upper part of the study area, where the snow melts earlier. Also, the occupied territories had an orientation towards the sun (sector S–W). Precipitation has increased strongly in the western parts of the Scandinavian Peninsula in recent decades. Falling as snow in the mountains, the increased precipitation leads to delays in spring thaw which could reduce the availability of breeding habitat for Lapland Longspurs during territorial establishment. We suggest that changes in spring conditions could be responsible for the species’ population decline in the western parts of the Scandinavian Peninsula.
  PubDate: 2023-01-25
  DOI: 10.15845/on.v46.3641
  Issue No: Vol. 46 (2023)
Lone male loser' Effects of spatial isolation on male pairing success in
the Ortolan Bunting (Emberiza hortulana)
- Authors: Øyvind Steifetten, Trude Starholm, Svein Dale
  Pages: 12 - 21
  Abstract: Cover photo: Male Ortolan Bunting. Photo: Frode Falkenberg. In small, isolated or fragmented bird populations, past studies have shown that there can be a high proportion of unpaired males. Low male pairing success is suggested to be the result of female-biased natal dispersal and low female recruitment. Indirect evidence indicates that such an effect operates among populations with different degrees of isolation, but little is known of how isolation affects male pairing success within populations. The Norwegian population of Ortolan Buntings (Emberiza hortulana) is distributed in about 50 discrete patches in an area of nearly 500 km2. In this study, we examined whether patch isolation and individual male isolation affected male pairing success. The population has a strongly male-biased sex ratio, with almost half of all males being unpaired. We found that male pairing successs was negatively related to isolation of patches and isolation of individual males in most analyses, and with significant effects in particular in some analyses of individual isolation. Patch population size was measured as the total number of males observed in a particular patch in a specific year and did not have an effect on male pairing success, and was not related to patch isolation. Even though some tests were statistically significant, the magnitude of effects were small and there was large variance in male pairing success. Variance in success suggests that other factors than isolation such as male age or experience may be just as important for male fitness within our study population. Furthermore, we suggest that small effects of isolation were due to the ability of Ortolan Buntings to move large distances within the breeding season, and that isolation effects on small spatial scales are more likely for species with restricted dispersal, such as resident species or species with high population density.
  PubDate: 2023-05-30
  DOI: 10.15845/on.v46.3873
  Issue No: Vol. 46 (2023)
Characteristics of cliff nest sites of Golden Eagles in forested hills of
southeast Norway
- Authors: Henning Dunker
  Pages: 22 - 27
  Abstract: Cover photo: Adult Golden Eagle. Photo: Kristian Henriksen. The characteristics of cliff nest sites of the Golden Eagle Aquila chrysaetos were evaluated from a sample of 57 nests, located during 2000–2020 in the forested valley of Valdres in southeast Norway. About 80% of nests were facing to the south and east, but availability of nest ledges seemed largely a consequence of cliff structure and orientation. Among the 57 nest sites, 4% were placed in a corner with vertical walls, 33% on a ledge with overhang, 10% on a ledge with a vertical back wall, 2% on a ledge with a reclining wall, 49% within a cavity and 2% within a cave. Thus, about 83% of the nest sites were sheltered by an overhang, a cavity or a cave in the cliff within 0.5–2 meters from the nest, and only 16% of sites lacked shelter from above. Heavy snowfall in early spring, torrential rain or strong winds in spring and summer may increase mortality among the nestlings unless the nest site is well sheltered. Moreover, a dry and snowless nest may allow the eagles to start early incubation in late March, thereby increasing fledgling survival. Cavitynests are sheltered sites with less visibility that might protect from attacks from other raptors and Ravens Corax corax.
  PubDate: 2023-06-25
  DOI: 10.15845/on.v46.3698
  Issue No: Vol. 46 (2023)