This study examined divergence in the foraging distribution, at-sea behaviour and provisioning strategies of a small procellarid, the Cook's petrel Pterodroma cookii, during chick-rearing at 2 islands off New Zealand, separated latitudinally by ~1000 km. There was little overlap in foraging distribution between adults from Little Barrier Island (LBI), which ranged to the west into the Northern Tasman Sea and east into the Pacific Ocean, and conspecifics from Codfish Island (CDF), which foraged west of the South Island in the south Tasman Sea in association with the subtropical convergence zone. Although birds from CDF ranged further than those from LBI, there was no difference in mean foraging trip duration. Cook's petrels from CDF foraged over deeper, cooler water, with higher primary productivity, than conspecifics from LBI. At-sea behaviour also differed: adults from LBI spent less time in flight, and showed less variation in total flight time per day. Overall, Cook's petrels spend much more time in flight than albatrosses, and approximately the same amounts of time on the water during the night as during the day, suggesting a high portion of nocturnal foraging. Dive depths did not differ between colonies but were greater than expected for a gadfly petrel. Stable isotope signatures of blood indicated population-specific diets, and suggested that birds from LBI primarily consume cephalopods and fish, whereas those from CDF eat more crustaceans. Chicks at CDF received more food. These results suggest a broad divergence in foraging strategies between geographically well-separated colonies in response to regional differences in oceanography. KEY WORDS: Foraging distribution · Geolocation loggers · Stable isotopes · Subtropical convergence · Gadfly petrel Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 370: [271][272][273][274][275][276][277][278][279][280][281][282][283][284] 2008 ever, there have been relatively few studies of highly pelagic species from more widely separated populations, where there is nonetheless the potential for some overlap and interaction at sea. Such comparisons are particularly interesting given the potential for genetic isolation between populations, as most seabirds display a high degree of natal philopatry (Warham 1996). In addition, the high degree of behavioural flexibility of adults may also lead to divergence in foraging strategies, particularly between distant colonies in dissimilar oceanographic domains.Until recently, owing to the relatively large size of the available technology, detailed studies on the movements of pelagic seabirds had been restricted to medium to large species to which attachment of equipment was feasible without impacting the animal's behaviour (Weimerskirch et al. 1993, Stahl & Sagar 2000a. Information on the distribution and behaviour of smaller species (< 300 g) at sea was therefore restricted to band recoveries (Patterson & Hunter 2000) and shipboard observations (Bartle et al. 1990). However,...

Reliable survey methods for detection are critically important for the monitoring and management of exotic species. The eastern rosella (Platycercus eximius), a broad-tailed parakeet endemic to southeastern Australia, was introduced to New Zealand a century ago and is now geographically widespread. We studied the necessary timeframe for surveying the eastern rosella within its introduced range, testing the hypothesis that there are seasonal differences in the likelihood of detection. Although our comparisons were limited to surveys conducted during a single year, they are suggestive of an important impact of season on the survey duration required to detect eastern rosella confidently. Median latency until first detection was less during summer months (2.55 min) in comparison with winter months (11.2 min). Furthermore, 90% of first detections occurred within the first 13 min in summer surveys, compared with 22 min in winter. These results have implications for the design of surveys aiming to monitor rosella populations in New Zealand, and reiterate the importance of tailoring survey methods to the species of interest.