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- Title
The breeding biology and causes of nest failure of Scottish Black-throated Divers Gavia arctica.
- Authors
MUDGE, G. P.; TALBOT, T. R.
- Abstract
The breeding biology and causes of nest failure were examined for Black-throated Divers Gavia arctica in core areas of their Scottish breeding range in 1983-1987. Breeding was confirmed for up to 88% of territorial pairs each year ( n= 28-62), and 76% of nests were on islands. Hatching success was consistently low with, on average, only 43% of territorial pairs managing to hatch a clutch each year; 64% of recorded nest failures occurred during the first week of the 4-week incubation period. Overall breeding success in West Sutherland in 1984-1987 averaged 0.23 chicks per territorial pair per year, while in Ross-shire for 1986-1987 it was 0.29. Forty percent of hatched chicks survived to fledge, and 92% of recorded deaths occurred in the first fortnight after hatching; 4.8% of fledged broods held two chicks. Causes of nest failure were assessed with the aid of surveillance cameras. Approximately 30% of losses were due to water level changes (mostly floods), 48% to predators (primarily nocturnal mammals, but also Hooded Crows Corvus corone), 13% to human egg collectors and 5% to desertion following human disturbance. Scottish Black-throated Divers produce only half the number of chicks tentatively estimated to be required to maintain a stable population. The main difference between the Scottish and more successful Swedish populations is in the degree of chick mortality.
- Publication
Ibis, 1993, Vol 135, Issue 2, p113
- ISSN
0019-1019
- Publication type
Article
- DOI
10.1111/j.1474-919X.1993.tb02822.x