Choi C-Y, Moffitt DJ, Fuller RA, Skilleter G, Rogers D, Coleman J & Klaassen M (2015) Annual Report: Migratory Shorebird Monitoring – Understanding Ecological Impact (CA12000284). Report produced for the Ecosystem Research and Monitoring Program Advisory Panel as part of Gladstone Ports Corporation’s Ecosystem Research and Monitoring Program. 76 pp.
EXECUTIVE SUMMARY
This project is focused around integrating migratory shorebird species into understanding the ecological impact of developments. Migratory species range widely, and in theory, the impacted population could be far greater than the spatial footprint of a development itself, because animals could be dependent on the site for only a short period while in transit to nonbreeding areas elsewhere, or use the site as part of a much larger foraging circuit. As well as being an interesting scientific problem, this is a key research challenge in minimising the harm of developments.
The scope of works divided the present project into two parts:
– Part A: Estimate Carrying Capacity; and
– Part B: Determine the Size of the Impacted Population.
We have completed approximately 50% of the work outlined in the scope of works. We had a weather-related setback in deploying the benthic sampling, but in response have accelerated many of the modelling and desktop analyses, such that pending the targeted collection of final field data in summer 2015/16, we will be able to move rapidly into the final analysis phase of the project during winter 2016. Despite the weather setbacks of 2015, we are on track to deliver the final report by the deadline of January 2017 (see timeline in section 4). We have planned all of the activities for the coming year, incorporating a risk assessment. The team is confident of delivering the remainder of the project within the planned timeframe. In Part A, we have mapped the extent of tidal flats in the ERMP Survey Area, and analysed pilot benthic sampling data showing that most variation in the abundance of the benthos occurs at a scale of ~2–4 m. This unexpected result, coupled with severe weather that interrupted the sampling program has meant we have deferred the full benthic sampling program until November 2015. The design is finalised using a cost-benefit analysis, and will comprise 800 benthic samples across eight major tidal flats from the Fitzroy Delta to Rodds Peninsula.
In view of the delays to the benthic sampling work, we have accelerated the analytical side of the project, by establishing a series of calculations to go from benthic sampling data to estimates of carrying capacity. We provide a worked example that suggests fewer birds occur at Cattle Point (Fitzroy Delta) than could potentially be supported by the available prey base. We have taken 105 videos of focal foraging birds to permit study of diet and further refine the carrying capacity estimation method.
In Part B, we have modelled the movement of birds through the ERMP Survey Area, by developing a method to infer total population size calibrated against historical data available from sites across eastern Australia. Coupled with five targeted counts to discover northward migration phenology in the study area, we have the tools in place to provide a complete estimate of the size of the migratory shorebird population using the study area once we have completed the southward migration counts for all shorebirds in the ERMP Survey Area in late 2015. This work, together with the tidal flat mapping work, has been submitted to an ISI listed journal.
We have begun monitoring the movements of shorebirds, by capturing and banding 45 birds, and have thus far obtained 51 re-sightings of 14 locally and 33 externally marked birds. This revealed some movements of up to 10 km by individual birds, much longer than previously expected. We will conduct a radio tracking study in summer 2015/16 to characterise bird movements in detail. This will allow us to delineate priority areas for shorebirds in the study area and estimate the number of birds potentially affected by future loss or degradation of habitat patches anywhere in the study area.