Machovsky-Capuska G.E.,University of Sydney |
Senior A.M.,University of Sydney |
Benn E.C.,University of Sydney |
Tait A.H.,Massey University |
And 9 more authors.
Marine Biology | Year: 2016
The foraging challenge for predators is to find and capture food with adequate levels of energy and nutrients. Marine predators require particularly sophisticated foraging strategies that enable them to balance self- and offspring-feeding, and also in many circumstances simultaneously consider the nutritional constraints of their partners. Here we combined the use of dietary analysis, proximate composition and nutritional geometry (right-angled mixture triangle nutritional models) to examine the macronutrient preferences of Australasian gannets (Morus serrator) at Farewell Spit gannetry in New Zealand. Our results showed intra- and inter-specific variation in the protein, lipid and water composition of prey captured by our sample of 111 Australasian gannets. In addition, we observed significant differences in the Australasian gannets’ nutritional niche between seasons. We provide evidence of sex-specific macronutrient foraging strategies in a successful marine predator in the wild. We have shown that in spite of fluctuations in the nutritional composition of foods available to Australasian gannets, males consistently capture prey with higher protein-to-lipid ratios and lower lipid-to-water ratios than females. These results aid to better understand the evolutionary relationship between macronutrient selection and sex-specific traits in wild animals. They also suggest an incentive for these predators to combine individually imbalanced but nutritionally complementary foods to achieve dietary balance, further highlighting the likelihood that prey selection is guided by the balance of macronutrients, rather than energy alone. © 2016, Springer-Verlag Berlin Heidelberg.
Machovsky-Capuska G.E.,University of Sydney |
Machovsky-Capuska G.E.,Massey University |
Hauber M.E.,York College - The City University of New York |
Dassis M.,CONICET |
And 8 more authors.
Journal of Ornithology | Year: 2014
Patchily distributed marine pelagic prey present considerable challenges to predatory seabirds, including Gannets (Morus spp.) departing from large breeding colonies. Here, for the first time, we used GPS data loggers to provide detailed spatial, temporal, and habitat metrics of chick-rearing Australasian Gannets (Morus serrator) foraging behaviours from two distant colonies in New Zealand. Our goal was to examine the extent to which Gannet foraging tactics vary across disparate habitats, and determine whether the observed differences are consistent with predictions derived from foraging studies of other gannet species. Foraging trip performance was highly consistent between colonies, and sexes, and no significant differences in any of the variables analyzed were observed. However, Gannets from Farewell Spit (FS) dove in shallower waters (0-50 m) than birds from Cape Kidnappers (CK, >50 m), which is consistent with previous dietary studies suggesting that FS Gannets feed mainly on coastal prey, whereas CK birds feed on species with a more oceanic distribution. Diving frequencies were similar in the two colonies suggesting that Gannets were foraging in habitats with similar levels of food availability. Further studies are needed to understand the relationship between prey availability, oceanography and geographic features, to better interpret foraging tactics of Australasian Gannets. © 2013 Dt. Ornithologen-Gesellschaft e.V.
Battley P.F.,Ornithological Society of New Zealand |
Schuckard R.,Ornithological Society of New Zealand |
Melville D.S.,Ornithological Society of New Zealand
Science for Conservation | Year: 2011
This study of the movements of two Arctic-breeding waders (bar-tailed godwit, Limosa lapponica baueri, and red knot, Calidris canutus rogersi) was commissioned in response to (A) a lack of knowledge of how individual birds use networks of sites around New Zealand, and (B) the threat of avian influenza viruses, as migrating waders are potential vectors of these pathogens. The Ornithological Society of New Zealand (OSNZ) ran a colour-banding programme to study the movements of these waders in New Zealand from 2004 to 2008. A total of 770 bar-tailed godwits and 345 red knots were colour-banded around the country, and OSNZ members and other observers made over 9500 sightings of 721 godwits and over 1500 sightings of 275 knots during the project. Most resightings were from the capture site, but movements of up to 1185 km (one way) were documented. On average, young birds of both species were more mobile than adults; knots were generally more mobile than godwits. Some juvenile or immature godwits wandered widely around New Zealand and apparently settled at long-term 'wintering' locations during these explorations. Small numbers of godwits were recorded making stopovers at northern sites upon arrival from migration before moving on to their eventual destination. Overall, it is clear that non-breeding knots use an extensive network of sites around New Zealand and probably move frequently between them. Knots banded in the Firth of Thames were recorded from Parengarenga Harbour in the north of the North Island down to Tasman Bay in the northern South Island, but it is not clear how regular these long-distance movements are. Godwits, in contrast, are much more likely to remain at one site or intertidal system and not venture far away when present in New Zealand during their non-breeding season. © December 2011, Department of Conservation.
Jones C.J.,Landcare Research |
Clifford H.,Ornithological Society of New Zealand |
Fletcher D.,University of Otago |
Cuming P.,Landcare Research |
Lyver P.O.B.,Landcare Research
Notornis | Year: 2011
We estimated apparent annual survival of adult and young grey-faced petrels (Pterodroma macroptera gouldi) and age of first return to the natal colony of young birds from 2 colonies in the Bay of Plenty, NZL, between 1991 and 2008. We analysed the capture histories of 5844 adult birds and 928 chicks in a mark-recapture framework. The apparent adult annual survival rate was 0.89 after accounting for transience effects, which were greater at the mainland site (Mauao, Mount Maunganui) than on the island colony (Motuotau, Rabbit Island). Annual survival of young birds between fledging and 2 years of age was 0.844 for Mauao and 0.865 for Motuotau. Around 50% of fledglings that returned to their natal colony did so by 4 years of age, and by age 6, the probability of a fledgling returning was approximately 1.0. These are the first reliable estimates of these parameters for grey-faced petrels and are vital for models aimed at predicting the effects of natural perturbations or management interventions on breeding populations. © The Ornithological Society of New Zealand, Inc.