E-Thesis 231 views 256 downloads
How does foraging success affect chick growth? The case of the Magellanic penguin (Spheniscus magellanicus) / MELISSA JOHNSTON
Swansea University Author: MELISSA JOHNSTON
Abstract
Seabirds are extreme examples of income breeders whereby chick growth is entirely dependent on the foraging skills of the parents and the availability of food. It has consequently been proposed that prey availability can be assessed by examining chick growth rates. For this to be verified, studies n...
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Swansea
2022
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| Institution: | Swansea University |
| Degree level: | Master of Research |
| Degree name: | MRes |
| Supervisor: | Rose, Kayleigh ; Wilson, Rory |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa59718 |
| Abstract: |
Seabirds are extreme examples of income breeders whereby chick growth is entirely dependent on the foraging skills of the parents and the availability of food. It has consequently been proposed that prey availability can be assessed by examining chick growth rates. For this to be verified, studies need to compare chick growth with a parental ‘Catch per Unit Effort’ (CPUE) metric as a measure of prey abundance. However, there is limited research on how CPUE affects chick growth and what it might mean in terms of parental quality and food abundance. I examined chick growth in Magellanic penguins (Spheniscus magellanicus) and compared it to CPUE using animal-attached accelerometer metrics assuming prey capture and time spent underwater as effort and showed that there is no significant relationship between CPUE and chick growth rates, in part due to high inter-individual variability. However, the growth rate of chicks was significantly affected by both the number of chicks within the nest (one and two chicks) and by the year (2015 and 2016), with the highest rate of growth in one-chick broods in 2016 (73.9 g/day) and the lowest in two-chick broods in 2015 (32.8 g/day). Variability of growth rates and CPUE can be caused by the size and species of prey that penguins catch during a foraging trip, whether the birds choose to allocate food accrued to themselves or their chicks, where and when the prey are found, and on prey aggregation size. Variability of food delivery on a day-to-day basis can cause misrepresented relationships between CPUE and chick growth rate. Therefore, chick growth rate and CPUE should be used with careful consideration as proxies for prey abundance in the area. |
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| Keywords: |
Income breeder, CPUE, VeDBA, Prey capture, Foraging ability, Parental quality, Seabird, Food abundance, Variability |
| College: |
Faculty of Science and Engineering |