Red-throated diver breeding ecology and nest survival on Shetland

• Main Author: Hulka, Simon
• Format: Thesis
• Language: English
• Published: 2010
• Subjects: QH Natural history; QL Zoology; Arctic; Blair; Visser; Climate change
• Online Access: http://theses.gla.ac.uk/82392/; https://theses.gla.ac.uk/82392/1/10867986.pdf; https://eleanor.lib.gla.ac.uk/record=b2977986

The aim of this thesis is to identify and measure biological, environmental and behavioural factors relevant to red-throated diver breeding ecology and then to distinguish their relative importance in determining breeding success and nest survival. Migratory birds that breed at high latitudes are at particular risk from human mediated climate change because the time window available for breeding in these areas is short, and if peak abundance of key prey items alters in response to climatic cues (Shultz et al. 2009), it may not be possible for birds to adjust their breeding strategies to compensate. Moreover, large scale environmental cues that migratory birds use to time their migration and breeding may become less reliable (Both & Visser 2001; Frederiksen et al. 2007). For such species it is particularly important to understand and monitor breeding biology, particularly the factors that determine breeding performance and nest survival, as these are likely to respond to large scale ecosystem changes before population changes are detected, and additionally provide valuable information that can be used to establish conservation priorities for the species. Red- throated divers are migratory fish-eating seabirds with a predominantly arctic breeding distribution that have apparently declined in large areas of their breeding range in the recent past (Groves et al. 1996; Hagemeijer & Blair 1997). In addition to the demonstrated effects of food availability (Eriksson & Sundberg 1991; Ball 1994), disturbance (Pakarinen & Järvinen 1984) and vulnerability to pollutants (Eriksson & Lindberg 2005) on breeding performance, direct and indirect effects of climate change are predicted, in particular a contracting of the European breeding range (Huntley et al. 2006) and vulnerability to both onshore and offshore renewable energy developments (Garthe & Huppop 2004; Halley & Hopshaug 2007).This research tests the importance of proximate factors influencing red-throated diver breeding performance using modern nest survival analysis with the intention that the findings will provide clues about the larger mechanisms driving population processes. First I developed a number of linear regression models using nest temperature signatures and photographic measures of chick size that; allowed timing of breeding to be estimated from a single field visit; were of comparable accuracy to established methods such as egg flotation (Westerkov 1950); and extended the period during the breeding cycle when timing of breeding estimates could be made, to include the later stages of incubation and chick rearing. I used these techniques to obtain timing of breeding estimates for the study sample. This allowed me to use an information-theoretic modelling approach (Burnham & Anderson 2002) to determine the daily nest survival rate and evaluate the importance of a set of biological and environmental effects on red-throated diver nest survival patterns. I found support for models that suggested that nest survival increased with nest age and individual quality and decreased with laying date. I explored the effects of habitat characteristics at different spatial scales and found support for models that suggested that both environmental conditions and predator avoidance were important determinants of nest survival rate. Finally I examined nest attendance behaviour and variation in nest temperature during incubation and found patterns in attendance in relation to nest age and through the day but no strong evidence of trends in survival in relation to attendance patterns.