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Niche divergence is expected for species that compete for shared resources, including migrants that occupy similar regions during the non-breeding season. Studies of temperate seabirds indicate that both spatial and behavioural segregation can be important mechanisms for reducing competition, but there have been few investigations of resource partitioning by closely related taxa in low productivity, tropical environments. We investigated niche partitioning in 3 gadfly petrel taxa, Pterodroma leucoptera leucoptera (n = 22), P. leucoptera caledonica (n = 7) and P. pycrofti (n = 12), during their non-breeding season in the eastern tropical Pacific Ocean by combining tracking data from geolocator-immersion loggers with remotely sensed environmental data in species distribution models (SDMs), and by comparing feather stable isotope ratios. The 3 taxa showed spatial partitioning: two foraged in the North Equatorial Counter Current and one in the South Equatorial Current. This reflected differences in their realised habitat niches, with significant taxon-specific responses to thermocline depth, sea surface temperature and bathymetry. There were also differences among taxa in activity patterns, and all birds spent a much larger proportion of time in flight at night than during the day, suggesting predominance of nocturnal foraging behaviour. Comparison of stable isotope ratios in feathers suggests that P. l. leucoptera and P. pycrofti mainly consume vertically migrating mesopelagic fishes, whereas the diet of P. l. caledonica also includes some lower trophic levels including crustaceans and squid. Unique insights can be gained from studies of the foraging ecology of tropical pelagic seabirds, in comparison with temperate and polar waters, and are urgently required for understanding and protecting tropical avifauna in key marine habitats.

1. The pituitary hormone prolactin is thought to play an important role in the promotion of parental care in birds and mammals. The level of care parents provide is, however, likely to be influenced by additional factors, such as their physiological condition at the time of breeding. 2. We examined relationships between parental body condition, plasma prolactin levels and reproductive performance in Gould's Petrels (Pterodroma leucoptera), a long-lived seabird. We predicted that parental body condition would correlate positively with both prolactin level and parenting intensity, as measured by the quality of the chick they produced. We also examined the effects of parenting intensity on parental body condition and reproductive success in the subsequent breeding season. 3. Body condition of male parents positively correlated with prolactin levels at the start of their second protracted incubation bout. The body condition of both parents correlated positively with the body condition of their chick at its peak mass. However, producing a good-quality chick did not negatively affect parental body condition or reproductive success the following year. 4. These results suggest that prolactin reinforces parental behaviour in parents in good body condition, which facilitates production of good-quality chicks. Moreover, good-quality parents consistently produce good-quality chicks with no apparent trade-off to their physical condition.

Together with land clearance, grazing by stock and inappropriate fire regimes, predation by the introduced European red fox Vulpes vulpes (Linnaeus, 1758) has decimated populations of malleefowl Leipoa ocellata Gould, 1840. The decline of the malleefowl has been most pronounced in New South Wales, where foxes prey so heavily on malleefowl that adult mortality exceeds recruitment of young into the breeding population. Although young malleefowl are particularly vulnerable to foxes, subadults and adults are also taken. Within New South Wales, heavy predation by foxes occurs both in the remnants of native vegetation within agricultural lands and in the large tracts of mallee that lie further inland. Foxes appear to be the prime cause of malleefowl mortality throughout much of the malleefowl’s geographic range. Both fire and grazing by domestic stock reduce the carrying capacity of the habitat for malleefowl. In reserves where stock are excluded, there is no evidence that food resources are limiting malleefowl populations. Exotic herbivores, such as goats and rabbits, probably contribute to the demise of the malleefowl by reducing vegetative cover. Malleefowl are particularly vulnerable to predation by raptors in habitats where vegetative cover is sparse. Greater canopy cover, together with greater stocks of seeds within the soil seed-bank, can explain why old-growth mallee is optimal habitat for malleefowl. Malleefowl survival can be enhanced substantially by fox control. Fox baiting, however, needs to be frequent, intensive and widespread to reduce fox density to levels where predation no longer threatens the survival or recovery of malleefowl populations. Poisoning of foxes on surrounding properties, together with