The influence of food supply on the breeding ecology of Kittiwakes Rissa tridactyla in Shetland

Abstract

We measured the breeding performance, body condition, time budgets and foraging ranges of Kittiwakes Rissa tridactyla at Sumburgh Head, Shetland, in two years of contrasting food availability. Kittiwakes in Shetland generally feed their young almost entirely on sandeels, and fisheries data indicated that stocks of sandeels in Shetland waters were at least ten times higher in 1991 than in 1990. Fledging success of Kittiwakes was nil in 1990 and 68% of eggs laid in 1991, although clutch-size and hatching success were no different between years. Post-hatching foraging trips in 1991 were of comparable duration to those recorded at other colonies in conditions of good food supply (2-3 h), while trips recorded during incubation or post-hatching in 1990 were approximately three times longer on average than at corresponding stages of the breeding season in 1991. Radio-tracking data indicated that adults generally stayed within 5 km of the colony in 1991 but flew more than 40 km from the colony on each trip in 1990. Eggs were apparently not left unattended in either year, despite the fact that this required adults to incubate for periods in excess of 4. 4 h in 1990. The extent to which adults were able to increase trip durations, foraging ranges and incubation shift lengths between years, while maintaining hatching success, indicates the degree to which Kittiwakes are normally buffered against adverse feeding conditions during incubation. Reduced nest attendance and lower body-condition of adults post-hatching in 1990. in conjunction with complete post-hatching breeding failure, indicate that adults were beyond the limits of their buffering capacity during chick-rearing in 1990.

Foraging effort does not influence body condition and stress level in little auks

“…adjusted according to offspring energy demands and environmental conditions of the breeding season, parents can increase the rate of chick provisioning by lengthening foraging flights to reach more distant food resources or spending more time foraging at suboptimal feeding grounds (e.g. Hamer et al 1993, Montevecchi 1993, Kitaysky 2001a, Weimerskirch et al 2001, Litzow & Piatt 2003. Each of these strategies could be costly in time and energy and may compromise adult survival and future reproductive success (Stearns 1992, Roff 1992, Golet et al 2004.…”

Action plan for seabirds in Western-Nordic areas

“…Sandeels and seabirds in the North Sea: Most breeding seabirds in the North Sea are heavily dependent on sufficient stocks of sandeels for suc-cessful reproduction (Hamer et al 1993, Furness & Tasker 2000. During the period when organised seabird monitoring in Scotland has taken place, there have been two episodes of widespread breeding failures.…”

“…During the period when organised seabird monitoring in Scotland has taken place, there have been two episodes of widespread breeding failures. The first affected Shetland in the late 1980s (Monaghan 1992, Hamer et al 1993, and the second covered the entire North Sea coast in (Heath et al 2009). In both cases, there is strong evidence that lack of suitable food (i.e.…”

“…The main proximate cause of these problems is clearly lack of food (e.g. Hamer et al 1993, Davis et al 2005, although predation from great skuas has also played a part. However, it is much less clear what has caused the lack of sandeels.…”

When things go wrong: intra‐season dynamics of breeding failure in a seabird

“…The monitoring of foraging trips via land-based surveys and, more recently, the use of miniaturized electronic tracking devices, have shown that kittiwake foraging ranges vary according to colony location and food availability, but is generally between 20-60 km (Furness and Barrett 1985, Hamer et al 1993, Suryan et al 2000, Daunt et al 2002, Ainley et al 2003, Kotzerka et al 2010, Paredes et al 2012) and several studies examining the inter-annual variability of kittiwake breeding performance revealed that breeding failure is common when food conditions are poor (Alaska: Suryan et al 2006;Newfoundland, Canada: Regehr andMontevecchi 1997, Carscadden et al 2002;North Sea: Frederiksen et al 2005; Barents Sea: Barrett andKrasnov 1996, Barrett 2007). However, such inter-annual studies do not give insights into the intra-season dynamics of breeding failure and its underlying mechanisms.…”