Líffræðifélag Íslands - biologia.is
Líffræðiráðstefnan 2021

Erindi/veggspjald / Talk/poster V17

Brood counts of common eider in Breiðafjörður 2007-2021

Höfundar / Authors: Jón Einar Jónsson (1), Svava Kristín Jónsdóttir (1), Jamie N. Carroll (1), Ellen Magnúsdóttir (1)

Starfsvettvangur / Affiliations: University of Iceland's Research Center at Snæfellsnes

Kynnir / Presenter: Jón Einar Jónsson

Eider females with broods were counted annually 2007-2021 in Breiðafjörður, i.e. along the coast from Brjánslækur west to Reykhólar, the north side of Snæfellsnes from Stykkishólmur to Hellissandur, and nearby Stykkishólmur. The broods were counted twice, at the end of June (7-10 days after peak hatch) and end of July when ducklings should be nearly half grown. Data from June and July are presented as 1) the ratio of ducklings per female, 2) numbers of females and 3) number of ducklings. Ducklings/female declined over the study period, particularly in July. There were negative year trends in number of females and ducklings. For June data, number of eider females per brood were grouped as lone-female tenders (1 female), two-female tenders, multi-tenders (3 or more females accompanying a merged brood) and females without ducklings. Number of ducklings had no relationship to no. of females without ducklings but there were similar, positive relationships between ducklings and no. of lone-female tenders, two-female tenders, and multi-tenders. Two years were influential values, i.e. 2008, which was a year with high number of females and broods, and 2011 was an all-time low in duckling numbers and record-high in number of females without broods (92% in June). A declining July duckling/female ratio and concurrently declining female numbers suggest low breeding success in the last decade.