Shorebird Community Ecology in the Firth of Thames

The ecology of four shorebirds were studied at their non-breeding habitat in the Firth of Thames to better understand foraging and community behaviour. Abstract from thesis: Shorebirds life histories are dominated by changing seasons, frequently spending the breeding and non-breeding portions of the year in different habitats (wintering grounds). This characteristic leads to particular life history traits adapted to these major changes. The ecology of four shorebirds were studied at their non-breeding habitat in the Firth of Thames; the bar-tailed godwit, lesser knot, South Island pied oystercatcher and the wrybill. These species were selected due to their ecological significance within this non-breeding habitat, and also because of specific behavioural and morphological traits that separate the niches of each species. Foraging observations were recorded during monthly visitations to the study site for a period of a year. These observations were used in conjunction with morphological and abiotic data to establish three specific attributes of each of the species: (1) the use of foraging methods, (2) the effect of abiotic factors on foraging behaviour and (3) the maintenance metabolism of each species. Each species was found to use a specific prey-searching method, which differed with season and tidal zone. The effect of abiotic factors was found to be variable, differing between species, depending on the aforementioned traits that differentiate each species. Maintenance metabolism estimates were made for each species, and seasonal variation are related to foraging behaviour and weight changes. Detailed studies were also conducted on the bar-tailed godwit, to investigate teh characteristics of pre-migration weight gain and sexual dimorphism. It was found that bar-tailed godwits departing New Zealand have one of the longest pre-migration weight gain periods of any shorebird. The nature of the sexual dimorphism that occurs within this species is indicative of ecological causation as the most likely factor that has lead to differences in bill morphology between the species, a phenomenon that is rarely found in nature.

Observations of bar-tailed godwit, lesser knot, South Island pied oystercatcher and wrybill. Observations of foraging methods, effects of abiotic factors on foraging behaviour and maintenance metabolism of each species. Also more detailed observation of bar-tailed godwit, to investigate pre-migration weight gain and sexual dimorphism.

Western coast of Firth of Thames.

Study undertaken in 2002-2003

Frequency of collection: Monthly visits for the period of a year.

Data presented in thesis.

Thesis available in University of Auckland library Sensitivity/Confidentiality: No confidentiality

Study completed.

Related information: Ornithological society has ongoing monitoring programmes in the Region.