Breeding ecology, migration and population genetics of lesser crested terns Thalasseus bengalensis emigrata

Hamza, Abdulmula Abdulmagid

Abstract

The ecological requirements of the Mediterranean breeding population of Lesser Crested Tern Thalasseus bengalensis emigrata were studied from 2009 to 2012 at its three breeding sites on the Libyan coast Libya: Gara, Elba islands and Jeliana islet. Four main research aspects were investigated: Breeding ecology, young diet structure and differences between sites, migration and recruitment, and population genetics. Threats and conservation measures were also discussed. This Mediterranean endangered population starts breeding at one site (Jeliana) three weeks earlier than in the other breeding sites, possible causes were discussed, including difference in migration routes and food diversity and availability among sites. Incubation period and nesting density were variable among sites; large colonies had more packed nests than in small colonies. A fourth breeding site was discovered in 2010 at Fteha Island. Nest counts at Jeliana colony tripled in 2012, following site restoration work that increased both the islet surface breeding area and height, to control nest inundation and competition on nesting space. Regurgitated food during young ringing was collected to study diet structure and diversity. Fish were the most common prey type with a small proportion of Cephalopods at Gara. Dominant fish families were Clupiedae, Exocoetidae, Hemiramphidae, Carangidae, Sparidae and Blennidae. Prey diversity was highest at Jeliana. There were more differences in prey structure among sites than within sites and seasons. Total length (TL) of fish was smaller at Elba compared to both Gara and Jeliana. Annual variability of prey mass were significant among sampling years, possible causes were discussed. Prey fish length increased with the progress of provisioning period, reflecting increased dietary demand by the growing young. Adults are potentially selecting actively for larger sizes. The relationship between the increase of Sea Surface Temperature and the primary productivity and fish spawning season coinciding with the Lesser Crested Tern breeding season have been discussed. 544 young terns were ringed during the study years, in addition to 808 that were previously ringed between 2006-2008 seasons. Ring sighting and recoveries constitute 2.07% of the total ringed terns; this allowed the gathering of more data on post-natal movements (staging and wintering ranges), breeding site philopatry and recruitment levels, in addition to a preliminary estimation the duration of migration journey. The population genetics of the study subspecies have been studied using two mitochondrial DNA molecular markers (ND2 and Cyt b). DNA samples were collected from Libya, the Red Sea and the Persian Gulf breeding populations. Irrespective of the relatively small sample size and the limited number of genetic markers used, there was significant genetic variability among the three populations. Several private haplotypes have been firstly identified for each population; few others were shared among all subspecies populations. Haplotype diversity was highest at the Persian Gulf subspecies T. b. torresii. The present three subspecies classification is found to be valid, which in turn making the Mediterranean breeding population a special conservation unit, given its relatively small population size and the limited breeding range. A model presents the breeding temporal and spatial aspects, related habitat requirements and present threats have been designed, based on data collected in this study. Habitat requirements and factors known to affect the population at wintering and staging sites were included in the model. The lack of legal protection, the potential oil pollution and site disturbance by visitors, poachers and habitat degradation were the top threats facing the Mediterranean subspecies. Mitigation measures and a proposed Action Plan was presented and discussed. The present research has answered several questions on the status, ecology, feeding, genetics and management of the Mediterranean breeding Lesser Crested Tern colonies in Libya. It is considered a significant step towards the conservation of this localised un-protected population.

Citation

Hamza, A. A. (2014). Breeding ecology, migration and population genetics of lesser crested terns Thalasseus bengalensis emigrata. (Thesis). University of Hull. Retrieved from https://hull-repository.worktribe.com/output/4215875

• Thesis Type: Thesis
• Deposit Date: Jul 22, 2014
• Publicly Available Date: Feb 23, 2023
• Keywords: Biological sciences
• Public URL: https://hull-repository.worktribe.com/output/4215875
• Additional Information: Department of Biological Sciences, The University of Hull
• Award Date: Feb 1, 2014