Abstract
Breeding activities in 133 nest-boxes of varying sizes, erected in mainly deciduous woods in Linderås, southeastern Sweden (57°58'N; 14°15'E), were recorded from 1986 to 2005. In total, 1,841 pairs representing 15 species bred in the boxes; mean occupancy was 75%. The Pied Flycatcher Ficedula hypoleuca was the most frequent species. Its population numbers showed no significant trend while its fluctuation pattern largely paralleled those of two contemporary Swedish studies. Dates of spring arrival and start of egg-laying varied independently without any trend. Mean clutch size was 6.32, equalling those obtained in other Swedish studies, even though the proportion of 6-egg clutches and mean number of fledglings (4.26) were significantly lower. Only 40% of the breeding attempts were entirely without losses, such as failed hatching (8% of 6,370 eggs), predation, or usurpation by other species. A total of 550 incubating females and 3,653 nestlings were ringed of which 12% and 0.3%, respectively, returned to the study area in the subsequent season. Of females that returned, 41% reappeared in the first and 48% in the second ensuing season.
Highlights
The study area is situated in the parish of Linderås (57°58'N, 14°15'E) between the towns of Tranås and Gränna in south-eastern Sweden
A total of 550 incubating females and 3653 nestlings were ringed of which 12% and 0.3%, respectively, returned to the study area in the subsequent season
Att jag aldrig kunde konstatera någon omläggning eller andrakull hos arten, trots att de flesta honor ringmärktes under början av ruvningsperioden
Summary
Från 2001 var jag av olika anledningar (biotopförändringar m.m.) tvingad att ta bort vissa holkgrupper och antalet undersökta holkar minskade till 94. Avståndet mellan holkarna var mellan 15 och 30 meter och de satt i grupper med 10 eller 15 stycken. Alla holkar satt på en höjd av endast 1,9–2,2 meter för att underlätta såväl studier som ringmärkning. Oftast blev det fler än ett besök i veckan, främst under perioden från färdigt bo till dess att första ägget lagts, då vissa holkar kontrollerades mer eller mindre dagligen. När jag i den fortsatta redovisningen analyserar beståndsutvecklingen för de olika arterna tar jag endast med de 94 holkar som under samtliga 20 år suttit på samma plats. När jag redovisar antalet häckningar av olika arter är kriteriet för en häckning att minst ett ägg lagts.
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