Reproductive costs and their expression in the common guillemot 'Uria aalge'

• Main Author: Van Pelt, Thomas Irion
• Format: Thesis
• Language: English
• Published: 2000
• Subjects: QL Zoology; common guillemot; Uria aalge; uria
• Online Access: http://theses.gla.ac.uk/71225/; https://theses.gla.ac.uk/71225/1/10390811.pdf; https://eleanor.lib.gla.ac.uk/record=b1923264

I present studies on reproductive costs in common guillemots Uria aalge, framed against a background of data from a larger study that provides context for feeding and breeding conditions dominating the study colonies. The components of seasonal declines in reproductive performance were examined at a colony breeding under consistently demanding conditions, in an effort to assess whether previously documented costs of breeding late in the season are expressed relatively strongly under poor conditions. I found the expected seasonal declines in egg quality and overall reproductive success. However, hatching success and offspring quality appeared to remain equal across the season. I discuss the interpretations of my correlative results. The relationship between reproductive performance and parental and offspring body condition is examined, using data from two years with contrasting productivity at a single colony, and data from two colonies with contrasting productivity in a single year. Adult and offspring condition was decoupled from inter-year productivity at one colony, and inversely related to productivity when compared between colonies. I tentatively conclude that a combination of colony- specific factors and the long-term integration of patterns of resource allocation in this long-lived seabird prohibit the simplistic use of body condition as an indicator of reproductive effort or investment. I present results of a manipulative experimental increase in egg production costs, carried out at a colony breeding under poor conditions. Compared to birds laying first eggs at the same time, reproductive success was sharply reduced in parents induced to lay replacement eggs, especially in naturally late-laying birds. Replacement eggs were smaller, but proximate composition did not differ, and chicks from replacement eggs grew as well as those from first eggs. My results demonstrate a strong state-dependence in replacement laying success.