The effects of human disturbance and climatic conditions on breeding Cassin’s auklets

QH301 Biology;QL Zoology

Albores-Barajas, Yuri V. ; Furness, Robert W.

University:University of Glasgow

关键词: Cassin's auklet, human disturbance, climatological conditions, breeding success, chick growth;   

Others  :  http://theses.gla.ac.uk/36/1/2007Albores-Barajasphd.pdf

来源: University of Glasgow

【 摘 要 】

Human disturbance has been observed to have effects on wildlife. These effects can be either positive or negative, depending on the study species; however, most of the research done to date has demonstrated negative effects that are reflective in the behaviour and reproductive biologyof the organisms. I focused on Cassin’s auklet, a burrow-nester species to study the effects of increasing tourism on the islands along the peninsula of Baja California, Mexico. I also studied the effects of adverse climatological conditions on breeding success of this species.First, using some biometrics of the individuals captured, I tested a method for aging Cassin’s auklet based on the iris colour. My results corroborate what was proposed before, juveniles have a dark-brown iris that shades into a complete white as they become adults. I also usedmorphometrics to determine the sex of the individual. When making intra-pair comparisons, it is possible to estimate the sex of the individual based on bill measurements. In 100% of the cases, individuals were correctly sexed usingbill depth and width, as corroborated with DNA analysis.Second, using distance as a measure of disturbance, I looked onto the effects of people walking around the island. In general, breeding success was lower in those sites closer to the path or the village; older and moreexperienced individuals represented the vast majority of the burrows further away from the disturbance source. After that, using an experimental approach, I manipulated the amount of disturbance received by the chicks and recorded growth rate, as well as fledging weight, that may influence the possibility of survival for the chicks. I found that at the early stages of development, chicks grew at the same rate; however, chicks in the experimental groups reached a lower peak weight, compared to chick in the control group, and once fully feathered, chicks in the experimental group had a higher rate of weight loss, fledging lighter and earlier than control chicks.I also had the opportunity to explore the effects of adverse climatic conditions on breeding success. My results show that under a warming of the upper layer of the ocean, as was registered in 2005, Cassin’s auklets struggleto maintain a good body condition and, although attempting to breed, abandon the nest later on, to guarantee survival and another attempt to breed the following season should the condition improve. Breeding success decreased from nearly 70% in 2004 to less than 10% in 2005. Body conditionwas also lower in 2005, with a slight improvement the following year.