Abstract
Globally, shorebirds face many threats as their migration paths span continents and twenty-three countries. Thirty-six species of shorebird breed in the northern hemisphere and visit Australian shores in the Austral summer. Shorebirds in the East Asian-Australasian Flyway are particularly threatened by habitat loss occurring at a key stop-over site in the Yellow Sea. In Australia, one of the key threats to shorebirds is disturbance which can include any form of activity that disrupts the normal patterns of activity displayed by the species. Disturbances impact shorebirds by using up vital energy stores during critical arrival and departure times of the year. Increased energy expenditure coupled with a lack of alternative roost-sites may impact migration and survival of a shorebird.
In this study, I focus on natural and anthropogenic disturbances to migratory shorebirds that spend their non-breeding season in Darwin, Northern Territory. I counted shorebirds at four roost-sites in northern Darwin from 2011-2012 and collected data on disturbance events to Knots (Calidris spp.) and Sand Plovers (Charadrius spp.) at Lee Point-Buffalo Creek beach from September to December, 2011. Shorebird responses to disturbance were classed as flight, non-flight and no response.
Various sites around northern Darwin supported high numbers of migratory shorebirds during January to April and September to November in 2011. Over a one-year period, Lee Point-Buffalo Creek beach supported the highest abundances and species richness compared to the other sites.
Shorebirds were disturbed by humans with and without dogs, and birds of prey. When shorebirds were disturbed they most commonly took flight. There were 0.92 disturbance flights per hour at Lee Point-Buffalo Creek beach. However, they did not depart from the study site, suggesting there are no suitable alternative roost-sites. The probability of taking flight decreased as the distance to the disturbance agent increased, as flock size increased and in mixed-species flocks. The mean time spent in flight following a disturbance was 49.5 s for Sand Plovers and 27.0 s for Knots. The time that shorebirds spent in flight following a disturbance was not demonstrably influenced by any of the variables that I recorded. I estimated that daily energy expenditure would increase by ~8% for the study taxa for 10 disturbance flights. If disturbance flights double or treble there is concern that shorebirds will have to increase their food intake rate. As the human population of Darwin grows there is a very real possibility that disturbances will increase, thus disturbance impacts such as increased energy expenditure will increase.
Reducing anthropogenic disturbances to shorebirds at key roosting and feeding sites is vital for shorebirds to exist. Management recommendations for migratory shorebirds at Lee Point-Buffalo Creek beach are: (i) to increase educational signage and re-position current dog-regulation signs; (ii) patrolling of the beach by Parks and Wildlife during critical times of the year and important times of the day (7:30 – 9:30 and 16:30 – 19:30) as these coincide with high tides when shorebirds roost, and penalties should be issued to people not obeying regulations; (iii) ongoing monitoring of shorebirds at roost-sites in northern Darwin.
| Date of Award | 29 Oct 2012 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Donald Franklin (Supervisor), Judit Szabo (Supervisor) & Mike Lawes (Supervisor) |